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Sample records for calcitic hydrated lime

  1. Removal of phosphate from greenhouse wastewater using hydrated lime.

    PubMed

    Dunets, C Siobhan; Zheng, Youbin

    2014-01-01

    Phosphate (P) contamination in nutrient-laden wastewater is currently a major topic of discussion in the North American greenhouse industry. Precipitation of P as calcium phosphate minerals using hydrated lime could provide a simple, inexpensive method for retrieval. A combination of batch experiments and chemical equilibrium modelling was used to confirm the viability of this P removal method and determine lime addition rates and pH requirements for greenhouse wastewater of varying nutrient compositions. Lime: P ratio (molar ratio of CaMg(OH)₄: PO₄‒P) provided a consistent parameter for estimating lime addition requirements regardless of initial P concentration, with a ratio of 1.5 providing around 99% removal of dissolved P. Optimal P removal occurred when lime addition increased the pH from 8.6 to 9.0, suggesting that pH monitoring during the P removal process could provide a simple method for ensuring consistent adherence to P removal standards. A Visual MINTEQ model, validated using experimental data, provided a means of predicting lime addition and pH requirements as influenced by changes in other parameters of the lime-wastewater system (e.g. calcium concentration, temperature, and initial wastewater pH). Hydrated lime addition did not contribute to the removal of macronutrient elements such as nitrate and ammonium, but did decrease the concentration of some micronutrients. This study provides basic guidance for greenhouse operators to use hydrated lime for phosphate removal from greenhouse wastewater. PMID:25176490

  2. Removal of phosphate from greenhouse wastewater using hydrated lime.

    PubMed

    Dunets, C Siobhan; Zheng, Youbin

    2014-01-01

    Phosphate (P) contamination in nutrient-laden wastewater is currently a major topic of discussion in the North American greenhouse industry. Precipitation of P as calcium phosphate minerals using hydrated lime could provide a simple, inexpensive method for retrieval. A combination of batch experiments and chemical equilibrium modelling was used to confirm the viability of this P removal method and determine lime addition rates and pH requirements for greenhouse wastewater of varying nutrient compositions. Lime: P ratio (molar ratio of CaMg(OH)₄: PO₄‒P) provided a consistent parameter for estimating lime addition requirements regardless of initial P concentration, with a ratio of 1.5 providing around 99% removal of dissolved P. Optimal P removal occurred when lime addition increased the pH from 8.6 to 9.0, suggesting that pH monitoring during the P removal process could provide a simple method for ensuring consistent adherence to P removal standards. A Visual MINTEQ model, validated using experimental data, provided a means of predicting lime addition and pH requirements as influenced by changes in other parameters of the lime-wastewater system (e.g. calcium concentration, temperature, and initial wastewater pH). Hydrated lime addition did not contribute to the removal of macronutrient elements such as nitrate and ammonium, but did decrease the concentration of some micronutrients. This study provides basic guidance for greenhouse operators to use hydrated lime for phosphate removal from greenhouse wastewater.

  3. Kinetic study of hydrated lime reaction with HCl.

    PubMed

    Yan, Rong; Chin, Terence; Liang, David Tee; Laursen, Karin; Ong, Wan Yean; Yao, Kaiwen; Tay, Joo Hwa

    2003-06-01

    Hydrochloride (HCl) is an acidic pollutant present in the flue gas of most municipal or hazardous waste incinerators. Hydrated lime (Ca(OH)2) is often used as a dry sorbent for injection in a spray reactor to remove HCI. However, due to the short residence time encountered, this control method has generally been found to have low conversion efficiencies which results in the high lime usage and generates large amount of fly ash as solid wastes. A fundamental study was carried outto investigate the kinetics of HCl-lime reaction under simulated flue gas conditions in order to better understand the process thereby providing a basis for an optimized lime usage and reduced fly ash production. The initial reaction rate and conversion of three limes were studied using a thermogravimetric analyzer by varying the gas flow rate, temperature (170-400 degrees C), and HCI concentrations (600-1200 mg/m3) as well as the associated particle size and surface area of the limes. The initial lime conversions were found to rely mostly on the residence time, while the ultimate lime conversions were strongly influenced by temperature and the reaction products. CaOHCI was found to be the primary product in most cases, while for one specific lime, CaCl2 was the ultimate conversion product after an extended time period. The true utilization of lime in flue gas cleanup is thus higher when CaOHCl is considered as the final product than those based on CaCl2 as the final product, which has been commonly used in previous studies. The initial reaction was controlled by diffusion of HCl in gas phase and the subsequent reaction by gaseous diffusion through the developing product layer. Increasing the HCI concentration raised the initial rate as well as conversion. However, overloading the lime with excessive HCI caused clogging at its surface and a drop in the ultimate conversion. Limes with smaller particle diameters and higher surface areas were found to be more reactive. The effect of gas

  4. Effects of direct land application of calcitic lime and lime- and cement kiln dust-sanitized biosolids on the chemical and spectroscopic characteristics of soil lipids

    SciTech Connect

    Dinel, H.; Schnitzer, M.; Pare, T.; Topp, E. ); Lemee, L.; Ambles, A. . Lab. de Chimie); Pelzer, N. )

    1999-05-01

    To determine the extent to which applications of calcitic lime and sanitized biosolids affect the quality of soil organic matter (SOM), lipids extracted from an unamended soil (CON) and from soils amended with calcitic lime (CAL), and lime (LSB)- and cement kiln dust (CDB)-sanitized biosolids were characterized by chemical analysis and Pyrolysis-Gas chromatography (Py-GC). From diethyl ether (DEE) and CHCl[sub 3] soluble lipids, and from weight ratios of the extracts, the organic matter in the soil amended with CDB-treated biosolids seemed to be more biodegraded and biochemically inert than the organic matter in soils that received LSB-treated biosolids and calcitic lime and that in the control soil.

  5. Hydrated lime for metals immobilization and explosives transformation: Treatability study.

    PubMed

    Martin, W Andy; Larson, S L; Nestler, C C; Fabian, G; O'Connor, G; Felt, D R

    2012-05-15

    Fragmentation grenades contain Composition B (RDX and TNT) within a steel shell casing. There is the potential for off-site migration of high explosives and metals from hand grenade training ranges by transport in surface water and subsurface transport in leachate. This treatability study used bench-scale columns and mesocosm-scale laboratory lysimeters to investigate the potential of hydrated lime as a soil amendment for in situ remediation of explosives and metals stabilization in hand grenade range soils. Compared to the unamended soil there was a 26-92% reduction of RDX in the leachate and runoff water from the lime treated soils and a 66-83% reduction of zinc in the leachate and runoff water samples; where the hand grenade range metals of concern were zinc, iron, and manganese. The amended soil was maintained at the target pH of greater than 10.5 for optimum explosives decomposition. The treatability study indicated a high potential of success for scale-up to an in situ field study. PMID:22445717

  6. Sludge ash/hydrated lime on the geotechnical properties of soft soil.

    PubMed

    Lin, Deng-Fong; Lin, Kae-Long; Hung, Min-Jui; Luo, Huan-Lin

    2007-06-25

    In this study, an effort to improve the properties and strength of soil, sewage sludge ash (SSA) and hydrated lime are applied to stabilize soft cohesive subgrade soil. Five different ratios (in weight percentage), 0%, 2%, 4%, 8%, and 16%, of sludge ash/hydrated lime are proposed for mixture with cohesive soil. Then, the effects of the different proportions of SSA/hydrated lime on soft cohesive soil are studied. Test results indicate that the unconfined compressive strength of specimens with additives was raised from three to seven times better than that of the untreated soil, and swelling behaviors were also effectively reduced for those specimens. Results of triaxial compression test indicate that the shear strength parameter, c, rose with an increased amount of additives and improved from 30 to 50-70kPa. On the whole, SSA/hydrated lime could particularly improve the geotechnical properties of cohesive subgrade soil. PMID:17141407

  7. Internal friction of hydrated soda-lime-silicate glasses.

    PubMed

    Reinsch, S; Müller, R; Deubener, J; Behrens, H

    2013-11-01

    The internal friction of hydrated soda-lime-silica glasses with total water content (C(W)) up to 1.9 wt. % was studied by dynamic mechanical analysis (DMA) using temperature-frequency sweeps from 723 K to 273 K and from 1 s(-1) to 50 s(-1). Total water content and concentrations of H2O molecules (C(H2O)) and OH groups (C(OH)) in the DMA specimens were determined by infrared spectroscopy. For low water contents (C(W) ≈ C(OH) < 0.25 wt. %) two discrete internal friction peaks below the glass transition (α relaxation) were assigned to the low-temperature motion of alkali ions (γ relaxation) and cooperative movements of dissimilar mobile species under participation of OH at higher temperature (β(OH) relaxation). For large water contents (C(W) > 1 wt. %), where significant amounts of molecular water are evident (C(H2O) > 0.15 wt. %), however, internal friction spectra change unexpectedly: the β(OH) peak heights saturate and a low temperature shoulder appears on the β-relaxation peak. This emerging relaxation mode (β(H2O) relaxation) was assigned to the motions of H2O molecules. β(H2O) relaxation was found to be faster than β(OH) but slower than γ relaxation. Activation energy of the different relaxation modes increased in the order γ < β(H2O) < β(OH) < α. PMID:24206315

  8. Survival of Cryptosporidium parvum oocysts in the presence of hydrated lime.

    PubMed

    Zintl, A; Keogh, B; Ezzaty-Mirhashemi, M; De Waal, T; Scholz, D; Mulcahy, G

    2010-03-01

    To investigate the effects of hydrated lime on the survival of Cryptosporidium oocysts, the percentage viability of oocysts was assessed using fluorescent in situ hybridisation. In the absence of lime and with lime at a concentration of 1 per cent, there was a gradual decline in oocyst viability during the 10-day trial. Although the addition of 5 or 10 per cent lime caused the total number of oocysts to decrease, there appeared to be an increase in the proportion of potentially viable oocysts. PMID:20208077

  9. The elimination of Salmonella typhimurium in sewage sludge by aerobic mesophilic stabilization and lime hydrated stabilization.

    PubMed

    Plachá, Iveta; Venglovský, Ján; Maková, Zuzana; Martinéz, José

    2008-07-01

    This study observed the effects of two methods, aerobic mesophilic stabilization and lime hydrated stabilization of sewage sludge upon the survival of Salmonella typhimurium. Raw (primary) sludges from the mechanical biological municipal sewage treatment plant were used. Aerobic stabilization and lime hydrated stabilization were carried out in a laboratory fermentor. Aerobic stabilization was carried out in the mesophilic temperature range (from 25.70+/-0.40 to 37.82+/-1.38 degrees C). Lime hydrated was used at an amount of 10 kg/m(3) for the stabilization. Sludge samples were inoculated with a broth culture of S. typhimurium. Quantitative and qualitative examinations of the presence of S. typhimurium were carried out. Aerobic mesophilic stabilization caused elimination S. typhimurium within 48 h. The T(90) value of S. typhimurium was 6.66+/-0.20 h. During the lime hydrated stabilization pH values significantly increased from 5.66+/-0.07 to 12.12+/-0.02 (P<0.01). S. typhimurium was inactivated within 1h and the T(90) value was 0.19+/-0.01 h. Our study confirmed that the treatment of sewage sludge with lime hydrated was significantly more effective than the aerobic mesophilic stabilization, (P<0.01). PMID:17931859

  10. Advanced treatment of swine wastewater using an agent synthesized from amorphous silica and hydrated lime.

    PubMed

    Tanaka, Yasuo; Hasegawa, Teruaki; Sugimoto, Kiyomi; Miura, Keiichi; Aketo, Tsuyoshi; Minowa, Nobutaka; Toda, Masaya; Kinoshita, Katsumi; Yamashita, Takahiro; Ogino, Akifumi

    2014-01-01

    Advanced treatment using an agent synthesized from amorphous silica and hydrated lime (M-CSH-lime) was developed and applied to swine wastewater treatment. Biologically treated wastewater and M-CSH-lime (approximately 6 w/v% slurry) were fed continuously into a column-shaped reactor from its bottom. Accumulated M-CSH-lime gradually formed a bed layer. The influent permeated this layer and contacted the M-CSH-lime, and the treatment reaction progressed. Treated liquid overflowing from the top of the reactor was neutralized with CO₂gas bubbling. The colour removal rate approximately exceeded 50% with M-CSH-lime addition rates of > 0.15 w/v%. The removal rate of PO(3⁻)(4) exceeded 80% with the addition of>0.03 w/v% of M-CSH-lime. The removal rates of coliform bacteria and Escherichia coli exceeded 99.9% with > 0.1 w/v%. Accumulated M-CSH-lime in the reactor was periodically withdrawn from the upper part of the bed layer. The content of citric-acid-soluble P₂O₅ in the recovered matter was>15% when the weight ratio of influent PO(3⁻)(4) -P to added M-CSH-lime was > 0.15. This content was comparable with commercial phosphorus fertilizer. The inhibitory effect of recovered M-CSH-lime on germination and growth of leafy vegetable komatsuna (Brassica rapa var. perviridis) was evaluated by an experiment using the Neubauer's pot. The recovered M-CSH-lime had no negative effect on germination and growth. These results suggest that advanced water treatment with M-CSH-lime was effective for simultaneous removal of colour, [Formula: see text] and coliform bacteria at an addition rate of 0.03-0.15 w/v%, and that the recovered M-CSH-lime would be suitable as phosphorus fertilizer. PMID:25189846

  11. Advanced treatment of swine wastewater using an agent synthesized from amorphous silica and hydrated lime.

    PubMed

    Tanaka, Yasuo; Hasegawa, Teruaki; Sugimoto, Kiyomi; Miura, Keiichi; Aketo, Tsuyoshi; Minowa, Nobutaka; Toda, Masaya; Kinoshita, Katsumi; Yamashita, Takahiro; Ogino, Akifumi

    2014-01-01

    Advanced treatment using an agent synthesized from amorphous silica and hydrated lime (M-CSH-lime) was developed and applied to swine wastewater treatment. Biologically treated wastewater and M-CSH-lime (approximately 6 w/v% slurry) were fed continuously into a column-shaped reactor from its bottom. Accumulated M-CSH-lime gradually formed a bed layer. The influent permeated this layer and contacted the M-CSH-lime, and the treatment reaction progressed. Treated liquid overflowing from the top of the reactor was neutralized with CO₂gas bubbling. The colour removal rate approximately exceeded 50% with M-CSH-lime addition rates of > 0.15 w/v%. The removal rate of PO(3⁻)(4) exceeded 80% with the addition of>0.03 w/v% of M-CSH-lime. The removal rates of coliform bacteria and Escherichia coli exceeded 99.9% with > 0.1 w/v%. Accumulated M-CSH-lime in the reactor was periodically withdrawn from the upper part of the bed layer. The content of citric-acid-soluble P₂O₅ in the recovered matter was>15% when the weight ratio of influent PO(3⁻)(4) -P to added M-CSH-lime was > 0.15. This content was comparable with commercial phosphorus fertilizer. The inhibitory effect of recovered M-CSH-lime on germination and growth of leafy vegetable komatsuna (Brassica rapa var. perviridis) was evaluated by an experiment using the Neubauer's pot. The recovered M-CSH-lime had no negative effect on germination and growth. These results suggest that advanced water treatment with M-CSH-lime was effective for simultaneous removal of colour, [Formula: see text] and coliform bacteria at an addition rate of 0.03-0.15 w/v%, and that the recovered M-CSH-lime would be suitable as phosphorus fertilizer.

  12. A Study on Solidification of Abandoned Mine Tailings with Hydrated Lime

    NASA Astrophysics Data System (ADS)

    Min, K.; Lee, H.

    2008-12-01

    Solidification is one of the stabilization processes for wastes and their components to reduce their toxicity and migration rates to surroundings. Hydrated limes were applied as cementing materials to solidify heavy metal contaminated tailings from the Geumjang mine and the solidified tailing specimens were tested for their appropriateness in accordance with the suggested test methods. In the preliminary tests for the solidified tailing specimens, all the specimens have higher uniaxial compressive strengths than 3.5kgf/cm2, the standard recommended for land reclamation solids by EPA(Environmental Protection Agency). Even in leaching tests for the solidified tailing specimens, concentrations of heavy metals such as As, Cd, Cu, Pb, and Zn were decreased significantly below the environmental warning standards in comparison with those of raw tailing samples. The optimum mixing ratio of tailings, hydrated lime, and water was determined through the preliminary tests. The solidified mixtures of mine tailings and hydrated lime through pozzolanic reaction were tested for their durability against repeated freezing and thawing processes. After repeated freezing and thawing, the uniaxial compressive strengths of all the solidified mixture specimens decreased in comparison with those before test but still higher than 3.5kgf/cm2, and concentrations of heavy metals such as As, Cd, Cu, Pb, and Zn were below the standards. Effluents in the repetitive artificial tests show pH's of 7.4 to 9.1 and concentrations of heavy metals such as As, Cd, Cu, Pb, and Zn of below 0.05ppm. Conclusively this study shows potential applicability of hydrated limes to in-situ stabilization of abandoned mine tailings.

  13. Iron blast furnace slag/hydrated lime sorbents for flue gas desulfurization.

    PubMed

    Liu, Chiung-Fang; Shih, Shin-Min

    2004-08-15

    Sorbents prepared from iron blast furnace slag (BFS) and hydrated lime (HL) through the hydration process have been studied with the aim to evaluate their reactivities toward SO2 under the conditions prevailing in dry or semidry flue gas desulfurization processes. The BFS/HL sorbents, having large surface areas and pore volumes due to the formation of products of hydration, were highly reactive toward SO2, as compared with hydrated lime alone (0.24 in Ca utilization). The sorbent reactivity increased as the slurrying temperature and time increased and as the particle size of BFS decreased; the effects of the liquid/solid ratio and the sorbent drying conditions were negligible. The structural properties and the reactivity of sorbent were markedly affected by the BFS/HL ratio; the sorbent with 30/70 ratio had the highest 1 h utilization of Ca, 0.70, and SO2 capture, 0.45 g SO2/g sorbent. The reactivity of a sorbent was related to its initial specific surface area (Sg0) and molar content of Ca (M(-1)); the 1 h utilization of Ca increased almost linearly with increasing Sg0/M. The results of this study are useful to the preparation of BFS/HL sorbents with high reactivity for use in the dry and semidry processes to remove SO2 from the flue gas.

  14. Iron blast furnace slag/hydrated lime sorbents for flue gas desulfurization.

    PubMed

    Liu, Chiung-Fang; Shih, Shin-Min

    2004-08-15

    Sorbents prepared from iron blast furnace slag (BFS) and hydrated lime (HL) through the hydration process have been studied with the aim to evaluate their reactivities toward SO2 under the conditions prevailing in dry or semidry flue gas desulfurization processes. The BFS/HL sorbents, having large surface areas and pore volumes due to the formation of products of hydration, were highly reactive toward SO2, as compared with hydrated lime alone (0.24 in Ca utilization). The sorbent reactivity increased as the slurrying temperature and time increased and as the particle size of BFS decreased; the effects of the liquid/solid ratio and the sorbent drying conditions were negligible. The structural properties and the reactivity of sorbent were markedly affected by the BFS/HL ratio; the sorbent with 30/70 ratio had the highest 1 h utilization of Ca, 0.70, and SO2 capture, 0.45 g SO2/g sorbent. The reactivity of a sorbent was related to its initial specific surface area (Sg0) and molar content of Ca (M(-1)); the 1 h utilization of Ca increased almost linearly with increasing Sg0/M. The results of this study are useful to the preparation of BFS/HL sorbents with high reactivity for use in the dry and semidry processes to remove SO2 from the flue gas. PMID:15382877

  15. Lime

    USGS Publications Warehouse

    Miller, M.

    2006-01-01

    In 2005, US lime production was 20 Mt with a value of $1.5 billion. Production was unchanged compared with 2004. Captive production was 1.4 Mt. US consumption was 20.2 Mt. Most of the US lime trade was with Canada and Mexico. Despite some disruptions due to hurricanes Katrina and Rita, normal sales activities remained healthy.

  16. Full quantitative phase analysis of hydrated lime using the Rietveld method

    SciTech Connect

    Lassinantti Gualtieri, Magdalena

    2012-09-15

    Full quantitative phase analysis (FQPA) using X-ray powder diffraction and Rietveld refinements is a well-established method for the characterization of various hydraulic binders such as Portland cement and hydraulic limes. In this paper, the Rietveld method is applied to hydrated lime, a non-hydraulic traditional binder. The potential presence of an amorphous phase in this material is generally ignored. Both synchrotron radiation and a conventional X-ray source were used for data collection. The applicability of the developed control file for the Rietveld refinements was investigated using samples spiked with glass. The results were cross-checked by other independent methods such as thermal and chemical analyses. The sample microstructure was observed by transmission electron microscopy. It was found that the consistency between the different methods was satisfactory, supporting the validity of FQPA for this material. For the samples studied in this work, the amount of amorphous material was in the range 2-15 wt.%.

  17. Methanogenic calcite, 13C-depleted bivalve shells, and gas hydrate from a mud volcano offshore southern California

    USGS Publications Warehouse

    Hein, J.R.; Normark, W.R.; McIntyre, B.R.; Lorenson, T.D.; Powell, C.L.

    2006-01-01

    Methane and hydrogen sulfide vent from a cold seep above a shallowly buried methane hydrate in a mud volcano located 24 km offshore southern California in?? 800 m of water. Bivalves, authigenic calcite, and methane hydrate were recovered in a 2.1 m piston core. Aragonite shells of two bivalve species are unusually depleted in 13C (to -91??? ??13C), the most 13C-depleted shells of marine macrofauna yet discovered. Carbon isotopes for both living and dead specimens indicate that they used, in part, carbon derived from anaerobically oxidized methane to construct their shells. The ??13C values are highly variable, but most are within the range -12??? to -91???. This variability may be diagnostic for identifying cold-seep-hydrate systems in the geologic record. Authigenic calcite is abundant in the cores down to ???1.5 m subbottom, the top of the methane hydrate. The calcite is depleted in 13C (??13C = -46??? to -58???), indicating that carbon produced by anaerobically oxidized methane is the main source of the calcite. Methane sources include a geologic hydrocarbon reservoir from Miocene source rocks, and biogenic and thermogenic degradation of organic matter in basin sediments. Oxygen isotopes indicate that most calcite formed out of isotopic equilibrium with ambient bottom water, under the influence of gas hydrate dissociation and strong methane flux. High metal content in the mud volcano sediment indicates leaching of basement rocks by fluid circulating along an underlying fault, which also allows for a high flux of fossil methane. ?? 2006 Geological Society of America.

  18. Engineering properties of water/wastewater-treatment sludge modified by hydrated lime, fly ash and loess.

    PubMed

    Lim, Sungjin; Jeon, Wangi; Lee, Jaebok; Lee, Kwanho; Kim, Namho

    2002-10-01

    The purpose of this research was to present engineering properties of modified sludge from water/wastewater treatment by modifiers such as hydrated lime, loess, and fly ash. The proper mixing ratio was determined to hold the pH of the modified sludge above 12.0 for 2 h. Laboratory tests carried out in this research included particle analysis, compaction and CBR, SEM and X-ray diffraction, unconfined compression test, permeability test, and TCLP test. The main role of lime was to sterilize microorganisms in the sludge. The unconfined strength of the modified sludge by fly ash and loess satisfied the criteria for construction materials, which was above 100 kPa. The permeability of all the mixtures was around 1.0 x 10(-7) cm/s. Extraction tests for hazardous components in modified sludge revealed below the regulated criteria, especially for cadmium, copper, and lead. The present study suggested that the use of lime, fly ash, and loess be an another alternative to modify or stabilize water/wastewater treatment sludge as construction materials in civil engineering. PMID:12420922

  19. Engineering properties of water/wastewater-treatment sludge modified by hydrated lime, fly ash and loess.

    PubMed

    Lim, Sungjin; Jeon, Wangi; Lee, Jaebok; Lee, Kwanho; Kim, Namho

    2002-10-01

    The purpose of this research was to present engineering properties of modified sludge from water/wastewater treatment by modifiers such as hydrated lime, loess, and fly ash. The proper mixing ratio was determined to hold the pH of the modified sludge above 12.0 for 2 h. Laboratory tests carried out in this research included particle analysis, compaction and CBR, SEM and X-ray diffraction, unconfined compression test, permeability test, and TCLP test. The main role of lime was to sterilize microorganisms in the sludge. The unconfined strength of the modified sludge by fly ash and loess satisfied the criteria for construction materials, which was above 100 kPa. The permeability of all the mixtures was around 1.0 x 10(-7) cm/s. Extraction tests for hazardous components in modified sludge revealed below the regulated criteria, especially for cadmium, copper, and lead. The present study suggested that the use of lime, fly ash, and loess be an another alternative to modify or stabilize water/wastewater treatment sludge as construction materials in civil engineering.

  20. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Marutschke, Christoph; Walters, Deron; Cleveland, Jason; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-01

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic—yet decisive—question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface.

  1. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy.

    PubMed

    Marutschke, Christoph; Walters, Deron; Walters, Deron; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-22

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface. PMID:25074402

  2. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy.

    PubMed

    Marutschke, Christoph; Walters, Deron; Walters, Deron; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-22

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface.

  3. Effects of hydrated lime and quicklime on the decay of buried human remains using pig cadavers as human body analogues.

    PubMed

    Schotsmans, Eline M J; Denton, John; Dekeirsschieter, Jessica; Ivaneanu, Tatiana; Leentjes, Sarah; Janaway, Rob C; Wilson, Andrew S

    2012-04-10

    Recent casework in Belgium involving the search for human remains buried with lime, demonstrated the need for more detailed understanding of the effect of different types of lime on cadaver decomposition and its micro-environment. Six pigs (Sus scrofa) were used as body analogues in field experiments. They were buried without lime, with hydrated lime (Ca(OH)(2)) and with quicklime (CaO) in shallow graves in sandy loam soil in Belgium and recovered after 6 months of burial. Observations from these field recoveries informed additional laboratory experiments that were undertaken at the University of Bradford, UK. The combined results of these studies demonstrate that despite conflicting evidence in the literature, hydrated lime and quicklime both delay the decay of the carcass during the first 6 months. This study has implications for the investigation of clandestine burials and for a better understanding of archaeological plaster burials. Knowledge of the effects of lime on decomposition processes also has bearing on practices involving burial of animal carcasses and potentially the management of mass graves and mass disasters by humanitarian organisations and DVI teams. PMID:22030481

  4. Modeling dry-scrubbing of gaseous HCl with hydrated lime in cyclones with and without recirculation.

    PubMed

    Chibante, Vania G; Fonseca, Ana M; Salcedo, Romualdo R

    2010-06-15

    A mathematical model describing the dry-scrubbing of gaseous hydrogen chloride (HCl) with solid hydrated lime particles (Ca(OH)(2)) was developed and experimentally verified. The model applies to cyclone systems with and without recirculation, where reaction and particle collection occurs in the same processing unit. The Modified Grain Model was selected to describe the behavior of the reaction process and it was assumed that the gas and the solid particles flow in the reactor with a plug flow. In this work, this behavior is approximated by a cascade of N CSTRs in series. Some of the model parameters were estimated by optimization taking into account the experimental results obtained. A good agreement was observed between the experimental results and those predicted by the model, where the main control resistance is the diffusion of the gaseous reactant in the layer of solid product formed. PMID:20185231

  5. Simultaneous removal of colour, phosphorus and disinfection from treated wastewater using an agent synthesized from amorphous silica and hydrated lime.

    PubMed

    Yamashita, Takahiro; Aketo, Tsuyoshi; Minowa, Nobutaka; Sugimoto, Kiyomi; Yokoyama, Hiroshi; Ogino, Akifumi; Tanaka, Yasuo

    2013-01-01

    An agent synthesized from amorphous silica and hydrated lime (CSH-lime) was investigated for its ability to simultaneously remove the colour, phosphorus and disinfection from the effluents from wastewater treatment plants on swine farms. CSH-lime removed the colour and phosphate from the effluents, with the colour-removal effects especially high at pH 12, and phosphorous removal was more effective in strongly alkaline conditions (pH > 10). Colour decreased from 432 +/-111 (mean +/- SD) to 107 +/- 41 colour units and PO4(3-)P was reduced from 45 +/- 39 mg/L to undetectable levels at the CSH-lime dose of 2.0% w/v. Moreover, CSH-lime reduced the total organic carbon from 99.0 to 37.9 mg/L at the dose of 2.0% w/v and was effective at inactivating total heterotrophic and coliform bacteria. However, CSH-lime did not remove nitrogen compounds such as nitrite, nitrate and ammonium. Colour was also removed from dye solutions by CSH-lime, at the same dose. PMID:23837353

  6. Simultaneous removal of colour, phosphorus and disinfection from treated wastewater using an agent synthesized from amorphous silica and hydrated lime.

    PubMed

    Yamashita, Takahiro; Aketo, Tsuyoshi; Minowa, Nobutaka; Sugimoto, Kiyomi; Yokoyama, Hiroshi; Ogino, Akifumi; Tanaka, Yasuo

    2013-01-01

    An agent synthesized from amorphous silica and hydrated lime (CSH-lime) was investigated for its ability to simultaneously remove the colour, phosphorus and disinfection from the effluents from wastewater treatment plants on swine farms. CSH-lime removed the colour and phosphate from the effluents, with the colour-removal effects especially high at pH 12, and phosphorous removal was more effective in strongly alkaline conditions (pH > 10). Colour decreased from 432 +/-111 (mean +/- SD) to 107 +/- 41 colour units and PO4(3-)P was reduced from 45 +/- 39 mg/L to undetectable levels at the CSH-lime dose of 2.0% w/v. Moreover, CSH-lime reduced the total organic carbon from 99.0 to 37.9 mg/L at the dose of 2.0% w/v and was effective at inactivating total heterotrophic and coliform bacteria. However, CSH-lime did not remove nitrogen compounds such as nitrite, nitrate and ammonium. Colour was also removed from dye solutions by CSH-lime, at the same dose.

  7. Short-term effects of hydrated lime and quicklime on the decay of human remains using pig cadavers as human body analogues: Laboratory experiments.

    PubMed

    Schotsmans, Eline M J; Denton, John; Fletcher, Jonathan N; Janaway, Robert C; Wilson, Andrew S

    2014-05-01

    Contradictions and misconceptions regarding the effect of lime on the decay of human remains have demonstrated the need for more research into the effect of different types of lime on cadaver decomposition. This study follows previous research by the authors who have investigated the effect of lime on the decomposition of human remains in burial environments. A further three pig carcasses (Sus scrofa), used as human body analogues, were observed and monitored for 78 days without lime, with hydrated lime (Ca(OH)2) and with quicklime (CaO) in the taphonomy laboratory at the University of Bradford. The results showed that in the early stages of decay, the unlimed and hydrated lime cadavers follow a similar pattern of changes. In contrast, the application of quicklime instigated an initial acceleration of decay. Microbial investigation demonstrated that the presence of lime does not eliminate all aerobic bacteria. The experiment also suggested that lime functions as a sink, buffering the carbon dioxide evolution. This study complements the field observations. It has implications for the investigation of time since death of limed remains. Knowledge of the effects of lime on decomposition processes is of interest to forensic pathologists, archaeologists, humanitarian organisations and those concerned with disposal of animal carcasses or human remains in mass disasters. PMID:24513401

  8. Investigation of fatigue properties of granite asphalt mixtures containing hydrated lime

    NASA Astrophysics Data System (ADS)

    Wu, Shaopeng; Huang, Xu

    2010-03-01

    This paper presents the results of a laboratory study of evaluating the fatigue characteristics of granite asphalt mixtures (GAM) using different testing methods. In the study, the fatigue performances of GAM were evaluated with Superpave indirect tensile test (IDT) and four-point beam fatigue test. Specimens were conditioned by four different methods: (1) one cycle of freeze-thaw (F-T), (2) two cycles of F-T, (3) immersion in 60°C water bath for 30min (4) immersion in 60°C water bath for 48h, and contrastive analysis was made with unconditioned specimens. Investigation of moisture damage influence on the fatigue properties of GAM with and without Hydrated Lime (HL) was done. The results from this study indicated that both Superpave IDT and four-point beam fatigue test agreed with each other in ranking the fatigue property of GAM. Increasing F-T cycles or immersion time would decrease fatigue life in GAM, and the addition of HL was effective to prolong the fatigue life in GAM.

  9. Investigation of fatigue properties of granite asphalt mixtures containing hydrated lime

    NASA Astrophysics Data System (ADS)

    Wu, Shaopeng; Huang, Xu

    2009-12-01

    This paper presents the results of a laboratory study of evaluating the fatigue characteristics of granite asphalt mixtures (GAM) using different testing methods. In the study, the fatigue performances of GAM were evaluated with Superpave indirect tensile test (IDT) and four-point beam fatigue test. Specimens were conditioned by four different methods: (1) one cycle of freeze-thaw (F-T), (2) two cycles of F-T, (3) immersion in 60°C water bath for 30min (4) immersion in 60°C water bath for 48h, and contrastive analysis was made with unconditioned specimens. Investigation of moisture damage influence on the fatigue properties of GAM with and without Hydrated Lime (HL) was done. The results from this study indicated that both Superpave IDT and four-point beam fatigue test agreed with each other in ranking the fatigue property of GAM. Increasing F-T cycles or immersion time would decrease fatigue life in GAM, and the addition of HL was effective to prolong the fatigue life in GAM.

  10. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    SciTech Connect

    Hargis, Craig W.; Telesca, Antonio; Monteiro, Paulo J.M.

    2014-11-15

    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite.

  11. Long-term effects of hydrated lime and quicklime on the decay of human remains using pig cadavers as human body analogues: Field experiments.

    PubMed

    Schotsmans, Eline M J; Fletcher, Jonathan N; Denton, John; Janaway, Robert C; Wilson, Andrew S

    2014-05-01

    An increased number of police enquiries involving human remains buried with lime have demonstrated the need for more research into the effect of different types of lime on cadaver decomposition and its micro-environment. This study follows previous studies by the authors who have investigated the effects of lime on the decay of human remains in laboratory conditions and 6 months of field experiments. Six pig carcasses (Sus scrofa), used as human body analogues, were buried without lime with hydrated lime (Ca(OH)2) and quicklime (CaO) in shallow graves in sandy-loam soil in Belgium and recovered after 17 and 42 months of burial. Analysis of the soil, lime and carcasses included entomology, pH, moisture content, microbial activity, histology and lime carbonation. The results of this study demonstrate that despite conflicting evidence in the literature, the extent of decomposition is slowed down by burial with both hydrated lime and quicklime. The more advanced the decay process, the more similar the degree of liquefaction between the limed and unlimed remains. The end result for each mode of burial will ultimately result in skeletonisation. This study has implications for the investigation of clandestine burials, for a better understanding of archaeological plaster burials and potentially for the interpretation of mass graves and management of mass disasters by humanitarian organisation and DVI teams. PMID:24513400

  12. Utilization of calcite and waste glass for preparing construction materials with a low environmental load.

    PubMed

    Maeda, Hirotaka; Imaizumi, Haruki; Ishida, Emile Hideki

    2011-11-01

    In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition. PMID:21794973

  13. Managing Salmonella Typhimurium and Escherichia coli O157:H7 in soil with hydrated lime - An outdoor study in lysimeters and field plots.

    PubMed

    Nyberg, Karin A; Vinnerås, Björn; Albihn, Ann

    2014-01-01

    An outbreak of Salmonella Typhimurium or E. coli O157:H7 among domestic animals can have great financial consequences for an animal enterprise but also be a threat for public health as there is a risk for transmission of the infection through the environment. In order to minimize disease transmission, it is important to treat not only the affected animals but also the areas on which they have been kept. In the present study, the effect of hydrated lime as a treatment for Salmonella Typhimurium or E. coli O157:H7 contaminated soil was investigated. The study was performed outdoors, in a lysimeter system and in field plots. The soils were spiked with Salmonella Typhimurium and/or E. coli O157:H7 and hydrated lime was added at three different concentrations (0.5, 1 and 2%). Sampling was performed over one month, and the levels of bacteria were analyzed by standard culture methods. In addition, the soil pH was monitored throughout the study. The results showed that application of 0.5-1 kg hydrated lime per m(2) reduced both Salmonella Typhimurium and E. coli O157:H7 numbers to below the detection limit (2 log10 CFU g-1 soil) in 3-7 days. Lower application rates of hydrated lime did not reduce pathogen numbers in the lysimeter study, but in the field plots no E. coli O157:H7 was detected at the end of the four-week study period regardless of hydrated lime application. A recommended strategy for treating a Salmonella Typhimurium or E. coli O157:H7 contaminated soil could therefore be to monitor the pH over the time of treatment and to repeat hydrated lime application if a decrease in pH is observed. PMID:24138468

  14. Managing Salmonella Typhimurium and Escherichia coli O157:H7 in soil with hydrated lime - An outdoor study in lysimeters and field plots.

    PubMed

    Nyberg, Karin A; Vinnerås, Björn; Albihn, Ann

    2014-01-01

    An outbreak of Salmonella Typhimurium or E. coli O157:H7 among domestic animals can have great financial consequences for an animal enterprise but also be a threat for public health as there is a risk for transmission of the infection through the environment. In order to minimize disease transmission, it is important to treat not only the affected animals but also the areas on which they have been kept. In the present study, the effect of hydrated lime as a treatment for Salmonella Typhimurium or E. coli O157:H7 contaminated soil was investigated. The study was performed outdoors, in a lysimeter system and in field plots. The soils were spiked with Salmonella Typhimurium and/or E. coli O157:H7 and hydrated lime was added at three different concentrations (0.5, 1 and 2%). Sampling was performed over one month, and the levels of bacteria were analyzed by standard culture methods. In addition, the soil pH was monitored throughout the study. The results showed that application of 0.5-1 kg hydrated lime per m(2) reduced both Salmonella Typhimurium and E. coli O157:H7 numbers to below the detection limit (2 log10 CFU g-1 soil) in 3-7 days. Lower application rates of hydrated lime did not reduce pathogen numbers in the lysimeter study, but in the field plots no E. coli O157:H7 was detected at the end of the four-week study period regardless of hydrated lime application. A recommended strategy for treating a Salmonella Typhimurium or E. coli O157:H7 contaminated soil could therefore be to monitor the pH over the time of treatment and to repeat hydrated lime application if a decrease in pH is observed.

  15. Removal of sulfur dioxide from a continuously operated binary fluidized bed reactor using inert solids and hydrated lime.

    PubMed

    Pisani, R; de Moraes, D

    2004-06-18

    Sulfur dioxide pollutant was treated in the laboratory with hydrated lime particles having a mean diameter of 9.1 microm in a continuously operating binary fluidized bed reactor also containing inert sand particles with sizes varying from 500 to 590 microm. The influence of temperature (500, 600, 700 and 800 degrees C) on the reaction medium, of the superficial velocity of the gas (0.8, 1.0 and 1.2 m/s), and of the Ca/S molar ratio (1, 2 and 3) on the SO2 removal efficiency were investigated for an inflow gas concentration of 1000 ppm and an initially static bed height of 10.0 cm. The pollutant removal efficiency proved to depend on the temperature and the velocity of the gaseous flow and was strongly influenced by the Ca/S molar ratio. The maximum efficiency of 97.7% was achieved at a temperature of 700 degrees C, a Ca/S ratio of 3 and a velocity of 0.8 m/s. The lime particles' mean residence time was determined by an indirect method, which consisted of integrating the gas concentration curves normalized with respect to time. Based on a calculation of the critical transition velocities, it was concluded that the reactor operated in a bubbling regime under each condition investigated here. PMID:15177758

  16. Preparation of a new sorbent with hydrated lime and blast furnace slag for phosphorus removal from aqueous solution.

    PubMed

    Gong, Guozhuo; Ye, Shufeng; Tian, Yajun; Wang, Qi; Ni, Jiandi; Chen, Yunfa

    2009-07-30

    The removal of dissolvable inorganic phosphate (H(2)PO(4)(-)) by sorbents prepared from hydrated lime (HL) and blast furnace slag (BFS) was fundamentally studied by an orthogonal experiment design. Based on statistic analysis, it is revealed that the weight ratio of BFS/HL is the most significant variable, and an optimized preparation condition is figured out. With the increase of HL content, the adsorption capacity increases, suggesting that the HL plays the important role in the removal process in the gross. However, in the lower HL content, it is interesting that the adsorption capacity of as-prepared sorbents exceed the sum of the capacities of the same ratio of BFS and HL. The further analysis indicate the excess capacities linearly depend on the specific surface area of sorbents, suggesting that the removal of H(2)PO(4)(-) is closely related with the microstructure of sorbents in the lower HL content, according to the characterization with SEM, XRD and pore analysis. Additionally, an adsorption model and kinetic are discussed in this paper. PMID:19124194

  17. Trichloroethylene decomposition and in-situ dry sorption of Cl-products by calcium oxides prepared from hydrated limes.

    PubMed

    Gotoh, Yoshimi; Iwata, Goichi; Choh, Kyaw; Kubota, Mitsuhiro; Matsuda, Hitoki

    2011-10-01

    A comparison of CaOs produced by calcining two types of hydrated lime and calcium carbonate was made for decomposition of trichloroethylene and in-situ dry sorption of the decomposed Cl-products using a lab-scale gas flow type tubular packed bed reactor. About 20 mg of CaO sample was mixed with about 2 g of Al2O3 particles and packed in the reactor and allowed to react with a flowing standard gas containing 500 ppm of C2HCl3 (N2 balance) at 673 and 873 K, under the condition that the reaction of CaO with C2HCl3 might be completed within a few hours. It was found that no thermal decomposition of C2HCl3 at or below 673 K was observed in a reactor packed only with Al2O3 particles. However, a considerable amount of decomposition of C2HCl3 was obtained in a reactor packed with CaO and Al2O3, even at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 673 K, decomposition of 0.42 mol of C2HCl3 and in-situ absorption product of 0.53 mol of CaCl2 were obtained. At 873 K, about 46% of C2HCl3 was thermally decomposed. The total amount of C2HCl3 decomposed in CaO-Al2O3 particle bed at 873 K became nearly twice larger than that at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 873 K, decomposition of 0.59 mol of C2HCl3 and in-situ absorption product of 0.67 mol of CaCl2 were obtained. Small amounts of C2Cl2, C2Cl4, CCl4, etc. were detected during decomposition of C2HCl3 at 673 and 873 K. It was recognized that the data on decomposition of C2HCl3 as well as in-situ dry sorption of Cl-products in CaO particle bed were correlated with specific surface area of the CaO employed. PMID:21821273

  18. Kinetics of the reaction of hydrated lime with SO{sub 2} at low temperatures: effects of the presence of CO{sub 2}, O{sub 2}, and NOx

    SciTech Connect

    Liu, C.F.; Shih, S.M.

    2008-12-15

    The effects of the presence Of CO{sub 2}, O{sub 2}, and NOx in the flue gas on the kinetics of the sulfation of hydrated lime at low temperatures were studied using a differential fixed-bed reactor. When O{sub 2} and NOx were not present together the reaction kinetics was about the same as that under gas mixtures containing SO{sub 2}, H{sub 2}O, and N2 only. When both O{sub 2} and NOx were present, sulfation of hydrated lime was greatly enhanced, forming a large amount of calcium sulfate in addition to calcium sulfite. Sulfation of hydrated lime was well described by the surface coverage model, despite the gas-phase conditions being different. Relative humidity is the major factor affecting the reaction, and its effect was more marked when both O{sub 2} and NOx were present. The kinetic model equations obtained in this work can be used to describe the sulfation of hydrated lime in the low-temperature dry and semidry flue gas desulfurization processes with or without an upstream NOx removal unit.

  19. Summary report on geochemical barrier special study. [Geochemically modify tailings to immobilize contaminants with modifiers such as peat, limestone, and hydrated lime

    SciTech Connect

    Not Available

    1988-12-01

    Long-term management of uranium mill tailings must provide assurance that soluble contaminants will not migrate beyond the Point of Compliance. Conventional management alternatives provide containment through the use of physical barriers which are designed to prevent migration of water through the tailings pile. An alternative is to geochemically modify the tailings to immobilize the contaminants. This investigation examined three potential geochemical modifiers to determine their ability to immobilize inorganic groundwater contaminants found in uranium mill tailings. These modifiers were hydrated lime (Ca(OH)[sub 2]), limestone (CaCO[sub 3]), and a sphaegnum peat moss. This investigation focused on both the geochemical interactions between the tailings and the modifiers, and the effects the modifiers had on the physical strength of the tailings. The geochemical investigations began with characterization of the tailings by X-ray diffraction and scanning electron microscopy. This was followed by batch leaching experiments in which various concentrations of each modifier were added to tailings in shaker flasks and allowed to come to equilibrium. Finally, column experiments were conducted to simulate flow through a tailings pile. The results show that all of the modifiers were at least moderately effective at immobilizing most of the groundwater contaminants of concern at uranium mill tailings sites. Hydrated lime was able to achieve 90 percent concentration reduction of arsenic, cadmium, selenium, uranium, and sulfate when added at a two percent concentration. Limestone was somewhat less effective and peat removed greater than 90 percent of arsenic, lead, uranium, and sulfate at a one percent concentration. The column tests showed that kinetic and/or mass transfer limitations are important and that sufficient time must be allowed for the immobilization reactions to occur.

  20. Geochemical constraints for coexisting CO"2 gas hydrate and calcite: implications for sheet cracks, stromatactis, zebra and tepee-like structures [rapid communication

    NASA Astrophysics Data System (ADS)

    DiFilippo, Erica L.; Hammond, Douglas E.; Corsetti, Frank A.

    2003-08-01

    The Ordovician Meiklejohn Peak mud-mound in western Nevada contains sedimentary structures (e.g., stromatactis and "zebra-rock") that resemble features found in modern methane hydrate deposits. However, the δ13C of the mud-mound carbonates (-1 to 1‰ PDB) does not suggest interaction with δ13C-depleted methane. Consequently, Krause (Sedimentary Geology 145 (2001) 189) proposed that the Meiklejohn structures might have been produced by the formation and dissociation of CO 2 gas hydrate rather than methane gas hydrate. Structures in Neoproterozoic cap carbonates, sheet cracks and tepee-like structures have also been suggested to represent gas hydrate interaction with carbonate sediments (Geology 29 (2001) 443), but, similarly, δ13C values do not suggest direct interaction with methane. The objective of this contribution is to see if the presence of CO 2 gas hydrate is plausible for either setting. To test the feasibility of CO 2 gas hydrate involvement in the formation of these structures, necessary concentrations of TCO 2 were calculated based on required phase equilibria using the quadruple points Q1 (-1.73 °C, 10.2 atm) and Q2 (10.2 °C, 44.5 atm) from the phase diagram for CO 2 gas hydrate (Miller, S.L., 1974. The Nature and Occurrence of Clathrate Hydrates. In: Kaplan, I.R. (Ed.), Natural Gases in Marine Sediments. Plenum, New York, NY, pp. 151-178). A limit for Ca +2 was established based on the lack of evidence for gypsum formation in this environment and the assumption that sulfate was up to 100% of its present oceanic value; the calculated TCO 2 concentration, however, is relatively insensitive to the concentration of SO 4-2 used. The lowest permissible value of pCO 2 and TCO 2 were found at Q1, where TCO 2 must be at least 300 times the present value. These conditions are implausible for the formation of the Meiklejohn Peak mud-mound. Although some models for Neoproterozoic "Snowball Earth" require highly elevated atmospheric CO 2, these models predict

  1. Nickel and manganese interaction with calcite

    SciTech Connect

    Doner, H; Zavarin, M

    1999-08-09

    Many divalent metal cations sorb to calcite surfaces and incorporate into calcite to varying degrees. Since calcite may sorb trace elements in the environment, the factors controlling metal-calcite interactions are critical to understanding element cycling. The interaction of divalent metal cations with calcite can be critical to toxic metal immobilization, nutrient cycling, interpretation of past redox conditions, tracing fluid flow, for example. Sorption of Ni and Mn on calcite surfaces was studied by Zachara et al.. At any particular pH, the sorption of Mn on calcite was greater than Ni. This was attributed in part to the similarity of divalent Mn and Ca with respect to ion size. Although direct spectroscopic evidence was not available, sorption/desorption results suggested that Mn quickly forms a surface precipitate or solid solution while Ni forms a hydrated surface complex that may incorporate into calcite much more slowly via recrystallization. Because Mn(II) ionic radius is similar to that of Ca(II) (0.80 versus 1.0{angstrom}), and because MnCO{sub 3} has a structure similar to calcite, it is likely that Mn can substitute directly for Ca in the calcite structure. The ionic radius of Ni(II) is significantly smaller (0.69{angstrom}) and Ni(OH){sub 2} precipitation is likely to be favored in most systems. For Ni, direct substitution for Ca is less likely or may require more significant calcite lattice deformation.

  2. Role of lime in salty spoil genesis

    SciTech Connect

    Grove, J.H.; Evangelou, V.P.

    1982-12-01

    Acid pyritic spoils are often limed to facilitate revegetation efforts. Substantial quantities of soluble sulfate salts are associated with such spoils, before and after liming. Such salts can cause revegetation attempts to fail at seeding and/or during drought stress periods. As magnesium sulfate (MgSO/sub 4/) is more soluble than gypsum (calcium sulfate) under field conditions, MgSO/sub 4/ has more often been associated with soluble salt problems. Since lime reaction chemistry can influence salt genesis in spoils, this was evaluated in a incubation study using calcite and dolomite amendments to an acid, pyritic spoil. Rates of 0, 14.4, and 28.8 meq/100 g (rate equal to total potential acidity) of lime were used. Amended spoils were maintained at 30/sup 0/C and -100 cm moisture tension. Samples were taken periodically and a portion suspended in water at a soil:solution ratio of 1:20 for two hours. Unamended spoil extract pH dropped from 4.8 to 3.2 in nine weeks. Soluble magnesium sulfate doubled (from 2.9 to 6.1 meq/100 g) in the unlimed spoil between weeks one and sixteen. Dolomite amended spoils generated twice as much magnesium salt as calcite amended spoils. Pyrite oxidation, acid generation, i.e., salt genesis, was reduced when calcitic lime was used at the recommended rate based on a measure of total potential acidity. A prompt liming program with calcitic lime can substantially alter the quantity and quality of soluble salts released. The results suggest that dolomite is unacceptable as a liming material for sandy spoils with an appreciable pyrite content.

  3. [Study on Archaeological Lime Powders from Taosi and Yinxu Sites by FTIR].

    PubMed

    Wei, Guo-feng; Zhang, Chen; Chen, Guo-liang; He, Yu-ling; Gao, Jiang-tao; Zhang, Bing-jian

    2015-03-01

    Archaeological lime powders samples from Taosi and Yinxu sites, natural limestone and experimentally prepared lime mortar were investigated by means of Fourier transform infrared spectrometry (FTIR) to identify the raw material of lime powders from Taosi and Yinxu sites. Results show that ν2/ν4 ratio of calcite resulted from carbonation reaction of man-made lime is around 6.31, which is higher than that of calcite in natural limestone and reflects the difference in the disorder of calcite crystal structure among the natural limestone and prepared lime mortar. With additional grinding, the values of v2 and ν4 in natural limestone and prepared lime mortar decrease. Meanwhile, the trend lines of ν2 versus ν4 for calcite in experimentally prepared lime mortar have a steeper slope when compared to calcite in natural limestone. These imply that ν2/ν4 ratio and the slope of the trend lines of ν2 versus ν4 can be used to determine the archaeological man-made lime. Based on the experiment results, it is possible that the archaeological lime powder from Taosi and Yinxu sites was prepared using man-made lime and the ancient Chinese have mastered the calcining technology of man-made lime in the late Neolithic period about 4 300 years ago.

  4. Lime Pretreatment

    NASA Astrophysics Data System (ADS)

    Sierra, Rocio; Granda, Cesar Benigno; Holtzapple, Mark T.

    Lime pretreatment has proven to be a useful method for selectively reducing the lignin content of lignocellulosic biomass without significant loss in carbohydrates, thus realizing an important increase in biodigestibility. In lime pretreatment, the biomass is pretreated with calcium hydroxide and water under different conditions of temperature and pressure. It can be accomplished in one of three fashions: (1) short-term pretreatment that lasts up to 6 h, requires temperatures of 100-160°C, and can be applied with or without oxygen (pressure ~200 psig); (2) long-term pretreatment taking up to 8 weeks, requiring only 55-65°C, and capable of running with or without air (atmospheric pressure); and (3) simple pretreatment requiring 1 h in boiling water, without air or oxygen. Nonoxidative conditions are effective at low lignin contents (below ~18% lignin), whereas oxidative conditions are required for high lignin contents (above ~18% lignin).

  5. Kinetics of the reaction of iron blast furnace slag/hydrated lime sorbents with SO{sub 2} at low temperatures: effects of the presence of CO{sub 2}, O{sub 2}, and NOx

    SciTech Connect

    Liu, C.F.; Shih, S.M.

    2009-09-15

    The effects of the presence of CO{sub 2}, O{sub 2}, and NOx in the flue gas on the kinetics of the sulfation of blast furnace slag/hydrated lime sorbents at low temperatures were studied using a differential fixed-bed reactor. When O{sub 2} and NOx were not present simultaneously, the reaction kinetics was about the same as that under the gas mixtures containing SO{sub 2}, H{sub 2}O, and N{sub 2} only, being affected mainly by the relative humidity. The sulfation of sorbents can be described by the surface coverage model and the model equations derived for the latter case. When both O{sub 2} and NOx, were present, the sulfation of sorbents was greatly enhanced, forming a great amount of sulfate in addition to sulfite. The surface coverage model is still valid in this case, but the model equations obtained show a more marked effect of relative humidity and negligible effects of SO{sub 2} concentration and temperature on the reaction. The effect of sorbent composition on the reaction kinetics was entirely represented by the effects of the initial specific surface area (S{sub g0}) and the Ca molar content (M{sup -1}) of sorbent. The initial conversion rate of sorbent increased linearly with increasing S{sub g0}, and the ultimate conversion increased linearly with increasing S{sub g0}M{sup -1}. The model equations obtained in this work are applicable to describe the kinetics of the sulfation of the sorbents in the low-temperature dry and semidry fine gas desulfurization processes either with an upstream NOx, removal unit or without.111

  6. High surface area calcite

    NASA Astrophysics Data System (ADS)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

    2013-05-01

    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  7. The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.

    PubMed

    Kudłacz, Krzysztof; Rodriguez-Navarro, Carlos

    2014-10-21

    Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed.

  8. Agricultural Liming, Irrigation, and Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    McGill, B. M.; Hamilton, S. K.

    2015-12-01

    Row crop farmers routinely add inorganic carbon to soils in the form of crushed lime (e.g., calcite or dolomite minerals) and/or inadvertently as bicarbonate alkalinity naturally dissolved in groundwater used for irrigation. In the soil these carbonates can act as either a source or sink of carbon dioxide, depending in large part on nitrogen fertilization and nitrification. The potentially variable fate of lime carbon is not accounted for in the IPCC greenhouse gas inventory model for lime emissions, which assumes that all lime carbon becomes carbon dioxide (irrigation additions are not accounted for). In a corn-soybean-wheat crop rotation at the Kellogg Biological Station Long Term Ecological Research site in southwest Michigan, we are collecting soil porewater from several depths in the vadose zone across a nitrogen fertilizer gradient with and without groundwater irrigation. The soil profile in this region is dominated by carbonate rich glacial outwash that lies 1.5 m below a carbonate-leached zone. We analyze the porewater stoichiometry of calcium, magnesium, and carbonate alkalinity in a conceptual model to reveal the source/sink fate of inorganic carbon. High nitrate porewater concentrations are associated with net carbon dioxide production in the carbonate-leached zone, according to our model. This suggests that the acidity associated with nitrification of the nitrogen fertilizer, which is evident from soil pH measurements, is driving the ultimate fate of lime carbon in the vadose zone. Irrigation is a significant source of both alkalinity and nitrate in drier years, compared to normal rates of liming and fertilization. We will also explore the observed dramatic changes in porewater chemistry and the relationship between irrigation and inorganic carbon fate above and within the native carbonate layer.

  9. Elastic constants of calcite

    USGS Publications Warehouse

    Peselnick, L.; Robie, R.A.

    1962-01-01

    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  10. Hydrate detection

    SciTech Connect

    Dillon, W.P.; Ahlbrandt, T.S.

    1992-06-01

    Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

  11. Hydrate detection

    SciTech Connect

    Dillon, W.P.; Ahlbrandt, T.S.

    1992-01-01

    Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

  12. LIME 0.5

    SciTech Connect

    2011-01-14

    LIME 0.5 is an initial version of a Lightweight Integrating Multi-physics Environment for coupling codes. LIME by itself is not a code for doing multiphysics simulations. Instead, LIME provides the key high-level software, a flexible but defined approach, and interface requirements for a collection of (potentially disparate) physics codes to be combined with strong coupling (when needed) though non-linear solution methods (e.g. JFNK, fixed point), thus creating a new multi-physics simulation capability customized for a particular need. ! ! The approach taken is designed to! •! preserve and leverage any important specialized algorithms and/or functionality an existing application may provide,! •! minimize the requirements barrier for an application to participate,! •! work within advanced solver frameworks (e.g. as extensions to the Trilinos/NOX nonlinear solver libraries, PETSc, . . .),! Of note is that components/physics codes that can be coupled within LIME are NOT limited to:! •! components written in one particular language,! •! a particular numerical discretization approach ( e.g. Finite Element), or! •! physical models expressed as PDEʼs.!

  13. LIME 0.5

    2011-01-14

    LIME 0.5 is an initial version of a Lightweight Integrating Multi-physics Environment for coupling codes. LIME by itself is not a code for doing multiphysics simulations. Instead, LIME provides the key high-level software, a flexible but defined approach, and interface requirements for a collection of (potentially disparate) physics codes to be combined with strong coupling (when needed) though non-linear solution methods (e.g. JFNK, fixed point), thus creating a new multi-physics simulation capability customized for amore » particular need. ! ! The approach taken is designed to! •! preserve and leverage any important specialized algorithms and/or functionality an existing application may provide,! •! minimize the requirements barrier for an application to participate,! •! work within advanced solver frameworks (e.g. as extensions to the Trilinos/NOX nonlinear solver libraries, PETSc, . . .),! Of note is that components/physics codes that can be coupled within LIME are NOT limited to:! •! components written in one particular language,! •! a particular numerical discretization approach ( e.g. Finite Element), or! •! physical models expressed as PDEʼs.!« less

  14. Water transfer properties and shrinkage in lime-based rendering mortars

    NASA Astrophysics Data System (ADS)

    Arizzi, A.; Cultrone, G.

    2012-04-01

    Rendering is the practice of covering a wall or a building façade with one or more layers of mortar, with the main aim to protect the masonry structure against weathering. The render applied must show high flexibility, good adhesion and compatibility with the support (i.e. stone, brick) and, overall, it should be characterised by low water absorption and high water vapour permeability. Water (in the solid, liquid and vapour state) is one of the main factors that drive construction materials to deterioration. Therefore, to evaluate the quality and durability of a rendering mortar, thus ensuring its protective function in the masonry structure, it is fundamental to assess the behaviour of this mortar towards water. Mortars were elaborated with a calcitic dry hydrated lime, a calcareous aggregate, a pozzolan, a lightweight aggregate, a water-retaining agent and a plasticiser. Four types of lime mortars were prepared, in which the binder-to-aggregate ratios were 1:3, 1:4, 1:6 and 1:9 by weight, whilst the pozzolan was kept at 10% of the lime (by mass) and the total admixtures proportion was less than 2% of the total mass. The influence of the characteristics of mortars pore system on the amount of water absorbed and the kinetics of absorption was investigated by means of: free water absorption and drying; capillary uptake; water permeability; water vapour permeability. Interesting deductions can be made from the values of water and water vapour permeability found for mortars: the former increases exponentially with the sand volume of the mortar, whilst the latter increases almost exponentially with the initial water content added to the mortar mixes during their elaboration. However, the relationship obtained between porosity of mortars and permeability values is not really clear. This finding suggests that the permeability of a material cannot be estimated on the basis of its porosity as it can be made for the capillary uptake and free water absorption. Another

  15. Incorporation of Eu(III) into Calcite under Recrystallization conditions.

    PubMed

    Hellebrandt, S E; Hofmann, S; Jordan, N; Barkleit, A; Schmidt, M

    2016-09-13

    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu(3+) occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na(+). These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

  16. Incorporation of Eu(III) into Calcite under Recrystallization conditions

    PubMed Central

    Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.

    2016-01-01

    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu3+ occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na+. These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site. PMID:27618958

  17. Incorporation of Eu(III) into Calcite under Recrystallization conditions

    NASA Astrophysics Data System (ADS)

    Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.

    2016-09-01

    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu3+ occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na+. These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

  18. Incorporation of Eu(III) into Calcite under Recrystallization conditions.

    PubMed

    Hellebrandt, S E; Hofmann, S; Jordan, N; Barkleit, A; Schmidt, M

    2016-01-01

    The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu(3+) occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na(+). These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site. PMID:27618958

  19. Tracing formation and durability of calcite in a Punic-Roman cistern mortar (Pantelleria Island, Italy).

    PubMed

    Dietzel, Martin; Schön, Frerich; Heinrichs, Jens; Deditius, Artur P; Leis, Albrecht

    2016-01-01

    Ancient hydraulic lime mortar preserves chemical and isotopic signatures that provide important information about historical processing and its durability. The distribution and isotopic composition of calcite in a mortar of a well-preserved Punic-Roman cistern at Pantelleria Island (Italy) was used to trace the formation conditions, durability, and individual processing periods of the cistern mortar. The analyses of stable carbon and oxygen isotopes of calcite revealed four individual horizons, D, E, B-1 and B-2, of mortar from the top to the bottom of the cistern floor. Volcanic and ceramic aggregates were used for the production of the mortar of horizons E/D and B-1/B-2, respectively. All horizons comprise hydraulic lime mortar characterized by a mean cementation index of 1.5 ± 1, and a constant binder to aggregate ratio of 0.31 ± 0.01. This suggests standardized and highly effective processing of the cistern. The high durability of calcite formed during carbonation of slaked lime within the matrix of the ancient mortar, and thus the excellent resistance of the hydraulic lime mortar against water, was documented by (i) a distinct positive correlation of δ(18)Ocalcite and δ(13)Ccalcite; typical for carbonation through a mortar horizon, (ii) a characteristic evolution of δ(18)Ocalcite and δ(13)Ccalcite through each of the four mortar horizons; lighter follow heavier isotopic values from upper to lower part of the cistern floor, and (iii) δ(18)Ocalcite varying from -10 to -5 ‰ Vienna Pee Dee belemnite (VPDB). The range of δ(18)Ocalcite values rule out recrystallization and/or neoformation of calcite through chemical attack of water stored in cistern. The combined studies of the chemical composition of the binder and the isotopic composition of the calcite in an ancient mortar provide powerful tools for elucidating the ancient techniques and processing periods. This approach helps to evaluate the durability of primary calcite and demonstrates the

  20. Experimental study of the replacement of calcite by calcium sulphates

    NASA Astrophysics Data System (ADS)

    Ruiz-Agudo, E.; Putnis, C. V.; Hövelmann, J.; Álvarez-Lloret, P.; Ibáñez-Velasco, A.; Putnis, A.

    2015-05-01

    Among the most relevant mineral replacement reactions are those involving sulphates and carbonates, which have important geological and technological implications. Here it is shown experimentally that during the interaction of calcite (CaCO3) cleavage surfaces with sulphate-bearing acidic solutions, calcite is ultimately replaced by gypsum (CaSO4 2H2O) and anhydrite (CaSO4), depending on the reaction temperature. Observations suggest that this occurs most likely via an interface-coupled dissolution-precipitation reaction, in which the substrate is replaced pseudomorphically by the product. At 120 and 200 °C gypsum and/or bassanite (CaSO4·0.5H2O) form as precursor phases for the thermodynamically stable anhydrite. Salinity promotes the formation of less hydrated precursor phases during the replacement of calcite by anhydrite. The reaction stops before equilibrium with respect to calcite is reached and during the course of the reaction most of the bulk solutions are undersaturated with respect to the precipitating phase(s). A mechanism consisting of the dissolution of small amounts of solid in a thin layer of fluid at the mineral-fluid interface and the subsequent precipitation of the product phase from this layer is in agreement with these observations. PHREEQC simulations performed in the framework of this mechanism highlight the relevance of transport and surface reaction kinetics on the volume change associated with the CaCO3-CaSO4 replacement. Under our experimental conditions, this reaction occurs with a positive volume change, which ultimately results in passivation of the unreacted substrate before calcite attains equilibrium with respect to the bulk solution.

  1. Setting process of lime-based conservation mortars with barium hydroxide

    SciTech Connect

    Karatasios, Ioannis . E-mail: ikarat@ims.demokritos.gr; Kilikoglou, Vassilis; Colston, Belinda; Theoulakis, Panagiotis; Watt, David

    2007-06-15

    This paper presents the effect of barium hydroxide on the setting mechanism of lime-based conservation mortars, when used as an additive material. The study focuses on the monitoring of the setting process and the identification of the mineral phases formed, which are essential for furthering the study of the durability of barium mixtures against chemical degradation. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and thermal analysis (DTA-TG) were used to monitor the setting processes of these mixtures and identify new phases formed. The results suggest that barium hydroxide is evenly distributed within the lime and produces a homogeneous binding material, consisting of calcite (CaCO{sub 3}), witherite (BaCO{sub 3}) and barium-calcium carbonate [BaCa(CO{sub 3}){sub 2}]. Finally, it was found that barium carbonate can be directly bonded to calcitic aggregates and therefore increases its chemical compatibility with the binding material.

  2. A study on engineering characteristics of asphalt concrete using filler with recycled waste lime.

    PubMed

    Sung Do, Hwang; Hee Mun, Park; Suk keun, Rhee

    2008-01-01

    This study focuses on determining the engineering characteristics of asphalt concrete using mineral fillers with recycled waste lime, which is a by-product of the production of soda ash (Na(2)CO(3)). The materials tested in this study were made using a 25%, 50%, 75%, and 100% mixing ratio based on the conventional mineral filler ratio to analyze the possibility of using recycled waste lime. The asphalt concretes, made of recycled waste lime, hydrated lime, and conventional asphalt concrete, were evaluated through their fundamental engineering properties such as Marshall stability, indirect tensile strength, resilient modulus, permanent deformation characteristics, moisture susceptibility, and fatigue resistance. The results indicate that the application of recycled waste lime as mineral filler improves the permanent deformation characteristics, stiffness and fatigue endurance of asphalt concrete at the wide range of temperatures. It was also determined that the mixtures with recycled waste lime showed higher resistance against stripping than conventional asphalt concrete. It was concluded from various test results that a waste lime can be used as mineral filler and, especially, can greatly improve the resistance of asphalt concrete to permanent deformation at high temperatures. PMID:17408942

  3. A study on engineering characteristics of asphalt concrete using filler with recycled waste lime.

    PubMed

    Sung Do, Hwang; Hee Mun, Park; Suk keun, Rhee

    2008-01-01

    This study focuses on determining the engineering characteristics of asphalt concrete using mineral fillers with recycled waste lime, which is a by-product of the production of soda ash (Na(2)CO(3)). The materials tested in this study were made using a 25%, 50%, 75%, and 100% mixing ratio based on the conventional mineral filler ratio to analyze the possibility of using recycled waste lime. The asphalt concretes, made of recycled waste lime, hydrated lime, and conventional asphalt concrete, were evaluated through their fundamental engineering properties such as Marshall stability, indirect tensile strength, resilient modulus, permanent deformation characteristics, moisture susceptibility, and fatigue resistance. The results indicate that the application of recycled waste lime as mineral filler improves the permanent deformation characteristics, stiffness and fatigue endurance of asphalt concrete at the wide range of temperatures. It was also determined that the mixtures with recycled waste lime showed higher resistance against stripping than conventional asphalt concrete. It was concluded from various test results that a waste lime can be used as mineral filler and, especially, can greatly improve the resistance of asphalt concrete to permanent deformation at high temperatures.

  4. The role of background electrolytes on the kinetics and mechanism of calcite dissolution

    NASA Astrophysics Data System (ADS)

    Ruiz-Agudo, E.; Kowacz, M.; Putnis, C. V.; Putnis, A.

    2010-02-01

    The influence of background electrolytes on the mechanism and kinetics of calcite dissolution was investigated using in situ Atomic Force Microscopy (AFM). Experiments were carried out far from equilibrium by passing alkali halide salt (NaCl, NaF, NaI, KCl and LiCl) solutions over calcite cleavage surfaces. This AFM study shows that all the electrolytes tested enhance the calcite dissolution rate. The effect and its magnitude is determined by the nature and concentration of the electrolyte solution. Changes in morphology of dissolution etch pits and dissolution rates are interpreted in terms of modification in water structure dynamics (i.e. in the activation energy barrier of breaking water-water interactions), as well as solute and surface hydration induced by the presence of different ions in solution. At low ionic strength, stabilization of water hydration shells of calcium ions by non-paired electrolytes leads to a reduction in the calcite dissolution rate compared to pure water. At high ionic strength, salts with a common anion yield similar dissolution rates, increasing in the order Cl - < I - < F - for salts with a common cation due to an increasing mobility of water around the calcium ion. Changes in etch pit morphology observed in the presence of F - and Li + are explained by stabilization of etch pit edges bonded by like-charged ions and ion incorporation, respectively. As previously reported and confirmed here for the case of F -, highly hydrated ions increased the etch pit nucleation density on calcite surfaces compared to pure water. This may be related to a reduction in the energy barrier for etch pit nucleation due to disruption of the surface hydration layer.

  5. Dislocation Creep in Magnesium Calcite

    NASA Astrophysics Data System (ADS)

    Xu, L.; Xiao, X.; Evans, B. J.

    2003-12-01

    To investigate the effect of dissolved Mg on plastic deformation of calcite, we performed triaxial deformation experiments on synthetic calcite with varying amount of Mg content. Mixtures of powders of calcite and dolomite were isostatically hot pressed (HIP) at 850° C and 300 MPa confining pressure for different intervals (2 to 20hrs) resulting in homogeneous aggregates of high-magnesium calcite; Mg content varied from 0.07 to 0.17 mol%. Creep tests were performed at differential stresses from 20 to 160 MPa at 700 to 800° C. Grain sizes before and after deformation were determined from the images obtained from scanning electron microscope (SEM) and optical microscope. Grain sizes are in the range of 5 to 20 microns depending on the HIP time, and decrease with increasing magnesium content. Both BSE images and chemical analysis suggest that all dolomite are dissolved and the Mg distribution is homogeneous through the sample, after 2 hrs HIP. At stresses below 40 MPa, the samples deformed in diffusion region (Coble creep), as described previously by Herwegh. The strength decreases with increasing magnesium content, owing to the difference of grain size. At stresses above 80 MPa, the stress exponent is greater than 3, indicating an increased contribution of dislocation creep. The transition between diffusion to dislocation creep occurs at higher stresses for the samples with higher magnesium content and smaller grain size. Preliminary data suggests a slight increase in strength with increasing magnesium content, but more tests are needed to verify this effect. In a few samples, some strain weakening may have been evident. The activation energy in the transition region (at 80 MPa) is ˜200 KJ/mol with no dependence on magnesium content, agreeing with previous measurements of diffusion creep in natural and synthetic marbles.

  6. Isotopic analysis for degradation diagnosis of calcite matrix in mortar.

    PubMed

    Dotsika, E; Psomiadis, D; Poutoukis, D; Raco, B; Gamaletsos, P

    2009-12-01

    Mortar that was used in building as well as in conservation and restoration works of wall paintings have been analysed isotopically (delta(13)C and delta(18)O) in order to evaluate the setting environments and secondary processes, to distinguish the structural components used and to determine the exact causes that incurred the degradation phenomena. The material undergoes weathering and decay on a large proportion of its surface and in depth, due to the infiltration of water through the structural blocks. Mineralogical analysis indicated signs of sulphation and dissolution/recrystallisation processes taking place on the material, whereas stable isotopes provided information relative to the origin of the CO(2) and water during calcite formation and degradation processes. Isotopic change of the initial delta(13)C and delta(18)O in carbonate matrix was caused by alteration of the primary source of CO(2) and H(2)O in mortar over time, particularly by recrystallisation of calcite with porewater, evaporated or re-condensed water, and CO(2) from various sources of atmospheric and biogenic origin. Human influence (surface treatment) and biological growth (e.g. fungus) are major exogenic processes which may alter delta(18)O and delta(13)C in lime mortar.

  7. Comparison of surface properties between kaolin and metakaolin in concentrated lime solutions.

    PubMed

    Konan, K L; Peyratout, C; Smith, A; Bonnet, J-P; Rossignol, S; Oyetola, S

    2009-11-01

    The surface adsorption of calcium hydroxide onto kaolin and metakaolin was investigated by monitoring with atomic emission spectroscopy and pH measurements the amounts of ions left in solution after exposing clays to calcium hydroxide solutions of various concentrations. Both clays adsorb calcium and hydroxyl ions but differently. Kaolin adsorbs calcium hydroxide not only at the edges of the clay particles but also onto the basal faces. The adsorbed hydrated calcium ions form a layer on the clay particle surfaces, preventing further dissolution of the clay mineral platelet. Metakaolin shows high pozzolanic activity, which provides the quick formation of hydrated phases at the interfaces between metakaolin and lime solutions. The nature of the hydration products has been investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA). The most important hydrated phases like CSH (hydrated calcium silicate) and C(2)ASH(8) (gehlenite) have been identified. PMID:19682702

  8. Formation and durability of hydrated layers for several oxide glasses

    SciTech Connect

    Nishii, Junji; Akai, Tomoko; Yamashita, Masaru; Yamanaka, Hiroshi; Wakabayashi, Hajimu

    1995-12-31

    Formations and durabilities of hydrated layers were compared between a soda-aluminosilicate (NAS), a soda-lime-aluminosilicate (NCAS) and a soda-lime-alumino-borosilicate (NCABS) glasses. The first step of the study was to prepare the optically transparent hydrated layers on the surface of specimens by an autoclave (400 C, 20 kgf/cm{sup 2}) treatment. Distributions of OH groups in hydrated layers were analyzed by an etch sectioning and FTIR measurement. The rates of hydration of the glasses were in the order NAS {much_gt} NCAS > NCABS. The hydration of the NCABS glass, which is a modified nuclear waste glass, required the treatment longer than those of the NAS and NCAS glasses. In the second step, the authors investigated the durabilities of hydrated layers by immersing the specimens into a distilled water at 100 C. The dissolutions of hydrated layers were confirmed for each glass. The dissolution rates of hydrated layers were in the order NCAS > NCABS {much_gt} NAS. It has become apparent by an XPS analysis that the highest durability of the hydrated NAS glass was due to the formation of a sodium free Al{sub 2}O{sub 3}-SiO{sub 2} layer on the surface. The hydrated layer of the NCAS glass, while the sodium ions were almost leached out during immersion, dissolved to water most quickly than those of other glasses. In the hydrated layer of the NCABS glass, a half amount of sodium and boron ions remained and inhibited the dissolution of hydrated layer.

  9. Lime pretreatment of lignocellulosic biomass

    NASA Astrophysics Data System (ADS)

    Chang, Shushien

    Lignocellulose is a valuable alternative energy source. The susceptibility of lignocellulosic biomass to enzymatic hydrolysis is constrained due to its structural features, so pretreatment is essential to enhance enzymatic digestibility. Of the chemicals used as pretreatment agents, it has been reported that alkalis improve biomass digestibility significantly. In comparison with other alkalis such as NaOH and ammonia, lime (calcium hydroxide) has many advantages; it is very inexpensive, is safe, and can be recovered by carbonating wash water. The effects of lime pretreatment were explored on switchgrass and poplar wood, representing herbaceous and woody biomass, respectively. The effects of pretreatment conditions (time, temperature, lime loading, water loading, particle size, and oxygen pressure) have been systematically studies. Lime alone enhances the digestibility of switchgrass significantly; under the recommended conditions, the 3-d total sugar (glucose + xylose) yields of lime-treated switchgrass were 7 times that of untreated sample. When treating poplar wood, lime must be combined with oxygen to achieve high digestibility; oxidative lime pretreatment increased the 3-d total sugar yield of poplar wood to 12 times that of untreated sample. In a fundamental study, to determine why lime pretreatment is effective, the effects of three structural features on enzymatic digestibility were studied: lignin content, acetyl content, and crystallinity index (CrI). Poplar wood was treated with peracetic acid, potassium hydroxide, and ball milling to produce model lignocelluloses with a broad spectrum of lignin contents, acetyl contents, and CrI, respectively. Enzymatic hydrolysis was performed on the model lignocelluloses to determine the digestibility. Correlations between lignin/carbohydrate ratio, acetyl/carbohydrate ratio, CrI and digestibility were developed. The 95% prediction intervals show that the correlations predict the 1-h and 3-d total sugar conversions of

  10. Structure of the (1014) Surfaces of Calcite, Dolomite, and Magnesite under Wet and Dry Conditions

    SciTech Connect

    WRIGHT,KATE; CYGAN,RANDALL T.; SLATER,BEN

    2000-06-12

    Atomistic computer simulation methods have been employed to model the structure of the (10{bar 1}4) surfaces of calcite, dolomite and magnesite. The authors calculations show that under vacuum conditions, calcite undergoes the greatest degree of surface relaxation with rotation and distortion of the carbonate group accompanied by movement of the calcium ion. The magnesite surface is the least distorted of the three carbonates, with dolomite being intermediate to the two end members. When water molecules are placed on the surface to produce complete monolayer coverage, the calcite surface is stabilized and the amount of relaxation is substantially reduced. In contrast, the dolomite and magnesite surfaces are destabilized by hydration as indicated by a significant increase in the surface energies relative to the dry surface.

  11. Simulating Succinate-Promoted Dissolution at Calcite {104} Steps

    NASA Astrophysics Data System (ADS)

    Mkhonto, D.; Sahai, N.

    2008-12-01

    Organic molecules of a wide range of molecular weights from small organic acids, amino-acids, acidic peptides and acidic proteins to humic and fulvic acids play a key role in modulating nucleation, crystal growth and dissolution of calcium carbonate polymorphs. In general, these acidic molecules inhibit calcite growth and, promote dissolution preferentially along specific crystallographic directions, in the process, regulating crystal shape and size, and even whether a metastable polymorph (e.g., vaterite or aragonite) is nucleated first. For example, chiral faces of calcite are selected by chiral amino-acids and the unusual {hk0} faces are expressed in the presence of amino-acids [Orme et al., 2001], and unusual heptagonal dissolution etch-pit are seen in the presence of succinate compared to the normal rhombohedral pits in water alone [Teng et al., 2006]. Thus, the presence of unusual crystal morphologies may indicate organic-mediated growth, thus serving as a biosignature. We have conducted the Molecular Dynamics (MD) simulations using the Consistent Valence Force Field (CVFF) as implemented in the FORCITE© module of the Materials Studio © software package (Accelrys, Inc. TM) to model the adsorption of succinate, a dicarboxylic acid, and charge- balancing Na+ ions on dry and hydrated steps in different directions on the {104} cleavage face of calcite [Mkhonto and Sahai, in prep.]. At the site of succinate adsorption, we find elongation of the interatomic distances (Ca-OCO3,i) between surface Ca2+ cation and the oxygen of the underlying inorganic CO32- anion the first surface layer of calcite, compared to the corresponding distances in the presence of water alone, suggesting greater ease of surface Ca2+ detachment. This result is consistent with the empirically observed increase in overall dissolution rate with succinate [Teng et al., 2006]. Furthermore, succinate adsorption lowers the step energies, which explains the appearance of steps in the unsusual [42

  12. Stabilities of calcite and aragonite

    USGS Publications Warehouse

    Christ, C.L.; Hostetler, P.B.; Siebert, R.M.

    1974-01-01

    A revaluation of the 25° C activity-product constants of calcite (KC) and aragonite (KA) was made on the basis of the known solubilities of these phases for which the activity of total dissolved calcium was corrected for the presence of the ion pair CaHCO3+ in the aqueous phase. The value of the dissociation constant of CaHCO3+ was taken to be 10-1.225±0.02. This value, combined with values of the analytical concentrations in solutions with partial pressure PCO2 =0.97 atmosphere, leads to KC=l0-8.52±0.04 and KA= 10-8.36±0.04. Based on these K values, standard free energies of formation of calcite and aragonite were calculated to be -270,144±375 and -269,926±375 calories mole-1, (-1,130,282±1,569 and -1,129,370±1,569 joules mole-1), respectively. From the 25°C K values, using appropriate entropy and heat capacity data, values of KC and KA were calculated over the temperature range 0° to 200°C. Possible errors in interpretation of measured pH values and inferred PCO2values and the bearing of these errors on calculations of K values are discussed.

  13. Raman scattering or fluorescence emission? Raman spectroscopy study on lime-based building and conservation materials.

    PubMed

    Kaszowska, Zofia; Malek, Kamilla; Staniszewska-Slezak, Emilia; Niedzielska, Karina

    2016-12-01

    This work presents an in-depth study on Raman spectra excited with 1064 and 532nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064nm, but absent in the corresponding spectra acquired with laser excitation at 532nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064nm excitation. PMID:27314909

  14. Raman scattering or fluorescence emission? Raman spectroscopy study on lime-based building and conservation materials.

    PubMed

    Kaszowska, Zofia; Malek, Kamilla; Staniszewska-Slezak, Emilia; Niedzielska, Karina

    2016-12-01

    This work presents an in-depth study on Raman spectra excited with 1064 and 532nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064nm, but absent in the corresponding spectra acquired with laser excitation at 532nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064nm excitation.

  15. A model for trace metal sorption processes at the calcite surface: Adsorption of Cd2+ and subsequent solid solution formation

    USGS Publications Warehouse

    Davis, J.A.; Fuller, C.C.; Cook, A.D.

    1987-01-01

    The rate of Cd2+ sorption by calcite was determined as a function of pH and Mg2+ in aqueous solutions saturated with respect to calcite but undersaturated with respect to CdCO3. The sorption is characterized by two reaction steps, with the first reaching completion within 24 hours. The second step proceeded at a slow and nearly constant rate for at least 7 days. The rate of calcite recrystallization was also studied, using a Ca2+ isotopic exchange technique. Both the recrystallization rate of calcite and the rate of slow Cd2+ sorption decrease with increasing pH or with increasing Mg2+. The recrystallization rate could be predicted from the number of moles of Ca present in the hydrated surface layer. A model is presented which is consistent with the rates of Cd2+ sorption and Ca2+ isotopic exchange. In the model, the first step in Cd2+ sorption involves a fast adsorption reaction that is followed by diffusion of Cd2+ into a surface layer of hydrated CaCO3 that overlies crystalline calcite. Desorption of Cd2+ from the hydrated layer is slow. The second step is solid solution formation in new crystalline material, which grows from the disordered mixture of Cd and Ca carbonate in the hydrated surface layer. Calculated distribution coefficients for solid solutions formed at the surface are slightly greater than the ratio of equilibrium constants for dissolution of calcite and CdCO3, which is the value that would be expected for an ideal solid solution in equilibrium with the aqueous solution. ?? 1987.

  16. Mineral resource of the month: lime

    USGS Publications Warehouse

    ,

    2009-01-01

    The article presents facts about lime, which is said to be a caustic chemical manufactured from limestone or other calcium carbonates in a kiln at temperatures ranging from 935 to 1,350 degrees Celsius. It states that lime is widely used in industries such as steelmaking, paper production and chemical manufacturing. It also mentions that global lime production amounts up to 280 million metric tons annually. However, it notes that international trade in lime is limited.

  17. Chloral hydrate

    Integrated Risk Information System (IRIS)

    Chloral hydrate ; CASRN 302 - 17 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic E

  18. Crystal lattice tilting in prismatic calcite.

    PubMed

    Olson, Ian C; Metzler, Rebecca A; Tamura, Nobumichi; Kunz, Martin; Killian, Christopher E; Gilbert, Pupa U P A

    2013-08-01

    We analyzed the calcitic prismatic layers in Atrina rigida (Ar), Haliotis iris (Hi), Haliotis laevigata (HL), Haliotis rufescens (Hrf), Mytilus californianus (Mc), Pinctada fucata (Pf), Pinctada margaritifera (Pm) shells, and the aragonitic prismatic layer in the Nautilus pompilius (Np) shell. Dramatic structural differences were observed across species, with 100-μm wide single-crystalline prisms in Hi, HL and Hrf, 1-μm wide needle-shaped calcite prisms in Mc, 1-μm wide spherulitic aragonite prisms in Np, 20-μm wide single-crystalline calcite prisms in Ar, and 20-μm wide polycrystalline calcite prisms in Pf and Pm. The calcite prisms in Pf and Pm are subdivided into sub-prismatic domains of orientations, and within each of these domains the calcite crystal lattice tilts gradually over long distances, on the order of 100 μm, with an angle spread of crystal orientation of 10-20°. Furthermore, prisms in Pf and Pm are harder than in any other calcite prisms analyzed, their nanoparticles are smaller, and the angle spread is strongly correlated with hardness in all shells that form calcitic prismatic layers. One can hypothesize a causal relationship of these correlated parameters: greater angle spread may confer greater hardness and resistance to wear, thus providing Pf and Pm with a structural advantage in their environment. This is the first structure-property relationship thus far hypothesized in mollusk shell prisms.

  19. Trace concentration - Huge impact: Nitrate in the calcite/Eu(III) system

    NASA Astrophysics Data System (ADS)

    Hofmann, Sascha; Voïtchovsky, Kislon; Schmidt, Moritz; Stumpf, Thorsten

    2014-01-01

    The interactions of trivalent lanthanides and actinides with secondary mineral phases such as calcite is of high importance for the safety assessment of deep geological repositories for high level nuclear waste (HLW). Due to similar ionic radii, calcium-bearing mineral phases are suitable host minerals for Ln(III) and An(III) ions. Especially calcite has been proven to retain these metal ions effectively by both surface complexation and bulk incorporation. Since anionic ligands (e.g., nitrate) are omnipresent in the geological environment and due to their coordinating properties, their influence on retentive processes should not be underestimated. Nitrate is a common contaminant in most HLW forms as a result of using nitric acid in fuel reprocessing. It is also formed by microbial activity under aerobic conditions. In this study, atomic force microscopy investigations revealed a major influence of nitrate upon the surface of calcite crystals. NaNO3 causes serious modifications even in trace amounts (<10-7 M) and forms a soft surface layer of low crystallinity on top of the calcite crystal. Time-resolved laser fluorescence spectroscopy of Eu(III) showed that, within this layer, Eu(III) ions are incorporated, while losing most of their hydration shell. The results show that solid solution modelling for actinides in calcite must take into account the presence of nitrate in pore and ground waters.

  20. The influence of inner hydrophobisation on water transport properties of modified lime plasters

    NASA Astrophysics Data System (ADS)

    Pavlíková, Milena; Pavlík, Zbyšek; Pernicová, Radka; Černý, Robert

    2016-06-01

    The effect of hydrophobic agent admixture on water vapour and liquid water transport properties of newly designed lime plasters is analysed in the paper. The major part of physico - chemical building deterioration is related to the penetration of moisture and soluble salts into the building structure. For that reason, the modified lime plasters were in the broad range of basic material properties tested. From the quantitative point of view, the measured results clearly demonstrate the big differences in the behaviour of studied materials depending on applied modifying admixtures. From the practical point of view, plaster made of lime hydrate, metakaolin, zinc stearate and air-entraining agent can be recommended for renovation purposes. The accessed material parameters will be used as input data for computational modelling of moisture transport in this type of porous building materials and will be stored in material database.

  1. Hydrothermal calcite in the Elephant Moraine

    SciTech Connect

    Faure, G.; Taylor, K.S.; Jones, L.M.

    1986-01-01

    In the course of geologic mapping of the Elephant Moraine on the east antarctic ice sheet, Faure and Taylor (1985) collected several specimens of black botryoidal calcite, composed of radiating acicular crystals that resemble stromatolites. Calcite from this and other specimens is significantly enriched in strontium-87 (the strontium-87/strontium-86 ratio equals 0.71417 +/- 0.00002), carbon-12 (delta carbon-13 equals -22.9 parts per thousand, PDB standard) and oxygen-16 (delta oxygen-18 equals -21.1 parts per thousand, standard mean ocean water) compared with calcite of marine origin. The enrichment in carbon-12 is similar to that of calcite associated with coal in the Allan Hills. The enrichment in oxygen-16 indicates that the calcite from the Elephant Moraine could only have precipitated in isotopic equilibrium with glacial melt water. Therefore, the temperature at which the black calcite precipitated from water of that isotope composition was about 85/sup 0/C. A temperature of this magnitude implies that the black calcite formed as a result of volcanic activity under the east antarctic ice sheet. The enrichment of the black calcite in carbon-12 suggests that it formed in part from carbon dioxide derived from the coal seams of the Weller Formation in the Beacon Supergroup. The isotopic composition of strontium in the black calcite is similar to that of carbonate beds and concretions in the Beacon rocks of southern Victoria Land. A volcanic-hydrothermal origin is also consistent with the very low total organic carbon content of 0.15% in the calcite.

  2. Lime application for the efficient production of nutraceutical glucooligosaccharides from Leuconostoc mesenteroides NRRL B-742 (ATCC13146).

    PubMed

    Moon, Young Hwan; Madsen, Lee; Chung, Chang-Ho; Kim, Doman; Day, Donal F

    2015-02-01

    We have previously demonstrated the production of glucooligosaccharides via a fermentation of sucrose with Leuconostoc mesenteroides NRRL B-742 using sodium hydroxide (NaOH) to control the pH. Because NaOH is expensive, we sought to minimize the cost of our process by substituting hydrated lime and saccharate of lime (lime sucrate) in its place. The yield of glucooligosaccharides using either 5 % lime (41.4 ± 0.5 g/100 g) or 5 % lime sucrate (40.0 ± 1.4 g/100 g) were both similar to the NaOH control (42.4 ± 1.5 g/100 g). Based on this, it appears that the cost associated with pH control in our process can be reduced by a factor of approximately 2.4 using lime instead of NaOH. Because our chromatographic stage is based on a Ca(2+)-form resin to separate glucooligosaccharides, the use of lime not only negates the need for costly de-salting via ion-exchange (elimination of two ion-exchange sections) prior to separation, but also greatly reduces the resin regeneration cost. PMID:25533635

  3. Lime application for the efficient production of nutraceutical glucooligosaccharides from Leuconostoc mesenteroides NRRL B-742 (ATCC13146).

    PubMed

    Moon, Young Hwan; Madsen, Lee; Chung, Chang-Ho; Kim, Doman; Day, Donal F

    2015-02-01

    We have previously demonstrated the production of glucooligosaccharides via a fermentation of sucrose with Leuconostoc mesenteroides NRRL B-742 using sodium hydroxide (NaOH) to control the pH. Because NaOH is expensive, we sought to minimize the cost of our process by substituting hydrated lime and saccharate of lime (lime sucrate) in its place. The yield of glucooligosaccharides using either 5 % lime (41.4 ± 0.5 g/100 g) or 5 % lime sucrate (40.0 ± 1.4 g/100 g) were both similar to the NaOH control (42.4 ± 1.5 g/100 g). Based on this, it appears that the cost associated with pH control in our process can be reduced by a factor of approximately 2.4 using lime instead of NaOH. Because our chromatographic stage is based on a Ca(2+)-form resin to separate glucooligosaccharides, the use of lime not only negates the need for costly de-salting via ion-exchange (elimination of two ion-exchange sections) prior to separation, but also greatly reduces the resin regeneration cost.

  4. Do organic ligands affect calcite dissolution rates?

    NASA Astrophysics Data System (ADS)

    Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale

    2011-04-01

    Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of <0.05 mol/kg of these organic anions changes calcite dissolution rates by less than a factor of 2.5 with the exception of citrate and EDTA 4-. The presence of 0.05 mol/kg citrate and EDTA 4- increases calcite dissolution rates by as much as a factor of 35 and 500, respectively, compared to rates in organic anion-free solutions. Further calcite dissolution experiments were performed in the presence of organic polymers similar to bacterial exudates, cell exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

  5. Hydrate habitat

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    Whoever said there is nothing new under the sun did not delve deeply enough to the bottom of the ocean. There in the Gulf of Mexico, about 150 miles south of New Orleans, scientists have just discovered what could be a new species of centipede—like worms living on or within gas hydrates— mounds of methane ice— rising from the ocean floor.Scientists have previously recognized an association between some bacteria and these hydrates. However, this is the first discovery of a higher life form there.

  6. Diffusion of Ca and Mg in Calcite

    SciTech Connect

    Cygan, R.T.; Fisler, D.K.

    1999-02-10

    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  7. Evidence for carbon sequestration by agricultural liming

    NASA Astrophysics Data System (ADS)

    Hamilton, Stephen K.; Kurzman, Amanda L.; Arango, Clay; Jin, Lixin; Robertson, G. Philip

    2007-06-01

    Agricultural lime can be a source or a sink for CO2, depending on whether reaction occurs with strong acids or carbonic acid. Here we examine the impact of liming on global warming potential by comparing the sum of Ca2+ and Mg2+ to carbonate alkalinity in soil solutions beneath unmanaged vegetation versus limed row crops, and of streams and rivers in agricultural versus forested watersheds, mainly in southern Michigan. Soil solutions sampled by tension indicated that lime can act as either a source or a sink for CO2. However, infiltrating waters tended to indicate net CO2 uptake, as did tile drainage waters and streams draining agricultural watersheds. As nitrate concentrations increased in infiltrating waters, lime switched from a net CO2 sink to a source, implying nitrification as a major acidifying process. Dissolution of lime may sequester CO2 equal to roughly 25-50% of its C content, in contrast to the prevailing assumption that all of the carbon in lime becomes CO2. The ˜30 Tg/yr of agricultural lime applied in the United States could thus sequester up to 1.9 Tg C/yr, about 15% of the annual change in the U.S. CO2 emissions (12 Tg C/yr for 2002-2003). The implications of liming for atmospheric CO2 stabilization should be considered in strategies to mitigate global climate change.

  8. PCM-enhanced lime plasters for vernacular and contemporary architecture

    NASA Astrophysics Data System (ADS)

    Theodoridou, Magdalini; Kyriakou, Loucas; Ioannou, Ioannis

    2016-04-01

    In 1997, the European Union (EU) pledged to reduce the amount of greenhouse gas emissions by 20% below the levels of 1990 by the end of 2020. In recent years it has become evident that, in order to reach that goal, EU Member States must take measures to encourage sustainability in the building industry, which is a major energy consumer. Such measures should involve the use of innovative, environmentally friendly materials and methods in new constructions, as well as the renovation of existing properties by upgrading their current state of energy efficiency. Phase Change Materials (PCMs) have the ability to absorb and release thermal energy, in the form of latent heat, during the melting or solidifying processes respectively. Thus, they may be used as additives in the production of thermally efficient composite building materials. A PCM-enhanced plaster is a heat storage medium combining an appropriate PCM with a cementitious or non-cementitious matrix to produce a low-cost thermal storage material with structural and thermostatic properties. Although innovative technologies, such as PCMs, have certainly contributed to the boost in the evolution of the building materials industry in recent years, a significant proportion of these technologies and practices have not yet been fully exploited in materials based on traditional principles. This paper focuses on the design and production of novel cementless PCM-enhanced lime plasters, in line with the traditional production technology of lime composites. The new plasters are produced using either hydrated or natural hydraulic lime binder, crushed calcarenite sand (0-2 mm) and commercial microencapsulated PCM in powder form (5% w/w of solids). Results from comparative tests between reference mixtures and mixtures with the addition of PCM, carried out 28, 56 and 90 days after laboratory production, prove the potential of PCMs in enhancing the thermal performance of traditional lime-based composites. The modified composites

  9. Calcite dissolution in two deep eutrophic lakes

    SciTech Connect

    Ramisch, F.; Dittrich, M.; Mattenberger, C.; Wehrli, B.; Wueest, A.

    1999-10-01

    The calcium cycle, in particular carbonate dissolution, was analyzed in two deep eutrophic lakes, Lago di Lugano (288 m maximum depth) and Sempachersee (87 m) located in Switzerland. A box model approach was used to calculate calcite dissolution in the water column and at the sediment-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water analysis. A model for stationary conditions allowing the calculation of calcite dissolution in the water column for a given particle size distribution was developed. The relative values of the simulated flux were consistent with sediment trap observations. The best fit of the dissolution rate constant of sinking calcite in Lago di Lugano was on the same order of magnitude (3 {center{underscore}dot} 10{sup {minus}10} kg{sup 1/3} s{sup {minus}1}) as published laboratory values for this surface controlled process. Both lakes show a similar specific calcite precipitation rate of 170 g Ca m{sup {minus}2} a{sup {minus}1}. The diffusive flux across the sediment-water interface amounts to about 15 and 10% of total calcite precipitation in Sempachersee and Lago di Lugano, respectively. However, 61% of the precipitated calcite is dissolved in the water column of Lago di Lugano compared to only 13% in Sempachersee. These results point towards the importance of grain size distributions and settling times in stratified deep waters as the two most important factors determining calcite retention in sediments of hard water lakes.

  10. Controlled calcite nucleation on polarized calcite single crystal substrates in the presence of polyacrylic acid

    NASA Astrophysics Data System (ADS)

    Wada, Norio; Horiuchi, Naohiro; Nakamura, Miho; Nozaki, Kosuke; Hiyama, Tetsuo; Nagai, Akiko; Yamashita, Kimihiro

    2015-04-01

    We studied theoretically and experimentally the effects of the surface electric field generated by polarization and polyacrylic acid (PAA) additives on the heterogeneous nucleation of calcite on the calcite single crystal substrates with (10.4), (10.0) and (00.1) orientations. A set of "in-situ" experiments with optical microscopy was performed to determine the waiting time of CaCO3 nucleation, defined as the time interval between the onset of the diffusion of CO2 and the appearance of the first visible precipitation. Calcite was nucleated on the oriented calcite substrates through diffusion of NH3 and CO2 gas from a solid ammonium carbonate into calcium chloride solutions. A theoretical analysis showed that the surface electric field of the polarized calcite substrate decrease the activation energy for nucleation and consequently promotes nucleation. Experimentally, the surface electric field and PAA addition were found to decrease both contact angles and waiting times, and as a result, promote the heterogeneous nucleation. Combined effect of PAA and surface electric field further reduced contact angles and waiting times regardless of orientation differences of the calcite substrates. The cooperation acts remarkably on N-surface of the respective calcite substrates. The results were explained by the Cassie's equation, a classical heterogeneous nucleation theory under a surface electric field, and matching of the charged sites on the PAA chain with the ion arrangement on the calcite substrate.

  11. Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule.

    PubMed

    Politi, Yael; Metzler, Rebecca A; Abrecht, Mike; Gilbert, Benjamin; Wilt, Fred H; Sagi, Irit; Addadi, Lia; Weiner, Steve; Gilbert, P U P A; Gilbert, Pupa

    2008-11-11

    Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40-200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism.

  12. Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

    PubMed Central

    Politi, Yael; Metzler, Rebecca A.; Abrecht, Mike; Gilbert, Benjamin; Wilt, Fred H.; Sagi, Irit; Addadi, Lia; Weiner, Steve; Gilbert, P. U. P. A.

    2008-01-01

    Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism. PMID:18987314

  13. Simple Analysis of Historical Lime Mortars

    ERIC Educational Resources Information Center

    Pires, Joa~o

    2015-01-01

    A laboratory experiment is described in which a simple characterization of a historical lime mortar is made by the determination of its approximate composition by a gravimetric method. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) are also used for the qualitative characterization of the lime mortar components. These…

  14. Soda lime adsorption of isoflurane and enflurane.

    PubMed

    Grodin, W K; Epstein, M A; Epstein, R A

    1985-01-01

    The authors demonstrated that soda lime will adsorb enflurane or isoflurane as a function of the water content of the soda lime. Various volumes of liquid enflurane or isoflurane were placed in an equilibration flask containing fresh (15% water by weight) or dried soda lime and the vapor phase anesthetic concentrations plotted. When dry soda lime was used, the plot of concentration as a function of volume of liquid added was biphasic: initially flat and then rising linearly. This is qualitatively similar to data reported previously for halothane. The authors hypothesize that drying soda lime produces a molecular sieve-like structure, as adsorption is greatest for molecules with small carbon chain lengths and kinetic diameters, or with structural characteristics such as cis/trans isomerism, which effectively reduce molecular size.

  15. Lactic Acid Fermentation, Urea and Lime Addition: Promising Faecal Sludge Sanitizing Methods for Emergency Sanitation.

    PubMed

    Anderson, Catherine; Malambo, Dennis Hanjalika; Perez, Maria Eliette Gonzalez; Nobela, Happiness Ngwanamoseka; de Pooter, Lobke; Spit, Jan; Hooijmans, Christine Maria; de Vossenberg, Jack van; Greya, Wilson; Thole, Bernard; van Lier, Jules B; Brdjanovic, Damir

    2015-10-29

    In this research, three faecal sludge sanitizing methods-lactic acid fermentation, urea treatment and lime treatment-were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m³ of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment.

  16. Lactic Acid Fermentation, Urea and Lime Addition: Promising Faecal Sludge Sanitizing Methods for Emergency Sanitation

    PubMed Central

    Anderson, Catherine; Malambo, Dennis Hanjalika; Gonzalez Perez, Maria Eliette; Nobela, Happiness Ngwanamoseka; de Pooter, Lobke; Spit, Jan; Hooijmans, Christine Maria; van de Vossenberg, Jack; Greya, Wilson; Thole, Bernard; van Lier, Jules B.; Brdjanovic, Damir

    2015-01-01

    In this research, three faecal sludge sanitizing methods—lactic acid fermentation, urea treatment and lime treatment—were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m3 of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment. PMID:26528995

  17. Lactic Acid Fermentation, Urea and Lime Addition: Promising Faecal Sludge Sanitizing Methods for Emergency Sanitation.

    PubMed

    Anderson, Catherine; Malambo, Dennis Hanjalika; Perez, Maria Eliette Gonzalez; Nobela, Happiness Ngwanamoseka; de Pooter, Lobke; Spit, Jan; Hooijmans, Christine Maria; de Vossenberg, Jack van; Greya, Wilson; Thole, Bernard; van Lier, Jules B; Brdjanovic, Damir

    2015-11-01

    In this research, three faecal sludge sanitizing methods-lactic acid fermentation, urea treatment and lime treatment-were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m³ of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment. PMID:26528995

  18. Effects of carbonation on the pore structure of non-hydraulic lime mortars

    SciTech Connect

    Lawrence, Robert M. . E-mail: mike@cc-w.co.uk; Mays, Timothy J.; Rigby, Sean P.; Walker, Peter; D'Ayala, Dina

    2007-07-15

    The pore structures of carbonated non-hydraulic lime mortars made with a range of different aggregates and concentrations of lime have been determined using mercury intrusion porosimetry (MIP). MIP data have been correlated with scanning electron microscopy images and other porosity data. During carbonation there is an increase in pore volume in the {approx} 0.1 {mu}m pore diameter range across all mortar types which is attributed to the transformation of portlandite to calcite. Also there is a monotonic increase in the volumes of pores with diameters below 0.03 {mu}m. A model is proposed for the changes in pore structure caused by carbonation. This attributes the increase in the volume of sub 0.03 {mu}m pores to the attachment of calcite crystals to the surface of aggregate particles, and in some cases to the surface of portlandite crystals. This phenomenon may explain the continuing presence of portlandite in mortars that, apparently, have fully carbonated.

  19. Marine Diagenesis of Shallow Marine Lime-Mud Sediments: Insights from dgrO18 and dgrC13 Data.

    PubMed

    Choquette, P W

    1968-09-13

    Shallow marine lime-mud sediments of the Ste. Genevieve Formation (Mississippian), in part of the Illinois Basin, underwent at least three diagenetic changes: (i) local dolomitization in seawater or a brine, producing dolostone having average deltaC(13) of +2.5 per mille and deltaO(18) of +1.9 per mille (versus PDB-1); (ii) more usually cementation of unreplaced CaCO(3), in intrasediment seawater, yielding isotopically marine lime mudstone mainly composed of calcite, 4-micron or finer, with deltaO(18) of from -1 to +1 per mille; (iii) later partial alteration of CaCO(3), in permeable dolomitic rocks, by isotopically "lighter" waters, to calcite with an estimated deltaO(18) of -10 per mille or less. Isotope data appraised by petrographic analysis thus suggest "submarine" cementation of these carbonates in shallow marine conditions. PMID:17812283

  20. Marine Diagenesis of Shallow Marine Lime-Mud Sediments: Insights from dgrO18 and dgrC13 Data.

    PubMed

    Choquette, P W

    1968-09-13

    Shallow marine lime-mud sediments of the Ste. Genevieve Formation (Mississippian), in part of the Illinois Basin, underwent at least three diagenetic changes: (i) local dolomitization in seawater or a brine, producing dolostone having average deltaC(13) of +2.5 per mille and deltaO(18) of +1.9 per mille (versus PDB-1); (ii) more usually cementation of unreplaced CaCO(3), in intrasediment seawater, yielding isotopically marine lime mudstone mainly composed of calcite, 4-micron or finer, with deltaO(18) of from -1 to +1 per mille; (iii) later partial alteration of CaCO(3), in permeable dolomitic rocks, by isotopically "lighter" waters, to calcite with an estimated deltaO(18) of -10 per mille or less. Isotope data appraised by petrographic analysis thus suggest "submarine" cementation of these carbonates in shallow marine conditions.

  1. X-ray diffraction study into the effects of liming on the structure of collagen.

    PubMed

    Maxwell, Clark A; Wess, Tim J; Kennedy, Craig J

    2006-08-01

    The manufacture of parchment from animal skin involves processes that remove hair, fats, and other macromolecules. Although it is well understood that the collagen fibers "open up" during processing, this study uses small and wide-angle X-ray diffraction to measure quantitatively the changes induced at the nanoscopic and microscopic levels. The axial rise per residue distance within the collagen molecules is unaffected by salt and lime treatments. Salting of the hides appears to remove noncollagenous materials. The intermolecular lateral packing distance between the hydrated collagen molecules (1.4 nm) increases after salting ( approximately 1.5 nm) and liming ( approximately 1.55 nm); drying is responsible for a reduction to approximately 1.2 nm in all samples. The axial staggered array (d spacing) is reduced by 1 nm after liming and is unaffected by drying. The average fibril diameter increases from 103.2 to 114.5 nm following liming, and the fibril-to-fibril distance increases from 122.6 to 136.1 nm. PMID:16903677

  2. Interaction of alcohols with the calcite surface.

    PubMed

    Bovet, N; Yang, M; Javadi, M S; Stipp, S L S

    2015-02-01

    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale. Controlling their growth requires complex polysaccharides. Polysaccharide activity depends on the functionality of OH groups, so to simplify the system in order to get closer to a molecular level understanding, we investigated the interaction of OH from a suite of alcohols with clean, freshly cleaved calcite surfaces. X-ray photoelectron spectroscopy (XPS) provided binding energies and revealed the extent of surface coverage. Molecular dynamics (MD) simulations supplemented with information about molecule ordering, orientation and packing density. The results show that all alcohols studied bond with the calcite surface through the OH group, with their carbon chains sticking away in a standing-up orientation. Alcohol molecules are closely packed and form a well-ordered monolayer on the surface.

  3. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.

    ERIC Educational Resources Information Center

    Wilkinson, Bruce H.

    1982-01-01

    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  4. Interaction of alcohols with the calcite surface.

    PubMed

    Bovet, N; Yang, M; Javadi, M S; Stipp, S L S

    2015-02-01

    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale. Controlling their growth requires complex polysaccharides. Polysaccharide activity depends on the functionality of OH groups, so to simplify the system in order to get closer to a molecular level understanding, we investigated the interaction of OH from a suite of alcohols with clean, freshly cleaved calcite surfaces. X-ray photoelectron spectroscopy (XPS) provided binding energies and revealed the extent of surface coverage. Molecular dynamics (MD) simulations supplemented with information about molecule ordering, orientation and packing density. The results show that all alcohols studied bond with the calcite surface through the OH group, with their carbon chains sticking away in a standing-up orientation. Alcohol molecules are closely packed and form a well-ordered monolayer on the surface. PMID:25533590

  5. Arsenic removal in conjunction with lime softening

    DOEpatents

    Khandaker, Nadim R.; Brady, Patrick V.; Teter, David M.; Krumhansl, James L.

    2004-10-12

    A method for removing dissolved arsenic from an aqueous medium comprising adding lime to the aqueous medium, and adding one or more sources of divalent metal ions other than calcium and magnesium to the aqueous medium, whereby dissolved arsenic in the aqueous medium is reduced to a lower level than possible if only the step of adding lime were performed. Also a composition of matter for removing dissolved arsenic from an aqueous medium comprising lime and one or more sources of divalent copper and/or zinc metal ions.

  6. [Halothane absorption by dry soda lime].

    PubMed

    Stuttmann, R; Knüttgen, D; Müller, M R; Winkert, A T; Doehn, M

    1993-03-01

    Humidified soda lime is commonly used to eliminate carbon dioxide from the circulatory system. Little is known about adverse reactions to accidentally dried soda lime. Therefore, a case of unexpected absorption of halothane by dry soda lime is reported. These observations were confirmed by a simulation with relevance to anaesthetic practice. CASE REPORT. A 46-year-old ASA class I patient was scheduled for elective surgery. After induction of general anaesthesia with 500 mg thiopentone, followed by 100 mg suxamethonium, the trachea was intubated. The patient was ventilated with nitrous oxide in oxygen and 1.5 vol% of halothane for several minutes in the induction room. After being connected to a new circulatory system in the operating theatre, the patient was ventilated but, in addition inspiratory and expiratory anaesthetic gas concentrations were measured. Despite a vaporizer position of 1.5 vol% the inspiratory concentration of halothane was below 0.2 vol%. Disconnecting the tube, the typical odour of halothane was missing in the inspiratory line of the circulatory system, but was present in the fresh gas tube. Furthermore, the lower part of the soda lime canister was surprisingly hot. After removing both the absorbers, the inspiratory halothane concentration immediately normalized. The absorbers were replaced by canisters filled with fresh soda lime, and the anaesthesia was terminated without further complications. An absorption of halothane by dried soda lime was suspected. METHODS OF SIMULATION. In the first simulation four circulatory systems with two soda lime canisters each were perfused with 21 of oxygen for 48 h. In the second simulation four soda lime canisters placed in one circulatory system were perfused with 1 l for 120 h. For measurement of halothane absorption each canister was placed in a circulatory system. The canister was perfused with a fresh gas flow of 2 l of oxygen and a vaporizer position up to 1.3 vol% of halothane. By the time an

  7. Lime-pozzolana mortars in Roman catacombs: composition, structures and restoration

    SciTech Connect

    Sanchez-Moral, Sergio; Soler, Vicente; Garcia-Guinea, Javier

    2005-08-01

    Analyses of microsamples collected from Roman catacombs and samples of lime-pozzolana mortars hardened in the laboratory display higher contents in carbonated binder than other subaerial Roman monuments. The measured environmental data inside the Saint Callistus and Domitilla catacombs show a constant temperature of 15-17 deg C, a high CO{sub 2} content (1700 to 3500 ppm) and a relative humidity close to 100%. These conditions and particularly the high CO{sub 2} concentration speed-up the lime calcitization roughly by 500% and reduce the cationic diffusion to form hydrous calcium aluminosilicates. The structure of Roman catacomb mortars shows (i) coarser aggregates and thicker beds on the inside, (ii) thin, smoothed, light and fine-grained external surfaces with low content of aggregates and (iii) paintings and frescoes on the outside. The observed high porosity of the mortars can be attributed to cracking after drying linked with the high binder content. Hardened lime lumps inside the binder denote low water/mortar ratios for slaking. The aggregate tephra pyroclasts rich in aluminosilicate phases with accessorial amounts of Ba, Sr, Rb, Cu and Pb were analysed through X-ray diffraction (XRD), electron microprobe analysis (EMPA) and also by environmental scanning electron microscopy (ESEM) to identify the size and distribution of porosity. Results support procedures using local materials, special mortars and classic techniques for restoration purposes in hypogeal backgrounds.

  8. Characterization of a lime-pozzolan plaster containing phase change material

    SciTech Connect

    Pavlíková, Milena; Pavlík, Zbyšek; Trník, Anton; Pokorný, Jaroslav; Černý, Robert

    2015-03-10

    A PCM (Phase Change Material) modified lime-pozzolan plaster for improvement of thermal energy storage of building envelopes is studied in the paper. The investigated plaster is composed of lime hydrate, pozzolan admixture based on metakaolin and mudstone, silica sand, water and paraffin wax encapsulated in polymer capsule. The reference plaster without PCM application is studied as well. The analyzed materials are characterized by bulk density, matrix density, total open porosity, compressive strength and pore size distribution. The temperature of phase change, heat of fusion and crystallization are studied using DSC (Difference Scanning Calorimetry) analysis performed in air atmosphere. In order to get information on materials hygrothermal performance, determination of thermal and hygric properties is done in laboratory conditions. Experimental data reveal a substantial improvement of heat storage capacity of PCM-modified plaster as compared to the reference material without PCM.

  9. in situ Calcite Precipitation for Contaminant Immobilization

    SciTech Connect

    Yoshiko Fujita; Robert W. Smith

    2009-08-01

    in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita (Yoshiko.fujita@inl.gov) (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at

  10. Stability of sevoflurane in soda lime.

    PubMed

    Strum, D P; Johnson, B H; Eger, E I

    1987-11-01

    Stability of halogenated volatile anesthetic is important because of the potential toxicity associated with the breakdown products. The authors enclosed 100 ml of gas containing sevoflurane with 100 g of soda lime in a 581-ml flask for periods up to 24 h. The rate of degradation of sevoflurane by soda lime was several-fold greater than previously reported, and the degradation was temperature-dependent. At 22 degrees C, soda lime degraded 6.5% of the sevoflurane per hour. The rate increased by 1.6% per hour per degree rise in temperature, reaching 57.4% degradation per hour at 54 degrees C. In contrast, isoflurane was not degraded by soda lime. Halothane did not degrade at 22 degrees C or 37 degrees C, but did degrade (2.2% per hour) at 54 degrees C.

  11. Dissolution Kinetics of Biogenic Magnesian Calcites

    NASA Astrophysics Data System (ADS)

    Thompson, R.; Guidry, M.; Mackenzie, F. T.; De Carlo, E. H.

    2014-12-01

    Ocean acidification (OA) is a serious concern for the health of calcifying ecosystems in the near future. During the past century, surface ocean pH has decreased by ~0.1 pH units, and is expected to decrease further by 0.3-0.4 pH units by the end of this century. The process of OA will likely result in both decreased calcification rates and increased rates of carbonate mineral dissolution, particularly involving the magnesian calcite (Mg-calcite) calcifiers found in shallow-water reef and other carbonate environments. Many Mg-calcite compositions are the most soluble of the carbonate phases commonly found in reef environments (often comprising much of the cementation and structure within a reef), and are therefore potentially the most susceptible to dissolution processes associated with OA. However, the dissolution kinetics of these phases is poorly known, limiting our ability to understand their behavior in nature. Laboratory experiments designed to investigate the mechanisms and dissolution rates of biogenic Mg-calcite mineral phases in distilled water and seawater over a range of CO2 and T conditions were conducted employing both batch and fluidized-bed reactor systems and using a variety of cleaned and annealed biogenic Mg-calcite phases. Our initial results have shown that the dissolution rate at 298 K and a pCO2 of ~350 ppm of the crustose coralline alga Amphiroa rigida (~20 mol% MgCO3) in seawater undersaturated with respect to this phase is 3.6 μmol g-1 hr-1, nearly 50% greater than that under similar conditions for aragonite. This rate and the derived experimental rate law are consistent with the preliminary findings of Walter and Morse (1985). Additional kinetic (and also solubility) data will be presented for the following species: Chiton tuberculatus (~0-4 mol% MgCO3); Echinometra mathei and/or Lytechinus variegatus (~8-12 mol% MgCO3); Homotrema rubrum (12-16 mol% MgCO3); and Lithothamnion sp. (~18-24 mol% MgCO3). Quantification of the rates of

  12. [Interaction of soda lime and halogenated anesthetics].

    PubMed

    Torri, G; Montani, C; Tommasino, C

    1997-05-01

    The increased use of soda lime for low flow anaesthesia leads to some problems related to the interaction with halogenated agents. These agents may be absorbed by soda lime or degradated according to their water content. Halothane and enflurane, in contact with soda lime, produce some metabolites, but their concentration is low when compared to their own lethal concentration. Sevoflurane degradates to four compounds. Compound A may reach a value between 13.3-42.1 ppm in the inspired fraction: these values are 50-100 times lower than the toxic concentrations. Isoflurane and desflurane are degradable at very low extent. Some case reports of unexpected high carboxyhemoglobin levels during anaesthesia indicate the possibility of CO production from soda lime and baralyme when halogenated agents are used. This reaction occurs only with anaesthetics containing CHF2-moiety (isoflurane, enflurane and desflurane) and when some specific factors make soda lime or baralyme completely dry. Low flow anaesthesia preserves the moisture content of the soda lime and protects from carbon monoxide production, by increasing water content in the circle.

  13. Recycled sand in lime-based mortars.

    PubMed

    Stefanidou, M; Anastasiou, E; Georgiadis Filikas, K

    2014-12-01

    The increasing awareness of the society about safe guarding heritage buildings and at the same time protecting the environment promotes strategies of combining principles of restoration with environmentally friendly materials and techniques. Along these lines, an experimental program was carried out in order to investigate the possibility of producing repair, lime-based mortars used in historic buildings incorporating secondary materials. The alternative material tested was recycled fine aggregates originating from mixed construction and demolition waste. Extensive tests on the raw materials have been performed and mortar mixtures were produced using different binding systems with natural, standard and recycled sand in order to compare their mechanical, physical and microstructure properties. The study reveals the improved behavior of lime mortars, even at early ages, due to the reaction of lime with the Al and Si constituents of the fine recycled sand. The role of the recycled sand was more beneficial in lime mortars rather than the lime-pozzolan or lime-pozzolan-cement mortars as a decrease in their performance was recorded in the latter cases due to the mortars' structure.

  14. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

    USGS Publications Warehouse

    Reddy, Michael M.

    2012-01-01

    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  15. Removal of strontium from drinking water by conventional treatment and lime softening in bench-scale studies.

    PubMed

    O'Donnell, Alissa J; Lytle, Darren A; Harmon, Stephen; Vu, Kevin; Chait, Hannah; Dionysiou, Dionysios D

    2016-10-15

    The United States Environmental Protection Agency Contaminant Candidate List 3 lists strontium as a contaminant for potential regulatory consideration in drinking water. Very limited data is available on strontium removal from drinking water and as a result, there is an immediate need for treatment information. The objective of this work is to evaluate the effectiveness of coagulation/filtration and lime-soda ash softening treatment methods to remove strontium from surface and ground waters. Coagulation/filtration jar test results on natural waters showed that conventional treatment with aluminum and iron coagulants were able to achieve only 12% and 5.9% strontium removal, while lime softening removed as high as 78% from natural strontium-containing ground water. Controlled batch experiments on synthetic water showed that strontium removal during the lime-soda ash softening was affected by pH, calcium concentration and dissolved inorganic carbon concentration. In all softening jar tests, the final strontium concentration was directly related to the initial strontium concentration and the removal of strontium was directly associated with calcium removal. Precipitated solids showed well-formed crystals or agglomerates of mixed solids, two polymorphs of calcium carbonate (vaterite and calcite), and strontianite, depending on initial water quality conditions. X-ray diffraction analysis suggested that strontium was likely incorporated in the calcium carbonate crystal lattice and was likely responsible for removal during lime softening. PMID:27475121

  16. Removal of strontium from drinking water by conventional treatment and lime softening in bench-scale studies.

    PubMed

    O'Donnell, Alissa J; Lytle, Darren A; Harmon, Stephen; Vu, Kevin; Chait, Hannah; Dionysiou, Dionysios D

    2016-10-15

    The United States Environmental Protection Agency Contaminant Candidate List 3 lists strontium as a contaminant for potential regulatory consideration in drinking water. Very limited data is available on strontium removal from drinking water and as a result, there is an immediate need for treatment information. The objective of this work is to evaluate the effectiveness of coagulation/filtration and lime-soda ash softening treatment methods to remove strontium from surface and ground waters. Coagulation/filtration jar test results on natural waters showed that conventional treatment with aluminum and iron coagulants were able to achieve only 12% and 5.9% strontium removal, while lime softening removed as high as 78% from natural strontium-containing ground water. Controlled batch experiments on synthetic water showed that strontium removal during the lime-soda ash softening was affected by pH, calcium concentration and dissolved inorganic carbon concentration. In all softening jar tests, the final strontium concentration was directly related to the initial strontium concentration and the removal of strontium was directly associated with calcium removal. Precipitated solids showed well-formed crystals or agglomerates of mixed solids, two polymorphs of calcium carbonate (vaterite and calcite), and strontianite, depending on initial water quality conditions. X-ray diffraction analysis suggested that strontium was likely incorporated in the calcium carbonate crystal lattice and was likely responsible for removal during lime softening.

  17. Phytoplankton responses to biomanipulated grazing pressure and nutrient additions--enclosure studies in unlimed and limed Lake Njupfatet, central Sweden.

    PubMed

    Blomqvist, P

    2001-01-01

    Enclosure experiments aimed to assess the role of Chaoborus larvae in regulating lower trophic levels under natural and nutrient-enriched conditions were performed in situ in the dimictic, oligotrophic clearwater Lake Njupfatet, central Sweden. One experiment was performed before, and one after, whole-lake calcite treatment. In the acidic system, total planktonic biomass (TPB; the sum of phyto-, bacterio-, protozoo-, and metazooplankton), dominated by the cyanobacterium Merismopedia, was only weakly stimulated by the nutrients while the predator had no effect. In the limed environment, TPB increased strongly in response to the nutrients in combination with a negative response to the predator. Principally phytoplankton, but also bacterioplankton and protozooplankton (ciliates) were stimulated by the nutrients. It is argued that Merismopedia acted as a dead-end in the energy flow in the acidic system. Liming resulted in the disappearance of Merismopedia and this opened the flow of material to higher trophic levels. Since liming also led to a significant reduction in the concentrations of phosphorus in the lake water, it is proposed that a combination of liming and gentle fertilization might be used to restore the productivity of acidified lakes.

  18. Effect of micromorphological development on the elastic moduli of fly ash-lime stabilized bentonite

    SciTech Connect

    Baykal, G.I.

    1987-01-01

    The mineralogical and micromorphological changes occurring in fly ash-lime stabilized bentonite were observed and related to changes in elastic moduli of the stabilized mixture. Compacted fly ash, fly ash-lime, bentonite-lime, bentonite-fly ash, and bentonite-fly ash-lime mixtures were prepared and cured at 23C and 50C, for 1, 28, 90 and 180 days. The development of microstructure and cementitous crystals were observed by a scanning electron microscope, and energy dispersive spectrum analyzer and a X-ray diffractometer. The elastic moduli and strengths were obtained from unconsolidated undrained triaxial and unconfined compressive strength tests. The physical test results were compared with changes observed by scanning electron microscopy and X-ray diffraction. CSH gel Type I, II and III, ettringite, afwillite and tetracalcium aluminate thirteen hydrate crystals were identified in the cured specimens. The elastic modulus of the fly ash-lime stabilized bentonite was higher than the untreated bentonite and the increase in elastic modulus corresponded to the curing times when new cementitious crystals were observed. Acicular crystals (CSH Type I and II) and ettringite crystals spanned the pores and increased the contact points where blocky aggregates of equant crystals (CSH III) engulfed the fly ash grains providing support. The compressive strength increased, and the strain at a failure decreased resulting in an increase in the elastic modulus. Some fly ash grains providing support for montmorillonite aggregates dissolved and created weak spots in the matrix, causing a decrease in elastic modulus at longer curing periods. At 50C curing temperature the same cementitious crystals were observed as at 23C. However, the rate of the reactions increased considerably.

  19. Frictional behavior of talc-calcite mixtures

    NASA Astrophysics Data System (ADS)

    Giorgetti, C.; Carpenter, B. M.; Collettini, C.

    2015-09-01

    Faults involving phyllosilicates appear weak when compared to the laboratory-derived strength of most crustal rocks. Among phyllosilicates, talc, with very low friction, is one of the weakest minerals involved in various tectonic settings. As the presence of talc has been recently documented in carbonate faults, we performed laboratory friction experiments to better constrain how various amounts of talc could alter these fault's frictional properties. We used a biaxial apparatus to systematically shear different mixtures of talc and calcite as powdered gouge at room temperature, normal stresses up to 50 MPa and under different pore fluid saturated conditions, i.e., CaCO3-equilibrated water and silicone oil. We performed slide-hold-slide tests, 1-3000 s, to measure the amount of frictional healing and velocity-stepping tests, 0.1-1000 µm/s, to evaluate frictional stability. We then analyzed microstructures developed during our experiments. Our results show that with the addition of 20% talc the calcite gouge undergoes a 70% reduction in steady state frictional strength, a complete reduction of frictional healing and a transition from velocity-weakening to velocity-strengthening behavior. Microstructural analysis shows that with increasing talc content, deformation mechanisms evolve from distributed cataclastic flow of the granular calcite to localized sliding along talc-rich shear planes, resulting in a fully interconnected network of talc lamellae from 20% talc onward. Our observations indicate that in faults where talc and calcite are present, a low concentration of talc is enough to strongly modify the gouge's frictional properties and specifically to weaken the fault, reduce its ability to sustain future stress drops, and stabilize slip.

  20. Bendable, free-standing calcite thin films.

    PubMed

    Nakamura, Shiho; Naka, Kensuke

    2015-02-17

    Since the hardness and toughness of natural nacre are determined by hierarchical microstructures with organic matters, it is of great importance to control the microstructures of artificial free-standing CaCO3 thin films. However, the fabrication of such films has so far been quite limited, to the extent that their mechanical properties have not been reported. To address this, free-standing calcite thin films were prepared through repeated cycles of layer-by-layer deposition of vaterite precursor composite particles with organic polymers, followed by a phase transition to calcite. In this way, two distinct calcite thin film types were produced based on either 3.2 or 1.0 wt % organic material, with subsequent three-point bending tests revealing that both exhibit elastic bending prior to fracture. More importantly, by increasing the organic content from 1.0 to 3.2 wt %, the bending strength increased from 0.95 ± 0.26 MPa to 1.90 ± 0.21 MPa. PMID:25621634

  1. Biogenic calcite granules--are brachiopods different?

    PubMed

    Pérez-Huerta, Alberto; Dauphin, Yannicke; Cusack, Maggie

    2013-01-01

    Brachiopods are still one of the least studied groups of organisms in terms of biomineralization despite recent studies indicating the presence of highly complex biomineral structures, particularly in taxa with calcitic shells. Here, we analyze the nanostructure of calcite biominerals, fibers and semi-nacre tablets, in brachiopod shells by high-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM). We demonstrate that basic mechanisms of carbonate biomineralization are not uniform within the phylum, with semi-nacre tablets composed of spherical aggregates with sub-rounded granules and fibers composed of large, triangular or rod-like particles composed of small sub-rounded granules (40-60 nm). Additionally, proteinaceous envelopes surrounding calcite fibers have been shown for the first time to have a dual function: providing a micro-environment in which granules are produced and acting as the organic template for particle orientation as fiber components. In summary, these new findings in brachiopod shells reveal a complex and distinctive style of biomineralization among carbonate-producing organisms. PMID:23026148

  2. Calcite cements in the modern Floridan aquifer

    SciTech Connect

    Hammes, U.; Budd, D.A. )

    1991-03-01

    Calcite cements in the Ocala (Eocene) and Suwannee (Oligocene) formations, southwestern Floridan aquifer have been studied to determine updip to downdip variations in cement chemistries and cathodoluminescence within a modern regional confined aquifer. Interparticle, intraparticle, and fracture-fill cements comprise 5-15% of the limestones. Five different calcite cement morphologies are distinguishable and occur throughout the aquifer: (1) circumgranular microspar, (2) fine- to medium-crystalline rhombs, (3) medium-crystalline syntaxial overgrowths on echinoderms, (4) fine-crystalline pore-filling mosaics, and (5) micrite. Type 5 occurs only below former exposure surfaces. Volumetrically, type 3 is the most important and type 4 is the least. Cathodoluminescence observations reveal only nonluminescent cements updip and an increase in luminescent zones and luminescent intensity downdip. Updip nonluminescent cements have very low Fe and Mn concentrations, but high Mg and Sr concentrations. These relations are interpreted to reflect oxidizing conditions and high rock/water interaction. Fe and Mn concentrations increase and Sr and Mg contents decrease downdip. These trends are interpreted to reflect reducing conditions, cross-formational flow, and slower rock/water interaction. Downdip cathodoluminescence zonations consist of a broad nonluminescent zone, followed by a thin bright orange zone, and then a dull luminescence zone. These geochemical and luminescent patterns along a regional flow line in the confined Floridan aquifer have many similarities to those observed in calcite cements described from ancient aquifers.

  3. Effect of whole catchment liming on the episodic acidification of two adirondack streams

    USGS Publications Warehouse

    Newton, R.M.; Burns, Douglas A.; Blette, V.L.; Driscoll, C.T.

    1996-01-01

    During the fall of 1989 7.7Mg/ha of calcium carbonate was applied on two tributary catchments (40 ha and 60 ha) to Woods Lake, a small (25 ha) acidic headwater lake in the western Adirondack region of New York. Stream-water chemistry in both catchment tributaries responded immediately. Acid-neutralizing capacity (ANC) increased by more than 200 ??eq/L in one of the streams and more than 1000 ??eq/L in the other, from pre-liming values which ranged from -25 to +40 ??eq/L. The increase in ANC was primarily due to increases in dissolved Ca2+ concentrations. Most of the initial response of the streams was due to the dissolution of calcite that fell directly into the stream channels and adjacent wetlands. A small beaver impoundment and associated wetlands were probably responsible for the greater response observed in one of the streams. After the liming of subcatchmentIV (60 ha), Ca2+ concentrations increased with increasing stream discharge in the stream during fall rain events, suggesting a contribution from calcite dissolved within the soil and transported to the stream by surface runoff or shallow interflow. Concentrations of other ions not associated with the calcite (e.g. Na+) decreased during fall rain events, presumably due to mixing of solute-rich base flow with more dilute shallow interflow. The strong relation between changes in Ca2+ and changes in NO3- concentrations during spring snowmelt, (r2 = 0.93, slope = 0.96, on an equivalent basis) suggests that both solutes had a common source in the organic horizon of the soil. Increases in NO3- concentrations during snowmelt were balanced by increases in Ca2+ that was released either directly from the calcite or from exchange sites, mitigating episodic acidification of the stream. However, high ambient NO3- concentrations and relatively low ambient Ca2+ concentrations in the stream during the spring caused the stream to become acidic despite the CaCO3 treatment. In stream WO2 (40ha), Ca2+ concentrations were much

  4. Improved control of sucrose losses and clarified juice turbidity with lime saccharate in hot lime clarification of sugarcane juice and other comparisons with milk of lime

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A comparative investigation of adding milk of lime (MOL) versus lime saccharate (SACCH) in hot lime clarification of juice at a U.S. sugarcane factory was undertaken to quantify performance across the 2009 processing season after a preliminary factory study in 2008. SACCH was prepared by adding hyd...

  5. Gas hydrate and humans

    USGS Publications Warehouse

    Kvenvolden, K.A.

    2000-01-01

    The potential effects of naturally occurring gas hydrate on humans are not understood with certainty, but enough information has been acquired over the past 30 years to make preliminary assessments possible. Three major issues are gas hydrate as (1) a potential energy resource, (2) a factor in global climate change, and (3) a submarine geohazard. The methane content is estimated to be between 1015 to 1017 m3 at STP and the worldwide distribution in outer continental margins of oceans and in polar regions are significant features of gas hydrate. However, its immediate development as an energy resource is not likely because there are various geological constraints and difficult technological problems that must be solved before economic recovery of methane from hydrate can be achieved. The role of gas hydrate in global climate change is uncertain. For hydrate methane to be an effective greenhouse gas, it must reach the atmosphere. Yet there are many obstacles to the transfer of methane from hydrate to the atmosphere. Rates of gas hydrate dissociation and the integrated rates of release and destruction of the methane in the geo/hydro/atmosphere are not adequately understood. Gas hydrate as a submarine geohazard, however, is of immediate and increasing importance to humans as our industrial society moves to exploit seabed resources at ever-greater depths in the waters of our coastal oceans. Human activities and installations in regions of gas-hydrate occurrence must take into account the presence of gas hydrate and deal with the consequences of its presence.

  6. Effects of calcite and magnesite application to a declining Masson pine forest on strongly acidified soil in Southwestern China.

    PubMed

    Huang, Yongmei; Kang, Ronghua; Ma, Xiaoxiao; Qi, Yu; Mulder, Jan; Duan, Lei

    2014-05-15

    Liming of strongly acidified soil under a Masson pine (Pinus massoniana Lamb.) forest was studied through a seven-year field manipulation experiment at Tieshanping, Chongqing in Southwestern China. To distinguish between the individual effects of Ca(2+) and Mg(2+) addition, we separately applied calcite (CaCO3) and magnesite (MgCO3), rather than using dolomite [CaMg(CO3)2]. Both calcite and magnesite additions caused a significant increase in pH and a decrease in dissolved inorganic monomeric aluminium (Ali) concentration of soil water. Ecological recovery included increases of herb biomass (both treatments) and Mg content in Masson pine needles (magnesite treatment only). However, the growth rate of Masson pine did not increase under either treatment, possibly because of nutrient imbalance due to phosphorus (P) deficiency or limited observation period. In China, acid deposition in forest ecosystems commonly coincides with large inputs of atmogenic Ca(2+), both enhancing Mg(2+) leaching. Calcite addition may further decrease the Mg(2+) availability in soil water, thereby exacerbating Mg(2+) deficiency in the acidified forest soils of southern and southwestern China. The effect of anthropogenic acidification of naturally acid forest soils on P availability needs further study.

  7. Effects of calcite and magnesite application to a declining Masson pine forest on strongly acidified soil in Southwestern China.

    PubMed

    Huang, Yongmei; Kang, Ronghua; Ma, Xiaoxiao; Qi, Yu; Mulder, Jan; Duan, Lei

    2014-05-15

    Liming of strongly acidified soil under a Masson pine (Pinus massoniana Lamb.) forest was studied through a seven-year field manipulation experiment at Tieshanping, Chongqing in Southwestern China. To distinguish between the individual effects of Ca(2+) and Mg(2+) addition, we separately applied calcite (CaCO3) and magnesite (MgCO3), rather than using dolomite [CaMg(CO3)2]. Both calcite and magnesite additions caused a significant increase in pH and a decrease in dissolved inorganic monomeric aluminium (Ali) concentration of soil water. Ecological recovery included increases of herb biomass (both treatments) and Mg content in Masson pine needles (magnesite treatment only). However, the growth rate of Masson pine did not increase under either treatment, possibly because of nutrient imbalance due to phosphorus (P) deficiency or limited observation period. In China, acid deposition in forest ecosystems commonly coincides with large inputs of atmogenic Ca(2+), both enhancing Mg(2+) leaching. Calcite addition may further decrease the Mg(2+) availability in soil water, thereby exacerbating Mg(2+) deficiency in the acidified forest soils of southern and southwestern China. The effect of anthropogenic acidification of naturally acid forest soils on P availability needs further study. PMID:24631610

  8. Removal of organic magnesium in coccolithophore calcite

    NASA Astrophysics Data System (ADS)

    Blanco-Ameijeiras, S.; Lebrato, M.; Stoll, H. M.; Iglesias-Rodriguez, M. D.; Méndez-Vicente, A.; Sett, S.; Müller, M. N.; Oschlies, A.; Schulz, K. G.

    2012-07-01

    Coccolithophore calcite refers to the plates of calcium carbonate (CaCO3) produced by the calcifying phytoplankton, coccolithophores. The empirical study of the elemental composition has a great potential in the development of paleoproxies. However, the difficulties to separate coccolithophore carbonates from organic phases hamper the investigation of coccoliths magnesium to calcium ratios (Mg/Ca) in biogeochemical studies. Magnesium (Mg) is found in organic molecules in the cells at concentrations up to 400 times higher than in inorganically precipitated calcite in present-day seawater. The aim of this study was to optimize a reliable procedure for organic Mg removal from coccolithophore samples to ensure reproducibility in measurements of inorganic Mg in calcite. Two baseline methods comprising organic matter oxidations with (1) bleach and (2) hydrogen peroxide (H2O2) were tested on synthetic pellets, prepared by mixing reagent grade CaCO3 with organic matter from the non-calcifying marine algae Chlorella autotrophica and measured with an ICP-AES (inductively coupled plasma-atomic emission spectrometer). Our results show that treatments with a reductive solution [using hydroxylamine-hydrochloride (NH2OH·HCl + NH4OH)] followed by three consecutive oxidations (using H2O2) yielded the best cleaning efficiencies, removing >99% of organic Mg in 24 h. P/Ca and Fe/Ca were used as indicators for organic contamination in the treated material. The optimized protocol was tested in dried coccolithophore pellets from batch cultures of Emiliania huxleyi, Calcidiscus leptoporus and Gephyrocapsa oceanica. Mg/Ca of treated coccolithophores were 0.151 ± 0.018, 0.220 ± 0.040, and 0.064 ± 0.023 mmol/mol, respectively. Comparison with Mg/Ca literature coccolith values, suggests a tight dependence on modern seawater Mg/Ca, which changes as a consequence of different seawater origins (<10%). The reliable determination of Mg/Ca and Sr/Ca, and the low levels of organic contamination

  9. VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS. CONVEYOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS. CONVEYOR MOVES HOT STONE TO MLT'S. THIS IS THE DRIVE END OF CONVEYOR BELT. - Solvay Process Company, Milk of Lime Towers Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  10. 62. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT THE LIME KILNS AND MOTOR DRIVES FOR THE KILNS. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  11. LIME KILN BUILDING, KILN BOTTOM SHOWING ROTATOR GEAR. (GEAR IS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LIME KILN BUILDING, KILN BOTTOM SHOWING ROTATOR GEAR. (GEAR IS POINTED DOWN FOR PROPER ORIENTATION). - Solvay Process Company, Lime Kiln Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  12. VIEW OF MLT BUILDING (LIME KILN BUILDING DIRECTLY BEHIND IT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF MLT BUILDING (LIME KILN BUILDING DIRECTLY BEHIND IT WITH GOOD VIEW OF SKIP CAR TRACK) LOOKING EAST. - Solvay Process Company, Lime Kiln Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  13. VIEW OF LIME KILN BUILDING LOOKING NORTHWEST, SHOWING STONE ELEVATOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF LIME KILN BUILDING LOOKING NORTHWEST, SHOWING STONE ELEVATOR (ON THE LEFT) AND SOUTH CONVEYOR. - Solvay Process Company, Lime Kiln Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  14. Origins of hydration lubrication.

    PubMed

    Ma, Liran; Gaisinskaya-Kipnis, Anastasia; Kampf, Nir; Klein, Jacob

    2015-01-14

    Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4-1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

  15. Low Temperature Synthesis of Belite Cement Based on Silica Fume and Lime

    PubMed Central

    Tantawy, M. A.; Shatat, M. R.; El-Roudi, A. M.; Taher, M. A.; Abd-El-Hamed, M.

    2014-01-01

    This paper describes the low temperature synthesis of belite (β-C2S) from silica fume. Mixtures of lime, BaCl2, and silica fume with the ratio of (Ca + Ba)/Si = 2 were hydrothermally treated in stainless steel capsule at 110–150°C for 2–5 hours, calcined at 600–700°C for 3 hours, and analyzed by FTIR, XRD, TGA/DTA, and SEM techniques. Dicalcium silicate hydrate (hillebrandite) was prepared by hydrothermal treatment of lime/silica fume mixtures with (Ca + Ba)/Si = 2 at 110°C for 5 hours. Hillebrandite partially dehydrates in two steps at 422 and 508°C and transforms to γ-C2S at 734°C which in turn transforms to α′-C2S at 955°C which in turn transforms to β-C2S when cooled. In presence of Ba2+ ions, β-C2S could be stabilized with minor transformation to γ-C2S. Mixture of silica fume, lime, and BaCl2 with the ratio of (Ca + Ba)/Si = 2 was successfully utilized for synthesis of β-C2S by hydrothermal treatment at 110°C for 5 hours followed by calcination of the product at 700°C for 3 hours. PMID:27437495

  16. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste.

    PubMed

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-16

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite.

  17. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

    NASA Astrophysics Data System (ADS)

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite.

  18. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste.

    PubMed

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

  19. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

    PubMed Central

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

  20. First annual post-liming monitoring report for the Western Maryland watershed liming pilot study

    SciTech Connect

    Price, R.M.; Keating, R.W.; Morgan, R.P.

    1993-07-01

    The Western Maryland Watershed Liming Pilot Study was initiated in 1989 to determine whether watershed liming was an appropriate, feasible, and cost-effective strategy to mitigate streams in western Maryland that were chronically acidified by acid deposition. The watershed liming method used in this pilot study involved applying limestone to the soils in ground water discharge areas located adjacent to the stream. The natural flow of water within the watershed was then relied upon to aid in dissolving the limestone and transporting it neutralizing effects to the stream.

  1. Calcite-seeded crystallization of calcium phosphate for phosphorus recovery.

    PubMed

    Song, Yonghui; Weidler, Peter G; Berg, Ute; Nüesch, Rolf; Donnert, Dietfried

    2006-04-01

    For phosphorus recovery from wastewater, the present paper aims at understanding the crystallization of calcium phosphate by using calcites (Juraperle and Coccolith) as seeds from hard water. Synthetic hard water with 60 mgCl(-1) carbonate and 10 mgPl(-1) phosphate was prepared and used in the batch experiments of calcite-seeded crystallization. The solution composition was measured throughout the batch crystallization process, and the corresponding saturation indices with respect to the minerals were calculated with PHREEQC Program. The surface of the calcite seeds was observed and measured with environmental scanning electron microscopy (ESEM), Fourier transform infrared (FTIR) and BET method. The studies show that both calcites are effective seeds for the crystallization of calcium phosphate from hard water; the used calcites are more efficient than the original ones because newly formed crystals with calcium phosphate have covered their surfaces. The studies show that the calcite seeds can be used for phosphorus recovery from hard waters.

  2. Global calcite cycling constrained by sediment preservation controls

    NASA Astrophysics Data System (ADS)

    Dunne, John P.; Hales, Burke; Toggweiler, J. R.

    2012-09-01

    We assess the global balance of calcite export through the water column and burial in sediments as it varies regionally. We first drive a comprehensive 1-D model for sediment calcite preservation with globally gridded field observations and satellite-based syntheses. We then reformulate this model into a simpler five-parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux. We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite. We find that 46% of burial and 88% of dissolution occurs in sediments overlain by undersaturated bottom water with sediment calcite burial strongly modulated by surface export. Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century-scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long-term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline toward much closer correspondence with the saturation horizon. Our analysis suggests that, over the transition from interglacial to glacial ocean, a resulting ˜0.029 PgC a-1decrease in deep Atlantic, Indian and Southern Ocean calcite burial leads to slow increase in ocean alkalinity until Pacific mid-depth calcite burial increases to compensate.

  3. Fibrous calcite from the Middle Ordovician Holston Formation (east Tennessee)

    SciTech Connect

    Tobin, K.J.; Walker, K.R. . Dept. of Geological Sciences)

    1993-03-01

    Fibrous calcite from buildups, which occur near the top of the Middle Ordovician Holston Formation, were examined from two localities near Knoxville, TN (Alcoa Highway and Deanne Quarry). Buildups at these localities were deposited under open-marine conditions, slightly down-slope from the platform edge. Fibrous calcite (mainly radiaxial fibrous) occur most commonly as cements in mainly stromatactis structures present in bioherms and intergranular porosity in beds that flank bioherms. Fibrous calcite is interpreted to have been precipitated in a marine setting. Fibrous calcite is uniformly turbid or banded with interlayered turbid and clearer cement. Fibrous calcite most commonly shows patchy or blotchy dull-non-luminescence under cathodoluminescence. Bands of uniformly non-luminescent and relatively bright luminescent calcite are present. [delta][sup 13]C compositions of fibrous calcite vary little (0.6 to 1.0%) but [delta][sup 18]O values are highly variable ([minus]4.8 to [minus]7.1%). Post-marine cement consists of ferroan and non-ferroan, dull luminescent equant calcite ([delta][sup 13]C = 0.3 to 0.8; [delta][sup 18]O = [minus]8.6 to [minus]11.5) and is interpreted as precipitated in a deep meteoric or burial setting. Depleted [delta][sup 18]O compositions of fibrous calcite reflect addition of post-depositional calcite during stabilization. Most enriched [delta][sup 13]C and [delta][sup 18]O fibrous calcite composition are similar to enriched values from other Middle Ordovician southern Appalachian buildups (other localities of Holston (TN) and Effna (VA) formations) ([delta][sup 13]C = 0.3 to 0.8; [delta][sup 18]O = [minus]3.9 to [minus]4.8) and may reflect fibrous calcite precipitated in isotopic equilibrium with Middle Ordovician sea water.

  4. 27 CFR 9.27 - Lime Kiln Valley.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Lime Kiln Valley. 9.27... Kiln Valley. (a) Name. The name of the viticultural area described in this section is “Lime Kiln Valley.” (b) Approved Map. The appropriate map for determining the boundaries of the Lime Kiln...

  5. 27 CFR 9.27 - Lime Kiln Valley.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Lime Kiln Valley. 9.27... Kiln Valley. (a) Name. The name of the viticultural area described in this section is “Lime Kiln Valley.” (b) Approved Map. The appropriate map for determining the boundaries of the Lime Kiln...

  6. 27 CFR 9.27 - Lime Kiln Valley.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Lime Kiln Valley. 9.27... Kiln Valley. (a) Name. The name of the viticultural area described in this section is “Lime Kiln Valley.” (b) Approved Map. The appropriate map for determining the boundaries of the Lime Kiln...

  7. 27 CFR 9.27 - Lime Kiln Valley.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Lime Kiln Valley. 9.27... Kiln Valley. (a) Name. The name of the viticultural area described in this section is “Lime Kiln Valley.” (b) Approved Map. The appropriate map for determining the boundaries of the Lime Kiln...

  8. 27 CFR 9.27 - Lime Kiln Valley.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Lime Kiln Valley. 9.27... Kiln Valley. (a) Name. The name of the viticultural area described in this section is “Lime Kiln Valley.” (b) Approved Map. The appropriate map for determining the boundaries of the Lime Kiln...

  9. Spectroscopic characterization of natural calcite minerals

    NASA Astrophysics Data System (ADS)

    Gunasekaran, S.; Anbalagan, G.

    2007-11-01

    The FT-IR, FT-Raman, NMR spectral data of ten different limestone samples have been compared. FT-IR and FT-Raman spectral data show that calcium carbonate in limestone, principally in the form of calcite, as identified by its main absorption bands at 1426, 1092, 876 and 712 cm -1. The sharp diffractions at the d-spacings, 3.0348, 1.9166 and 1.8796 confirm the presence of calcite structure and the calculated lattice parameters are: a = 4.9781 Å, c = 17.1188 Å. The range of 13C chemical shifts for different limestone samples is very small, varying from 198.38 to 198.42 ppm. The observed chemical shifts are consistent with the identical C-O bonding in different limestone samples. 27Al MAS NMR spectra of the samples exhibit a central line at 1 ppm and another line at 60 ppm corresponding to octahedral and tetrahedral Al ions, respectively. The five component resonances were observed in 29Si MAS NMR spectrum of limestone and these resonances were assigned to Si (4 Al), Si (3 Al), Si (2 Al), Si (1 Al) and Si (0 Al) from low field to high field.

  10. Use of wastes of the sugar industry as pozzolana in lime-pozzolana binders: Study of the reaction

    SciTech Connect

    Hernandez, J.F.M.; Middendorf, B.; Gehrke, M.; Budelmann, H.

    1998-11-01

    Mineralogical studies of different wastes of the sugar industry, mainly sugar cane bagasse ash and sugar cane straw ash, have shown that such by-products are likely to be pozzolanic. Their use in lime-pozzolana binders could become an interesting alternative for developing countries. This paper presents a study that was aimed at monitoring the reaction between lime and wastes of the sugar industry having pozzolanic properties by evaluating (1) content of calcium hydroxide, dependent on time; (2) development of the pore structure, dependent on time; (3) study on the reaction products at different stages; and (4) mechanical properties of hardened pastes. The presence of calcium hydroxide was confirmed by x-ray diffraction analysis and thermogravimetric analysis of powder from samples of hydrated lime-pozzolana pastes. The reaction products in hydrated pastes were observed in a scanning electron microscope, and the pore structure was assessed using a mercury intrusion porosimeter. The results of the study show that sugar cane bagasse ash does not act like a reactive pozzolana, mainly due to the presence of unburned material and carbon, whereas sugar cane straw ash shows good pozzolanic activity comparable to that of rice husk ash.

  11. Microstructure evolution of lime putty upon aging

    NASA Astrophysics Data System (ADS)

    Mascolo, Giuseppe; Mascolo, Maria Cristina; Vitale, Alessandro; Marino, Ottavio

    2010-08-01

    The microstructure evolution of lime putty upon aging was investigated by slaking quicklime (CaO) with an excess of water for 3, 12, 24, 36, 48 and 66 months. The as-obtained lime putties were characterized in the water retention and in the particle size distribution using the static laser scattering (SLS). The same lime putties, dehydrated by lyophilization, were also investigated in the pore size distribution by mercury intrusion porosimetry, in the surface area by the BET method and, finally, in particle morphology by scanning electron microscopy (SEM). The effect of the extended exposure of quicklime to water confirms a shape change from prismatic crystals of portlandite, Ca(OH) 2, into platelike ones. Simultaneously a growth of larger hexagonal crystals at the expense of the smallest ones (Ostwald ripening) favours a secondary precipitation of submicrometer platelike crystals of portlandite. The shape change and the broader particles size distribution of portlandite crystals upon aging seem to contribute to a better plasticity of lime putty.

  12. A new lime material for container substrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The primary component in greenhouse potting substrates is sphagnum peatmoss. Substrate solution pH of non-amended peatmoss ranges from 4.0 to 4.5. Ideal pH for most greenhouse floriculture crops ranges from 5.8 to 6.2. Dolomitic lime is most often used to elevate substrate pH in peatmoss-based me...

  13. Fertilizer and Lime: Why They Are Used.

    ERIC Educational Resources Information Center

    McCaslin, Judith Strand

    This unit teaching guide is designed to help teachers explain the principles of fertilizer and lime use. The first of four major sections is a teaching outline keyed to transparency masters and student handouts. Thirteen major areas are covered in the teaching outline: (1) plant needs; (2) uses of fertilizer; (3) nutrients for plant growth; (4)…

  14. Neptunium(V) adsorption to calcite

    NASA Astrophysics Data System (ADS)

    Heberling, Frank; Brendebach, Boris; Bosbach, Dirk

    2008-12-01

    The migration behavior of the actinyl ions U(VI)O 22+, Np(V)O 2+ and Pu(V,VI)O 2(+,2+) in the geosphere is to a large extend controlled by sorption reactions (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) with minerals. Here NpO 2+ adsorption onto calcite is studied in batch type experiments over a wide range of pH (6.0-9.4) and concentration (0.4 μM-40 μM) conditions. pH is adjusted by variation of CO 2 partial pressure. Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH. pH dependence of adsorption decreases with increasing Np(V) concentration. EXAFS data of neptunyl adsorbed to calcite and neptunyl in the supernatant shows differences in the Np(V)-O-yl distance, 1.85 ± 0.01 Å for the adsorbed and 1.82 ± 0.01 Å for the solution species. The equatorial environment of the neptunyl in solution shows about 5 oxygen neighbours at 2.45 ± 0.02 Å. For adsorbed neptunyl there are also about 5 oxygen neighbours at 2.46 ± 0.01 Å. An additional feature in the adsorbed species' R-space spectrum can be related to carbonate neighbours, 3 to 6 carbon backscatterers (C-eq) at 3.05 ± 0.03 Å and 3 to 6 oxygen backscatterers (O-eq2) at 3.31 ± 0.02 Å. The differences in the Np(V)-O-yl distance and the C-eq and O-eq2 backscatterers which are only present for the adsorbed species indicate inner-sphere bonding of the adsorbed neptunyl species to the calcite surface. Experiments on adsorption kinetics indicate that after a fast surface adsorption process a continuous slow uptake occurs which may be explained by incorporation via surface dissolution and reprecipitation processes. This is also indicated by the part irreversibility of the adsorption as shown by increased KD values after desorption compared to adsorption.

  15. TOUGH-Fx/Hydrate

    SciTech Connect

    Moridis, George Julius

    2005-02-01

    TOUGH-Fx/HYORATL can model the non-isothermal gas release. phase behavior and flow of fluids and heat in complex geologic media. The code can simulate production from natural gas hydrate deposits in the subsurtace (i.e., in the permafrost and in deep ocean sediments), as well as laboratory experiments of hydrate dissociation/formation in porous/fractured media. T006H-Fx/HYDRATE vi .0 includes both an equilibrium and a kinetic model of hydrate Ibmiation and dissociation. The model accounts for heat and up to four mass components-- i.e., water, CH4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dIssociation or formation, phase changes, and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects, and inhibItor-Induced effects.

  16. TOUGH-Fx/Hydrate

    2005-02-01

    TOUGH-Fx/HYORATL can model the non-isothermal gas release. phase behavior and flow of fluids and heat in complex geologic media. The code can simulate production from natural gas hydrate deposits in the subsurtace (i.e., in the permafrost and in deep ocean sediments), as well as laboratory experiments of hydrate dissociation/formation in porous/fractured media. T006H-Fx/HYDRATE vi .0 includes both an equilibrium and a kinetic model of hydrate Ibmiation and dissociation. The model accounts for heat and upmore » to four mass components-- i.e., water, CH4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dIssociation or formation, phase changes, and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects, and inhibItor-Induced effects.« less

  17. Friction characteristics of Cd-rich carbonate films on calcite surfaces: implications for compositional differentiation at the nanometer scale

    PubMed Central

    2009-01-01

    Lateral Force Microscopy (LFM) studies were carried out on cleaved calcite sections in contact with solutions supersaturated with respect to otavite (CdCO3) or calcite-otavite solid solutions (SS) as a means to examine the potential for future application of LFM as a nanometer-scale mineral surface composition mapping technique. Layer-by-layer growth of surface films took place either by step advancement or by a surface nucleation and step advancement mechanisms. Friction vs. applied load data acquired on the films and the calcite substrate were successfully fitted to the Johnson Kendall Roberts (JKR) model for single asperity contacts. Following this model, friction differences between film and substrate at low loads were dictated by differences in adhesion, whereas at higher load they reflect differences in contact shear strength. In most experiments at fixed load, the film showed higher friction than the calcite surface, but the friction-load dependence for the different surfaces revealed that at low loads (0–40 nN), a calcian otavite film has lower friction than calcite; a result that is contrary to earlier LFM reports of the same system. Multilayer films of calcian-otavite displayed increasing friction with film thickness, consistent with the expectation that the film surface composition will become increasingly Cd-rich with increasing thickness. Both load- and thickness-dependence trends support the hypothesis that the contact shear strength correlates with the hydration enthalpy of the surface ions, thereby imparting friction sensitivity in the LFM to mineral-water interface composition. PMID:19549312

  18. The application of lime sorbents in municipal waste combustors

    SciTech Connect

    Benson, L.; Licata, A.

    1998-07-01

    Lime is the sorbent most utilized to control acid gas emissions from Municipal Waste Combustors (MWCs) throughout the world. Line is safe, economical, and easy to handle. In addition to acid gas controls, lime has been demonstrated to reduce mercury and dioxin emissions when used in spray dryers. Lime also has applications in controlling the leachability of heavy metals from MWC ash. Although lime is used throughout the industry, the authors see many misapplications and misunderstandings of this technology. They have seen the wrong type of silos used as well as the wrong size silos. Slaking is a major problem for some plants because they use the wrong water and lime products. This paper will discuss the selection criteria and economics for lime handling and feeding systems with design data. Definitions and the chemistry of lime will be presented to enable design engineers to better prepare systems specifications. This paper will be beneficial to plants planning to upgrade to the MACT standards.

  19. Emission polarization study on quartz and calcite.

    PubMed

    Vincent, R K

    1972-09-01

    Spectral emission polarization of quartz and calcite polished plates for observation angles of 20 degrees and 70 degrees is calculated by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width (Deltalambda approximately 1.5 microm) spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band (Deltalambda approximately 6microm) for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected mediumwidth filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

  20. A Microkinetic Model of Calcite Step Growth.

    PubMed

    Andersson, M P; Dobberschütz, S; Sand, K K; Tobler, D J; De Yoreo, J J; Stipp, S L S

    2016-09-01

    In spite of decades of research, mineral growth models based on ion attachment and detachment rates fail to predict behavior beyond a narrow range of conditions. Here we present a microkinetic model that accurately reproduces calcite growth over a very wide range of published experimental data for solution composition, saturation index, pH and impurities. We demonstrate that polynuclear complexes play a central role in mineral growth at high supersaturation and that a classical complexation model is sufficient to reproduce measured rates. Dehydration of the attaching species, not the mineral surface, is rate limiting. Density functional theory supports our conclusions. The model provides new insights into the molecular mechanisms of mineral growth that control biomineralization, mineral scaling and industrial material synthesis. PMID:27532505

  1. Dissolution of coccolithophorid calcite by microzooplankton and copepod grazing

    NASA Astrophysics Data System (ADS)

    Antia, A. N.; Suffrian, K.; Holste, L.; Müller, M. N.; Nejstgaard, J. C.; Simonelli, P.; Carotenuto, Y.; Putzeys, S.

    2008-01-01

    Independent of the ongoing acidification of surface seawater, the majority of the calcium carbonate produced in the pelagial is dissolved by natural processes above the lysocline. We investigate to what extent grazing and passage of coccolithophorids through the guts of copepods and the food vacuoles of microzooplankton contribute to calcite dissolution. In laboratory experiments where the coccolithophorid Emiliania huxleyi was fed to the rotifer Brachionus plicatilis, the heterotrophic flagellate Oxyrrhis marina and the copepod Acartia tonsa, calcite dissolution rates of 45-55%, 37-53% and 5-22% of ingested calcite were found. We ascribe higher loss rates in microzooplankton food vacuoles as compared to copepod guts to the strongly acidic digestion and the individual packaging of algal cells. In further experiments, specific rates of calcification and calcite dissolution were also measured in natural populations during the PeECE III mesocosm study under differing ambient pCO2 concentrations. Microzooplankton grazing accounted for between 27 and 70% of the dynamic calcite stock being lost per day, with no measurable effect of CO2 treatment. These measured calcite dissolution rates indicate that dissolution of calcite in the guts of microzooplankton and copepods can account for the calcite losses calculated for the global ocean using budget and model estimates.

  2. Transformation of echinoid Mg calcite skeletons by heating

    NASA Astrophysics Data System (ADS)

    Dickson, J. A. D.

    2001-02-01

    Interambularcral plates of echinoid Heterocentrotus trigonarius, composed of Mg calcite 1 (≈14 mol% MgCO 3), were heated in three timed series of experiments at 300°C. Dried plate fragments and fragments with added water were heated separately in pressurized bombs. X-ray powder diffractometry, unit cell dimensions, and phase compositions are used to monitor reaction progress. After 10 h heating in the bombs dolomite (43.5 mol% MgCO 3) and Mg calcite appear (4-7 mol% MgCO 3); by 20 h all Mg calcite 1 is consumed, and at 120 h dolomite composition has evolved to ≈47 mol% MgCO 3 and calcite to ≈2 mol% MgCO 3. Whole plates heated at 300°C in an open muffle furnace develop dolomite (≈42 mol% MgCO 3) and Mg calcite 2 (≈6 mol% MgCO 3) after 10 h and remain compositionally invariant throughout subsequent heating to 620 h. Limited skeletal water catalyzes the early reaction but escapes from the open furnace and consequently reaction ceases after ≈10 h. The experimentally produced dolomite has relative Mg-Ca ordering of 75% to 79%. The stabilization of echinoid Mg calcite by heating at 300°C to a mixture of dolomite and calcite occurs through a dissolution/precipitation reaction. The alteration fabric produced within the stereom consists of irregularly shaped, branched dolomite crystals > 5 μm homoaxially set in a calcite 2 (bomb) or Mg calcite 2 (furnace) matrix. Round and tubular pores 1 to 5 μm are randomly distributed throughout this fabric. The stereom pore system remains intact during furnace heating but is destroyed during heating in bombs. The texture of experimentally stabilized echinoid skeletons is different from that of fossil echinoderms that are composed of microrhomic dolomite homoaxially set in a single calcite crystal.

  3. Hydration rate of obsidian.

    PubMed

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years. PMID:17782901

  4. Hydration rate of obsidian.

    PubMed

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  5. Methane Hydrates: Chapter 8

    USGS Publications Warehouse

    Boswell, Ray; Yamamoto, Koji; Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott

    2008-01-01

    Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be

  6. Here's butane hydrates equilibria

    SciTech Connect

    Peettman, F.H.

    1984-06-01

    In 1961 McLeod and Campbell studied hydrates formation for binary mixtures of methane with ethane through butane at pressures up to 10,000 psia. Their data showed that butane lowered the pressure of hydrate formation for methane up to pressures ranging from 1,500 to 2,000 psia. At pressures above this range methane-n-butane mixtures generally followed the curve for pure methane or were slightly above it. McLeod and Campbell conclude that the crystal lattice is deformed at higher pressures (above 6,000 psia) and that hydrate composition on a water-free basis is the same as the gas.

  7. Combustion of Methane Hydrate

    NASA Astrophysics Data System (ADS)

    Roshandell, Melika

    A significant methane storehouse is in the form of methane hydrates on the sea floor and in the arctic permafrost. Methane hydrates are ice-like structures composed of water cages housing a guest methane molecule. This caged methane represents a resource of energy and a potential source of strong greenhouse gas. Most research related to methane hydrates has been focused on their formation and dissociation because they can form solid plugs that complicate transport of oil and gas in pipelines. This dissertation explores the direct burning of these methane hydrates where heat from the combustion process dissociates the hydrate into water and methane, and the released methane fuels the methane/air diffusion flame heat source. In contrast to the pipeline applications, very little research has been done on the combustion and burning characteristics of methane hydrates. This is the first dissertation on this subject. In this study, energy release and combustion characteristics of methane hydrates were investigated both theoretically and experimentally. The experimental study involved collaboration with another research group, particularly in the creation of methane hydrate samples. The experiments were difficult because hydrates form at high pressure within a narrow temperature range. The process can be slow and the resulting hydrate can have somewhat variable properties (e.g., extent of clathration, shape, compactness). The experimental study examined broad characteristics of hydrate combustion, including flame appearance, burning time, conditions leading to flame extinguishment, the amount of hydrate water melted versus evaporated, and flame temperature. These properties were observed for samples of different physical size. Hydrate formation is a very slow process with pure water and methane. The addition of small amounts of surfactant increased substantially the hydrate formation rate. The effects of surfactant on burning characteristics were also studied. One finding

  8. Effect of Microorganism Sporosarcina pasteurii on the Hydration of Cement Paste.

    PubMed

    Lee, Jun Cheol; Lee, Chang Joon; Chun, Woo Young; Kim, Wha Jung; Chung, Chul-Woo

    2015-08-01

    Years of research have shown that the application of microorganisms increases the compressive strength of cement-based material when it is cured in a culture medium. Because the compressive strength is strongly affected by the hydration of cement paste, this research aimed to investigate the role of the microorganism Sporosarcina pasteurii in hydration of cement paste. The microorganism's role was investigated with and without the presence of a urea-CaCl2 culture medium (i.e., without curing the specimens in the culture medium). The results showed that S. pasteurii accelerated the early hydration of cement paste. The addition of the urea-CaCl2 culture medium also increased the speed of hydration. However, no clear evidence of microbially induced calcite precipitation appeared when the microorganisms were directly mixed with cement paste. PMID:25876598

  9. Fly ash as a liming material for corn production

    SciTech Connect

    Tarkalson, D.D.; Hergert, G.W.; Stevens, W.B.; McCallister, D.L.; Kackman, S.D.

    2005-05-01

    Fly ash produced as a by-product of subbituminous coal combustion can potentially serve as an alternative liming material without negatively affecting corn (Zea mays L.) production in areas where use of conventional liming materials can be uneconomical due to transportation costs. A study was conducted to determine if fly ash produced from the Nebraska Public Power District Gerald Gentleman Power Station located in Sutherland, NE could be used as an alternative liming material. Combinations of dry fly ash (DFA), wet fly ash (WFA), beet lime (by-product of sugar beet (Beta vulgaris L.) processing) (BL), and agricultural lime (AGL) were applied at rates ranging from 0.43 to 1.62 times the recommended lime rate to plots on four acidic soils (Anselmo fine sandy loam, Hord fine sandy loam, Holdrege sandy loam, and Valentine fine sand). Soil samples were collected to a depth of 0.2 m from plots and analyzed for pH before lime applications and twice periodically after lime application. The Hord and Valentine soils were analyzed for exchangeable Ca, Mg, K, Na,and Al for determination of percent Al saturation on selected treatments and sampling dates. Corn grain yields were determined annually. It is concluded that the fly ash utilized in this study and applied at rates in this study, increases soil pH comparable to agricultural lime and is an appropriate alternative liming material.

  10. Transformations in methane hydrates

    USGS Publications Warehouse

    Chou, I.-Ming; Sharma, A.; Burruss, R.C.; Shu, J.; Mao, Ho-kwang; Hemley, R.J.; Goncharov, A.F.; Stern, L.A.; Kirby, S.H.

    2000-01-01

    Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) A?? and volume V = 5051.3(13) A??3; structure H at 600 MPa has a hexagonal unit cell of a = 11.980(2) A??, c = 9.992(3) A??, and V = 1241.9(5) A??3. The compositions of these two investigated phases are still not known. With the effects of pressure and the presence of other gases in the structure, the structure II phase is likely to dominate over the known structure I methane hydrate within deep hydrate-bearing sediments underlying continental margins.

  11. Withdrawing Nutrition, Hydration

    Cancer.gov

    Module eleven of the EPEC-O Self-Study Original Version discusses the general aspects of withholding or withdrawing of life-sustaining therapies, and presents a specific application to artificial nutrition and hydration.

  12. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NASA Astrophysics Data System (ADS)

    Wolthers, Mariëtte; Nehrke, Gernot; Gustafsson, Jon Petter; Van Cappellen, Philippe

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the chemical structure of the calcite-aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy (AFM, Teng et al., 2000; Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.

  13. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    USGS Publications Warehouse

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  14. Strontium incorporation into calcite generated by bacterial ureolysis

    NASA Astrophysics Data System (ADS)

    Fujita, Yoshiko; Redden, George D.; Ingram, Jani C.; Cortez, Marnie M.; Ferris, F. Grant; Smith, Robert W.

    2004-08-01

    Strontium incorporation into calcite generated by bacterial ureolysis was investigated as part of an assessment of a proposed remediation approach for 90Sr contamination in groundwater. Urea hydrolysis produces ammonium and carbonate and elevates pH, resulting in the promotion of calcium carbonate precipitation. Urea hydrolysis by the bacterium Bacillus pasteurii in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho resulted in a pH rise from 7.5 to 9.1. Measured average distribution coefficients (D EX) for Sr in the calcite produced by ureolysis (0.5) were up to an order of magnitude higher than values reported in the literature for natural and synthetic calcites (0.02-0.4). They were also higher than values for calcite produced abiotically by ammonium carbonate addition (0.3). The precipitation of calcite in these experiments was verified by X-ray diffraction. Time-of-flight secondary ion mass spectrometry (ToF SIMS) depth profiling (up to 350 nm) suggested that the Sr was not merely sorbed on the surface, but was present at depth within the particles. X-ray absorption near edge spectra showed that Sr was present in the calcite samples as a solid solution. The extent of Sr incorporation appeared to be driven primarily by the overall rate of calcite precipitation, where faster precipitation was associated with greater Sr uptake into the solid. The presence of bacterial surfaces as potential nucleation sites in the ammonium carbonate precipitation treatment did not enhance overall precipitation or the Sr distribution coefficient. Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of 90Sr contamination in environments where calcite is stable over the long term.

  15. Liming of acidified waters: issues and research - a report of the International Liming Workshop

    USGS Publications Warehouse

    Schreiber, R. Kent

    1982-01-01

    Acidic deposition is a problem of significant national and international concern. It is strongly suspected that acidic deposition has adversely affected aquatic resources in Scandinavia and North America. While substantial resources are being devoted to understanding the causative factors associated with surface water acidification, much less research is being conducted on mitigative strategies. Mitigative techniques involving liming may be useful for short-term protection of specific component of aquatic communities or for renovation of seriously impacted aquatic ecosystems. The selection of effective liming strategies is based on an integrated understanding of the following key factors: biological systems, water chemistry, sediment chemistry, hydrology, and watershed characteristics, effectiveness of neutralizing materials, and application techniques. Research in Scandinavia, Canada, and the U.S. has led to a partial understanding of some of the key factors for successful neutralization of surface waters (Bengtsson, 1982; Fraser and Britt, 1982). However, conflicting results of liming operations and experiments have been reported. (Fraser et al., 1982; Fraser and Britt, 1982; Sverdrup and Bjerle, 1982). Additional research is required to improve the ability of scientists and resource managers to select effective liming strategies. An International Liming workshop was convened during 19-25 September 1982 at the University of Washington's Friday Harbor Laboratories. The major objective of this workshop were: - To identify the most critical deficiencies in the scientific understanding of liming techniques and their long-term consequences. - To develop and document a research strategy to address information deficiencies that are pertinent to the protection or renovation of acidic surface waters in the United States. The participants who contributed to this workshop are listed in Table 1.

  16. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface.

    PubMed

    Wolthers, M; Di Tommaso, D; Du, Z; de Leeuw, N H

    2012-11-21

    Calcite-water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different surface sites is distinct. In addition to observing the expected formation of more calcium-water interactions and hydrogen-bonds at lower-coordinated sites, we also observed subtle differences in hydrogen bonding around acute versus obtuse edges and corners. We subsequently used this information to refine the protonation constants for the calcite surface sites, according to the Charge Distribution MUltiSite Ion Complexation (CD-MUSIC) approach. The subtle differences in hydrogen bonding translate into markedly different charging behaviour versus pH, in particular for acute versus obtuse corner sites. The results show quantitatively that calcite surface reactivity is directly related to surface topography. The information obtained in this study is not only crucial for the improvement of existing macroscopic surface models of the reactivity of calcite towards contaminants, but also improves our atomic-level understanding of mineral-water interactions.

  17. Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips.

    PubMed

    Wastl, Daniel S; Judmann, Michael; Weymouth, Alfred J; Giessibl, Franz J

    2015-01-01

    Characterization and imaging at the atomic scale with atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomically resolved imaging of the calcite (101̅4) surface plane using stiff quartz cantilevers ("qPlus sensors", stiffness k = 1280 N/m) equipped with sapphire tips in ambient conditions without any surface preparation. With 10 atoms in one surface unit cell, calcite has a highly complex surface structure comprising three different chemical elements (Ca, C, and O). We obtain true atomic resolution of calcite in air at relative humidity ranging from 20% to 40%, imaging atomic steps and single atomic defects. We observe a great durability of sapphire tips with their Mohs hardness of 9, only one step below diamond. Depending on the state of the sapphire tip, we resolve either the calcium or the oxygen sublattice. We determine the tip termination by comparing the experimental images with simulations and discuss the possibility of chemical tip identification in air. The main challenges for imaging arise from the presence of water layers, which form on almost all surfaces and have the potential to dissolve the crystal surface. Frequency shift versus distance spectra show the presence of at least three ordered hydration layers. The measured height of the first hydration layer corresponds well to X-ray diffraction data and molecular dynamic simulations, namely, ∼220 pm. For the following hydration layers we measure ∼380 pm for the second and third layer, ending up in a total hydration layer thickness of at least 1 nm. Understanding the influence of water layers and their structure is important for surface segregation, surface reactions including reconstructions, healing of defects, and corrosion.

  18. Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips.

    PubMed

    Wastl, Daniel S; Judmann, Michael; Weymouth, Alfred J; Giessibl, Franz J

    2015-01-01

    Characterization and imaging at the atomic scale with atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomically resolved imaging of the calcite (101̅4) surface plane using stiff quartz cantilevers ("qPlus sensors", stiffness k = 1280 N/m) equipped with sapphire tips in ambient conditions without any surface preparation. With 10 atoms in one surface unit cell, calcite has a highly complex surface structure comprising three different chemical elements (Ca, C, and O). We obtain true atomic resolution of calcite in air at relative humidity ranging from 20% to 40%, imaging atomic steps and single atomic defects. We observe a great durability of sapphire tips with their Mohs hardness of 9, only one step below diamond. Depending on the state of the sapphire tip, we resolve either the calcium or the oxygen sublattice. We determine the tip termination by comparing the experimental images with simulations and discuss the possibility of chemical tip identification in air. The main challenges for imaging arise from the presence of water layers, which form on almost all surfaces and have the potential to dissolve the crystal surface. Frequency shift versus distance spectra show the presence of at least three ordered hydration layers. The measured height of the first hydration layer corresponds well to X-ray diffraction data and molecular dynamic simulations, namely, ∼220 pm. For the following hydration layers we measure ∼380 pm for the second and third layer, ending up in a total hydration layer thickness of at least 1 nm. Understanding the influence of water layers and their structure is important for surface segregation, surface reactions including reconstructions, healing of defects, and corrosion. PMID:25816927

  19. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  20. Paleoclimatic and paleohydrologic records from secondary calcite: Yucca Mountain, Nevada

    SciTech Connect

    Whelan, J.F.; Stuckless, J.S.; Moscati, R.J.; Vaniman, D.T.

    1994-12-31

    Stable isotope analyses of calcite and opal, fluid inclusion formation conditions and gas compositions, Sr isotope ratios, and REE compositions all support formation of secondary calcite in the unsaturated zone of Yucca Mountain from infiltration of surface-derived (and soil zone buffered) waters of meteoric origin. Detailed sampling of growth-banding preserved by the secondary calcite should provide a record of past variations in the stable isotope chemistry of these infiltrating waters, and, hence, of precipitation at Yucca Mountain, i.e., a proxy of past climate at Yucca Mountain. The precision of this record depends on how well it can be dated. The distribution and texture of secondary calcite occurrences, if mapped in careful detail from existing bore hole samples and underground workings (as exposures become accessible), could provide a time/space map of fracture and fault unsaturated-zone ground water flow-paths during past wetter climates which might prevail in the future with change in climate.

  1. Kinetics and Mechanisms of Calcite Reactions with Saline Waters

    SciTech Connect

    Chapman, Piers; *Morse, John W.

    2010-11-15

    1. Objective The general objective of this research was to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, carbon dioxide partial pressure (pCO2), and modest ranges of T and P. This would be done by studying both reaction rates and solubility from changes in solution chemistry. Also, nanoscale observations of calcite surface morphology and composition would be made to provide an understanding of rate controlling mechanisms.

  2. Mg isotope fractionation during calcite precipitation: An experimental study

    NASA Astrophysics Data System (ADS)

    Saulnier, Ségolène; Rollion-Bard, Claire; Vigier, Nathalie; Chaussidon, Marc

    2012-08-01

    Experimental precipitations of calcite and other carbonate minerals were performed under various conditions of pH, temperature and solution Mg/Ca to determine the Mg partition coefficient and Mg isotope fractionation. Fifteen experiments were performed at pH ranging from 7.41 ± 0.07 to 8.51 ± 0.39, temperature ranging from 16.2 ± 0.7 to 26.5 ± 0.3 °C and Mg/Casolution ranging from 0.11 to 0.52 mol/mol. The apparent Mg partition coefficient between calcite and solution (DMg) spans a large range of values from 0.018 ± 0.014 to 0.15 ± 0.11 and carbonate Mg isotope fractionation (Δ26Mg) ranges from -2.53 ± 0.25‰ to -1.33 ± 0.14‰ and does not correlate with either pH or temperature. The range in DMg and Δ26Mg suggests non-equilibrium partitioning controlled by the processes of calcite growth, i.e. mixing between calcite grown at equilibrium and fluid inclusions, and entrapment of a surface Mg-rich calcite layer in isotopic equilibrium with the solution. The equilibrium Mg isotope fractionation between inorganic calcite and solution is estimated to be -2.13 ± 0.24‰. Additional Mg elemental and isotopic fractionations are observed to occur during biogenic formation of calcite due to variable removal of Mg by the organisms (high-Mg calcite corals, foraminifera) of seawater Mg from their calcification medium.

  3. Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate

    SciTech Connect

    Mesbah, Adel; Cau-dit-Coumes, Celine; Frizon, Fabien

    2012-08-15

    Decommissioning of old nuclear reactors may produce waste streams containing chlorides and carbonates, including radioactive {sup 36}Cl{sup -} and {sup 14}CO{sub 3}{sup 2-}. Their insolubilization by calcium monosulfoaluminate hydrate was investigated. Carbonates were readily depleted from the solution, giving at thermodynamic equilibrium monocarboaluminate, monocarboaluminate + calcite, or calcite only, depending on the initial ratio between the anion and calcium monosulfoaluminate hydrate. Chloride ions reacted more slowly and were precipitated as Kuzel's salt, Kuzel's and Friedel's salts, or Friedel's salt only. Rietveld refinement of X-Ray powder diffraction patterns was successfully used to quantify the phase distributions, which were compared to thermodynamic calculations. Moreover, analysing the lattice parameters of Kuzel's salt as a function of its chloride content showed the occurrence of a restricted solid solution towards the sulfate side with general formula 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}xCaCl{sub 2}{center_dot}(1 - x)CaSO{sub 4}{center_dot}(12 - 2x){center_dot}H{sub 2}O (0.36 {<=} x {<=} 0.50).

  4. Natural gas hydrates

    SciTech Connect

    Sloan, E.D. Jr. )

    1991-12-01

    This paper reports on gas clathrates (commonly called hydrates), which are crystalline compounds that occur when water form a cage-like structure around smaller guest molecules. Gas hydrates of interest to the natural gas hydrocarbon industry are composed of water and eight molecules: methane, ethane, propane, isobutane, normal butane, nitrogen, carbon dioxide, and hydrogen sulfide. Hydrate formation is possible in any place where water exists with such molecules - in natural or artificial environments and at temperatures above and below 32{degrees} F when the pressure is elevated. Hydrates are considered a nuisance because they block transmission lines, plug blowout preventers, jeopardize the foundations of deepwater platforms and pipelines, cause tubing and casing collapse, and foul process heat exchangers, valves, and expanders. Common examples of preventive measures are the regulation of pipeline water content, unusual drilling-mud compositions, and large quantities of methanol injection into pipelines. We encounter conditions that encourage hydrate formation as we explore more unusual environments for gas and oil, including deepwater frontiers and permafrost regions.

  5. Capture of gas-phase arsenic oxide by lime: kinetic and mechanistic studies.

    PubMed

    Jadhav, R A; Fan, L S

    2001-02-15

    Trace metal emission from coal combustion is a major concern for coal-burning utilities. Toxic compounds such as arsenic species are difficult to control because of their high volatility. Mineral sorbents such as lime and hydrated lime have been shown to be effective in capturing arsenic from the gas phase over a wide temperature range. In this study, the mechanism of interaction between arsenic oxide (As2O3) and lime (CaO) is studied over the range of 300-1000 degrees C. The interaction between these two components is found to depend on the temperature; tricalcium orthoarsenate (Ca3As2O8) is found to be the product of the reaction below 600 degrees C, whereas dicalcium pyroarsenate (Ca2As2O7) is found to be the reaction product in the range of 700-900 degrees C. Maximum capture of arsenic oxide is found to occur in the range of 500-600 degrees C. At 500 degrees C, a high reactivity calcium carbonate is found to capture arsenic oxide by a combination of physical and chemical adsorption. Intrinsic kinetics of the reaction between calcium oxide and arsenic oxide in the medium-temperature range of 300-500 degrees C is studied in a differential bed flow-through reactor. Using the shrinking core model, the order of reaction with respect to arsenic oxide concentration is found to be about 1, and the activation energy is calculated to be 5.1 kcal/mol. The effect of initial surface area of CaO sorbent is studied over a range of 2.7-45 m2/g using the grain model. The effect of other major acidic flue gas species (SO2 and HCl) on arsenic capture is found to be minimal under the conditions of the experiment. PMID:11349294

  6. Sulfate attack in lime-treated subbases

    SciTech Connect

    Day, D.C.; Salami, M.R.; Rollings, R.S.

    1995-06-01

    Sulfate-induced heave or buckling in pavements is the phenomenon that occurs when the calcium in various lime-based stabilizers combines with the alumina and sulfate present in clay to form calcium sulfoaluminate, or ettringite. Ettringite, a crystal, can grow between clay particles, pushing them apart and causing swelling in the soil. When this happens in pavement subbases, the resulting heaving may cause the pavement to rupture and fail, sometimes in a dramatic way. In this paper the authors examine the mechanism of sulfate attack, review some of the work done on this problem, and present some examples of pavement failures.

  7. Calcite Farming at Hollow Ridge Cave: Calibrating Net Rainfall and Cave Microclimate to Dripwater and Calcite Chemical Variability

    NASA Astrophysics Data System (ADS)

    Tremaine, D. M.; Kilgore, B. P.; Froelich, P. N.

    2012-04-01

    Stable isotope (δ18O and δ13C) and trace element records in cave speleothems are often interpreted as climate changes in rainfall amount or source, cave air temperature, overlying vegetation and atmospheric pCO2. However, these records are difficult to verify without in situ calibration of changes in cave microclimate (e.g., net rainfall, interior ventilation changes) to contemporaneous variations in dripwater and speleothem chemistry. In this study at Hollow Ridge Cave (HRC) in Marianna, Florida (USA), cave dripwater, bedrock, and modern calcite (farmed in situ) were collected in conjunction with continuous cave air pCO2, temperature, barometric pressure, relative humidity, radon-222 activity, airflow velocity and direction, rainfall amount, and drip rate data [1]. We analyzed rain and dripwater δD and δ18O, dripwater Ca2+, pH, δ13C and TCO2, cave air pCO2 and δ13C, and farmed calcite δ18O and δ13C to examine the relationships among rainwater isotopic composition, cave air ventilation, cave air temperature, calcite growth rate and seasonal timing, and calcite isotopic composition. Farmed calcite δ13C decreases linearly with distance from the front entrance to the interior of the cave during all seasons, with a maximum entrance-to-interior gradient of Δδ13C = -7‰ . A whole-cave "Hendy test" at distributed contemporaneous farming sites reveals that ventilation induces a +1.9 ± 0.96‰ δ13C offset between calcite precipitated in a ventilation flow path and out of flow paths. Farmed calcite δ18O exhibits a +0.82 ± 0.24‰ offset from values predicted by both theoretical calcite-water calculations and by laboratory-grown calcite [2]. Unlike calcite δ13C, oxygen isotopes show no ventilation effects and are a function only of temperature. Combining our data with other speleothem studies, we find a new empirical relationship for cave-specific water-calcite oxygen isotope fractionation across a range of temperatures and cave environments: 1000 ln α = 16

  8. HYDRATE CORE DRILLING TESTS

    SciTech Connect

    John H. Cohen; Thomas E. Williams; Ali G. Kadaster; Bill V. Liddell

    2002-11-01

    The ''Methane Hydrate Production from Alaskan Permafrost'' project is a three-year endeavor being conducted by Maurer Technology Inc. (MTI), Noble, and Anadarko Petroleum, in partnership with the U.S. DOE National Energy Technology Laboratory (NETL). The project's goal is to build on previous and ongoing R&D in the area of onshore hydrate deposition. The project team plans to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope includes drilling and coring one well on Anadarko leases in FY 2003 during the winter drilling season. A specially built on-site core analysis laboratory will be used to determine some of the physical characteristics of the hydrates and surrounding rock. Prior to going to the field, the project team designed and conducted a controlled series of coring tests for simulating coring of hydrate formations. A variety of equipment and procedures were tested and modified to develop a practical solution for this special application. This Topical Report summarizes these coring tests. A special facility was designed and installed at MTI's Drilling Research Center (DRC) in Houston and used to conduct coring tests. Equipment and procedures were tested by cutting cores from frozen mixtures of sand and water supported by casing and designed to simulate hydrate formations. Tests were conducted with chilled drilling fluids. Tests showed that frozen core can be washed out and reduced in size by the action of the drilling fluid. Washing of the core by the drilling fluid caused a reduction in core diameter, making core recovery very difficult (if not impossible). One successful solution was to drill the last 6 inches of core dry (without fluid circulation). These tests demonstrated that it will be difficult to capture core when drilling in permafrost or hydrates without implementing certain safeguards. Among the coring tests was a simulated hydrate formation comprised of coarse, large

  9. Controls on Calcite Solubility in Metamorphic and Magmatic Fluids

    NASA Astrophysics Data System (ADS)

    Manning, C. E.; Eguchi, J.; Galvez, M.

    2015-12-01

    Calcite is an important hydrothermal alteration product in a wide range of environments. The role of calcite in hydrothermal alteration depends on its solubility in geologic fluids, especially H2O. At ambient T and P, calcite solubility is low and it exhibits well-known declining, or "reverse", solubility with rising T. However, experimental and theoretical studies show that increasing P yields higher solubility and restricts the region of reverse solubility behavior to higher temperature. At 0.2 GPa the reverse solubility region lies at T>600°C; at 0.5 GPa, >800°C. Thus, whereas calcite possesses relatively low solubility in pure H2O in shallow hydrothermal systems (typically <10 ppm C), it is substantially more soluble at conditions of middle and lower crustal metamorphism and magmatism, reaching concentrations ≥1000 ppm. At the higher P of subduction zones, aragonite solubility in H2O is even greater. Thus, neglecting other solubility controls, calcite precipitation is favored as crustal fluids cool and/or decompress. However, the solubility of calcite in H2O also depends strongly on other solutes, pH, and fO2. Sources of alkalinity decrease calcite solubility. In contrast, sources of acidity such as CO2 and Cl increase solubility. Crustal fluids can be enriched in alkali halides such as NaCl. Calcite solubility increases with increasing salt content at a given P and T. From approximately seawater salinity to salt saturation, the fluid behaves as a dilute molten salt and calcite solubility increases as the square of the salt mole fraction regardless of the alkali (Li, Na, K, Cs) or halogen (F, Cl, Br, I) considered. Similar behavior is seen in mixed salt solutions. At lower salinities, solubility behavior is as expected in dilute electrolyte solutions. The transition from dilute electrolyte to molten salt is fundamental to the properties of crustal fluids. Reduction of carbonate species or CO2 in the fluid to CH4, which is common during serpentinization of

  10. The relative merits of dolomitic and calcitic limestone in detoxifying and revegetating acidic, nickel- and copper-contaminated soils in the Sudbury mining and smelting region of Canada

    SciTech Connect

    McHale, D.; Winterhalder, K.

    1996-12-31

    Soils in the Sudbury mining and smelting region have been rendered phytotoxic and barren by acidification and Particulate metal contamination, but can be detoxified revegetated by the surface application of an growth is better on soil treated ground limestone. On certain barren sites, plant growth is better on soil treated with dolomitic limestone than with calcitic limestone and greenhouse experiments using mung beans (Vigna radiata) have shown superior root and shoot growth on certain contaminated soils when the limestone is dolomitic rather than calcitic. Results of experiments with species used in revegetation (Agrostis gigantea and Lotus corniculatus) suggest that leguminous species are more sensitive to Ca:Mg ratio than grasses, that the plant response to this ratio is greater at lowering liming levels, and that the response is more marked on more toxic soils. The effects of calcium:magnesium ratio of the limestone used in revegetating acidic, metal-contaminated soils are clearly complex, interactive and difficult to interpret. Further studies are needed, but meanwhile it is recommended that the practice of using dolomitic limestone to detoxify barren Sudbury soils be continued, since there is a risk of induced magnesium deficiency at certain sites when calcitic limestone is used.

  11. Preheating and incubation of cane juice prior to liming: a comparison of intermediate and cold lime clarification.

    PubMed

    Eggleston, Gillian; Monge, Adrian; Pepperman, Armand

    2002-01-30

    In the U.S., cold lime clarification remains the clarification process of choice in raw sugar manufacturing. A comparative study of cold vs intermediate lime clarification was undertaken at a factory that operated intermediate liming (approximately 30% mixed juice (MJ) of pH 5.2 +/- 0.3 was preheated to 87-93 degrees C to help maintain clean limed juice heaters, incubated at approximately 54 degrees C, and then limed) but still had the pipes to revert to cold liming (MJ incubated and limed at approximately 40 degrees C) for this study. Hourly samples were collected over a 6 h sampling period across cold and intermediate clarification processes on two consecutive days, respectively, and this was repeated three times across the 1999 grinding season. A total of 1.57% less sucrose was lost to inversion reactions across intermediate rather than cold liming. In intermediate liming, which required approximately 4.6% less lime, preheating of only 30% of the MJ markedly removed color (-29%), dextran (-10%), and starch (-24%) and caused large flocs to form that settled faster in the clarifiers. Faster settling led to an impressive 4.6% (season average) more turbidity removal across the clarifiers in intermediate rather than cold liming. Intermediate clarified juice (CJ) turbidity (season average 2028 ICU +/- 675) was approximately half of cold CJ turbidity (average 3952 ICU +/- 1450) with over 2-fold more CJ turbidity control. Subsequent turbidity values and control were significantly improved in the final evaporator syrup samples too. For both processes, juice incubation caused approximately 10% color removal, but this was offset by color formation on liming, because of the alkaline degradation of invert; however, overall, more color was removed than formed in intermediate liming. Starch was reduced in the incubator tank, for both processes, because added filtrate reduced the acidity enabling natural diastase from the cane to degrade starch. Some dextran occasionally formed

  12. Investigation of Copper Sorption by Sugar Beet Processing Lime Waste

    EPA Science Inventory

    In the western United States, sugar beet processing for sugar recovery generates a lime-based waste product (~250,000 Mg yr-1) that has little liming value in the region’s calcareous soils. This area has recently experienced an increase in dairy production, with dairi...

  13. 76 FR 82295 - Central Power & Lime LLC; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-30

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Central Power & Lime LLC; Notice of Filing December 23, 2011. Take notice that on December 22, 2011, Central Power & Lime LLC, pursuant to sections 18 CFR 292.205(c) and...

  14. Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum

    NASA Astrophysics Data System (ADS)

    Kumar, Sujeet; Dutta, Rakesh Kumar; Mohanty, Bijayananda

    2014-12-01

    Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

  15. Lime slurry use at the Industrial Wastewater Pretreatment Facility

    SciTech Connect

    Rice, L.E.; Hughes, R.W.; Baggett, G.

    1996-04-01

    The use of lime slurry at the IWPF demonstrated many benefits. Hazardous chemical use was reduced, solids handling was improved, water quality was enhanced and there has been a cost savings. The lime slurry also enabled the plant to begin treating the soluble oil waste, which we were not able to do in the past.

  16. Mitigation of acid deposition: Liming of surface waters. Final report

    SciTech Connect

    Bartoshesky, J.; Price, R.; DeMuro, J.

    1989-05-01

    In recent years acid deposition has become a serious concern internationally. Scientific literature has documented the acidification of numerous lakes and streams in North America and Scandinavia resulting in the depletion or total loss of fisheries and other aquatic biota. Liming represents the only common corrective practice aimed specifically at remediating an affected acid receptor. This report reviews a range of liming technologies and liming materials, as well as the effect of surface-water liming on water quality and aquatic biota. As background to the liming discussion, the hydrologic cycle and the factors that make surface waters sensitive to acid deposition are also discussed. Finally, a brief review of some of the liming projects that have been conducted, or are currently in operation is presented, giving special emphasis to mitigation efforts in Maryland. Liming has been effectively used to counteract surface-water acidification in parts of Scandinavia, Canada, and the U.S. To date, liming has generally been shown to improve physical and chemical conditions and enhance the biological recovery of aquatic ecosystems affected by acidification.

  17. 46 CFR 148.230 - Calcium oxide (lime, unslaked).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF BULK SOLID... of this part and the dangerous cargo manifest requirements in § 148.70 of this part do not apply to... (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in...

  18. 46 CFR 148.230 - Calcium oxide (lime, unslaked).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF BULK SOLID... of this part and the dangerous cargo manifest requirements in § 148.70 of this part do not apply to... (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in...

  19. 46 CFR 148.230 - Calcium oxide (lime, unslaked).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF BULK SOLID... of this part and the dangerous cargo manifest requirements in § 148.70 of this part do not apply to... (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in...

  20. 46 CFR 148.230 - Calcium oxide (lime, unslaked).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF BULK SOLID... of this part and the dangerous cargo manifest requirements in § 148.70 of this part do not apply to... (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in...

  1. Immobilization of lead and cadmium in solid residues from the combustion of refuse using lime and phosphate

    SciTech Connect

    O'Hara, M.J.; Surgi, M.R.

    1988-04-12

    This patent describes a method of immobilizing lead and cadmium in a free flowing particulate dry solid residue which maintains its free flowing particulate nature after the immobilizing treatment. The dry solid residue comprises fly ash and mixtures of fly ash with bottom ash resulting from the incineration of municipal waste, comprising contacting the dry solid residue with at least one water soluble phosphate in an amount equivalent to about 1 to about 8% by weight of phosphoric acid based on the total residue in the presence of a free lime source selected from the group consisting of lime, hydrated lime, flue gas scrubber product, and combinations thereof, in an amount sufficient to furnish from about 1 to about 25 parts by weight calcium hydroxide per 5 parts by weight of fly ash whereby the leaching of cadmium and lead is reduced to a level no more than 1 ppm cadium and 5 ppm lead as determined in an EPA test performed on the resulting dry treated residue.

  2. Photoinduced synthesis of single-digit micrometer-size spheroidal calcite composites in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-06-01

    Photoinduced crystallization of calcium carbonate (CaCO3), which was based on the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphyenyl)propionic acid) under alkaline conditions of pH 8.4 and 10 was studied for preparation of CaCO3 composite particles in single-digit micrometer-sizes. In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol%) was used as a precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. After the UV irradiation for 50 min, calcite spheroids in single-digit micrometer-sizes were obtained as major products at pH 8.4. The obtained calcite spheroids contained organic components of about 10 wt%. The comparison of the characteristics of the CaCO3 obtained at pH 8.4 and 10 suggests that the nucleation and crystallization of both vaterite and calcite continuously took place in a moderated supersaturation owing to the CO2 hydration equilibrium as long as the photodecarboxylation of KP continued. Consequently, the aggregation-based crystal growth in the presence of PVAPS seemed to enable the formation of the spheroidal composites of calcite in single-digit micrometer-sizes.

  3. Dynamics of protein hydration water.

    PubMed

    Wolf, M; Emmert, S; Gulich, R; Lunkenheimer, P; Loidl, A

    2015-09-01

    We present the frequency- and temperature-dependent dielectric properties of lysozyme solutions in a broad concentration regime, measured at subzero temperatures, and compare the results with measurements above the freezing point of water and on hydrated lysozyme powder. Our experiments allow examining the dynamics of unfreezable hydration water in a broad temperature range. The obtained results prove the bimodality of the hydration shell dynamics. In addition, we find indications of a fragile-to-strong transition of hydration water. PMID:26465518

  4. Defluoridation of drinking water by boiling with brushite and calcite.

    PubMed

    Larsen, M J; Pearce, E I F

    2002-01-01

    Existing methods for defluoridating drinking water involve expensive high technology or are slow, inefficient and/or unhygienic. A new method is now suggested, encompassing brushite and calcite suspension followed by boiling. Our aim was to examine the efficiency of the method and the chemical reactions involved. Brushite, 0.3-0.5 g, and an equal weight of calcite were suspended in 1 litre water containing 5-20 ppm fluoride. The suspensions were boiled in an electric kettle, left to cool and the calcium salts to sediment. Solution ion concentrations were determined and sediments were examined by X-ray diffraction. In distilled water initially containing 5, 10 and 20 ppm fluoride the concentration was reduced to 0.06, 0.4 and 5.9 ppm, respectively. Using Aarhus tap water which contained 2.6 mmol/l calcium the final concentrations were 1.2, 2.5 and 7.7 ppm, respectively, and runs without calcite gave results similar to those with calcite. Without boiling the fluoride concentration remained unaltered, as did the brushite and calcite salts, despite occasional agitation by hand. All solutions were supersaturated with respect to fluorapatite and hydroxyapatite and close to saturation with respect to brushite. Boiling produced well-crystallised apatite and traces of calcite, while boiling of brushite alone left a poorly crystallised apatite. We conclude that boiling a brushite/calcite suspension rapidly converts the two salts to apatite which incorporates fluoride if present in solution, and that this process may be exploited to defluoridate drinking water.

  5. On the complex conductivity signatures of calcite precipitation

    SciTech Connect

    Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan

    2009-11-01

    Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl{sub 2} and Na{sub 2}CO{sub 3} solutions. The experiment continued for 12 days with a constant precipitation rate of {approx}0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

  6. Elastic and Transport Properties of Steam-Cured Pozzolanic-Lime Rock Composites Upon CO2 Injection

    NASA Astrophysics Data System (ADS)

    Emery, Dan; Vanorio, Tiziana

    2016-04-01

    Understanding the effect of pozzolanic ash-lime reactions on the rock physics properties of the resulting rock microstructure is important for monitoring unrest conditions in volcanic-hydrothermal systems as well as for devising concrete with enhanced performance. By mixing pozzolana ash with lime, the ancient Romans unwittingly incorporated these reactions in the production of their famous concrete. Recently, it has been discovered that a fiber-reinforced, concrete-like rock is forming naturally at depth of 1.5 km within the Campi Flegrei volcanic-hydrothermal systems due to upwelling lime-rich fluids permeating a pozzolana rich layer. This study aims to investigate possible physico-chemical conditions contributing to both enhance and undermine the properties of the subsurface rocks of volcanic-hydrothermal systems and, in turn, build upon those processes that the ancient Romans exploited to create their famous concrete. We prepared samples by mixing the pozzolana volcanic ash, slaked lime, aggregates of Neapolitan Yellow tuff, and seawater from Campi Flegrei in the same ratios as the ancient Romans. To mimic the conditions of the caldera, we used alkaline water from a well in the Campi Flegrei region rich in sulfate, bicarbonate, calcium, potassium, and magnesium ions. Yet, the samples were cured for 28 days in steam-rich environment to favor hydration and hence, enhancing the stability of calcium- alumino-silicate hydrates and setting strength of the rock samples. We measured baseline properties of porosity, permeability, P-wave velocity, and S-wave velocity of the samples as well as imaged the fibrous microstructure. P and S-wave velocities were used to derive bulk, shear, and Young's moduli. Subsequently, samples were injected with an aqueous carbon dioxide, CO2 (aq), solution and the changes in their microstructure and physical properties measured. Exposure of the concrete-like rock samples to CO2 -rich fluid lowers pH below 12.5, thus affecting the stability

  7. Heat generation as an index of exhaustion of soda lime.

    PubMed

    Tsuchiya, M; Ueda, W

    1989-06-01

    The wall temperatures of the absorptive chambers of a divided soda lime canister were measured in 70 patients to determine the relationship between the difference in temperature of the two chambers and CO2 passage through the first chamber. CO2 passage through the first chamber was detected when the temperature of the second chamber became equal to that of the first. A significant correlation (R = 0.94; P less than 0.001) was found between the magnitude of CO2 passage through the first chamber and the difference in temperature between the chambers. When the maximal absorptive capacity of soda lime was reached, the pH of the surface of soda lime granules was still too high to change the indicator color. Exhaustion of soda lime is more reliably recognized by measuring wall temperatures of the chambers than by observing color change of the soda lime granules.

  8. Dry soda lime markedly degrades sevoflurane during simulated inhalation induction.

    PubMed

    Funk, W; Gruber, M; Wild, K; Hobbhahn, J

    1999-02-01

    We have investigated gas composition during simulated inhalation induction with sevoflurane to elucidate possible mechanisms of incidental prolonged induction times and airway irritation. Using a circle system, 8% sevoflurane in oxygen 6 litre min-1 was washed into an absorbing canister filled with fresh soda lime containing 2.9% KOH (Draegersorb, 'D') or no KOH (< 0.01%, Sofnolime, 'S'). The absorbent was dried by oxygen 20,000 litre before every second experiment. Maximum soda lime temperatures attained after 4-6 min were 107 degrees C using dry D and 62 degrees C (61 degrees C) with dry S. Temperature did not increase with fresh soda lime. With dry soda lime, sevoflurane was not detected at the T-piece for 3 min and reached 6-7% within 6-10 min. After 1 min, we detected methanol and compound A (CH2F-O-C(= CF2) (CF3)). Total amounts over 20 min were: methanol 1125 mg (D dry), 334 mg (S dry) and < 5 mg (fresh soda lime); compound A 148 mg (D dry), 13 mg (S dry) and 3-8 mg (fresh); and fluoride 8.5 mg (D dry), 3.3 mg (S dry) and 1 mg (fresh). Formaldehyde was detected only with dry lime (D > 2.5 mg, S > 0.6 mg). In summary, the use of moist soda lime is of crucial importance during inhalation induction. With dry soda lime, the patient may inhale potentially toxic degradation products in significant amounts. Sevoflurane degradation is aggravated by a high KOH content of the lime. The observed airway irritation may be caused by formic acid, which is generated in isomolar concentrations with methanol (Cannizzaro reaction). The amount of compound A found with dry KOH-containing lime is unlikely to be noxious.

  9. Wetland vegetation responses to liming an Adirondack watershed

    SciTech Connect

    Mackun, I.R.

    1993-01-01

    Watershed liming as a long-term mitigation strategy to neutralize lake acidity, from increasing acid deposition, was initiated in North America at Woods Lake in the west central Adirondack region of New York. In October 1989, a dose of 10 MT lime (83.5% CaCO[sub 3]) ha[sup [minus]1] was aerially applied to 48% of the watershed. The wetlands adjacent to Woods Lake showed two distinct community types: one dominated by Chamaedaphne calyculata, and one dominated by graminoids and other herbaceous species. Within two years, liming did not alter the structure of either community type, and changed the cover or frequency of only 6 of 64 individual taxa. Most of these changes occurred in the herbaceous community type. The only strong positive response to liming was a nearly threefold increase in cover of the rhizomatous sedge Cladium mariscoides. The cover of Carex interior and Sphagnum spp. benefited from lime addition, while cover of Drosera intermedia and Muhlenbergia uniflora, and frequency of Hypericum canadense responded negatively to lime. Liming influenced the competitive release of only three taxa, all forbs with small growth forms. The tissue chemistry of foliage and twigs of Myrica gale, Chamaedaphne calyculata, and Carex stricta in the Chamaedaphne calyculata community type clearly illustrated species-specific patterns of nutrient accumulation and allocation both before and after liming. Concentrations of 17 of 20 elements responded to liming, although the responses varied among species and plant parts. Carex foliage was least responsive to liming, and Chamaedaphne twigs were most responsive. Elemental changes in plant tissues will be reflected in litter and many influence long-term nutrient dynamics in the wetland community.

  10. Aluminum Sulfate 18 Hydrate

    ERIC Educational Resources Information Center

    Young, Jay A.

    2004-01-01

    A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

  11. [Hydration in clinical practice].

    PubMed

    Maristany, Cleofé Pérez-Portabella; Segurola Gurruchaga, Hegoi

    2011-01-01

    Water is an essential foundation for life, having both a regulatory and structural function. The former results from active and passive participation in all metabolic reactions, and its role in conserving and maintaining body temperature. Structurally speaking it is the major contributer to tissue mass, accounting for 60% of the basis of blood plasma, intracellular and intersticial fluid. Water is also part of the primary structures of life such as genetic material or proteins. Therefore, it is necessary that the nurse makes an early assessment of patients water needs to detect if there are signs of electrolyte imbalance. Dehydration can be a very serious problem, especially in children and the elderly. Dehydrations treatment with oral rehydration solution decreases the risk of developing hydration disorders, but even so, it is recommended to follow preventive measures to reduce the incidence and severity of dehydration. The key to having a proper hydration is prevention. Artificial nutrition encompasses the need for precise calculation of water needs in enteral nutrition as parenteral, so the nurse should be part of this process and use the tools for calculating the patient's requirements. All this helps to ensure an optimal nutritional status in patients at risk. Ethical dilemmas are becoming increasingly common in clinical practice. On the subject of artificial nutrition and hydration, there isn't yet any unanimous agreement regarding hydration as a basic care. It is necessary to take decisions in consensus with the health team, always thinking of the best interests of the patient.

  12. Calcite and Picocyanobacteria in Lakes: Factors Affecting Their Interaction

    NASA Astrophysics Data System (ADS)

    Dittrich, M.; Obst, M.; Mavrocordatos, D.

    2003-12-01

    Calcites build large deposits which have been observed in the rock record throughout geological time at various localities around the globe. Carbonate deposits have affected atmospheric carbon dioxide concentration. As it has been generally accepted, inorganic precipitation represents a source of carbon dioxide on short geological time scales and a sink of inorganic carbon at long time scales from millions to thousands of millions years. However, recent research indicates that calcite deposits may result from microbial calcification instead of inorganic precipitation. In this case the process may reduce atmospheric carbon dioxide on geologically short time scales. Thus the effect of carbonate sediment deposition on global carbon cycling depends on the origin of carbonate. Thus it is essential to understand the cause and the key parameters affecting calcite precipitation. The role of algae and bacteria in calcite formation in lakes has not been evaluated in detail. Some evidence, however, exists supporting precipitation of calcium carbonate by microbes as the origin of whiting. Several field studies on lakes have also produced puzzling results: The peaks of algal blooms were often not found at the same time as precipitation events of calcite. We suspect that parts of the discrepancies in the interpretation of field observations are due to the activity of autotrophic picoplankton. The unicellular autotrophic picoplankton (APP) is a ubiquitous component of pelagic ecosystems. But it has often been overlooked due to its small cell size of 0.2 - 2 μ m in diameter. Coccoid picocyanobacteria of the Synechococcus-type dominate the picoplankton community in most oligotrophic systems. Recently, laboratory experiments and field observations suggested that APP may play an important role in calcite precipitation. The aim of this study was to examine the influence of environmental factors such as saturation state, concentration of different dissolved ions and characteristics of

  13. Hydrochemical controls on aragonite versus calcite precipitation in cave dripwaters

    NASA Astrophysics Data System (ADS)

    Rossi, Carlos; Lozano, Rafael P.

    2016-11-01

    Despite the paleoclimatic relevance of primary calcite to aragonite transitions in stalagmites, the relative role of fluid Mg/Ca ratio, supersaturation and CO32- concentration in controlling such transitions is still incompletely understood. Accordingly, we have monitored the hydrochemistry of 50 drips and 8 pools that are currently precipitating calcite and/or aragonite in El Soplao and Torca Ancha Caves (N. Spain), investigating the mineralogy and geochemistry of the CaCO3 precipitates on the corresponding natural speleothem surfaces. The data reveal that, apart from possible substrate effects, dripwater Mg/Ca is the only obvious control on CaCO3 polymorphism in the studied stalagmites and pools, where calcite- and aragonite-precipitating dripwaters are separated by an initial (i.e. at stalactite tips) Mg/Ca threshold at ≈1.1 mol/mol. Within the analyzed ranges of pH (8.2-8.6), CO32- concentration (1-6 mg/L), supersaturation (SIaragonite: 0.08-1.08; SIcalcite: 0.23-1.24), drip rate (0.2-81 drops/min) and dissolved Zn (6-90 μg/L), we observe no unequivocal influence of these parameters on CaCO3 mineralogy. Despite the almost complete overlapping supersaturations of calcite- and aragonite-precipitating waters, the latter are on average less supersaturated because the waters having Mg/Ca above ∼1.1 have mostly achieved such high ratios by previously precipitating calcite. Both calcite and aragonite precipitated at or near oxygen isotopic equilibrium, and Mg incorporation into calcite was consistent with literature-based predictions, indicating that in the studied cases CaCO3 precipitation was not significantly influenced by strong kinetic effects. In the studied cases, the calcites that precipitate at ∼11 °C from dripwaters with initial Mg/Ca approaching ∼1.1 incorporate ∼5 mol% MgCO3, close to the published value above which calcite solubility exceeds aragonite solubility, suggesting that aragonite precipitation in high-relative-humidity caves is

  14. A Raman spectroscopic comparison of calcite and dolomite

    NASA Astrophysics Data System (ADS)

    Sun, Junmin; Wu, Zeguang; Cheng, Hongfei; Zhang, Zhanjun; Frost, Ray L.

    2014-01-01

    Raman spectroscopy was used to characterize and differentiate the two minerals calcite and dolomite and the bands related to the mineral structure. The (CO3)2- group is characterized by four prominent Raman vibrational modes: (a) the symmetric stretching, (b) the asymmetric deformation, (c) asymmetric stretching and (d) symmetric deformation. These vibrational modes of the calcite and dolomite were observed at 1440, 1088, 715 and 278 cm-1. The significant differences between the minerals calcite and dolomite are observed by Raman spectroscopy. Calcite shows the typical bands observed at 1361, 1047, 715 and 157 cm-1, and the special bands at 1393, 1098, 1069, 1019, 299, 258 and 176 cm-1 for dolomite are observed. The difference is explained on the basis of the structure variation of the two minerals. Calcite has a trigonal structure with two molecules per unit cell, and dolomite has a hexagonal structure. This is more likely to cause the splitting and distorting of the carbonate groups. Another cause for the difference is the cation substituting for Mg in the dolomite mineral.

  15. Nuclear anomalies in the buccal cells of calcite factory workers

    PubMed Central

    2010-01-01

    The micronucleus (MN) assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers) calcite factory workers and 50 (25 smokers and 25 non-smokers) age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA) other than micronuclei, such as binucleates, karyorrhexis, karyolysis and ‘broken eggs', were also evaluated. Micronuclei and the other aforementioned anomalies were analysed by two way analysis of covariance. The linear correlations between the types of micronucleus and nuclear abnormalities were determined by Spearman's Rho. There was a positive correlation between micronuclei and other types of nuclear abnormalities in accordance with the Spearman's Rho test. Results showed statistically significant difference between calcite fabric workers and control groups. MN and NA frequencies in calcite fabric workers were significantly higher than those in control groups (p < 0.05). The results of this study indicate that calcite fabric workers are under risk of significant cytogenetic damage. PMID:21637497

  16. Microstructures and elastic properties of sheared calcite flowstone

    NASA Astrophysics Data System (ADS)

    Mitrovic, Ivanka; Grasemann, Bernhard; Plan, Lukas; Tesei, Telemaco; Baron, Ivo

    2016-04-01

    Flowstone is a monomineralic rock precipitated along cave walls and floors, composed of columnar centimeter-scale calcite crystals with strong growth orientation perpendicular to the growth surface. Broken and scratched flowstone can serve as evidence for active faulting and has been found in several alpine caves in Austria. In order to understand the fault mechanics, and associated potential earthquake hazard, experimentally deformed flowstone is studied using microstructural analysis and EBSD-measured physical properties of calcite crystals. For that purpose, we have performed sliding experiments using a rock deformation biaxial apparatus on rectangular blocks of flowstone that were sheared perpendicular to the calcite growth direction. The experiments were performed under room conditions, with sub-seismic sliding velocity (0.001-0.01 mm/s) and constant effective normal stress (3-10 MPa). The deformed samples show diverse brittle features, including high fracture density, the development of calcite-rich fault gouge with Riedel shears within a foliated cataclasite, and drastic grain size reduction down to nm-scale grains. The dominant plastic microstructure is mechanical twinning. Due to the strong growth orientation of calcite in flowstone, crystals can be bent due to shearing. We examine the bending by applying orientation distribution, Schmid factor and elasticity tensor calculations using MTEX Toolbox from EBSD data. In this unique case the flowstone deformation experiments bridge the gap between single crystal and rock powder experiments. This study is supported by the Austrian Science Foundation: SPELEOTECT project (P25884-N29).

  17. Mechanical and leaching behaviour of slag-cement and lime-activated slag stabilised/solidified contaminated soil.

    PubMed

    Kogbara, Reginald B; Al-Tabbaa, Abir

    2011-05-01

    Stabilisation/solidification (S/S) is an effective technique for reducing the leachability of contaminants in soils. Very few studies have investigated the use of ground granulated blast furnace slag (GGBS) for S/S treatment of contaminated soils, although it has been shown to be effective in ground improvement. This study sought to investigate the potential of GGBS activated by cement and lime for S/S treatment of a mixed contaminated soil. A sandy soil spiked with 3000mg/kg each of a cocktail of heavy metals (Cd, Ni, Zn, Cu and Pb) and 10,000mg/kg of diesel was treated with binder blends of one part hydrated lime to four parts GGBS (lime-slag), and one part cement to nine parts GGBS (slag-cement). Three binder dosages, 5, 10 and 20% (m/m) were used and contaminated soil-cement samples were compacted to their optimum water contents. The effectiveness of the treatment was assessed using unconfined compressive strength (UCS), permeability and acid neutralisation capacity (ANC) tests with determination of contaminant leachability at the different acid additions. UCS values of up to 800kPa were recorded at 28days. The lowest coefficient of permeability recorded was 5×10(-9)m/s. With up to 20% binder dosage, the leachability of the contaminants was reduced to meet relevant environmental quality standards and landfill waste acceptance criteria. The pH-dependent leachability of the metals decreased over time. The results show that GGBS activated by cement and lime would be effective in reducing the leachability of contaminants in contaminated soils. PMID:21420148

  18. Mechanical and leaching behaviour of slag-cement and lime-activated slag stabilised/solidified contaminated soil.

    PubMed

    Kogbara, Reginald B; Al-Tabbaa, Abir

    2011-05-01

    Stabilisation/solidification (S/S) is an effective technique for reducing the leachability of contaminants in soils. Very few studies have investigated the use of ground granulated blast furnace slag (GGBS) for S/S treatment of contaminated soils, although it has been shown to be effective in ground improvement. This study sought to investigate the potential of GGBS activated by cement and lime for S/S treatment of a mixed contaminated soil. A sandy soil spiked with 3000mg/kg each of a cocktail of heavy metals (Cd, Ni, Zn, Cu and Pb) and 10,000mg/kg of diesel was treated with binder blends of one part hydrated lime to four parts GGBS (lime-slag), and one part cement to nine parts GGBS (slag-cement). Three binder dosages, 5, 10 and 20% (m/m) were used and contaminated soil-cement samples were compacted to their optimum water contents. The effectiveness of the treatment was assessed using unconfined compressive strength (UCS), permeability and acid neutralisation capacity (ANC) tests with determination of contaminant leachability at the different acid additions. UCS values of up to 800kPa were recorded at 28days. The lowest coefficient of permeability recorded was 5×10(-9)m/s. With up to 20% binder dosage, the leachability of the contaminants was reduced to meet relevant environmental quality standards and landfill waste acceptance criteria. The pH-dependent leachability of the metals decreased over time. The results show that GGBS activated by cement and lime would be effective in reducing the leachability of contaminants in contaminated soils.

  19. Lime kiln source characterization: Lime manufacturing industry Fourier transform infrared spectroscopy. Final report

    SciTech Connect

    Toney, M.L.

    1999-07-01

    The purpose of this testing program is to obtain uncontrolled and controlled hydrogen chloride (HCl) and speciated hydrocarbon Hazardous Air Pollutants (HAPs) emissions data from lime production plants to support a national emission standard for hazardous air pollutants (NESHAP). This report presents data from the Fourier Transform Infrared Spectroscopy (FTIR) measurements. FTIR source testing was conducted for the following purposes: Quantify HCl emission levels; and Gather screening (i.e., qualitative) data on other HAP emissions.

  20. Monoclinic deformation of calcite crystals at ambient conditions

    NASA Astrophysics Data System (ADS)

    Przeniosło, R.; Fabrykiewicz, P.; Sosnowska, I.

    2016-09-01

    High resolution synchrotron radiation powder diffraction shows that the average crystal structure of calcite at ambient conditions is described with the trigonal space group R 3 bar c but there is a systematic hkl-dependent Bragg peak broadening. A modelling of this anisotropic peak broadening with the microstrain model from Stephens (1999) [15] is presented. The observed lattice parameters' correlations can be described by assuming a monoclinic-type deformation of calcite crystallites. A quantitative model of this monoclinic deformation observed at ambient conditions is described with the space group C 2 / c . The monoclinic unit cell suggested at ambient conditions is related with the monoclinic unit cell reported in calcite at high pressure (Merrill and Bassett (1975) [10]).

  1. Time and metamorphic petrology: calcite to aragonite experiments.

    PubMed

    Hacker, B R; Kirby, S H; Bohlen, S R

    1992-10-01

    Although the equilibrium phase relations of many mineral systems are generally well established, the rates of transformations, particularly in polycrystalline rocks, are not. The results of experiments on the calcite to aragonite transformation in polycrystalline marble are different from those for earlier experiments on powdered and single-crystal calcite. The transformation in the polycrystalline samples occurs by different mechanisms, with a different temperature dependence, and at a markedly slower rate. This work demonstrates the importance of kinetic studies on fully dense polycrystalline aggregates for understanding mineralogic phase changes in nature. Extrapolation of these results to geological time scales suggests that transformation of calcite to aragonite does not occur in the absence of volatiles at temperatures below 200 degrees C. Kinetic hindrance is likely to extend to higher temperatures in more complex transformations.

  2. Time and metamorphic petrology: Calcite to aragonite experiments

    USGS Publications Warehouse

    Hacker, B.R.; Kirby, S.H.; Bohlen, S.R.

    1992-01-01

    Although the equilibrium phase relations of many mineral systems are generally well established, the rates of transformations, particularly in polycrystalline rocks, are not. The results of experiments on the calcite to aragonite transformation in polycrystalline marble are different from those for earlier experiments on powdered and single-crystal calcite. The transformation in the polycrystalline samples occurs by different mechanisms, with a different temperature dependence, and at a markedly slower rate. This work demonstrates the importance of kinetic studies on fully dense polycrystalline aggregates for understanding mineralogic phase changes in nature. Extrapolation of these results to geological time scales suggests that transformation of calcite to aragonite does not occur in the absence of volatiles at temperatures below 200??C. Kinetic hindrance is likely to extend to higher temperatures in more complex transformations.

  3. Effect of lime concentration on gelatinized maize starch dispersions properties.

    PubMed

    Lobato-Calleros, C; Hernandez-Jaimes, C; Chavez-Esquivel, G; Meraz, M; Sosa, E; Lara, V H; Alvarez-Ramirez, J; Vernon-Carter, E J

    2015-04-01

    Maize starch was lime-cooked at 92 °C with 0.0-0.40% w/w Ca(OH)2. Optical micrographs showed that lime disrupted the integrity of insoluble remnants (ghosts) and increased the degree of syneresis of the gelatinized starch dispersions (GSD). The particle size distribution was monomodal, shifting to smaller sizes and narrower distributions with increasing lime concentration. X-ray patterns and FTIR spectra showed that crystallinity decreased to a minimum at lime concentration of 0.20% w/w. Lime-treated GSD exhibited thixotropic and viscoelastic behaviour. In the linear viscoelastic region the storage modulus was higher than the loss modulus, but a crossover between these moduli occurred in the non-linear viscoelastic region. The viscoelastic properties decreased with increased lime concentration. The electrochemical properties suggested that the amylopectin-rich remnants and the released amylose contained in the continuous matrix was firstly attacked by calcium ions at low lime levels (<0.20% w/w), disrupting the starch gel microstructure.

  4. Effect of lime concentration on gelatinized maize starch dispersions properties.

    PubMed

    Lobato-Calleros, C; Hernandez-Jaimes, C; Chavez-Esquivel, G; Meraz, M; Sosa, E; Lara, V H; Alvarez-Ramirez, J; Vernon-Carter, E J

    2015-04-01

    Maize starch was lime-cooked at 92 °C with 0.0-0.40% w/w Ca(OH)2. Optical micrographs showed that lime disrupted the integrity of insoluble remnants (ghosts) and increased the degree of syneresis of the gelatinized starch dispersions (GSD). The particle size distribution was monomodal, shifting to smaller sizes and narrower distributions with increasing lime concentration. X-ray patterns and FTIR spectra showed that crystallinity decreased to a minimum at lime concentration of 0.20% w/w. Lime-treated GSD exhibited thixotropic and viscoelastic behaviour. In the linear viscoelastic region the storage modulus was higher than the loss modulus, but a crossover between these moduli occurred in the non-linear viscoelastic region. The viscoelastic properties decreased with increased lime concentration. The electrochemical properties suggested that the amylopectin-rich remnants and the released amylose contained in the continuous matrix was firstly attacked by calcium ions at low lime levels (<0.20% w/w), disrupting the starch gel microstructure. PMID:25442564

  5. Preferential accumulation of gas hydrate in the Andaman accretionary wedge and relationship to anomalous porosity preservation

    NASA Astrophysics Data System (ADS)

    Rose, K.; Torres, M. E.; Johnson, J. E.; Hong, W.; Giosan, L.; Solomon, E. A.; Kastner, M.; Cawthern, T.; Long, P.; Schaef, T.

    2015-12-01

    In the marine environment, sediments in the gas hydrate stability zone often correspond to slope and basin settings. These settings are dominantly composed of fine-grained silt and clay lithofacies with typically low vertical permeability, and pore fluids frequently under-saturated with respect to methane. As a result, the pressure-temperature conditions requisite for a GHSZ to be present occur widely worldwide across marine settings, however, the distribution of gas hydrate in these settings is neither ubiquitous nor uniform. This study uses sediment core and borehole related data recovered by drilling at Site 17 in the Andaman Sea during the Indian National Gas Hydrate Program Expedition 1 in 2006, to investigate reservoir-scale controls on gas hydrate distribution. In particular, this study finds that conditions beyond reservoir pressure, temperature, salinity, and gas concentration, appear to influence the concentration of gas hydrate in host sediments. Using field-generated datasets along with newly acquired sedimentology, physical property, imaging and geochemical data with mineral saturation and ion activity products of key mineral phases such as amorphous silica and calcite, we document the presence and nature of secondary precipitates that contributed to anomalous porosity preservation at Site 17 in the Andaman Sea. This study demonstrates the importance of grain-scale subsurface heterogeneities in controlling the occurrence and distribution of concentrated gas hydrate accumulations in marine sediments, and document the importance that increased permeability and enhanced porosity play in supporting gas concentrations sufficient to support gas hydrate formation. This illustrates the complex balance and lithology-driven controls on hydrate accumulations of higher concentrations and offers insights into what may control the occurrence and distribution of gas hydrate in other sedimentary settings.

  6. Small scale shear zone in calcite: AMS and microstructure

    NASA Astrophysics Data System (ADS)

    Roxerová, Zuzana; Machek, Matěj; Kusbach, Vladimír; Racek, Martin; Silva, Pedro F.

    2016-04-01

    Two structural profiles across thin shear zone in calcite from quarry in Estremoz (Portugal) were studied to find a relationship between AMS and strain in natural rocks. The mesoscopic fabric is characterized by the change from the subhorizontal coarse-grained foliation towards the ~2cm-wide shear zone center with subvertical fine-grained foliation. In microstructure, the shear zone records dynamic recrystallization of calcite aggregate which resulted in development of porphyroclastic microstructure with increasing proportion of fine-grained recrystallized matrix towards the shear zone center. Two distinct crystallographic preferred orientations of calcite were recorded. One related with porphyroclasts, characterized by subvertical orientation of calcite axes and another associated with recrystallized matrix showing subhorizontal calcite axes orientation. The magnetic susceptibility ranges from -8e-6SI to 9e-6SI, with the average -4e-6SI. The majority of the rock mass is diamagnetic, corresponding well with the thermomagnetic curves, with local paramagnetic accumulations in form of thin bands. The AMS of the both profiles exhibits stable subvertical foliation bearing vertical lineation which is locally alternated by the medium-angle foliation. We interpret the AMS fabric pattern which is perpendicular to the mineral one as a type of inverse AMS fabric, due to high iron content in major part of calcite grains The magnetic and microstructural description of the shear zone is accompanied by numerical modeling of AMS based on CPO and different proportion of porphyroclasts, matrix and mica for purposes of deciphering the influence of present microstructural features on AMS.

  7. Radiaxial-fibrous calcites of shallow subsurface diagenetic origin

    SciTech Connect

    Mazzullo, S.J.; Bischoff, W.D.; Lobitzer, H.

    1989-03-01

    Radiaxial-fibrous calcites (RFC) in marine carbonates are generally considered syndepositional cements. In Upper Triassic and basal Liassic reef and platform limestones in Austria (Steinplatte complex), however, isopachous RFC is demonstrably a postdepositional diagenetic component that precipitated in shallow-burial phreatic environments during a time of periodic meteoric exposure. Isopachous RFC occurs solely within solution cavities and is interlayered with internal red sediment; discontinuities due to leaching separate sequential generations of RFC in the rocks. Accordingly, one possibility is that the RFC was originally low-magnesium calcite that precipitated in the meteoric phreatic zone during lowstands. Such calcites contain relatively low magnesium concentrations (average 0.87 mole % MgCO/sub 3/) and are /sup 18/O depleted (average - 5.81 /per thousand/ PDB). However, most other RFC cements in the sequence average slightly higher magnesium comparable to crinoidal calcites (1.13 mole % MgCO/sub 3/), are less depleted in /sup 18/O (average - 1.88 /per thousand/ PDB), and are partly dolomitized. Additionally, all the RFC cements are enriched in /sup 13/C to values similar to that of Triassic and Jurassic seawater (+ 2.86 /per thousand/ PDB) and are nonluminescent. Trace element studies indicate alteration of the rocks in partly closed, rock-dominated diagenetic systems. By these facts, the authors favor a precursor high-magnesium calcite mineralogy for the RFC cements, which possibly precipitated during highstands when meteoric pore waters were replaced by marine fluids. Thus, the geochemical trends observed are likely due to variations in the degree of meteoric alteration of high-magnesium calcite RFC rather than to differences in original mineralogy.

  8. Is bicarbonate stable in and on the calcite surface?

    NASA Astrophysics Data System (ADS)

    Andersson, M. P.; Rodriguez-Blanco, J. D.; Stipp, S. L. S.

    2016-03-01

    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3- <=> CO32- + H+, when HCO3- is included in, and adsorbed on, a calcite surface. We have used cluster models (80-100 atoms) to represent the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from -6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 < pH < 6.35, where H2CO30 is the dominant dissolved species. When bicarbonate is adsorbed on calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution, 10.35. This means that adsorbed carbonate is stable even when the concentration of dissolved CO32- is several orders of magnitude lower. This has a significant effect on surface charge and thus the behaviour of the calcite surface. Our results help explain the potential determining behaviour of the carbonate species in calcite-water systems, particularly in the pH range where the bicarbonate species dominates in water and where the carbonate species dominates at the surface, i.e. when 7.5 < pH < 10.35. Our atomic scale data for the various calcite surface sites provide the needed input to improve and constrain surface complexation modelling and are especially useful for predicting behaviour in systems where experiments are difficult or impossible, such as at high temperature and pressure.

  9. Microbially Induced Calcite Precipitation for Subsurface Immobilization of Contaminants

    NASA Astrophysics Data System (ADS)

    Smith, R. W.; Fujita, Y.; Ginn, T. R.; Hubbard, S. S.; Dafflon, B.; Delwiche, M.; Gebrehiwet, T.; Henriksen, J. R.; Peterson, J.; Taylor, J. L.

    2011-12-01

    Subsurface radionuclide and metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of the greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide 90Sr, is co-precipitation in calcite. We have found that calcite precipitation and co-precipitation of Sr can be accelerated by the activity of urea hydrolyzing microorganisms, that higher calcite precipitation rates can result in increased Sr partitioning, and that nutrient additions can stimulate ureolytic activity. To extend our understanding of microbially induced calcite precipitation (MICP) in an aquifer setting a continuous recirculation field experiment evaluating MICP was conducted at the Integrated Field Research Challenge (IFRC) site located at Rifle, CO. In this experiment, groundwater extracted from an onsite well was amended with urea (total mass of 42.5 kg) and molasses (a carbon and electron donor) and re-injected into a well approximately 4 meters up-gradient for a period of 12 days followed by 10 months of groundwater sampling and monitoring. Crosshole radar and electrical tomographic data were collected prior, during, and after the MICP treatment. The urea and molasses treatment resulted in an enhanced population of sediment associated urea hydrolyzing organisms as evidenced by increases in the number of ureC gene copies, increases in 14C urea hydrolysis rates, and long-term observations of ammonium (a urea hydrolysis product) in the injection, extraction and down gradient monitoring wells. Permeability changes and increases in the calcite saturation indexes in the well field suggest that mineral precipitation has occurred; ongoing analysis of field samples seeks to confirm this. Changes in dielectric constant and electrical conductivity were used to interpret the spatiotemporal distribution of the injectate and subsequent calcite precipitation. Modeling activities are underway to

  10. Absorption of nitrogen dioxide and nitric oxide by soda lime.

    PubMed

    Ishibe, T; Sato, T; Hayashi, T; Kato, N; Hata, T

    1995-09-01

    Inhaled nitric oxide (NO) is used for the treatment of pulmonary hypertension as a selective pulmonary vasodilator. However, NO is oxidized rapidly to the more toxic nitrogen dioxide (NO2). Elimination of NO2 from inspired gas is essential for safe clinical use NO. We therefore investigated the efficacy of soda lime in absorbing NO2 from NO2-containing gases. Commercially available soda limes (Soda sorb and Wako lime-A), were exposed to the following six gas mixtures containing NO and NO2 in a hypoxic carrier gas for 20 min: No. 1: NO 40 ppm; No. 2: NO 35 ppm and NO2 5 ppm; No. 3: NO 30 ppm and NO2 10 ppm; No. 4: NO 20 ppm and NO2 20 ppm; No. 5: NO 10 ppm and NO2 30 ppm; and No. 6: NO2 40 ppm. Both types of soda lime completely absorbed the NO2 in all samples when it was present (Nos 2-6). NO concentration in these gas mixtures was reduced by an amount equal to the NO2 absorbed by soda lime. NO was absorbed minimally when NO2 was not present in the mixture. Nitrite was detected from the Wako lime-A granules exposed to the test gas by the chemical analysis. These findings suggest that soda lime completely absorbs NO2 by chemical neutralization, but NO is absorbed as simultaneously absorbed NO2 only where NO and NO2 coexist. Therefore, we conclude that soda lime is useful for NO2 absorption during NO inhalation therapy but NO monitoring from a point distal to the soda lime is required for precise control of inspired NO concentration.

  11. Leaching behavior of lime-fly ash mixtures

    SciTech Connect

    Daniels, J.L.; Das, G.P.

    2006-01-15

    As part of a larger investigation that included numerical and field-based components, the use of lime to reduce the leachability of a coal combustion fly ash was evaluated in the laboratory. The focus of this paper is on the experimental assessment of lime-fly ash leachability through sequential leach (SL), freeze-thaw (FT), and wet-dry (WD) leaching as well as multileachant sequential extraction (SE) tests. The results suggest that lime addition reduces the leachability for Cd, Se, and to some extent As. They also suggest that Cr is rendered more leachable with increasing lime content, for the conditions and low levels tested. It appears that there is a threshold lime content ({gt} 1.0%) that must be exceeded prior to reducing the leachability of As and Se. In particular, this threshold likely corresponds to the level at which appreciable cementitious reactions have developed. For example, in the case of As after the first cycle of leaching, the concentration was below the reporting limit (10 {mu} g/L) for 0% lime. However, at 0.5% lime amendment, the leached concentration increased to nearly 50 {mu} g/L. Subsequent lime additions reduced this concentration. No such threshold was observed for Cd leachability as was expected as a direct consequence of hydroxide precipitation, which is well established under the measured pH conditions. As such, Cd mobility is insensitive to the extent to which cementitious reactions are initiated. Overall, the results suggest that while lime stabilization may be effective for reducing leachability, sufficient amounts must be added; otherwise, the leachability of some constituents can actually be exacerbated.

  12. Effect of microstructure and microchemistry on improvement of hydration and slag attack resistance of ilmenite-doped refractory limestone

    NASA Astrophysics Data System (ADS)

    Soltan, Abdel Monem; Serry, Mohamed

    2015-02-01

    This work studies densification, resistance to hydration and slag attack of 0.0-2.0 wt% ilmenite-doped lime refractories in relation to their thermal equilibrium and microfabric after firing at 1,400-1,700 °C. XRF, XRD, SEM-EDAX, transmitted light microscopy and mercury intrusion methods were used to characterize the fired samples. The ternary diagram CaO-C2S-C4AF was applied to the thermal equilibrium data. The rates of hydration and attack by steel-slag were also assessed using cathode-luminescence microscope. Doping limestone with 0.5 wt% ilmenite leads maximizes the rate of densification after firing for 2 h at 1,600 °C. A direct-bonded CaO-CaO network is found in the doped sample with separated islands of Ca-silicate, alumino-ferrite and TiO2-rich Ca, Mg- solid solutions all filling the pores and triple points of the lime grains. Due to the dense microstructure of the doped sample with the direct-bonded lime grains, hydration and slag-attack resistance are enhanced compared with the un-doped sample.

  13. Sulfated Macromolecules as Templates for Calcite Nucleation and Growth

    NASA Astrophysics Data System (ADS)

    David, M.; Passalacqua, K.; Neira, A. C.; Fernandez, M. S.

    2003-12-01

    Mineralization of egg and seashells is controlled by an intimate association of inorganic materials with organic macromolecules. Among them, particular polyanionic sulfated macromolecules referred to as proteoglycans have been described to be involved in the calcification of these biominerals. The sulfated moieties of the proteoglycans are part of polymer chains constituted of building-blocks of disaccharide units, referred to as sulfated glycosaminoglycans (GAGs), which are covalently attached to a protein core. By using a sitting drop crystallization assay under controlled conditions of time, pH and reactants concentration, we have tested several sulfated and non-sulfated GAGs (i.e.: dermatan and keratan sulfate, hyaluronic acid and heparin), differing in their sulfonate and carboxylate degree and pattern, in their ability to modify calcium carbonate crystal morphology as observed under scanning electron microscopy. Without the addition of GAGs, regular \\{104\\} rhombohedral calcite crystals were obtained. When hyaluronic acid (HA), a non-sulfated but carboxylated GAG, was added, 20 mm long piles of unmodified calcite crystals were observed. When desulfated dermatan, which is an epimeric form of HA but shorter polymer, having their carboxylate groups in an inverted configuration, was added, isolated rhombohedral \\{104\\} calcite crystals showing rounded corners with planes oriented parallel to the c axis were observed. When dermatan sulfated was added, isolated calcite crystals exhibit a columnar morphology as a \\{hk0\\} cylinder with three \\{104\\} faces forming a cap at both ends. Heparin activity depends on the fraction added. Fast-moving heparin fraction (FM), is an undersulfated, low-molecular-weight heterogeneous polymer, while slow-moving heparin fraction (SM) is an high-molecular-weight homogeneous polymer rich in trisulfated-disaccharide units. When FM was added, isolated calcite crystals displayed rhombohedrical \\{104\\} faces but flat corners of

  14. Magnesium incorporation in calcite in the presence of organic ligands

    NASA Astrophysics Data System (ADS)

    Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2015-04-01

    The formation of authigenic Mg-calcites in marine early diagenetic environments is commonly driven by a bio-induced process, the anaerobic oxidation of methane (AOM), which provides inorganic carbon required for the precipitation of such authigenic carbonates. In such settings the availability of major and/or trace divalent metal cations (Me2+) incorporated in calcite and their aqueous speciation are controlled by the presence of aqueous organic molecules that are produced either as (by-)products of biological activity (i.e. exopolymeric substances) or during degradation of allochthonous organic matter in the sediments. Despite the fact that the presence of aqueous organic ligands strongly affects the growth rates and the mineralogy of precipitating CaCO3 polymorphs, till now no study addresses the role of Me2+-ligand aqueous complexes on the extent of Mg and/or other trace element content of Mg-calcites. In order to shed light on this process, relevant to authigenic calcite formation in organic-rich marine sediments and continental soils, we precipitated calcite in the presence of aqueous Mg and a variety of low molecular weight carboxylic- and aminoacids. Our experimental data indicate that the presence of organic ligands augments significantly the saturation state of calcite in the parent fluid during its precipitation. Moreover, they suggest that the higher the ligand concentration, the higher the obtained distribution coefficient of Mg in calcite. The latter is directly proportional to the ratio of Mg2+/Ca2+ aqueous ions for all ligands used. Hydrogeochemical modelling of the aqueous fluids indicate that the observed correlation can be explained by the stronger complexation of Ca2+ with organic ligands compared to Mg2+, which results in higher availability of Mg2+ vs. Ca2+ aqueous ions. Overall the obtained results suggest that the higher the organic ligand aqueous concentration the higher the Mg content of calcite forming from this fluid. These findings are

  15. Magnesium stable isotope fractionation in marine biogenic calcite and aragonite

    NASA Astrophysics Data System (ADS)

    Wombacher, F.; Eisenhauer, A.; Böhm, F.; Gussone, N.; Regenberg, M.; Dullo, W.-Chr.; Rüggeberg, A.

    2011-10-01

    This survey of magnesium stable isotope compositions in marine biogenic aragonite and calcite includes samples from corals, sclerosponges, benthic porcelaneous and planktonic perforate foraminifera, coccolith oozes, red algae, and an echinoid and brachiopod test. The analyses were carried out using MC-ICP-MS with an external repeatability of ±0.22‰ (2SD for δ 26Mg; n = 37), obtained from a coral reference sample (JCp-1). Magnesium isotope fractionation in calcitic corals and sclerosponges agrees with published data for calcitic speleothems with an average Δ 26Mg calcite-seawater = -2.6 ± 0.3‰ that appears to be weakly related to temperature. With one exception ( Vaceletia spp.), aragonitic corals and sclerosponges also display uniform Mg isotope fractionations relative to seawater with Δ 26Mg biogenic aragonite-seawater = -0.9 ± 0.2. Magnesium isotopes in high-Mg calcites from red algae, echinoids and perhaps some porcelaneous foraminifera as well as in all low-Mg calcites (perforate foraminifera, coccoliths and brachiopods) display significant biological influences. For planktonic foraminifera, the Mg isotope data is consistent with the fixation of Mg by organic material under equilibrium conditions, but appears to be inconsistent with Mg removal from vacuoles. Our preferred model, however, suggests that planktonic foraminifera synthesize biomolecules that increase the energetic barrier for Mg incorporation. In this model, the need to remove large quantities of Mg from vacuole solutions is avoided. For the high-Mg calcites from echinoids, the precipitation of amorphous calcium carbonate may be responsible for their weaker Mg isotope fractionation. Disregarding superimposed biological effects, it appears that cation light isotope enrichments in CaCO 3 principally result from a chemical kinetic isotope effect, related to the incorporation of cations at kink sites. In this model, the systematics of cation isotope fractionations in CaCO 3 relate to the

  16. Regeneration of lime from sulfates for fluidized-bed combustion

    DOEpatents

    Yang, Ralph T.; Steinberg, Meyer

    1980-01-01

    In a fluidized-bed combustor the evolving sulfur oxides are reacted with CaO to form calcium sulfate which is then decomposed in the presence of carbonaceous material, such as the fly ash recovered from the combustion, at temperatures of about 900.degree. to 1000.degree. C., to regenerate lime. The regenerated lime is then recycled to the fluidized bed combustor to further react with the evolving sulfur oxides. The lime regenerated in this manner is quite effective in removing the sulfur oxides.

  17. Methane Clathrate Hydrate Prospecting

    NASA Technical Reports Server (NTRS)

    Duxbury, N.; Romanovsky, V.

    2003-01-01

    A method of prospecting for methane has been devised. The impetus for this method lies in the abundance of CH4 and the growing shortages of other fuels. The method is intended especially to enable identification of subpermafrost locations where significant amounts of methane are trapped in the form of methane gas hydrate (CH4(raised dot)6H2O). It has been estimated by the U.S. Geological Survey that the total CH4 resource in CH4(raised dot) 6H2O exceeds the energy content of all other fossil fuels (oil, coal, and natural gas from non-hydrate sources). Also, CH4(raised dot)6H2O is among the cleanest-burning fuels, and CH4 is the most efficient fuel because the carbon in CH4 is in its most reduced state. The method involves looking for a proxy for methane gas hydrate, by means of the combination of a thermal-analysis submethod and a field submethod that does not involve drilling. The absence of drilling makes this method easier and less expensive, in comparison with prior methods of prospecting for oil and natural gas. The proposed method would include thermoprospecting in combination with one more of the other non-drilling measurement techniques, which could include magneto-telluric sounding and/or a subsurface-electrical-resistivity technique. The method would exploit the fact that the electrical conductivity in the underlying thawed region is greater than that in the overlying permafrost.

  18. Hydration-dependent dynamic crossover phenomenon in protein hydration water

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Fratini, Emiliano; Li, Mingda; Le, Peisi; Mamontov, Eugene; Baglioni, Piero; Chen, Sow-Hsin

    2014-10-01

    The characteristic relaxation time τ of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level hc=0.2-0.25 and becomes more visible as h increases. When h is lower than hc, τ only exhibits Arrhenius behavior in the measured temperature range. The activation energy of the Arrhenius behavior is insensitive to h, indicating a local-like motion. Moreover, the h dependence of the crossover temperature shows that the protein dynamic transition is not directly or solely induced by the dynamic crossover in the hydration water.

  19. 63. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT THE FIRE BOX AND KILN FOR DILLUTANT. APRIL 22, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  20. Sevoflurane degradation by soda lime in a circle breathing system.

    PubMed

    Munday, I T; Ward, P M; Foden, N D; Jones, R M; Van Pelt, F N; Kenna, J G

    1996-07-01

    Sevoflurane is degraded by soda lime to a vinyl ether commonly referred to as compound A. We measured the concentration of compound A in the circle breathing system of 31 patients receiving sevoflurane anaesthesia. Inspiratory and expiratory gas samples were analysed using gas chromatography and flame ionisation detection. The end-tidal sevoflurane concentration and soda lime temperature were recorded. The peak compound A concentration ranged between 10 to 32 ppm in the inspiratory limb and 7 to 26 ppm in the expiratory limb. There was a positive correlation between the peak compound A concentration and the end-tidal sevoflurane concentration (r2 = 0.545, p < 0.0001) and the soda lime temperature (r2 = 0.301, p = 0.0014). We conclude that the end-tidal concentration of sevoflurane and the temperature of the soda lime are important variables in determining concentration of compound A in a circle system.

  1. Utricular otoconia of some amphibians have calcitic morphology

    NASA Technical Reports Server (NTRS)

    Pote, K. G.; Ross, M. D.

    1993-01-01

    This report concerns the morphological features of otoconia removed from the inner ear of four amphibian species. Results from scanning electron microscopic examination are compared based on the site of origin. These results show that utricular otoconia have a mineral structure that mimics calcite, rather than the widely accepted idea that they are mineralized by calcium carbonate of the aragonite polymorph.

  2. Atomistic simulation of the differences between calcite and dolomite surfaces

    SciTech Connect

    Titiloye, J.O.; Leeuw, N.H. de; Parker, S.C.

    1998-08-01

    Atomistic simulation methods have been used to calculate and compare the surface structures and energies of the {l_brace}10{bar 1}4{r_brace}, {l_brace}0001{r_brace}, {l_brace}10{bar 1}0{r_brace}, {l_brace}11{bar 2}0{r_brace} and {l_brace}10{bar 1}1{r_brace} surfaces of calcite and dolomite and to evaluate their equilibrium morphologies. The calcite {l_brace}10{bar 1}4{r_brace} and the dolomite {l_brace}10{bar 1}0{r_brace} and {l_brace}11{bar 2}0{r_brace} surfaces are the most stable crystal planes. Investigation of the segregation of Mg and Ca ions in the dolomite crystal shows a clear preference for Ca{sup 2+} ions at the surface sites and for Mg{sup 2+} ions in the bulk sites and hence growth onto dolomite results in calcium carbonate or high magnesian calcite crystals which helps explain the difficulty in crystallizing dolomite vs. calcite under laboratory conditions.

  3. Isolation and identification of Pseudomonas azotoformans for induced calcite precipitation.

    PubMed

    Heidari Nonakaran, Siamak; Pazhouhandeh, Maghsoud; Keyvani, Abdullah; Abdollahipour, Fatemeh Zahra; Shirzad, Akbar

    2015-12-01

    Biomineralization is a process by which living organisms produce minerals. The extracellular production of these biominerals by microbes has potential for various bioengineering applications. For example, crack remediation and improvement of durability of concrete is an important goal for engineers and biomineral-producing microbes could be a useful tool in achieving this goal. Here we report the isolation, biochemical characterization and molecular identification of Pseudomonas azotoformans, a microbe that produces calcite and which potentially be used to repair cracks in concrete structures. Initially, 38 bacterial isolates were isolated from soil and cements. As a first test, the isolates were screened using a urease assay followed by biochemical tests for the rate of urea hydrolysis, calcite production and the insolubility of calcite. Molecular amplification and sequencing of a 16S rRNA fragment of selected isolates permitted us to identify P. azotoformans as a good candidate for preparation of biotechnological concrete. This species was isolated from soil and the results show that among the tested isolates it had the highest rate of urea hydrolysis, produced the highest amount of calcite, which, furthermore was the most adhesive and insoluble. This species is thus of interest as an agent with the potential ability to repair cracks in concrete. PMID:26386580

  4. Inhibition by glycosaminoglycans of CaCO3 (calcite) crystallization.

    PubMed Central

    Grant, D; Long, W F; Williamson, F B

    1989-01-01

    Of a range of glycosaminoglycans, heparin and heparan sulphate were the most effective inhibitors in vitro of CaCO3 (calcite) crystallization as assayed by conductimetric measurements. The possible role of such glycosaminoglycans in modulating calcium-salt crystallizations in vivo is discussed. PMID:2719649

  5. Aragonite / Calcite seas and the evolution of biomineralization

    NASA Astrophysics Data System (ADS)

    Balthasar, Uwe

    2015-04-01

    The vast majority of marine invertebrate skeletons are composed of the CaCO3 polymorphs aragonite and calcite, yet the influence of seawater composition on the evolution of calcareous skeletal composition is poorly understood. The main theoretical framework in which the evolution of CaCO3 shell mineralogy is assessed is the aragonite-calcite sea hypothesis with conventional thinking suggesting that a threshold in the marine Mg:Ca ratio determines CaCO3 polymorph formation. I present data from CaCO3 precipitation experiments to show that the concept of a distinct threshold is misleading because Mg:Ca ratio and temperature combined result in a Phanerozoic continuum of co-existing aragonite-calcite seas with aragonite-facilitating conditions existing throughout the Phanerozoic in shallow warm-water (>20° C) environments. The stable reservoir of aragonite-favouring conditions in shallow warm water environments potentially explains the trend of increasing occurrences of skeletal aragonite throughout the Phanerozoic, particularly in the context of the 'out of the tropics' hypothesis. By contrast, the most prominent fluctuations with respect to aragonite-calcite sea conditions can be expected to have occurred in mid- to high latitudes.

  6. Rapid gas hydrate formation process

    DOEpatents

    Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

    2013-01-15

    The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

  7. Global occurrences of gas hydrate

    USGS Publications Warehouse

    Kvenvolden, K.A.; Lorenson, T.D.

    2001-01-01

    Natural gas hydrate is found worldwide in sediments of outer continental margins of all oceans and in polar areas with continuous permafrost. There are currently 77 localities identified globally where geophysical, geochemical and/or geological evidence indicates the presence of gas hydrate. Details concerning individual gas-hydrate occurrences are compiled at a new world-wide-web (www) site (http://walrus.wr.usgs.gov/globalhydrate). This site has been created to facilitate global gas-hydrate research by providing information on each of the localities where there is evidence for gas hydrate. Also considered are the implications of gas hydrate as a potential (1) energy resource, (2) factor in global climate change, and (3) geohazard.

  8. Uranium Isotope Fractionation During Coprecipitation with Aragonite and Calcite

    NASA Astrophysics Data System (ADS)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2014-12-01

    Natural variations in the 238U/235U ratio of marine carbonates may provide a useful way of constraining past variations in ocean redox conditions. However, before applying this novel redox proxy, it is essential to explore possible isotopic fractionation during U coprecipitation with aragonite and calcite. We investigated these effects in laboratory experiments. Aragonite and calcite coprecipitation experiments were conducted at pH 8.5±0.1 using a constant addition method [1]. More than 90% of the U was incorporated into the solid phase at the end of each experiment. Samples were purified using UTEVA chemistry and δ238/235U was measured using 233U-236U double-spike MC-ICP-MS with a precision of ±0.10‰ [2]. The aragonite experiment demonstrated a 238U/235U Rayleigh fractionation factor of α=1.00008±0.00002 with the 238U preferentially incorporated. In contrast, the calcite experiment demonstrated no resolvable U isotope fractionation (α=1.00001±0.00003). To determine if U isotopes are affected during the early diagenetic conversion of aragonite to calcite, natural carbonate samples were collected along an aragonite-calcite transition across a single coral head in the Key Largo limestone, and characterized for U concentration and δ238/235U [3]. We found that the mean δ238/235U in aragonite (-0.33±0.07‰ 2se) was slightly heavier than that in calcite (-0.37±0.02‰ 2se). Further work is needed to address the mechanisms leading to differential isotopic fractionation of U(VI) during incorporation into aragonite and calcite. Possible drivers include differences in coordination in the crystal structure or equilibrium isotopic fractionation between various aqueous U(VI) species prior to incorporation. [1] Reeder et al. (2001) GCA 65, 3491-3503. [2] Weyer et al., (2008) GCA 72, 345-359. [3] Gill et al., (2008) GCA 72, 4699-4722.

  9. NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

    NASA Astrophysics Data System (ADS)

    Phillips, Brian L.; Zhang, Zelong; Kubista, Laura; Frisia, Silvia; Borsato, Andrea

    2016-06-01

    Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31P{1H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm. These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31P/13C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13C-labeled carbonate. All coprecipitates showed significant 31P dephasing effects upon 13C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small

  10. Investigation of copper sorption by sugar beet processing lime waste.

    PubMed

    Ippolito, J A; Strawn, D G; Scheckel, K G

    2013-01-01

    In the western United States, sugar beet processing for sugar recovery generates a lime-based waste product (∼250,000 Mg yr) that has little liming value in the region's calcareous soils. This area has recently experienced an increase in dairy production, with dairies using copper (Cu)-based hoof baths to prevent hoof diseases. A concern exists regarding soil Cu accumulation because spent hoof baths may be disposed of in waste ponds, with pond waters being used for irrigation. The objective of this preliminary study was to evaluate the ability of lime waste to sorb Cu. Lime waste was mixed with increasing Cu-containing solutions (up to 100,000 mg Cu kg lime waste) at various buffered pH values (pH 6, 7, 8, and 9) and shaken over various time periods (up to 30 d). Copper sorption phenomenon was quantified using sorption maximum fitting, and the sorption mechanism was investigated using X-ray absorption spectroscopy. Results showed that sorption onto lime waste increased with decreasing pH and that the maximum Cu sorption of ∼45,000 mg kg occurred at pH 6. X-ray absorption spectroscopy indicated that Cu(OH) was the probable species present, although the precipitate existed as small multinuclear precipitates on the surface of the lime waste. Such structures may be precursors for larger surface precipitates that develop over longer incubation times. Findings suggest that sugar beet processing lime waste can viably sorb Cu from liquid waste streams, and thus it may have the ability to remove Cu from spent hoof baths.

  11. Gas hydrate cool storage system

    DOEpatents

    Ternes, M.P.; Kedl, R.J.

    1984-09-12

    The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

  12. Molecular ordering of ethanol at the calcite surface.

    PubMed

    Pasarín, I S; Yang, M; Bovet, N; Glyvradal, M; Nielsen, M M; Bohr, J; Feidenhans'l, R; Stipp, S L S

    2012-02-01

    To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S. Palentology 2004, 43 (Part 3), 725-743] and molecular dynamics (MD) modeling [Yang, M., Stipp, S. L. S., and Harding, J. H. Cryst. Growth Des. 2008, 8 (11), 4066-4074], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH(3)-CH(2)-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH(3) ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems.

  13. Interpretation of the lime column penetration test

    NASA Astrophysics Data System (ADS)

    Liyanapathirana, D. S.; Kelly, R. B.

    2010-06-01

    Dry soil mix (DSM) columns are used to reduce the settlement and to improve the stability of embankments constructed on soft clays. During construction the shear strength of the columns needs to be confirmed for compliance with technical assumptions. A specialized blade shaped penetrometer known as the lime column probe, has been developed for testing DSM columns. This test can be carried out as a pull out resistance test (PORT) or a push in resistance test (PIRT). The test is considered to be more representative of average column shear strength than methods that test only a limited area of the column. Both PORT and PIRT tests require empirical correlations of measured resistance to an absolute measure of shear strength, in a similar manner to the cone penetration test. In this paper, finite element method is used to assess the probe factor, N, for the PORT test. Due to the large soil deformations around the probe, an Arbitrary Lagrangian Eulerian (ALE) based finite element formulation has been used. Variation of N with rigidity index and the friction at the probe-soil interface are investigated to establish a range for the probe factor.

  14. Anomalous porosity preservation and preferential accumulation of gas hydrate in the Andaman accretionary wedge, NGHP-01 site 17A

    SciTech Connect

    Rose, Kelly K.; Johnson, Joel E.; Torres, Marta E.; Hong, WeiLi; Giosan, Liviu; Solomon, E.; Kastner, Miriam; Cawthern, Thomas; Long, Philip E.; Schaef, Herbert T.

    2014-12-01

    In addition to well established properties that control the presence or absence of the hydrate stability zone, such as pressure, temperature, and salinity, additional parameters appear to influence the concentration of gas hydrate in host sediments. The stratigraphic record at Site 17A in the Andaman Sea, eastern Indian Ocean, illustrates the need to better understand the role pore-scale phenomena play in the distribution and presence of marine gas hydrates in a variety of subsurface settings. In this paper we integrate field-generated datasets with newly acquired sedimentology, physical property, imaging and geochemical data with mineral saturation and ion activity products of key mineral phases such as amorphous silica and calcite, to document the presence and nature of secondary precipitates that contributed to anomalous porosity preservation at Site 17A in the Andaman Sea. This study demonstrates the importance of grain-scale subsurface heterogeneities in controlling the occurrence and distribution of concentrated gas hydrate accumulations in marine sediments, and document the importance that increased permeability and enhanced porosity play in supporting gas concentrations sufficient to support gas hydrate formation. The grain scale relationships between porosity, permeability, and gas hydrate saturation documented at Site 17A likely offer insights into what may control the occurrence and distribution of gas hydrate in other sedimentary settings.

  15. Fluid mediated transformation of aragonitic cuttlebone to calcite

    NASA Astrophysics Data System (ADS)

    Perdikouri, C.; Kasioptas, A.; Putnis, A.

    2009-04-01

    The aragonite to calcite transition has been studied extensively over the years because of its wide spectra of applications and of its significant geochemical interest. While studies of kinetics (e.g. Topor et al., 1981), thermodynamics (e.g. Wolf et al., 1996) and behavior of ions such as Sr and Mg (e.g. Yoshioka et al., 1986) have been made there are still unanswered questions regarding this reaction especially in the cases where the effects of fluid composition are considered. It is well known that when heated in air, aragonite transforms by a solid state reaction to calcite. The aragonite cuttlebone of the sepia officinalis that was used for our experiments undergoes a phase transition at ~370-390˚ C, measured by in situ heating experiments in a Philips X'pert X-ray powder diffractometer equipped with a HTK 1200 High temperature oven. Successive X-ray scans were taken at isothermal temperatures at 200C intervals. A similar temperature range was found by Vongsavat et al. 2006, who studied this transition in Acropora corals. It is possible however to promote this transition at considerably lower temperatures by means of a fluid mediated reaction where the replacement takes place by a dissolution-precipitation mechanism (Putnis & Putnis, 2007). We have successfully carried out hydrothermal experiments where cuttlebone has been converted to calcite at 200˚ C. Using the PhreeqC program we calculated the required composition of a solution that would be undersaturated with respect to aragonite and saturated with respect to calcite leading to dissolution of the aragonite and to a consequent precipitation of the new calcite phase, similar to the experiments described in an earlier study (Perdikouri et al, 2008). This reaction is not pseudomorphic and results in the destruction of the morphology, presumably due to the molar volume increase. A total transformation of the cuttlebone produced a fine calcite powder. The cuttlebone exhibits a unique microstructure, made

  16. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    NASA Astrophysics Data System (ADS)

    Kimball, J.; Tripati, R. E.; Dunbar, R.

    2015-12-01

    corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite, although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect that crystals may attain nominal mineral equilibrium clumped isotope signatures only under conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological "vital-effect" influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological "vital" effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation.

  17. Effect of Lime on Mechanical and Durability Properties of Blended Cement Based Concrete

    NASA Astrophysics Data System (ADS)

    Acharya, Prasanna Kumar; Patro, Sanjaya Kumar; Moharana, Narayana C.

    2016-06-01

    This work presents the results of experimental investigations performed to evaluate the effect of lime on mechanical and durability properties of concrete mixtures made with blended cement like Portland Slag Cement (PSC) and Portland Pozzolana Cement (PPC) with lime content of 0, 5, 7 and 10 %. Test result indicated that inclusion of hydraulic lime on replacement of cement up to 7 % increases compressive strength of concrete made with both PSC and PPC. Flexural strength increased with lime content. Highest flexural strength is reported at 7 % lime content for both PSC and PPC. Workability is observed to decrease with lime addition which could be compensated with introduction of super plasticizer. Acid and sulphate resistance increase slightly up to 7 % of lime addition and is found to decrease with further addition of lime. Lime addition up to 10 % does not affect the soundness of blended cements like PSC and PPC.

  18. Growth rate controlled barium partitioning in calcite and aragonite

    NASA Astrophysics Data System (ADS)

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2016-04-01

    The barium (Ba) content and the Ba/Ca molar ratios in biogenic and abiotic carbonates have been widely used from the scientific community as a geochemical proxy especially in marine and early diagenetic settings. The Ba content of carbonate minerals has been earlier associated to changes in oceanic circulation that may have been caused by upwelling, changes in weathering regimes and river-runoff as well as melt water discharge. The physicochemical controls of Ba ion incorporation in the two most abundant CaCO3 polymorphs found in Earth's surface environments, i.e. calcite and aragonite, have adequately been studied only for calcite. These earlier studies (i.e. [1]) suggest that at increasing growth rate, Ba partitioning in calcite is increasing as well. In contrast, to date the effect of growth rate on the partitioning of Ba in aragonite remains questionable, despite the fact that this mineral phase is the predominant carbonate-forming polymorph in shallow marine environments. To shed light on the mechanisms controlling Ba ion uptake in carbonates in this study we performed steady-state Ba co-precipitation experiments with calcite and aragonite at 25°C. The obtained results for the partitioning of Ba in calcite are in good agreement with those reported earlier by [1], whereas those for aragonite indicate a reduction of Ba partitioning at elevated aragonite growth rates, with the partitioning coefficient value between solid and fluid to be approaching the unity. This finding is good agreement with the formation of a solid solution in the aragonite-witherite system, owing to the isostructural crystallography of the two mineral phases. Moreover, our data set provides new insights that are required for reconstructing the evolution of the Ba content of pristine marine versus diagenetically altered carbonate minerals commonly occurring in marine subfloor settings, as the thermodynamically less stable aragonite will transform to calcite enriched in Ba, whilst affecting

  19. Fracture-aperture alteration induced by calcite precipitation

    NASA Astrophysics Data System (ADS)

    Jones, T.; Detwiler, R. L.

    2013-12-01

    Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 μm. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, Ω, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation

  20. Soil pH management without lime, a strategy to reduce greenhouse gas emissions from cultivated soils

    NASA Astrophysics Data System (ADS)

    Nadeem, Shahid; Bakken, Lars; Reent Köster, Jan; Tore Mørkved, Pål; Simon, Nina; Dörsch, Peter

    2015-04-01

    For decades, agricultural scientists have searched for methods to reduce the climate forcing of food production by increasing carbon sequestration in the soil and reducing the emissions of nitrous oxide (N2O). The outcome of this research is depressingly meagre and the two targets appear incompatible: efforts to increase carbon sequestration appear to enhance the emissions of N2O. Currently there is a need to find alternative management strategies which may effectively reduce both the CO2 and N2O footprints of food production. Soil pH is a master variable in soil productivity and plays an important role in controlling the chemical and biological activity in soil. Recent investigations of the physiology of denitrification have provided compelling evidence that the emission of N2O declines with increasing pH within the range 5-7. Thus, by managing the soil pH at a near neutral level appears to be a feasible way to reduce N2O emissions. Such pH management has been a target in conventional agriculture for a long time, since a near-neutral pH is optimal for a majority of cultivated plants. The traditional way to counteract acidification of agricultural soils is to apply lime, which inevitably leads to emission of CO2. An alternative way to increase the soil pH is the use of mafic rock powders, which have been shown to counteract soil acidification, albeit with a slower reaction than lime. Here we report a newly established field trail in Norway, in which we compare the effects of lime and different mafic mineral and rock powders (olivine, different types of plagioclase) on CO2 and N2O emissions under natural agricultural conditions. Soil pH is measured on a monthly basis from all treatment plots. Greenhouse gas (GHG) emission measurements are carried out on a weekly basis using static chambers and an autonomous robot using fast box technique. Field results from the first winter (fallow) show immediate effect of lime on soil pH, and slower effects of the mafic rocks. The

  1. Hydration and physical performance.

    PubMed

    Murray, Bob

    2007-10-01

    There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings.

  2. Ductile flow of methane hydrate

    USGS Publications Warehouse

    Durham, W.B.; Stern, L.A.; Kirby, S.H.

    2003-01-01

    Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

  3. Some thermodynamical aspects of protein hydration water.

    PubMed

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Vasi, Cirino; Stanley, H Eugene; Chen, Sow-Hsin

    2015-06-01

    We study by means of nuclear magnetic resonance the self-diffusion of protein hydration water at different hydration levels across a large temperature range that includes the deeply supercooled regime. Starting with a single hydration shell (h = 0.3), we consider different hydrations up to h = 0.65. Our experimental evidence indicates that two phenomena play a significant role in the dynamics of protein hydration water: (i) the measured fragile-to-strong dynamic crossover temperature is unaffected by the hydration level and (ii) the first hydration shell remains liquid at all hydrations, even at the lowest temperature.

  4. Some thermodynamical aspects of protein hydration water

    SciTech Connect

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Vasi, Cirino; Stanley, H. Eugene; Chen, Sow-Hsin

    2015-06-07

    We study by means of nuclear magnetic resonance the self-diffusion of protein hydration water at different hydration levels across a large temperature range that includes the deeply supercooled regime. Starting with a single hydration shell (h = 0.3), we consider different hydrations up to h = 0.65. Our experimental evidence indicates that two phenomena play a significant role in the dynamics of protein hydration water: (i) the measured fragile-to-strong dynamic crossover temperature is unaffected by the hydration level and (ii) the first hydration shell remains liquid at all hydrations, even at the lowest temperature.

  5. Molecular dynamics investigation on the adsorption behaviors of H2O, CO2, CH4 and N2 gases on calcite (1 1 bar 0) surface

    NASA Astrophysics Data System (ADS)

    Wang, Shimeng; Zhou, Guanggang; Ma, Yue; Gao, Lei; Song, Ranran; Jiang, Guancheng; Lu, Guiwu

    2016-11-01

    Molecular dynamics simulations (MD) were carried out to investigate the adsorption behaviors of H2O, CO2, CH4 and N2 gases, which are the main and important components in gas wells, on the calcite surface at reservoir conditions. By analyzing the binding energy and Helmholtz free energy, we found that the preferential adsorption order of these four gases is: H2O > CO2 > CH4 > N2. Moreover, we have also calculated the radial distribution function profiles of the system. It shows that the H2O molecules will form two compact adsorbed layers on the surface, which denotes the calcite (1 1 bar 0) surface is hydrophilic. The CO2 molecules can also form a adsorbed layer on the surface, while there are no significant features indicating that the CH4 and N2 molecules were apparently adsorbed on calcite (1 1 bar 0) surface. Our calculations results can not only give a microscopic insight into the wettability of gas reservoirs but also provide theoretical instructions for hydrate risk evaluation of enhanced gas recovery.

  6. Hydration of a low-alkali CEM III/B-SiO{sub 2} cement (LAC)

    SciTech Connect

    Lothenbach, Barbara; Le Saout, Gwenn; Ben Haha, Mohsen; Figi, Renato; Wieland, Erich

    2012-02-15

    The hydration of a low-alkali cement based on CEM III/B blended with 10 wt.% of nanosilica has been studied. The nanosilica reacted within the first days and 90% of the slag reacted within 3.5 years. C-S-H (Ca/Si {approx} 1.2, Al/Si {approx} 0.12), calcite, hydrotalcite, ettringite and possibly straetlingite were the main hydrates. The pore water composition revealed ten times lower alkali concentrations than in Portland cements. Reducing conditions (HS{sup -}) and a pH value of 12.2 were observed. Between 1 month and 3.5 years of hydration more hydrates were formed due to the ongoing slag reaction but no significant differences in the composition of the pore solution or solid phase assemblage were observed. On the basis of thermodynamic calculations it is predicted that siliceous hydrogarnet could form in the long-term and, in the presence of siliceous hydrogarnet, also thaumasite. Nevertheless, even after 3.5 year hydration, neither siliceous hydrogarnet nor thaumasite have been observed.

  7. Gas Hydrate Petroleum System Analysis

    NASA Astrophysics Data System (ADS)

    Collett, T. S.

    2012-12-01

    In a gas hydrate petroleum system, the individual factors that contribute to the formation of gas hydrate accumulations, such as (1) gas hydrate pressure-temperature stability conditions, (2) gas source, (3) gas migration, and (4) the growth of the gas hydrate in suitable host sediment can identified and quantified. The study of know and inferred gas hydrate accumulations reveal the occurrence of concentrated gas hydrate is mostly controlled by the presence of fractures and/or coarser grained sediments. Field studies have concluded that hydrate grows preferentially in coarse-grained sediments because lower capillary pressures in these sediments permit the migration of gas and nucleation of hydrate. Due to the relatively distal nature of the deep marine geologic settings, the overall abundance of sand within the shallow geologic section is usually low. However, drilling projects in the offshore of Japan, Korea, and in the Gulf of Mexico has revealed the occurrence of significant hydrate-bearing sand reservoirs. The 1999/2000 Japan Nankai Trough drilling confirmed occurrence of hydrate-bearing sand-rich intervals (interpreted as turbidite fan deposits). Gas hydrate was determined to fill the pore spaces in these deposits, reaching saturations up to 80% in some layers. A multi-well drilling program titled "METI Toaki-oki to Kumano-nada" also identified sand-rich reservoirs with pore-filling hydrate. The recovered hydrate-bearing sand layers were described as very-fine- to fine-grained turbidite sand layers measuring from several centimeters up to a meter thick. However, the gross thickness of the hydrate-bearing sand layers were up to 50 m. In 2010, the Republic of Korea conducted the Second Ulleung Basin Gas Hydrate (UBGH2) Drilling Expedition. Seismic data clearly showed the development of a thick, potential basin wide, sedimentary sections characterized by mostly debris flows. The downhole LWD logs and core data from Site UBGH2-5 reveal that each debris flows is

  8. Does calcite encrustation in Chara provide a phosphorus nutrient sink?

    PubMed

    Siong, Kian; Asaeda, Takashi

    2006-01-01

    We studied the effect of calcite encrustation in stoneworts (Chara spp.) on P cycling in an aquatic ecosystem. Sequential fractionation was performed to quantify P fractions of the internodes of calcified (Ca-CF) and uncalcified (UCa-CF) Chara fibrosa Agardh ex Bruzelius. Our results showed that Ca-CF was able to store more P and about 14 to 23% of total P in Ca-CF was co-precipitated with encrusted calcite, while only 2 to 3% was found in UCa-CF. Furthermore, in Ca-CF, an increased amount of total P did not result in a higher release of bioavailable water-soluble and sodium hydroxide-extractable P. Extracellular calcification in Chara enhanced nutrient sink for P, provided a further bottom-up control of phytoplankton, and should be regarded as a positive feedback in stabilizing Chara dominance in lakes.

  9. Tuning hardness in calcite by incorporation of amino acids

    NASA Astrophysics Data System (ADS)

    Kim, Yi-Yeoun; Carloni, Joseph D.; Demarchi, Beatrice; Sparks, David; Reid, David G.; Kunitake, Miki E.; Tang, Chiu C.; Duer, Melinda J.; Freeman, Colin L.; Pokroy, Boaz; Penkman, Kirsty; Harding, John H.; Estroff, Lara A.; Baker, Shefford P.; Meldrum, Fiona C.

    2016-08-01

    Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure-property relationships of even the simplest building unit--mineral single crystals containing embedded macromolecules--remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0-7 mol%) or aspartic acid (0-4 mol%), we elucidate the origin of the superior hardness of biogenic calcite. We analysed lattice distortions in these model crystals by using X-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules.

  10. U(VI) behaviour in hyperalkaline calcite systems

    NASA Astrophysics Data System (ADS)

    Smith, Kurt F.; Bryan, Nicholas D.; Swinburne, Adam N.; Bots, Pieter; Shaw, Samuel; Natrajan, Louise S.; Mosselmans, J. Frederick W.; Livens, Francis R.; Morris, Katherine

    2015-01-01

    The behaviour of U(VI) in hyperalkaline fluid/calcite systems was studied over a range of U(VI) concentrations (5.27 × 10-5 μM to 42.0 μM) and in two high pH systems, young and old synthetic cement leachate in batch sorption experiments. These systems were selected to be representative of young- (pH 13.3) and old-stage (pH 10.5) leachate evolution within a cementitious geological disposal facility. Batch sorption experiments, modelling, extended X-ray absorption fine structure spectroscopy, electron microscopy, small angle X-ray scattering and luminescence spectroscopy were used to define the speciation of U(VI) across the systems of study. At the lowest concentrations (5.27 × 10-5 μM 232U(VI)) significant U removal was observed for both old and young cement leachates, and this was successfully modelled using a first order kinetic adsorption modelling approach. At higher concentrations (>4.20 μM) in the young cement leachate, U(VI) showed no interaction with the calcite surface over an 18 month period. Small angle X-ray scattering techniques indicated that at high U concentrations (42.0 μM) and after 18 months, the U(VI) was present in a colloidal form which had little interaction with the calcite surface and consisted of both primary and aggregated particles with a radius of 7.6 ± 1.1 and 217 ± 24 Å, respectively. In the old cement leachate, luminescence spectroscopy identified two surface binding sites for U(VI) on calcite: in the system with 0.21 μM U(VI), a liebigite-like Ca2UO2(CO3)3 surface complex was identified; at higher U(VI) concentrations (0.42 μM), a second binding site of undetermined coordination was identified. At elevated U(VI) concentrations (>2.10 μM) in old cement leachate, both geochemical data and luminescence spectroscopy suggested that surface mediated precipitation was controlling U(VI) behaviour. A focused ion beam mill was used to create a section across the U(VI) precipitate-calcite interface. Transmission electron

  11. Tuning hardness in calcite by incorporation of amino acids.

    PubMed

    Kim, Yi-Yeoun; Carloni, Joseph D; Demarchi, Beatrice; Sparks, David; Reid, David G; Kunitake, Miki E; Tang, Chiu C; Duer, Melinda J; Freeman, Colin L; Pokroy, Boaz; Penkman, Kirsty; Harding, John H; Estroff, Lara A; Baker, Shefford P; Meldrum, Fiona C

    2016-08-01

    Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure-property relationships of even the simplest building unit-mineral single crystals containing embedded macromolecules-remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0-7 mol%) or aspartic acid (0-4 mol%), we elucidate the origin of the superior hardness of biogenic calcite. We analysed lattice distortions in these model crystals by using X-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules. PMID:27135858

  12. The effect of sulfated polysaccharides on the crystallization of calcite superstructures

    NASA Astrophysics Data System (ADS)

    Fried, Ruth; Mastai, Yitzhak

    2012-01-01

    Calcite with unique morphology and uniform size has been successfully synthesized in the presence of classes of polysaccharides based on carrageenans. In the crystallization of calcite, the choice of different carrageenans, (iota, lambda and kappa), as additives concedes systematic study of the influence of different chemical structures and particularly molecular charge on the formation of CaCO 3 crystals. The uniform calcite superstructures are formed by assemblies and aggregation of calcite crystals. The mechanism for the formation of calcite superstructures was studied by a variety of techniques, SEM, TEM, XRD, time-resolved conductivity and light scattering measurements, focusing on the early stages of crystals' nucleation and aggregation.

  13. Interaction of copper with the surface of calcite

    SciTech Connect

    Franklin, M.L.; Morse, J.W.

    1981-05-01

    The interaction of Cu ions in solution with the surface of calcite has been studied in a range of solutions from pure water to seawater. Observations of the uptake of Cu from solution onto calcite indicates that the process is rapid and strong in both distilled water and seawater. In distilled water, Cu uptake is directly proportional to the concentration of Cu in solution; Cu/sub s/ = K/sub s/Cu/sub 1/. This Cu/sub s/ dependence on Cu/sub 1/ is linear over the entire Cu concentration range studied (0.1 to 200 ..mu..M). Results do not indicate the formation of a precipitate of either malachite or copper carbonate. In seawater, the uptake of Cu is also directly proportional to the concentration of Cu/sub 1/ up to a limiting value of approximately 13 ..mu..M. The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water. This is probably the result of smaller Cu/sub 1/ activity coefficients and increased site competition by other ions in seawater. Attempts to increase the Cu/sub 1/ concentration above 13 ..mu..M resulted in the additional Cu being deposited on the surface of the calcite. A possible explanation for this behavior is the formation of a precipitate of malachite on the calcite surface. The value of K/sub s/ decreased slightly with increasing solid to solution ratios in seawater.

  14. Calcite mylonites in the Central Alpine ``root zone''

    NASA Astrophysics Data System (ADS)

    Heitzmann, Peter

    1987-04-01

    North of the Insubric line, in the Central Alpine "root zone", carbonate rocks are concentrated in very narrow zones and have been metamorphosed under amphibolite facies conditions by the Tertiary Lepontine metamorphism (grain size ~1 mm). Post-metamorphic deformation under greenschist facies conditions produced calcite mylonite bands a few millimeters to tens of meters wide in these marble zones. Microstructural development begins with twin formation, bending of twin boundaries, grain and twin boundary migration and recrystallization in high stress regions. Progressive mylonitization—by dynamic recrystallization—results in a microstructure with elongated calcite crystals (long axis 20-50 μm, axial ration 1:4). In this fine-grained matrix, porphyroclasts of calcite, quartz, white mica, biotite, diopside, tremolite, scapolite and plagioclase are preserved. Ultra-mylonite bands in pure calcite rocks show an even finer grain size of 5-10 μm. Lattice preferred orientation is not present in the undeformed marbles, but it develops during mylonitization. The c-axis orientation in the mylonites forms an asymmetric point maximum. In the ultra-mylonite no preferred orientation is left. It is concluded from microstructural and textural aspects, that during mylonitization, dislocation creep accompanied by dynamic recrystallization were the most important processes, whilst grain-boundary sliding was the dominant mechanism during the formation of the ultra-mylonites. Shear-sense determinations indicate a horizontal right-lateral strike-slip shear system. This is in good agreement with evidence regarding other movements along the Insubric line which can be observed in ductile and brittle shear zones.

  15. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    PubMed

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  16. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    PubMed

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-03-24

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

  17. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    PubMed Central

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  18. Visualization of acoustic cavitation effects on suspended calcite crystals.

    PubMed

    Wagterveld, R M; Boels, L; Mayer, M J; Witkamp, G J

    2011-01-01

    The acoustic cavitation (42,080 Hz, 7.1 W cm(-2) or 17 W) effects on suspended calcite crystals, sized between 5 and 50 μm, have been visualized for the first time using high speed photography. High speed recordings with a duration of 1 s containing up to 300,000 frames per second, revealed the effect of cluster and streamer cavitation on several calcite crystals. Cavitation clusters, evolved from cavitation inception and collapse, caused attrition, disruption of aggregates and deagglomeration, whereas streamer cavitation was observed to cause deagglomeration only. Cavitation on the surface gave the crystals momentum. However, it is shown that breakage of accelerated crystals by interparticle collisions is unrealistic because of their small sizes and low velocities. Crystals that were accelerated by bubble expansion, subsequently experienced a deceleration much stronger than expected from drag forces, upon bubble collapse. Experiments with pre-dried crystals seemed to support the current theory on bubble nucleation through the presence of pre-existing gas pockets. However, experiments with fully wetted crystals also showed the nucleation of bubbles on the crystal surface. Although microjet impingement on the crystal surface could not be directly visualized with high speed photography, scanning electron microscopy (SEM) analysis of irradiated calcite seeds showed deep circular indentations. It was suggested that these indentations might be caused by shockwave induced jet impingement. Furthermore, the appearance of voluminous fragments with large planes of fracture indicated that acoustic cavitation can also cause the breakage of single crystal structures.

  19. Heterogeneous conversion of calcite aerosol by nitric acid.

    PubMed

    Preszler Prince, A; Grassian, V H; Kleiber, P; Young, M A

    2007-02-01

    The reaction of nitric acid with calcite aerosol at varying relative humidities has been studied under suspended particle conditions in an atmospheric reaction chamber using infrared absorption spectroscopy. The reactant concentration in the chamber, as well as the appearance of gas phase products and surface adsorbed species, was spectroscopically monitored before and after mixing with CaCO(3) (calcite) particles. The interaction with HNO(3) was found to lead to gas phase CO(2) evolution and increased water uptake due to heterogeneous conversion of the carbonate to particulate nitrate. The reaction was enhanced as the relative humidity of the system was increased, especially at relative humidities above the reported deliquescence point of particulate Ca(NO(3))(2). The measured reaction extent demonstrates that the total calcite particulate mass is available for reaction with HNO(3) and the conversion process is not limited to the particle surface. The spectroscopy of the surface formed nitrate suggests a highly concentrated solution environment with a significant degree of ion pairing. The implications of the HNO(3) loss and the formation of the particulate nitrate product for atmospheric chemistry are discussed. PMID:17242744

  20. Interactions of salicylic acid derivatives with calcite crystals.

    PubMed

    Ukrainczyk, Marko; Gredičak, Matija; Jerić, Ivanka; Kralj, Damir

    2012-01-01

    Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated. PMID:21963207

  1. How tightly does calcite e-twin constrain stress?

    NASA Astrophysics Data System (ADS)

    Yamaji, Atsushi

    2015-03-01

    Mechanical twinning along calcite e-planes has been used for paleostress analyses. Since the twinning has a critical resolved shear stress at ˜10 MPa, not only principal stress axes but also differential stress can be determined from the twins. In this article, five-dimensional stress space used in plasticity theory was introduced to describe the yield loci of calcite e-twinning. The constraints to paleostress from twin and untwin data and from calcite grains twinned on 0, 1, 2 and 3 e-planes were quantified by using their information contents, which were defined in the stress space. The orientations of twinned and untwinned e-planes are known to constrain not only stress axes but also differential stress, D, but they loose the resolution of D if the twin lamellae were formed at D greater than 50-100 MPa. On the other hand, it is difficult to observe twin lamellae subparallel to a thin section. The stochastic modeling of this effect showed that 20-25% of twin lamellae can be overlooked. The degradation of the constraints by this sampling bias can be serious especially for the determination of D.

  2. Nucleation, growth and evolution of calcium phosphate films on calcite.

    PubMed

    Naidu, Sonia; Scherer, George W

    2014-12-01

    Marble, a stone composed of the mineral calcite, is subject to chemically induced weathering in nature due to its relatively high dissolution rate in acid rain. To protect monuments and sculpture from corrosion, we are investigating the application of thin layers of hydroxyapatite (HAP) onto marble. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite. A mild, wet chemical synthesis route, in which diammonium hydrogen phosphate salt was reacted with marble, alone and with cationic and anionic precursors under different reaction conditions, was used to produce inorganic HAP layers on marble. Nucleation and growth on the calcite substrate was studied, as well as metastable phase evolution, using scanning electron microscopy, grazing incidence X-ray diffraction, and atomic force microscopy. Film nucleation was enhanced by surface roughness. The rate of nucleation and the growth rate of the film increased with cationic (calcium) and anionic (carbonate) precursor additions. Calcium additions also influenced phase formation, introducing a metastable phase (octacalcium phosphate) and a different phase evolution sequence.

  3. Interactions of salicylic acid derivatives with calcite crystals.

    PubMed

    Ukrainczyk, Marko; Gredičak, Matija; Jerić, Ivanka; Kralj, Damir

    2012-01-01

    Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated.

  4. Nucleation, growth and evolution of calcium phosphate films on calcite.

    PubMed

    Naidu, Sonia; Scherer, George W

    2014-12-01

    Marble, a stone composed of the mineral calcite, is subject to chemically induced weathering in nature due to its relatively high dissolution rate in acid rain. To protect monuments and sculpture from corrosion, we are investigating the application of thin layers of hydroxyapatite (HAP) onto marble. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite. A mild, wet chemical synthesis route, in which diammonium hydrogen phosphate salt was reacted with marble, alone and with cationic and anionic precursors under different reaction conditions, was used to produce inorganic HAP layers on marble. Nucleation and growth on the calcite substrate was studied, as well as metastable phase evolution, using scanning electron microscopy, grazing incidence X-ray diffraction, and atomic force microscopy. Film nucleation was enhanced by surface roughness. The rate of nucleation and the growth rate of the film increased with cationic (calcium) and anionic (carbonate) precursor additions. Calcium additions also influenced phase formation, introducing a metastable phase (octacalcium phosphate) and a different phase evolution sequence. PMID:25233226

  5. Earthworm-produced calcite granules: A new terrestrial palaeothermometer?

    NASA Astrophysics Data System (ADS)

    Versteegh, Emma A. A.; Black, Stuart; Canti, Matthew G.; Hodson, Mark E.

    2013-12-01

    In this paper we show for the first time that calcite granules, produced by the earthworm Lumbricus terrestris, and commonly recorded at sites of archaeological interest, accurately reflect temperature and soil water δ18O values. Earthworms were cultivated in an orthogonal combination of two different (granule-free) soils moistened by three types of mineral water and kept at three temperatures (10, 16 and 20 °C) for an acclimatisation period of three weeks followed by transfer to identical treatments and cultivation for a further four weeks. Earthworm-secreted calcite granules were collected from the second set of soils. δ18O values were determined on individual calcite granules (δ18Oc) and the soil solution (δ18Ow). The δ18Oc values reflect soil solution δ18Ow values and temperature, but are consistently enriched by 1.51 (± 0.12)‰ in comparison to equilibrium in synthetic carbonates. The data fit the equation 1000 ln α = [20.21 ± 0.92] (103 T-1) - [38.58 ± 3.18] (R2 = 0.95; n = 96; p < 0.0005). As the granules are abundant in modern soils, buried soils and archaeological contexts, and can be dated using U-Th disequilibria, the developed palaeotemperature relationship has enormous potential for application to Holocene and Pleistocene time intervals.

  6. Alternative origins for nannobacteria-like objects in calcite

    NASA Astrophysics Data System (ADS)

    Kirkland, Brenda L.; Lynch, F. Leo; Rahnis, Michael A.; Folk, Robert L.; Molineux, Ian J.; McLean, Robert J. C.

    1999-04-01

    More than 40 calcite-precipitation experiments were performed under sterile conditions in order to investigate the origins of 25 300 nm spherical-, rod-, and ovoid-shaped objects that have been widely interpreted as evidence of nanometer-scale life (i.e., nannobacteria). Individual experiments included the addition of soluble organic compounds, common species of eubacteria, or phage-induced eubacterial lysates. These experiments indicate that many of the nanometer-scale objects have inorganic or nonnannobacterial origins. In the precipitation experiments, calcite formed euhedral crystals 50 800 nm in diameter and smaller (<50 nm) anhedral or rounded particles or protocrystals. The small anhedral or rounded solids resembled nannobacteria. The relative amount of anhedral or rounded calcite was greatest in experiments with a dissolved organic component. These controlled experiments are in accord with observations that rounded nanometer-scale objects are more common in minerals formed in organic-rich environments. Bacterial fragments occur as rounded to irregularly shaped particles that included cell-wall fragments, expulsed cytoplasm, and relict capsules that also closely resembled nannobacteria. Acid etching of the large euhedral crystals produced in the precipitation experiments also resulted in the formation of nanometer-scale features that resembled nannobacteria in natural carbonates. The shapes of the etching artifacts vary as a function of the strength of the acid and the duration of etching. Much caution is advisable in interpreting the origin of rounded features <50 nm.

  7. Liming Induced Changes in Arsenic Dissolution from Mine Wastes

    NASA Astrophysics Data System (ADS)

    Dudley, L. M.

    2009-12-01

    Incorporation of lime amendments into mine wastes is an effective treatment to neutralize active and potential acidity, reduce soluble metals, and facilitate plant growth. Many mine wastes contain arsenic. In general, the solubility of As (a metalloid) increases with increasing pH. However, a number of laboratory and field studies with mine waste have shown decreased solubility of arsenic with increasing pH. These studies have not identified what factors are influencing the fate of arsenic in these mine wastes, nor determined the mechanisms involved in reducing the soluble arsenic. This research project evaluated the physical, chemical, and morphological factors affecting a decrease in soluble arsenic concentrations upon liming and whether characteristics of an unamended waste can be used to determine the mobility of arsenic in the amended waste. Testing a mine waste for the parameters soluble Fe plus Al plus Mn; percent clay; total lime requirement; arsenic oxyanions; sequential extraction of metals; mineralogy; soluble Ca and Ni; and potentially EC and CEC/AEC will enable prediction of the potential fate of arsenic following liming of an arsenic-laden, acidic-metalliferrous mine waste. Inverse geochemical modeling was used to identify potential reaction pathways explaining the difference in As solubility induced by liming.

  8. Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany

    USGS Publications Warehouse

    Komor, S.C.

    1995-01-01

    The KTB pilot borehole in northeast Bavaria, Germany, penetrates 4000 m of gneiss, amphibolite, and subordinate calc-silicate, lamprophyre and metagabbro. There are three types of calcite in the drilled section: 1) metamorphic calcite in calc-silicate and marble; 2) crack-filling calcite in all lithologies; and 3) replacement calcite in altered minerals. Crack-filling and replacement calcite postdate metamorphic calcite. Multiple calcite generations in individual cracks suggest that different generations of water repeatedly flowed through the same cracks. Crack-filling mineral assemblages that include calcite originally formed at temperatures of 150-350??C. Presently, crack-filling calcite is in chemical and isotopic equilibrium with saline to brackish water in the borehole at temperatures of ???120??C. The saline to brackish water contains a significant proportion of meteoric water. Re-equilibration of crack-filling calcite to lower temperatures means that calcite chemistry tells us little about water-rock interactions in the crystal section of temperatures higher than ~120??C. -from Author

  9. Geobacillus thermoglucosidasius Endospores Function as Nuclei for the Formation of Single Calcite Crystals

    PubMed Central

    Murai, Rie

    2013-01-01

    Geobacillus thermoglucosidasius colonies were placed on an agar hydrogel containing acetate, calcium ions, and magnesium ions, resulting in the formation of single calcite crystals (calcites) within and peripheral to the plating area or parent colony. Microscopic observation of purified calcites placed on the surface of soybean casein digest (SCD) nutrient medium revealed interior crevices from which bacterial colonies originated. Calcites formed on the gel contained [1-13C]- and [2-13C]acetate, demonstrating that G. thermoglucosidasius utilizes carbon derived from acetate for calcite formation. During calcite formation, vegetative cells swam away from the parent colony in the hydrogel. Hard-agar hydrogel inhibited the formation of calcites peripheral to the parent colony. The calcite dissolved completely in 1 M HCl, with production of bubbles, and the remaining endospore-like particles were easily stained with Brilliant green dye. The presence of DNA and protein in calcites was demonstrated by electrophoresis. We propose that endospores initiate the nucleation of calcites. Endospores of G. thermoglucosidasius remain alive and encapsulated in calcites. PMID:23455343

  10. Imaging surface contacts: power law contact distributions and contact stresses in quartz, calcite, glass and acrylic plastic

    NASA Astrophysics Data System (ADS)

    Dieterich, James H.; Kilgore, Brian D.

    1996-05-01

    A procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials, while the surfaces are subjected to static loads or undergoing frictional slip. Static loading experiments with quartz, calcite, soda-lime glass and acrylic plastic at normal stresses to 30 MPa yield power law distributions of contact areas from the smallest contacts that can be resolved (3.5 μm 2) up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces. In each material, increasing normal stress results in a roughly linear increase of the real area of contact. Mechanisms of contact area increase are by growth of existing contacts, coalescence of contacts and appearance of new contacts. Mean contacts stresses are consistent with the indentation strength of each material. Contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self-similar. The contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies. The contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap. Synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography.

  11. Imaging surface contacts: Power law contact distributions and contact stresses in quartz, calcite, glass and acrylic plastic

    USGS Publications Warehouse

    Dieterich, J.H.; Kilgore, B.D.

    1996-01-01

    A procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials, while the surfaces are subjected to static loads or undergoing frictional slip. Static loading experiments with quartz, calcite, soda-lime glass and acrylic plastic at normal stresses to 30 MPa yield power law distributions of contact areas from the smallest contacts that can be resolved (3.5 ??m2) up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces. In each material, increasing normal stress results in a roughly linear increase of the real area of contact. Mechanisms of contact area increase are by growth of existing contacts, coalescence of contacts and appearance of new contacts. Mean contacts stresses are consistent with the indentation strength of each material. Contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self-similar. The contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies. The contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap. Synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography.

  12. Microbially-Mediated Subsurface Calcite Precipitation for Removal of Hazardous Divalent Cations

    SciTech Connect

    Colwell, Frederick S.; Smith, R.W.; Ferris, F. Gratn; Ingram, Jani C.; Reysenbach, A.-L.; Fujita, Yoshiko; Tyler, T.L.; Taylor, J.L.; Banta, A.; Delwiche, M.E.; McLing, T.; Cortez, Marnie, M.; Watwood, M.E.

    2003-03-27

    We are investigating microbially-mediated acceleration of calcite precipitation and co-precipitation of hazardous divalent cations (e.g., 90Sr) in calcite saturated subsurface systems. In theory, the addition of urea to an aquifer or vadose zone and its subsequent hydrolysis by indigenous microbes will cause an increase in alkalinity, pH and calcite precipitation. Lab studies indicated the ability of various bacteria to precipitate calcite through urea hydrolysis and that incorporation of strontium in biogenically-formed calcite is greater than in abiotically formed calcite. Results from a field experiment in a pristine location in the Snake River Plain aquifer involving the phased addition of molasses and then urea showed increases in total cell numbers, rate of urea hydrolysis and calcite formation during the study. The combined diagnostic approaches of microbiology, molecular ecology and analytical chemistry demonstrate the feasibility of this biogeochemical manipulation for subsurface remediation at arid Western DOE sites such as Hanford and INEEL.

  13. Water, Hydration and Health

    PubMed Central

    Popkin, Barry M.; D’Anci, Kristen E.; Rosenberg, Irwin H.

    2010-01-01

    This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient whose absence will be lethal within days. Water’s importance for prevention of nutrition-related noncommunicable diseases has emerged more recently because of the shift toward large proportions of fluids coming from caloric beverages. Nevertheless, there are major gaps in knowledge related to measurement of total fluid intake, hydration status at the population level, and few longer-term systematic interventions and no published random-controlled longer-term trials. We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic. PMID:20646222

  14. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  15. Influence of chemical and physical characteristics of cement kiln dusts (CKDs) on their hydration behavior and potential suitability for soil stabilization

    SciTech Connect

    Peethamparan, Sulapha Olek, Jan Lovell, Janet

    2008-06-15

    The interaction of CKDs with a given soil depends on the chemical and physical characteristics of the CKDs. Hence, the characterization of CKDs and their hydration products may lead to better understanding of their suitability as soil stabilizers. In the present article, four different CKD powders are characterized and their hydration products are evaluated. A detailed chemical (X-ray diffraction), thermogravimetric and morphological (scanning electron microscope) analyses of both the CKD powders and the hydrated CKD pastes are presented. In general, high free-lime content ({approx} 14-29%) CKDs, when reacted with water produced significant amounts of calcium hydroxide, ettringite and syngenite. These CKDs also developed higher unconfined compressive strength and higher temperature of hydration compared to CKDs with lower amounts of free-lime. An attempt was made to qualitatively correlate the performance of CKD pastes with the chemical and physical characteristics of the original CKD powders and to determine their potential suitability as soil stabilizers. To that effect a limited unconfined compressive strength testing of CKD-treated kaolinite clays was performed. The results of this study suggest that both the compressive strength and the temperature of hydration of the CKD paste can give early indications of the suitability of particular CKD for soil stabilization.

  16. Interaction of copper with the surface of calcite

    SciTech Connect

    Franklin, M.L.; Morse, J.W.

    1981-12-01

    The interaction of Cu ions in solution with the surface of calcite has been studied in a range of solutions from pure water to seawater. Observations of the uptake of Cu from solution onto calcite indicates that the process is rapid and strong in both distilled water and seawater. In distilled water, Cu uptake is directly proportional to the concentration of Cu in solution; Cu/sub s/ = K/sub s/Cu/sub 1/. The average value for K/sub s/ is 3.5 +- 1.7. The Cu/sub s/ dependence on Cu/sub 1/ is linear over the entire Cu concentration range studied (0.1 to 200 ..mu..M). Results do not indicate the formation of a precipitate of either malachite or copper carbonate. A precipitate of the form Cu/sub x/Ca/sub 1-x/CO/sub 3/ may be deposited onto the calcite surface in distilled water. The value of K/sub s/ in distilled water decreased sharply over the solid to solution ratio range of 0.1 to 2 g CaCO/sub 3/ 1/sup -1/. This was followed by a small change in K/sub s/ for solid to solution ratios in the range of 2 to 10 g CaCO/sub 3/ 1/sup -1/. In seawater, the uptake of Cu is also directly proportional to the concentration of Cu/sub 1/ up to a limiting value of approximately 13 ..mu..M. The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water. This is probably the result of smaller Cu/sub 1/ activity coefficients and increased site competition by other ions in seawater. Attempts to increase the Cu/sub 1/ concentration above 13 ..mu..M resulted in the additional Cu being deposited on the surface of the calcite. A possible explanation for this behavior is the formation of a precipitate of malachite on the calcite surface. The value of K/sub s/ decreased slightly with increasing solid to solution ratios in seawater.

  17. Growth, nitrogen fixation, yield and kernel quality of peanut in response to lime, organic and inorganic fertilizer levels.

    PubMed

    Basu, Manisha; Bhadoria, P B S; Mahapatra, S C

    2008-07-01

    The aim of this investigation was to study the effect of different levels of chemical fertilizers alone and in combination with farmyard manure and lime on growth, nitrogen fixation, yield and kernel quality of peanut in an acid lateritic soil. Five fertilization levels viz., no chemical fertilizer (CF) (F0), CF @ 20:40:30 (F1), CF @ 40:80:60 (F2) kg ha(-1) NPK, F1 +2.5 t ha(-1) FYM (F3) and F2 +5 t ha(-1) FYM (F4) with and without liming (2 t ha(-1)) were tested. Results revealed that integrated application of FYM+CF at F3 level significantly (P0.05) improved the nitrogen content of nodules (12.4%), kernel yield (19.3%), mineral composition, oil content (4.8%), protein content (28.2%) and hydration coefficient (11.6%) of kernels over sole CF at F1 level. Maximum level of CF or FYM+CF though improved the population of symbiotic nitrogen fixing bacteria in the peanut rhizosphere, however, could not improve nitrogen fixation, yield and kernel quality. PMID:17993273

  18. Kinetics of lime/bentonite pozzolanic reactions at 20 and 50 °C: Batch tests and modeling

    SciTech Connect

    De Windt, Laurent; Deneele, Dimitri; Maubec, Nicolas

    2014-05-01

    The effects of duration (1–100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by {sup 29}Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C–S–H and then C–A–S–H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40–50 kJ/mol.

  19. Hydrothermal replacement of calcite by Mg-carbonates

    NASA Astrophysics Data System (ADS)

    Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

    2014-05-01

    The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product

  20. Liming, reacidification, and the mobilization of cadmium from sediments

    SciTech Connect

    Fimreite, N.; Nenseter, B.; Steen, B.

    1996-12-01

    Over several decades severe acidification of streams and lakes has taken place in Scandinavia and North America, with catastrophic consequences for aquatic life. In certain water systems in southern Norway fish populations have been completely eliminated by severe acidification. This fish mortality has been attributed largely to increased concentrations of toxic aluminum and, since liming counteracts acidification and reduces the aluminum levels in the water, it has become the most widespread remedy to restore fish habitats. Cadmium concentrations in the water are also pH-dependent and, therefore, affected by liming. This laboratory experiment was conducted to clarify the significance of liming as a factor in reducing cadmium concentrations from lake water and the behavior of cdamium following reacidification. In addition the behavior of organic materials under varying pH conditions was studied. 16 refs., 4 figs., 2 tabs.

  1. Shock response of soda lime glass at 6 GPA

    NASA Astrophysics Data System (ADS)

    Dandekar, Dattatraya

    2012-03-01

    This paper describes the results of a variety of shock wave experiments performed on soda lime glass to understand the modifying influence of so called "Failure wave" on its compression, under single shock, release, and tension. These experiments were done to a peak shock induced stress of around 6-7 GPa. Shock induced response was recorded by means of VISAR. The results of these experiments performed on soda lime glass at 6-7 GPa indicate that: (i) The effect of failure wave propagation is to lower the impedances of failed glass under both shocked compressed and released states and the effect is not initiated instantaneously at the impact surface. (ii) Failure wave velocity is determined to be 1.42 km/s. (iii) The spall strength of soda lime glass in the region transversed by failure wave is not negligible i.e., the pull-back velocity is around 50 m/s.

  2. Liming Poultry Manures to Kill Pathogens and Decrease Soluble Phosphorus

    SciTech Connect

    Maguire,R.; Hesterberg, D.; Gernat, A.; Anderson, K.; Wineland, M.; Grimes, J.

    2006-01-01

    Received for publication September 9, 2005. Stabilizing phosphorus (P) in poultry waste to reduce P losses from manured soils is important to protect surface waters, while pathogens in manures are an emerging issue. This study was conducted to evaluate CaO and Ca(OH){sub 2} for killing manure bacterial populations (pathogens) and stabilizing P in poultry wastes and to investigate the influence on soils following amendment with the treated wastes. Layer manure and broiler litter varying in moisture content were treated with CaO and Ca(OH){sub 2} at rates of 2.5, 5, 10, and 15% by weight. All treated wastes were analyzed for microbial plate counts, pH, and water-soluble phosphorus (WSP), while a few selected layer manures were analyzed by phosphorus X-ray absorption near edge structure (XANES). A loamy sand and a silt loam were amended with broiler litter and layer manure treated with CaO at rates of 0, 2.5, 5, 10, and 15% and soil WSP and pH were measured at times 1, 8, and 29 d. Liming reduced bacterial populations, with greater rates of lime leading to greater reductions; for example 10% CaO applied to 20% solids broiler litter reduced the plate counts from 793 000 to 6500 mL{sup -1}. Liming also reduced the WSP in the manures by over 90% in all cases where at least 10% CaO was added. Liming the manures also reduced WSP in soils immediately following application and raised soil pH. The liming process used successfully reduced plate counts and concerns about P losses in runoff following land application of these limed products due to decreased WSP.

  3. REMOVAL OF BERYLLIUM FROM DRINKING WATER BY CHEMICAL COAGULATION AND LIME SOFTENING

    EPA Science Inventory

    The effectiveness of conventional drinking water treatment and lime softening was evaluated for beryllium removal from two drinking water sources. ar test studies were conducted to determine how common coagulants (aluminum sulfate and ferric chloride and lime softening performed ...

  4. EVALUATION OF BIOAEROSOL COMPONENTS, GENERATION FACTORS, AND AIRBORNE TRANSPORT ASSOCIATED WITH LIME TREATMENT OF CONTAMINATED SEDIMENT

    EPA Science Inventory

    Lime treatment has been used in contaminated sediment management activities for many purposes such as dewatering, improvement of physical properties, and reducing contaminant mobility. Exothermic volatilization of volatile organic compounds from lime-treated sediment is well kno...

  5. Catalytic iron oxide for lime regeneration in carbonaceous fuel combustion

    DOEpatents

    Shen, Ming-Shing; Yang, Ralph T.

    1980-01-01

    Lime utilization for sulfurous oxides absorption in fluidized combustion of carbonaceous fuels is improved by impregnation of porous lime particulates with iron oxide. The impregnation is achieved by spraying an aqueous solution of mixed iron sulfate and sulfite on the limestone before transfer to the fluidized bed combustor, whereby the iron compounds react with the limestone substrate to form iron oxide at the limestone surface. It is found that iron oxide present in the spent limestone acts as a catalyst to regenerate the spent limestone in a reducing environment. With only small quantities of iron oxide the calcium can be recycled at a significantly increased rate.

  6. Catalytic iron oxide for lime regeneration in carbonaceous fuel combustion

    SciTech Connect

    Shen, M.; Yang, R.T.

    1980-09-30

    Lime utilization for sulfurous oxides absorption in fluidized combustion of carbonaceous fuels is improved by impregnation of porous lime particulates with iron oxide. The impregnation is achieved by spraying an aqueous solution of mixed iron sulfate and sulfite on the limestone before transfer to the fluidized bed combustor, whereby the iron compounds react with the limestone substrate to form iron oxide at the limestone surface. It is found that iron oxide present in the spent limestone acts as a catalyst to regenerate the spent limestone in a reducing environment. With only small quantities of iron oxide the calcium can be recycled at a significantly increased rate.

  7. Status reports on selected environmental issues: Volume 1, Liming of acidified waters

    SciTech Connect

    Zengerle, M.W.; Allan, M.A.

    1987-04-01

    Liming has been used to reestablish or maintain fisheries in acidic lakes located primarily in Scandinavia and northeastern North America. Reported liming costs have ranged between $28 and $500/ha ($10 and $200/acre) depending on material used and lake accessibility. Researchers have observed short-term chemical, biological and physical changes from liming but long-term effects are poorly understood. Federal and private research currently underway should provide better information on acute and long-term effects of liming.

  8. Obsidian hydration dates glacial loading?

    PubMed

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow. PMID:17806883

  9. Proton affinities of hydrated molecules

    NASA Astrophysics Data System (ADS)

    Valadbeigi, Younes

    2016-09-01

    Proton affinities (PA) of non-hydrated, M, and hydrated forms, M(H2O)1,2,3, of 20 organic molecules including alcohols, ethers, aldehydes, ketones and amines were calculated by the B3LYP/6-311++G(d,p) method. For homogeneous families, linear correlations were observed between PAs of the M(H2O)1,2,3 and the PAs of the non-hydrated molecules. Also, the absolute values of the hydration enthalpies of the protonated molecules decreased linearly with the PAs. The correlation functions predicted that for an amine with PA < 1100 kJ/mol the PA(M(H2O)) is larger than the corresponding PA, while for an amine with PA > 1100 kJ/mol the PA(M(H2O)) is smaller than the PA.

  10. Obsidian hydration dates glacial loading?

    PubMed

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  11. Obsidian Hydration: A New Paleothermometer

    SciTech Connect

    Anovitz, Lawrence {Larry} M; Riciputi, Lee R; Cole, David R; Fayek, Mostafa; Elam, J. Michael

    2006-01-01

    The natural hydration of obsidian was first proposed as a dating technique for young geological and archaeological specimens by Friedman and Smith (1960), who noted that the thickness of the hydrated layer on obsidian artifacts increases with time. This approach is, however, sensitive to temperature and humidity under earth-surface conditions. This has made obsidian hydration dating more difficult, but potentially provides a unique tool for paleoclimatic reconstructions. In this paper we present the first successful application of this approach, based on combining laboratory-based experimental calibrations with archaeological samples from the Chalco site in the Basin of Mexico, dated using stratigraphically correlated 14C results and measuring hydration depths by secondary ion mass spectrometry. The resultant data suggest, first, that this approach is viable, even given the existing uncertainties, and that a cooling trend occurred in the Basin of Mexico over the past 1450 yr, a result corroborated by other paleoclimatic data.

  12. Obsidian hydration dates glacial loading?

    USGS Publications Warehouse

    Friedman, I.; Pierce, K.L.; Obradovich, J.D.; Long, W.D.

    1973-01-01

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming . The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  13. The hydration of dental cements.

    PubMed

    Wilson, A D; Paddon, J M; Crisp, S

    1979-03-01

    A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged. PMID:284040

  14. Conformation and hydration of aspartame.

    PubMed

    Kang, Y K

    1991-07-01

    Conformational free energy calculations using an empirical potential (ECEPP/2) and the hydration shell model were carried out on the neutral, acidic, zwitterionic, and basic forms of aspartame in the hydrated state. The results indicate that as the molecule becomes more charged, the number of low energy conformations becomes smaller and the molecule becomes less flexible. The calculated free energies of hydration of charged aspartames show that hydration has a significant effect on the conformation in solution. Only two feasible conformations were found for the zwitterionic form, and these are consistent with the conformations deduced from NMR and X-ray diffraction experiments. The calculated free energy difference between these two conformations was 1.25 kcal/mol. The less favored of the two solvated conformations can be expected to be stabilized by hydrophobic interaction of the phenyl groups in the crystal.

  15. 40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Lime-sulfur; exemption from the... Exemptions From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a tolerance. An exemption from the requirement of a tolerance is established for residues of lime-sulfur....

  16. 40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Lime-sulfur; exemption from the... Exemptions From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a tolerance. An exemption from the requirement of a tolerance is established for residues of lime-sulfur....

  17. 40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Lime-sulfur; exemption from the... Exemptions From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a tolerance. An exemption from the requirement of a tolerance is established for residues of lime-sulfur....

  18. 40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Lime-sulfur; exemption from the... Exemptions From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a tolerance. An exemption from the requirement of a tolerance is established for residues of lime-sulfur....

  19. 40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Lime-sulfur; exemption from the... Exemptions From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a tolerance. An exemption from the requirement of a tolerance is established for residues of lime-sulfur....

  20. Adhesive carrier particles for rapidly hydrated sorbent for moderate-temperature dry flue gas desulfurization.

    PubMed

    Li, Yuan; You, Changfu; Song, Chenxing

    2010-06-15

    A rapidly hydrated sorbent for moderate-temperature dry flue gas desulfurization was prepared by rapidly hydrating adhesive carrier particles and lime. The circulation ash from a circulating fluidized bed boiler and chain boiler ash, both of which have rough surfaces with large specific surface areas and specific pore volumes, can improve the adhesion, abrasion resistance, and desulfurization characteristics of rapidly hydrated sorbent when used as the adhesive carrier particles. The adhesion ability of sorbent made from circulation ash is 67.4% higher than that of the existing rapidly hydrated sorbent made from fly ash, the abrasion ratio is 76.2% lower, and desulfurization ability is 14.1% higher. For sorbent made from chain boiler ash, the adhesion ability is increased by 74.7%, the desulfurization ability is increased by 30.3%, and abrasion ratio is decreased by 52.4%. The abrasion ratios of the sorbent made from circulation ash having various average diameters were all about 9%, and their desulfurization abilities were similar (approximately 150 mg/g). PMID:20481549

  1. Principles of Calcite Dissolution in Human and Artificial Otoconia

    PubMed Central

    Walther, Leif Erik; Blödow, Alexander; Buder, Jana; Kniep, Rüdiger

    2014-01-01

    Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV). The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM). Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution) whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution) of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV. PMID:25048115

  2. The sensitized luminescence of manganese-activated calcite

    USGS Publications Warehouse

    Schulman, J.H.; Evans, L.W.; Ginther, R.J.; Murata, K.J.

    1947-01-01

    Synthetic manganese-activated calcites are shown to be practically inert to ultraviolet excitation in the range 2000-3500A, while they are luminescent under cathode-ray excitation. The incorporation of small amounts of an auxiliary impurity along with the manganese produces the strong response to ultraviolet radiation hitherto ascribed to CaCO3:Mn itself. Three such impurities have been studied: lead, thallium, and cerium. The first two induce excitation in the neighborhood of the mercury resonance line, while the cerium introduces a response principally to longer wave ultraviolet. The strong response to 2537A excitation shown by some natural calcites is likewise found to be due to the presence of lead along with the manganese, rather than to the manganese alone. The data do not warrant ascribing the longer wave-length ultraviolet-excited luminescence of all natural calcites to the action of an auxiliary impurity. The essential identity of the cathode-ray excited luminescence spectra of CaCO 3:Mn, CaCO3: (Pb+Mn), CaCO3:(Tl+Mn), and CaCO3:(Ce+Mn) with the 2537A-excited spectra of the latter three is evidence that the luminescent center in all cases is the manganese ion or the MnO6 group. It is shown that a "cascade" mechanism for the action of the auxiliary impurities, lead, thallium, and cerium, is incorrect; and that the phenomenon must be considered as a case of sensitized luminescence. Owing to the nature of cathode-ray excitation, the manganese activator can be excited by this agent even in the absence of a second impurity. For optical excitation, however, an absorption band for the ultraviolet must be established by building into the CaCO3:Mn a second impurity or "sensitizer.".

  3. Simulations of calcite crystallization on self-assembled monolayers.

    PubMed

    Freeman, Colin L; Harding, John H; Duffy, Dorothy M

    2008-09-01

    This paper presents simulations of calcium carbonate ordering in contact with self-assembled monolayers. The calculations use potential-based molecular dynamics to model the crystallization of calcium carbonate to calcite expressing both the (00.1) and (01.2) surfaces. The effect of monolayer properties: ionization; epitaxial matching; charge density; and headgroup orientation on the crystallization process are examined in detail. The results demonstrate that highly charged surfaces are vital to stimulate ordering and crystallization. Template directed crystallization requires charge epitaxy between both the crystal surface and the monolayer. The orientation of the headgroup appears to make no contribution to the selection of the crystal surface.

  4. Calcite dissolution: an in situ study in the Panama Basin

    SciTech Connect

    Thunell, R.C.; Keir, R.S.; Honjo, S.

    1981-05-08

    The results of an in situ study of calcite dissolution in the Panama Basin indicate that the rate of dissolution in the water column increases suddenly below a water depth of about 2800 meters. This coincides with the depth at which the calcium carbonate content of surface sediments begins to decrease rapidly or the sedimentary lysocline. Since this level of increased dissolution both in the water column and on the sea floor does not appear to be related to the transition from supersaturation to undersaturation with respect to carbonate, there may be a kinetic origin for the lysocline in this region.

  5. Airway Hydration and COPD

    PubMed Central

    Ghosh, Arunava; Boucher, R.C.; Tarran, Robert

    2015-01-01

    Chronic obstructive pulmonary disease (COPD) is one of the prevalent causes of worldwide mortality and encompasses two major clinical phenotypes, i.e., chronic bronchitis (CB) and emphysema. The most common cause of COPD is chronic tobacco inhalation. Research focused on the chronic bronchitic phenotype of COPD has identified several pathological processes that drive disease initiation and progression. For example, the lung’s mucociliary clearance (MCC) system performs the critical task of clearing inhaled pathogens and toxic materials from the lung. MCC efficiency is dependent on: (i) the ability of apical plasma membrane ion channels such as the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na+ channel (ENaC) to maintain airway hydration; (ii) ciliary beating; and, (iii) appropriate rates of mucin secretion. Each of these components is impaired in CB and likely contributes to the mucus stasis/accumulation seen in CB patients. This review highlights the cellular components responsible for maintaining MCC and how this process is disrupted following tobacco exposure and with CB. We shall also discuss existing therapeutic strategies for the treatment of chronic bronchitis and how components of the MCC can be used as biomarkers for the evaluation of tobacco or tobacco-like-product exposure. PMID:26068443

  6. K'qizaghetnu Ht'ana (Stories from Lime Village).

    ERIC Educational Resources Information Center

    Bobby, Pete; And Others

    A cross section of Athabascan life as related by eight inhabitants of Lime Village, Alaska, is given in this document. The short narratives are printed in English and in Dena'ina. Illustrations accompany the text. The stories tell of making eagle feather robes, birchbark or mooseskin boats, a raincoat from black bear intestines, and boots from…

  7. Permeability studies in marine clays stabilized with lime column

    SciTech Connect

    Rao, S.N.; Mathew, P.K.

    1994-12-31

    Soft marine clays are very sensitive to changes in stress system, moisture content and system chemistry of the pore fluid. There is a necessity to improve the behavior of these deposits using any one of the available ground improvement techniques. In the present investigation an attempt is made to improve the permeability using lime column techniques in marine clays. The experimental program was carried out with model lime columns installed in two test setups. In the first setup a central lime column was installed in a circular tank and in the second setup number of columns were installed in a rectangular tank. A marine clay from east coast of India was used as a test bed. Number of samples were taken at different radial distances and time periods. From the tests conducted on these samples, it has been established that lime has seeped into the surrounding soil for large distances and this is indicated by pH values and XRD analysis. There is enormous improvement in permeability and the k values are improved by 10 to 15 times. This shows a good promise for improving the reclaimed coastal soft deposits and offshore deposits.

  8. EFFECTS OF LIME (CAO) ON THE ENDOTOXIN LEVELS OF BIOSOLIDS

    EPA Science Inventory

    Lime addition is a common practice for treating biosolids in order to meet EPA 503 requirements for land application. Since this treatment kills the majority of microorganisms, will it increase the level of endotoxins present in biosolids? And, if endotoxin levels are increased, ...

  9. Shock-wave properties of soda-lime glass

    SciTech Connect

    Grady, D.E.; Chhabildas, L.C.

    1996-11-01

    Planar impact experiments and wave profile measurements provided single and double shock equation of state data to 30 GPa. Both compression wave wave profile structure and release wave data were used to infer time-dependent strength and equation of state properties for soda-lime glass.

  10. Distribution of polycyclic aromatic hydrocarbons in lime spray dryer ash

    SciTech Connect

    Ping Sun; Panuwat Taerakul; Linda K. Weavers; Harold W. Walker

    2005-10-01

    Four lime spray dryer (LSD) ash samples were collected from a spreader stoker boiler and measured for their concentrations of 16 U.S. EPA specified polycyclic aromatic hydrocarbons (PAHs). Results showed that the total measured PAH concentration correlated with the organic carbon content of the LSD ash. Each LSD ash sample was then separated using a 140 mesh sieve into two fractions: a carbon-enriched fraction ({gt}140 mesh) and a lime-enriched fraction ({lt}140 mesh). Unburned carbon was further separated from the carbon-enriched fraction with a lithiumheteropolytungstate (LST) solution. PAH measurements on these different fractions showed that unburned carbon had the highest PAH concentrations followed by the carbon-enriched fraction, indicating that PAHs were primarily associated with the carbonaceous material in LSD ash. However, detectable levels of PAHs were also found in the lime-enriched fraction, suggesting that the fine spray of slaked lime may sorb PAH compounds from the flue gas in the LSD process. 37 refs., 5 figs., 4 tabs.

  11. Soda ash improves lead removal in lime precipitation process

    SciTech Connect

    Hsu, D.Y.; Riddell, M.D.R.; Bonamico, B.

    1982-01-01

    Both laboratory-scale and plant-scale studies were conducted to evaluate the feasibility of using soda ash as a supplemental chemical in the existing lime neutralization-sedimentation process. The purpose was to improve the efficiency of lead removal from a metal finishing wastewater by taking advantage of the lower solubility of lead carbonate. Plant-scale studies indicated that addition of soda ash at about 2 mg Na/sub 2/CO/sub 3/ per mg Pb and at a pH between 8 and 11.5 reduced lead content in the settled effluent consistently to less than 0.3 mg/l. This is considerably lower than the 0.5 mg/1 specified in the sewer use ordinance. After about one year's operation, this modified lime neutralization-sedimentation process has been found to be more stable and reliable, and requires less attendance than the simple lime process. The process can also now be operated at a lower pH (minimum: 7.0) with the addition of soda ash, which has resulted in a lower amount of sludge production, lower lime usage and significantly lower manpower requirements.

  12. 46 CFR 148.04-23 - Unslaked lime in bulk.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF SOLID... and the dangerous cargo manifest requirements in § 148.02-3 do not apply to the transportation of... in bulk. (a) Unslaked lime in bulk must be transported in unmanned, all steel, double-hulled...

  13. Lime pretreatment and fermentation of enzymatically hydrolyzed sugarcane bagasse.

    PubMed

    Rabelo, Sarita C; Maciel Filho, Rubens; Costa, Aline C

    2013-03-01

    Sugarcane bagasse was subjected to lime (calcium hydroxide) pretreatment and enzymatic hydrolysis for second-generation ethanol production. A central composite factorial design was performed to determine the best combination of pretreatment time, temperature, and lime loading, as well as to evaluate the influence of enzymatic loadings on hydrolysis conversion. The influence of increasing solids loading in the pretreatment and enzymatic hydrolysis stages was also determined. The hydrolysate was fermented using Saccharomyces cerevisiae in batch and continuous mode. In the continuous fermentation, the hydrolysates were concentrated with molasses. Lime pretreatment significantly increased the enzymatic digestibility of sugarcane bagasse without the need for prior particle size reduction. In the optimal pretreatment conditions (90 h, 90 °C, 0.47 glime/g bagasse) and industrially realistic conditions of hydrolysis (12.7 FPU/g of cellulase and 7.3 CBU/g of β-glucosidase), 139.6 kglignin/ton raw bagasse and 126.0 kg hemicellulose in the pretreatment liquor per ton raw bagasse were obtained. The hydrolysate from lime pretreated sugarcane bagasse presented low amounts of inhibitors, leading to ethanol yield of 164.1 kgethanol/ton raw bagasse.

  14. A Model for Dissolution of Lime in Steelmaking Slags

    NASA Astrophysics Data System (ADS)

    Sarkar, Rahul; Roy, Ushasi; Ghosh, Dinabandhu

    2016-08-01

    In a previous study by Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015), a dynamic model of the LD steelmaking was developed. The prediction of the previous model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) for the bath (metal) composition matched well with the plant data (Cicutti et al. in Proceedings of 6th International Conference on Molten Slags, Fluxes and Salts, Stockholm City, 2000). However, with respect to the slag composition, the prediction was not satisfactory. The current study aims to improve upon the previous model Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015) by incorporating a lime dissolution submodel into the earlier one. From the industrial point of view, the understanding of the lime dissolution kinetics is important to meet the ever-increasing demand of producing low-P steel at a low basicity. In the current study, three-step kinetics for the lime dissolution is hypothesized on the assumption that a solid layer of 2CaO·SiO2 should form around the unreacted core of the lime. From the available experimental data, it seems improbable that the observed kinetics should be controlled singly by any one kinetic step. Accordingly, a general, mixed control model has been proposed to calculate the dissolution rate of the lime under varying slag compositions and temperatures. First, the rate equation for each of the three rate-controlling steps has been derived, for three different lime geometries. Next, the rate equation for the mixed control kinetics has been derived and solved to find the dissolution rate. The model predictions have been validated by means of the experimental data available in the literature. In addition, the effects of the process conditions on the dissolution rate have been studied, and compared with the experimental results wherever possible. Incorporation of this submodel into the earlier global model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) enables the prediction of the lime dissolution rate

  15. The ubiquitous nature of accessory calcite in granitoid rocks: Implications for weathering, solute evolution, and petrogenesis

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Lowenstern, J. B.; Vivit, D.V.; Bullen, T.D.

    2005-01-01

    Calcite is frequently cited as a source of excess Ca, Sr and alkalinity in solutes discharging from silicate terrains yet, no previous effort has been made to assess systematically the overall abundance, composition and petrogenesis of accessory calcite in granitoid rocks. This study addresses this issue by analyzing a worldwide distribution of more than 100 granitoid rocks. Calcite is found to be universally present in a concentration range between 0.028 to 18.8 g kg-1 (mean = 2.52 g kg-1). Calcite occurrences include small to large isolated anhedral grains, fracture and cavity infillings, and sericitized cores of plagioclase. No correlation exists between the amount of calcite present and major rock oxide compositions, including CaO. Ion microprobe analyses of in situ calcite grains indicate relatively low Sr (120 to 660 ppm), negligible Rb and 87Sr/86Sr ratios equal to or higher than those of coexisting plagioclase. Solutes, including Ca and alkalinity produced by batch leaching of the granitoid rocks (5% CO2 in DI water for 75 d at 25??C), are dominated by the dissolution of calcite relative to silicate minerals. The correlation of these parameters with higher calcite concentrations decreases as leachates approach thermodynamic saturation. In longer term column experiments (1.5 yr), reactive calcite becomes exhausted, solute Ca and Sr become controlled by feldspar dissolution and 87Sr/ 86Sr by biotite oxidation. Some accessory calcite in granitoid rocks is related to intrusion into carbonate wall rock or produced by later hydrothermal alteration. However, the ubiquitous occurrence of calcite also suggests formation during late stage (subsolidus) magmatic processes. This conclusion is supported by petrographic observations and 87Sr/86Sr analyses. A review of thermodynamic data indicates that at moderate pressures and reasonable CO2 fugacities, calcite is a stable phase at temperatures of 400 to 700??C. Copyright ?? 2005 Elsevier Ltd.

  16. Impacts of Hydrate Pore Habit on Physical Properties of Hydrate Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Seol, Y.; Dai, S.; Choi, J. H.

    2014-12-01

    The physical properties of gas hydrate bearing sediments, to a large extent, are governed by the volume fraction and spatial distribution of the hydrate phase. For sediments containing the same amount of hydrates, their overall physical properties may vary several orders of magnitude depending on hydrate pore habit. We investigate the interplay among hydrate formation methods, hydrate pore habits, and fundamental physical properties of hydrate bearing sediments. We have developed a new method to synthesize noncementing hydrate in sands, a multi-properties characterization chamber to test the hydrate bearing sediments, and pore network models to simulate fluid flow processes in hydrate bearing sediments. We have found that (1) the growth pattern of hydrate crystal in the pore spaces of water saturated sediments is dominated by the relative magnitude of the capillary force (between hydrate crystal and pore fluid) and the skeleton force, which will result in pore-filling or grain-displacing type of hydrate pore character; (2) the existing capillary tube models of water permeability in hydrate bearing sediments are sensitive to pore geometry and hydrate pore habit; and (3) preliminary CT results suggest that hydrate nucleation in partially water saturated sands tends to agglomerate in patches, rather than in an uniformly-distributed contact-cementing morphology. Additional CT results with a small amount of fines (5wt%) and visualization via micro-CT of hydrate pore habits in sediments using different hydrate formation methods will be discussed.

  17. New waste based clinkers: Belite and lime formulations

    SciTech Connect

    Raupp-Pereira, Fabiano; Ball, Richard James Rocha, Joao; Labrincha, Joao A.; Allen, Geoffrey C.

    2008-04-15

    This work describes the formulation of new belite-based (CR2) and lime-based (CR3) cementitious materials derived from industrial wastes, such as sludges (generated in the Al-anodising and surface coating industrial processes, potable water filtration/cleaning operations and in marble sawing processes) and foundry sand. Powder mixtures were prepared and fired at different temperatures. For comparison, similar formulations were prepared with pre-treated and commercially available natural raw materials and processed in similar conditions. The thermal process was followed by differential scanning calorimetry (DSC) and high-temperature powder X-ray diffraction (HT-XRD) studies. The CR2 clinker was found to contain belite as the main cementitious phase, the main polymorph being identified by NMR. The CR3 clinker contained common cementitious phases, such as C{sub 3}A and C{sub 3}S, but free lime and calcium aluminium oxide sulphates were also identified by high temperature XRD and NMR. Then the corresponding cement was prepared and the evolution of the mechanical strength with time was evaluated. The lime-based cement obtained from wastes shows a stronger hardening character than the standard material, which tends to show dusting phenomena due to the presence of a reasonable amount of free lime (as the result of its expansive reaction with ambient moisture). Some fluxing impurities (e.g. alkalis) present in the waste materials improve the overall reactivity of the mixture and induces the combination of the lime in CR3. Raman, XPS and FIB techniques were used to fully characterise the aged cements.

  18. Speciation and mobility of arsenic in agricultural lime.

    PubMed

    Schmidt, Gerald T; Lui, Ka Hei; Kersten, Michael

    2009-01-01

    Agricultural liming materials are used to correct soil acidity and to improve plant growth and microbial functionality. A relatively low-grade agricultural lime was found to contain up to 125 mg kg(-1) arsenic (As), which is above any fertilizing materials code threshold. The color of the milled material is brown due to ample oxide dendrites. Microprobe elemental maps confirmed that these accessory oxide mineral phases are responsible for the elevated As concentrations in the limestone. The black Mn-bearing dendrites contain minor amounts of As, whereas the brown Fe-bearing dendrites contain the major part of the As inventory, with an Fe/As molar ratio around 100. Because the elemental maps represent only a few sample regions of interest (ROI), the results are corroborated by a bulk five-step sequential extraction of the lime, which suggests that a majority of the As is bound to acid-reducible phases. Because repartitioning of the As oxyanion during extraction cannot be ruled out, X-ray absorption spectroscopy with micrometer resolution (micro-XAS) was used as a solid-state speciation analysis approach. The micro-XAS results at the Fe K-edge for the selected ROIs revealed the brown dendrites to consist of ferrihydrite and goethite, whereas those at the As K-edge revealed that the pentavalent As species arsenate predominates, with As-Fe distance and coordination indicating binding as a mononuclear inner-spheric adsorbate complex. Batch experiments with soil exposed to submerged conditions of up to 41 d revealed a negligible As release rate from the lime (approximately 40 ng kg(-1) d(-1)). The results of this study corroborate regulatory codes that set the permissible As content in agricultural lime relative to the respective Fe content.

  19. Halothane adsorption complicating the use of soda-lime to humidify anaesthetic gases.

    PubMed

    Grodin, W K; Epstein, R A

    1982-05-01

    If the anaesthetic circle system is arranged to increase the humidity of fresh anaesthetic gases by placing the carbon dioxide absorbent canister between the fresh gas inlet and the patient, drying of the soda-lime can occur. Very dry soda-lime adsorbs significant quantities of halothane. Using fresh soda-lime, effluent halothane concentration reached 50% of the input concentration in 35s, but this time increased to 500 s when dry soda-lime was used. The use of dry soda-lime can result in a slow inhalation induction or in the release of absorbed halothane during a subsequent anaesthetic.

  20. Energy resource potential of natural gas hydrates

    USGS Publications Warehouse

    Collett, T.S.

    2002-01-01

    The discovery of large gas hydrate accumulations in terrestrial permafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved before gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m3. Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.

  1. Structure and reactivity of the calcite-water interface.

    PubMed

    Heberling, Frank; Trainor, Thomas P; Lützenkirchen, Johannes; Eng, Peter; Denecke, Melissa A; Bosbach, Dirk

    2011-02-15

    The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO(2) partial pressure. Changes in pH have only a weak effect in non-equilibrium solutions. The surface structure of (104)-faces of single crystal calcite in contact to solutions corresponding to those of the zetapotential investigations is determined from surface diffraction measurements. The results reveal no direct indication of calcium or carbonate inner-sphere surface species. The surface ions are found to relax only slightly from their bulk positions; the most significant relaxation is a ∼4° tilt of the surface carbonate ions towards the surface. Two ordered layers of water molecules are identified, the first at 2.35±0.05Å above surface calcium ions and the second layer at 3.24±0.06Å above the surface associated with surface carbonate ions. A Basic-Stern surface complexation model is developed to model observed zetapotentials, while only considering outer-sphere complexes of ions other than protons and hydroxide. The Basic-Stern SCM successfully reproduces the zetapotential data and gives reasonable values for the inner Helmholtz capacitance, which are in line with the Stern layer thickness estimated from surface diffraction results. PMID:21087772

  2. [Removal of Phosphate by Calcite in Open-System].

    PubMed

    Li, Zhen-xuan; Diao, Jia-yong; Huang, Li-dong; Chen, Yan-fan; Liu, Da-gang; Xu, Zheng-wen

    2015-12-01

    Batch methods were deployed to study the removal of phosphate by calcite in an open-system. Results showed that: (1) The pre-equilibrium process of calcite in open system could be achieved within 24 hours (2) The kinetic results showed that, at initial concentration of 0.5 mg · L⁻¹, the phosphate removal was almost completed within 10 hours of the first phase. The observation may be attributed to surface adsorption. At initial concentration of 2.5 mg · L⁻¹, the phosphate removal was mainly carried out by the precipitation of phosphate at later stage of the process; (3) At initial concentration of ≤ 2.5 mg · L⁻¹ setting 10 h as reaction time, the phosphate removal process was described well by the Langmuir model. It is hypothesized that surface adsorption was the principal removal way of phosphate; (4) With the addition of phthalate, at initial concentration of < 2.5 mg · L⁻¹, the phosphate removal rate experienced a small decrease. That was because phosphate was mainly removed by surface adsorption, and thus, phthalate was a competitor to phosphate for the same adsorption site. The phosphate removal rate increased a little at initial concentration of > 2.5 mg · L⁻¹, this was because the phosphate precipitation was reinforced by the increase of calcium concentration, which was caused by phthalate addition. PMID:27011989

  3. Porosity and hydric behavior of typical calcite microfabrics in stalagmites

    NASA Astrophysics Data System (ADS)

    Muñoz-García, M. B.; López-Arce, P.; Fernández-Valle, M. E.; Martín-Chivelet, J.; Fort, R.

    2012-07-01

    Petrophysical techniques commonly used for material characterization are applied for the first time to speleothem samples to investigate the porosity and hydric behavior of calcite stalagmites used in paleoclimatology. These techniques allow the determination of the stalagmites' potential to undergo diagenetic transformations when substantial changes in drip waters occur in the cave environment. The petrophysical techniques include water absorption under vacuum and by capillarity, nuclear magnetic resonance, environmental scanning electron microscopy, and mercury intrusion porosimetry. The studied samples comprise five common calcite microfabrics, which have markedly different porosities and hydric behaviors and, as a consequence, different sensibilities to diagenetic processes related to the influx of water. The experiments show that stalagmites can behave as complex, small-scale hydrological systems and that the circulation of water through them by complex nets of interconnected pores might be common. As the circulation of water favors diagenetic transformations that involve geochemical and isotopic changes, the characterization of flow patterns is key for outlining areas that are susceptible to such modifications, which is critical to paleoclimatic studies that are based on speleothems because geochemical and stable isotopic data are used as paleoenvironmental proxies and absolute ages are obtained by using radioactive isotope ratios. These potential modifications also have obvious implications for studies based on fluid inclusions in speleothems. The integrated methodology, which uses primarily non-destructive techniques, shows a high potential for characterization of any type of speleothem and other continental carbonates such as tufas or sinters.

  4. Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite.

    PubMed

    Checa, Antonio G; Bonarski, Jan T; Willinger, Marc G; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M; Pospiech, Jan; Morawiec, Adam

    2013-09-01

    The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy-electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research.

  5. Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite

    PubMed Central

    Checa, Antonio G.; Bonarski, Jan T.; Willinger, Marc G.; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M.; Pospiech, Jan; Morawiec, Adam

    2013-01-01

    The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research. PMID:23804442

  6. Acceleration of calcite kinetics by abalone nacre proteins

    SciTech Connect

    Fu, G; Qiu, S R; Orme, C A; Morse, D E; De Yoreo, J J

    2005-06-09

    The fascinating shapes and hierarchical designs of biomineralized structures have long been an inspiration to materials scientists because of the potential they suggest for biomolecular control over synthesis of crystalline materials. One prevailing view is that mineral-associated macromolecules are responsible for initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineral surfaces. Indeed, numerous studies have demonstrated that bio-organic additives can dramatically alter crystal shapes and growth-rates in vitro. However, previous molecular-scale studies revealing mechanisms of growth modification focused on small molecules such as amino acids or peptides and always observed growth inhibition. In contrast, studies using full proteins were non-quantitative and underlying sources of growth modification were ill-defined. Here we investigate interactions between proteins isolated from abalone shell nacre and growing surfaces of calcite. We find that these proteins significantly accelerate the molecular-scale kinetics and, though much larger than atomic steps, alter growth morphology through step-specific interactions that lower their free energies. We propose that these proteins act as surfactants to promote ion attachment at calcite surfaces.

  7. Anisotropic parallel self-diffusion coefficients near the calcite surface: A molecular dynamics study.

    PubMed

    Franco, Luís F M; Castier, Marcelo; Economou, Ioannis G

    2016-08-28

    Applying classical molecular dynamics simulations, we calculate the parallel self-diffusion coefficients of different fluids (methane, nitrogen, and carbon dioxide) confined between two {101̄4} calcite crystal planes. We have observed that the molecules close to the calcite surface diffuse differently in distinct directions. This anisotropic behavior of the self-diffusion coefficient is investigated for different temperatures and pore sizes. The ion arrangement in the calcite crystal and the strong interactions between the fluid particles and the calcite surface may explain the anisotropy in this transport property. PMID:27586936

  8. Anisotropic parallel self-diffusion coefficients near the calcite surface: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Franco, Luís F. M.; Castier, Marcelo; Economou, Ioannis G.

    2016-08-01

    Applying classical molecular dynamics simulations, we calculate the parallel self-diffusion coefficients of different fluids (methane, nitrogen, and carbon dioxide) confined between two { 10 1 ¯ 4 } calcite crystal planes. We have observed that the molecules close to the calcite surface diffuse differently in distinct directions. This anisotropic behavior of the self-diffusion coefficient is investigated for different temperatures and pore sizes. The ion arrangement in the calcite crystal and the strong interactions between the fluid particles and the calcite surface may explain the anisotropy in this transport property.

  9. Investigation of organic matter entrapped during calcite growth by a multi-method approach

    NASA Astrophysics Data System (ADS)

    Chalmin, E.; Perrette, Y.; Fanget, B.; Drysdale, R.

    2012-04-01

    Organic matter (OM) entrapped in calcite is regularly used for environmental studies; however, incorporation mechanisms and types of interaction remain poorly understood. This study used a new methodology to investigate interactions between OM and the calcite matrix during crystallization processes using humic acid entrapment. A multi-method approach confirmed that OM is both adsorbed onto the calcite surface and incorporated into the calcite lattice during crystallization. Our results also confirm the log-linear correlation between fluorescence intensity and calcite matrix OM concentration. Fourier transform infrared spectroscopy (FTIR) showed that OM in colloidal conformation is adsorbed onto the calcite surface as a result of the structure of the OH stretching band. Based on synchrotron analysis (XRF and XANES), we also developed a new method in which sulfur is used as a tracer for entrapped humic acid and for locating the OM electrostatically adsorbed onto the calcite surface. Changes in the sulfur environment, determined using XANES, indicated partitioning during calcite crystallization due to the effect of the matrix on OM incorporation. Desorption experiments revealed the stability of the OM atomic structure and the layered nature of that structure. These results have allowed us to devise a general model of OM incorporation into calcite.

  10. Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping

    NASA Astrophysics Data System (ADS)

    McNamara, David D.; Lister, Aaron; Prior, Dave J.

    2016-09-01

    Fractures play an important role as fluid flow pathways in geothermal resources hosted in indurated greywacke basement of the Taupo Volcanic Zone, New Zealand, including the Kawerau Geothermal Field. Over time, the permeability of such geothermal reservoirs can be degraded by fracture sealing as minerals deposit out of transported geothermal fluids. Calcite is one such fracture sealing mineral. This study, for the first time, utilises combined data from electron backscatter diffraction and chemical mapping to characterise calcite vein fill morphologies, and gain insight into the mechanisms of calcite fracture sealing in the Kawerau Geothermal Field. Two calcite sealing mechanisms are identified 1) asymmetrical syntaxial growth of calcite, inferred by the presence of single, twinned, calcite crystals spanning the entire fracture width, and 2) 3D, interlocking growth of bladed vein calcite into free space as determined from chemical and crystallographic orientation mapping. This study also identifies other potential uses of combined EBSD and chemical mapping to understand geothermal field evolution including, potentially informing on levels of fluid supersaturation from the study of calcite lattice distortion, and providing information on a reservoir's history of stress, strain, and deformation through investigation of calcite crystal deformation and twinning patterns.

  11. Evaluation of a lime-mediated sewage sludge stabilisation process. Product characterisation and technological validation for its use in the cement industry.

    PubMed

    Rodríguez, N Husillos; Granados, R J; Blanco-Varela, M T; Cortina, J L; Martínez-Ramírez, S; Marsal, M; Guillem, M; Puig, J; Fos, C; Larrotcha, E; Flores, J

    2012-03-01

    This paper describes an industrial process for stabilising sewage sludge (SS) with lime and evaluates the viability of the stabilised product, denominated Neutral, as a raw material for the cement industry. Lime not only stabilised the sludge, raised the temperature of the mix to 80-100°C, furthering water evaporation, portlandite formation and the partial oxidation of the organic matter present in the sludge. Process mass and energy balances were determined. Neutral, a white powder consisting of portlandite (49.8%), calcite (16.6%), inorganic oxides (13.4%) and organic matter and moisture (20.2%), proved to be technologically apt for inclusion as a component in cement raw mixes. In this study, it was used instead of limestone in raw mixes clinkerised at 1400, 1450 and 1500°C. These raw meals exhibited greater reactivity at high temperatures than the limestone product and their calcination at 1500°C yielded clinker containing over 75% calcium silicates, the key phases in Portland clinker. Finally, the two types of raw meal (Neutral and limestone) were observed to exhibit similar mineralogy and crystal size and distribution.

  12. Crystal growth of calcite from calcium bicarbonate solutions at constant PCO2 and 25°C: a test of a calcite dissolution model

    USGS Publications Warehouse

    Reddy, Michael M.; Plummer, L. Neil; Busenberg, E.

    1981-01-01

    A highly reproducible seeded growth technique was used to study calcite crystallization from calcium bicarbonate solutions at 25°C and fixed carbon dioxide partial pressures between 0.03 and 0.3 atm. The results are not consistent with empirical crystallization models that have successfully described calcite growth at low PCO2 (< 10−3 atm). Good agreement was found between observed crystallization rates and those calculated from the calcite dissolution rate law and mechanism proposed by Plummer et al. (1978).

  13. Making solutions from hydrated compounds.

    PubMed

    Adams, Dany Spencer

    2008-05-01

    INTRODUCTIONSolution making typically involves dissolving dry chemicals in water or other specified solvent. The amount of chemical to be added to a solvent depends on the final concentration or molarity (M) needed for the finished solution and the total amount in liters (L) of solution required. However, some chemicals come with water molecules attached. The molecular weight (MW) of such compounds, listed as formula weight (FW) on the bottle, includes the mass of the water. Whenever you would use the MW of an unhydrated compound in calculations, use instead the MW of the hydrated compound. If a recipe tells how many grams to use of the unhydrated compound, determine the target concentration and then calculate the grams to use of hydrated compound. When using a hydrated compound, the attached water molecules contribute water to the solution, potentially diluting the final concentration (if the solvent is water). Therefore, you must account for the contribution of water from the hydrated compound when determining the volume of solvent (water) to add. This article describes the calculations involved in making solutions from hydrated compounds.

  14. Well log evaluation of natural gas hydrates

    SciTech Connect

    Collett, T.S.

    1992-10-01

    Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence? Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

  15. Well log evaluation of natural gas hydrates

    SciTech Connect

    Collett, T.S.

    1992-10-01

    Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

  16. Kinetics and Mechanisms of Calcite Reactions with Saline Waters

    SciTech Connect

    Gorman, Brian P

    2015-09-02

    Project Description: The general objective of the proposed research is to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, pCO2, and modest ranges in T and P. This will be accomplished by studying both reaction rates and solubility from changes in solution chemistry, and making nanoscale observations of calcite precipitate surface morphology and composition at the micro-to-nano-scale to provide an understanding of controlling reaction mechanisms and pathways. The specific objectives necessary to reach the general objective are: a) determination of how pCO2, Ca2+, ionic strength and “foreign” ions influence reaction rates; and b) investigate the influence of these parameters on apparent kinetic solubility from dissolution and precipitation reactions. This information will clearly be central to the construction of reliable reaction-transport models to predict reservoir and formation response to increased CO2 in saline waters. This program was initially collaborative with John Morse at Texas A&M, however his passing shortly after the beginning of this program resulted in abbreviated research time and effort. Summary of Results: Early studies using electron microscopy and spectroscopy indicated that carbonate precipitation from natural seawater (NSW) conditions onto aragonite substrates was mediated by a surface amorphous calcium carbonate layer. It was hypothesized that this ACC layer (observed after < 5days reaction time) was responsible for the abnormal reaction kinetics and also served as a metastable seed layer for growth of epitaxial aragonite. Further studies of the ACC formation mechanism indicated a strong dependence on the Mg concentration in solution. Subsequent studies at shorter times (10 hrs) on calcite substrates and in a wide range of supersaturation conditions did not indicate any ACC layer. Instead, an epitaxial layer by layer

  17. Hydrated interfacial ions and electrons.

    PubMed

    Abel, Bernd

    2013-01-01

    Charged particles such as hydrated ions and transient hydrated electrons, the simplest anionic reducing agents in water, and the special hydronium and hydroxide ions at water interfaces play an important role in many fields of science, such as atmospheric chemistry, radiation chemistry, and biology, as well as biochemistry. This article focuses on these species near hydrophobic interfaces of water, such as the air or vacuum interface of water or water protein/membrane interfaces. Ions at interfaces as well as solvated electrons have been reviewed frequently during the past decade. Although all species have been known for some time with seemingly familiar features, recently the picture in all cases became increasingly diffuse rather than clearer. The current account gives a critical state-of-the art overview of what is known and what remains to be understood and investigated about hydrated interfacial ions and electrons.

  18. Rheology of hydrate forming emulsions.

    PubMed

    Peixinho, Jorge; Karanjkar, Prasad U; Lee, Jae W; Morris, Jeffrey F

    2010-07-20

    Results are reported on an experimental study of the rheology of hydrate-forming water-in-oil emulsions. Density-matched concentrated emulsions were quenched by reducing the temperature and an irreversible transition was observed where the viscosity increased dramatically. The hydrate-forming emulsions have characteristic times for abrupt viscosity change dependent only on the temperature, reflecting the importance of the effect of subcooling. Mechanical transition of hydrate-free water-in-oil emulsions may require longer times and depends on the shear rate, occurring more rapidly at higher rates but with significant scatter which is characterized through a probabilistic analysis. This rate dependence together with dependence on subcooling reflects the importance of hydrodynamic forces to bring drops or particles together.

  19. Gas Hydrate and Pore Pressure

    NASA Astrophysics Data System (ADS)

    Tinivella, Umberta; Giustiniani, Michela

    2014-05-01

    Many efforts have been devoted to quantify excess pore pressures related to gas hydrate dissociation in marine sediments below the BSR using several approaches. Dissociation of gas hydrates in proximity of the BSR, in response to a change in the physical environment (i.e., temperature and/or pressure regime), can liberate excess gas incrising the local pore fluid pressure in the sediment, so decreasing the effective normal stress. So, gas hydrate dissociation may lead to excess pore pressure resulting in sediment deformation or failure, such as submarine landslides, sediment slumping, pockmarks and mud volcanoes, soft-sediment deformation and giant hummocks. Moreover, excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation, tectonic uplift, sea level fall, heating or inhibitor injection. In order to detect the presence of the overpressure below the BSR, we propose two approachs. The fist approach models the BSR depth versus pore pressure; in fact, if the free gas below the BSR is in overpressure condition, the base of the gas hydrate stability is deeper with respect to the hydrostatic case. This effect causes a discrepancy between seismic and theoretical BSR depths. The second approach models the velocities versus gas hydrate and free gas concentrations and pore pressure, considering the approximation of the Biot theory in case of low frequency, i.e. seismic frequency. Knowing the P and S seismic velocity from seismic data analysis, it is possibile to jointly estimate the gas hydrate and free gas concentrations and the pore pressure regime. Alternatively, if the S-wave velocity is not availbale (due to lack of OBS/OBC data), an AVO analysis can be performed in order to extract information about Poisson ratio. Our modeling suggests that the areas characterized by shallow waters (i.e., areas in which human infrastructures, such as pipelines, are present) are significantly affected by the presence of overpressure condition

  20. Heavy metals in wastewater: Modelling the hydroxide precipitation of copper(II) from wastewater using lime as the precipitant

    SciTech Connect

    Baltpurvins, K.A.; Burns, R.C.; Lawrance, G.A.

    1996-12-31

    The effect of effluent composition (Cl{sup {minus}}, SO{sub 4}{sup 2{minus}} or CO{sub 3}{sup 2{minus}}) on the efficiency of the hydroxide precipitation of Cu(II) modelling lime (CaO) as the precipitant has been predicted using the solubility domain approach and has been experimentally validated. Solubility domains were based on the phases that were found to be solubility-limiting for systems representing potential effluent chemical composition limits. The generated solubility domains generally encompassed the experimentally observed solubilities, thereby providing effluent treatment quality assurance ranges for the hydroxide precipitation process. The presence of gypsum (CaSO{sub 4{center_dot}}2H{sub 2}O) and calcite (CaCO{sub 3}) as secondary precipitates had little effect on the observed residual Cu(II) solubilities, with Cu(II) mobility being governed by the least-soluble kinetically precipitated (rather than thermodynamically favored) phase in the system under study.

  1. Natural Gas Hydrates Update 1998-2000

    EIA Publications

    2001-01-01

    Significant events have transpired on the natural gas hydrate research and development front since "Future Supply Potential of Natural Gas Hydrates" appeared in Natural Gas 1998 Issues and Trends and in the Potential Gas Committee's 1998 biennial report.

  2. Physical properties of hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Waite, W. F.; Santamarina, J. C.; Cortes, D. D.; Dugan, B.; Espinoza, D. N.; Germaine, J.; Jang, J.; Jung, J. W.; Kneafsey, T. J.; Shin, H.; Soga, K.; Winters, W. J.; Yun, T.-S.

    2009-12-01

    Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

  3. Calcite and dolomite in intrusive carbonatites. I. Textural variations

    NASA Astrophysics Data System (ADS)

    Chakhmouradian, Anton R.; Reguir, Ekaterina P.; Zaitsev, Anatoly N.

    2016-04-01

    Carbonatites are nominally igneous rocks, whose evolution commonly involves also a variety of postmagmatic processes, including exsolution, subsolidus re-equilibration of igneous mineral assemblages with fluids of different provenance, hydrothermal crystallization, recrystallization and tectonic mobilization. Petrogenetic interpretation of carbonatites and assessment of their mineral potential are impossible without understanding the textural and compositional effects of both magmatic and postmagmatic processes on the principal constituents of these rocks. In the present work, we describe the major (micro)textural characteristics of carbonatitic calcite and dolomite in the context of magma evolution, fluid-rock interaction, or deformation, and provide information on the compositional variation of these minerals and its relation to specific evolutionary processes.

  4. Age constraints on fluid inclusions in calcite at Yucca Mountain

    SciTech Connect

    Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.; Peterman, Zell E.; Whelan, Joseph F.

    2001-04-29

    The {sup 207}Pb/{sup 235}U ages for 14 subsamples of opal or chalcedony layers younger than calcite formed at elevated temperature range between 1.88 {+-} 0.05 and 9.7 {+-} 1.5 Ma with most values older than 6-8 Ma. These data indicate that fluids with elevated temperatures have not been present in the unsaturated zone at Yucca Mountain since about 1.9 Ma and most likely since 6-8 Ma. Discordant U-Pb isotope data for chalcedony subsamples representing the massive silica stage in the formation of the coatings are interpreted using a model of the diffusive loss of U decay products. The model gives an age estimate for the time of chalcedony formation around 10-11 Ma, which overlaps ages of clay minerals formed in tuffs below the water table at Yucca Mountain during the Timber Mountain thermal event.

  5. Calcite orientations and composition ranges within teeth across Echinoidea.

    PubMed

    Stock, Stuart R; Ignatiev, Konstantin; Lee, Peter L; Almer, Jonathan D

    2014-08-01

    Sea urchin's teeth from four families of order Echinoida and from orders Temnopleuroida, Arbacioida and Cidaroida were studied with synchrotron X-ray diffraction. The high and very high Mg calcite phases of the teeth, i.e. the first and second stage mineral constituents, respectively, have the same crystallographic orientations. The co-orientation of first and second stage mineral, which the authors attribute to epitaxy, extends across the phylogenic width of the extant regular sea urchins and demonstrates that this is a primitive character of this group. The range of compositions Δx for the two phases of Ca1-xMgxCO3 is about 0.20 or greater and is consistent with a common biomineralization process. PMID:25158180

  6. Shock-induced effects in calcite from Cactus Crater

    NASA Technical Reports Server (NTRS)

    Vizgirda, J.; Ahrens, T. J.; Tsay, F.-D.

    1980-01-01

    The paper discusses shock metamorphism of calcite from coralline limestone samples retrieved from a borehole drilled into rocks beneath Cactus Crater, a nuclear explosion crater at Eniwetok Atoll. The metamorphism was detected and quantified using electron spin resonance (ESR); the ESR spectra of Mn(+) present as a trace constituent in the coral samples, show a consistent decrease in hyperfine peak splitting with decreasing depth of sample. It is suggested that the decrease in hyperfine peak splitting reflects a decrease in crystal field splitting, and therefore, small increases on cation-anion distances produced by mechanical energy input during the shock process. Two alternative crater models suggested by the ESR results are a depiction of a steady decay of the shock wave, and a delineation of a breccia lens with a breccia-bedrock interface at 20 plus or minus 5 m.

  7. Calcite orientations and composition ranges within teeth across Echinoidea

    PubMed Central

    Stock, Stuart R.; Ignatiev, Konstantin; Lee, Peter L.; Almer, Jonathan D.

    2016-01-01

    Sea urchin’s teeth from four families of order Echinoida and from orders Temnopleuroida, Arbacioida and Cidaroida were studied with synchrotron x-ray diffraction. The high and very high Mg calcite phases of the teeth, i.e. the first and second stage mineral constituents, respectively, have the same crystallographic orientations. The co-orientation of first and second stage mineral, which the authors attribute to epitaxy, extends across the phylogenic width of the extant regular sea urchins and demonstrates that this is a primitive character of this group. The range of compositions Δx for the two phases of Ca1−xMgxCO3 is about 0.20 or greater and is consistent with a common biomineralization process. PMID:25158180

  8. Structural evolution of calcite at high temperatures: Phase V unveiled

    PubMed Central

    Ishizawa, Nobuo; Setoguchi, Hayato; Yanagisawa, Kazumichi

    2013-01-01

    The calcite form of calcium carbonate CaCO3 undergoes a reversible phase transition between Rc and Rm at ~1240 K under a CO2 atmosphere of ~0.4 MPa. The joint probability density function obtained from the single-crystal X-ray diffraction data revealed that the oxygen triangles of the CO3 group in the high temperature form (Phase V) do not sit still at specified positions in the space group Rm, but migrate along the undulated circular orbital about carbon. The present study also shows how the room temperature form (Phase I) develops into Phase V through an intermediate form (Phase IV) in the temperature range between ~985 K and ~1240 K. PMID:24084871

  9. On the origin of fiber calcite crystals in moonmilk deposits

    NASA Astrophysics Data System (ADS)

    Cañaveras, Juan Carlos; Cuezva, Soledad; Sanchez-Moral, Sergio; Lario, Javier; Laiz, Leonila; Gonzalez, Juan Miguel; Saiz-Jimenez, Cesareo

    2006-01-01

    In this study, we show that moonmilk subaerial speleothems in Altamira Cave (Spain) consist of a network of fiber calcite crystals and active microbial structures. In Altamira moonmilks, the study of the typology and distribution of fiber crystals, extracellular polymeric substances, and microorganisms allowed us to define the initial stages of fiber crystal formation in recent samples as well as the variations in the microstructural arrangement in more evolved stages. Thus, we have been able to show the existence of a relationship among the different types of fiber crystals and their origins. This allowed us to outline a model that illustrates the different stages of formation of the moonmilk, developed on different substrata, concluding that microbes influence physicochemical precipitation, resulting in a variety of fiber crystal morphologies and sizes.

  10. Predicting Calcite (CaCO3) Requirements of Sphagnum Peat Moss from pH Titration Curves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Liming materials are required to neutralize acidity in peat moss to make it a suitable substrate for growing container crops. A series of time-consuming incubations of peat:lime mixtures are typically used to determine the liming rate to achieve a desired pH. Our objective was to evaluate the util...

  11. Methods to determine hydration states of minerals and cement hydrates

    SciTech Connect

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars

    2014-11-15

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na{sub 2}SO{sub 4}–H{sub 2}O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions.

  12. A global deglacial negative carbon isotope excursion in speleothem calcite

    NASA Astrophysics Data System (ADS)

    Breecker, D.

    2015-12-01

    δ13C values of speleothem calcite decreased globally during the last deglaciation defining a carbon isotope excursion (CIE) despite relatively constant δ13C values of carbon in the ocean-atmosphere system. The magnitude of the CIE varied with latitude, increasing poleward from ~2‰ in the tropics to as much as 7‰ at high latitudes. This recent CIE provides an interesting comparison with CIEs observed in deep time. A substantial portion of this CIE can be explained by the increase in atmospheric pCO2 that accompanied deglaciation. The dependence of C3 plant δ13C values on atmospheric pCO2 predicts a 2‰ δ13C decrease driven by the deglacial pCO2 increase. I propose that this signal was transferred to caves and thus explains nearly 100% of the CIE magnitude observed in the tropics and no less than 30% at the highest latitudes in the compilation. An atmospheric pCO2 control on speleothem δ13C values, if real, will need to be corrected for using ice core data before δ13C records can be interpreted in a paleoclimate context. The decrease in the magnitude of the equilibrium calcite-CO2 carbon isotope fractionation factor explains a maximum of 1‰ of the CIE at the highest northern latitude in the compilation, which experienced the largest deglacial warming. Much of the residual extratropical CIE was likely driven by increasing belowground respiration rates, which were presumably pronounced at high latitudes as glacial retreat exposed fresh surfaces and/or vegetation density increased. The largest increases in belowground respiration would have therefore occurred at the highest latitudes, explaining the meridional trend. This work supports the notion that increases in atmospheric pCO2 and belowground respiration rates can result in large CIEs recorded in terrestrial carbonates, which, as previously suggested, may explain the magnitude of the PETM CIE as recorded by paleosol carbonates.

  13. Kinetic model of impurity poisoning during growth of calcite

    SciTech Connect

    DeYoreo, J; Wasylenki, L; Dove, P; Wilson, D; Han, N

    2004-05-18

    The central role of the organic component in biologically controlled mineralization is widely recognized. These proteins are characterized by a high proportion of acidic amino acid residues, especially aspartate, Asp. At the same time, biomineralization takes place in the presence of a number of naturally-occurring, inorganic impurities, particularly Mg and Sr. In an attempt to decipher the controls on calcite growth imposed by both classes of modifiers, we have used in situ AFM to investigate the dependence of growth morphology and step kinetics on calcite in the presence of Sr{sup 2+}, as well as a wide suite of Aspartic acid-bearing polypeptides. In each case, we observe a distinct and step-specific modification. Most importantly, we find that the step speed exhibits a characteristic dependence on impurity concentration not predicted by existing crystal growth models. While all of the impurities clearly induce appearance of a 'dead zone,' neither the width of that dead zone nor the dependence of step speed on activity or impurity content can be explained by invoking the Gibbs-Thomson effect, which is the basis for the Cabrera-Vermilyea model of impurity poisoning. Common kink-blocking models also fail to explain the observed dependencies. Here we propose a kinetic model of inhibition based on a 'cooperative' effect of impurity adsorption at adjacent kink sites. The model is in qualitative agreement with the experimental results in that it predicts a non-linear dependence of dead zone width on impurity concentration, as well as a sharp drop in step speed above a certain impurity content. However, a detailed model of impurity adsorption kinetics that give quantitative agreement with the data has yet to be developed.

  14. Isotopic composition of a calcite-cemented layer in the Lower Jurassic Bridport Sands, southern England: Implications for formation of laterally extensive calcite-cemented layers

    SciTech Connect

    Bjoerkum, P.A. ); Walderhaug, O. )

    1993-07-01

    [delta][sup 18]O[sub PDB] and [delta][sup 13]C[sub PDB] values have been measured on 107 calcite cement samples from a laterally extensive (> 3 km) and continuous calcite-cemented layer 0.5 m thick in the coastal exposures of the Lower Jurassic shallow-marine Bridport Sands in Dorset, southern England. The samples were taken from a two-dimensional grid with 10-cm horizontal and vertical spacing between samples and along individual vertical lines across the calcite-cemented layer, [delta][sup 18]O[sub PDB] values vary between [minus]4.8% and [minus]9.2% and decrease radially outwards from points with lateral spacings on the order of 0.5-1 m in the middle of the calcite-cemented layer. The [delta][sup 18]O[sub PDB] values therefore indicate that the calcite-cemented layer was formed by merging of concretions. All [delta][sup 13]C[sub PDB] values measured are in the narrow range [minus]2.2% to [minus]0.5%, which suggests that the dominant source of calcite cement in the layer was biogenic carbonate.

  15. Natural gas hydrates; vast resource, uncertain future

    USGS Publications Warehouse

    Collett, T.S.

    2001-01-01

    Gas hydrates are naturally occurring icelike solids in which water molecules trap gas molecules in a cagelike structure known as a clathrate. Although many gases form hydrates in nature, methane hydrate is by far the most common; methane is the most abundant natural gas. The volume of carbon contained in methane hydrates worldwide is estimated to be twice the amount contained in all fossil fuels on Earth, including coal.

  16. Partly exhausted soda lime or soda lime with water added, inhibits the increase in compound A concentration in the circle system during low-flow sevoflurane anaesthesia.

    PubMed

    Moriwaki, G; Bito, H; Ikeda, K

    1997-12-01

    We performed low-flow sevoflurane anaesthesia at a flow rate of 1 litre min-1 in three groups (n = 8 each) using 600 g of fresh soda lime (control group), 600 g of soda lime with 60 ml of water added (water group) or 600 g of soda lime saturated with carbon dioxide, that is partly exhausted soda lime (carbon dioxide group). Degradation products in the system were measured hourly. Inspired and end-tidal carbon dioxide and sevoflurane concentrations, carbon dioxide and temperature of the soda lime were monitored. CF2 = C(CF3)-O-CH2F (compound A) was the only sevoflurane degradation product detected. The mean maximum concentration of compound A was significantly higher in the control group (mean 16.0 (SD 5.0) ppm) than in the water (1.4 (1.0) ppm) or carbon dioxide (4.0 (1.8) ppm) group, and the maximum temperature of the soda lime was significantly lower in the carbon dioxide group (30.7 (3.5) degrees C) than in the control (43.4 (1.8) degrees C) or water (40.8 (1.8) degrees C) group (P < 0.05). The use of partly exhausted soda lime or soda lime with water added reduced compound A concentrations in the system during low-flow sevoflurane anaesthesia.

  17. LOW VELOCITY SHPERE IMPACT OF SODA LIME SILICATE GLASS

    SciTech Connect

    Morrissey, Timothy G; Fox, Ethan E; Wereszczak, Andrew A; Vuono, Daniel J

    2012-01-01

    This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity ( 30 m/s or 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations.

  18. Carbon and oxygen isotopes in apatite CO/sub 2/ and co-existing calcite

    SciTech Connect

    Kolodny, Y.; Kaplan, I. R.

    1981-04-01

    Carbon and oxygen isotopes were analyzed in carbonate apatite CO/sub 2/ and in co-existing calcite. Both C and O in apatite CO/sub 2/ are enriched in the respective light isotopes relative to calcite. These results confirm the proposition that carbonate is part of the apatite structure.

  19. Biotic Control of Skeletal Growth by Scleractinian Corals in Aragonite–Calcite Seas

    PubMed Central

    Higuchi, Tomihiko; Fujimura, Hiroyuki; Yuyama, Ikuko; Harii, Saki; Agostini, Sylvain; Oomori, Tamotsu

    2014-01-01

    Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas. PMID:24609012

  20. Characteristics and reactivity of rapidly hydrated sorbent for semidry flue gas desulfurization

    SciTech Connect

    Jie Zhang; Changfu You; Suwei Zhao; Changhe Chen; Haiying Qi

    2008-03-01

    The semidry flue gas desulfurization (FGD) process has many advantages over the wet FGD process for moving sulfur dioxide emissions from pulverized coal-fired power plants. Semidry FGD with a rapidly hydrated sorbent was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. The sorbent was made from lumps of lime and coal fly ash. The desulfurization efficiency was measured for various operating parameters, including the sorbent recirculation rate and the water spray method. The experimental results show that the desulfurization efficiencies of the rapidly hydrated sorbent were 1.5-3.0 times higher than a commonly used industrial sorbent for calcium to sulfur molar ratios from 1.2 to 3.0, mainly due to the higher specific surface area and pore volume. The Ca(OH){sub 2} content in the cyclone separator ash was about 2.9% for the rapidly hydrated sorbent and was about 0.1% for the commonly used industrial sorbent, due to the different adhesion between the fine Ca(OH){sub 2} particles and the fly ash particles, and the low cyclone separation efficiency for the fine Ca(OH){sub 2} particles that fell off the sorbent particles. Therefore the actual recirculation rates of the active sorbent with Ca(OH){sub 2} particles were higher for the rapidly hydrated sorbent, which also contributed to the higher desulfurization efficiency. The high fly ash content in the rapidly hydrated sorbent resulted in good operating stability. The desulfurization efficiency with upstream water spray was 10-15% higher than that with downstream water spray. 20 refs., 7 figs., 1 tab.

  1. Improvement in hardness of soda-lime-silica glass

    NASA Astrophysics Data System (ADS)

    Chakraborty, Riya; De, Moumita; Roy, Sudakshina; Dey, Arjun; Biswas, Sampad K.; Middya, Tapas Ranjan; Mukhopadhyay, Anoop K.

    2012-06-01

    Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vicker's hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s-1. Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate.

  2. 75 FR 9886 - Methane Hydrate Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-04

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. Federal... Methane Hydrate Advisory Committee is to provide advice on potential applications of methane hydrate...

  3. The quantitative determination of calcite associated with the carbonate-bearing apatites

    USGS Publications Warehouse

    Silverman, Sol R.; Fuyat, Ruth K.; Weiser, Jeanne D.

    1951-01-01

    The CO2 combined as calcite in carbonate-bearing apatites as been distinguished from that combined as carbonate-apatite, or present in some form other than calcite, by use of X-ray powder patterns, differential thermal analyses, and differential solubility tests. These methods were applied to several pure apatite minerals, to one fossil bone, and to a group of phosphorites from the Phosphoria formation of Permian age from Trail Canyon and the Conda mine, Idaho, and the Laketown district, Utah. With the exceptions of pure fluorapatite, pure carbonate-flueorapatite, and one phosphorite from Trail Canyon, these substances contain varying amounts of calcite, but in all the samples an appreciable part of the carbonite content is not present as calcite. The results of solubility tests, in which the particle size of sample and the length of solution time were varied, imply that the carbonate content is not due to shielded calcite entrapped along an internal network of surfaces.

  4. Low limit of Mn 2+-activated cathodoluminescence of calcite: state of the art

    NASA Astrophysics Data System (ADS)

    Habermann, Dirk; Neuser, Rolf D.; Richter, Detlev K.

    1998-02-01

    In the literature, the lower limit for Mn 2+-activated cathodoluminescence (CL) of calcite is variously reputed to over a very wide range of values above 10 ppm Mn. Our spectroscopic investigations of the CL response in natural calcite reveal that below 10 ppm manganese content Mn 2+-activation is also present. Using the Quantitative High Resolution Spectral analysis of CL (QHRS-CL) an activation by Mn 2+ in the range of 700 ppb is proved, which cannot be determined visually. So, if not quenched, the minimum Mn 2+ content for Mn 2+-activation is one atom in the irradiated calcite crystal lattice volume. As the intrinsic (background blue) luminescence is used to determine non-altered biogenic calcite, the limit of Mn 2+-activation plays an important role in the interpretation of diagenetic processes. Our results of spectroscopic analyses require a revision of current opinions about the diagenesis of calcite as revealed by CL investigation.

  5. Unusual micrometric calcite-aragonite interface in the abalone shell Haliotis (Mollusca, Gastropoda).

    PubMed

    Dauphin, Yannicke; Cuif, Jean-Pierre; Castillo-Michel, Hiram; Chevallard, Corinne; Farre, Bastien; Meibom, Anders

    2014-02-01

    Species of Haliotis (abalone) show high variety in structure and mineralogy of the shell. One of the European species (Haliotis tuberculata) in particular has an unusual shell structure in which calcite and aragonite coexist at a microscale with small patches of aragonite embedded in larger calcitic zones. A detailed examination of the boundary between calcite and aragonite using analytical microscopies shows that the organic contents of calcite and aragonite differ. Moreover, changes in the chemical composition of the two minerals seem to be gradual and define a micrometric zone of transition between the two main layers. A similar transition zone has been observed between the layers in more classical and regularly structured mollusk shells. The imbrication of microscopic patches of aragonite within a calcitic zone suggests the occurrence of very fast physiological changes in these taxa.

  6. Influence of calcite on uranium(VI) reactive transport in the groundwater–river mixing zone

    SciTech Connect

    Ma, Rui; Liu, Chongxuan; Greskowiak, Janek; Prommer, Henning; Zachara, John M.; Zheng, Chunmiao

    2014-01-23

    Calcite is an important mineral that can affect uranyl reactive transport in subsurface sediments. This study investigated the distribution of calcite and its influence on uranyl adsorption and reactive transport in the groundwater-river mixing zone at US Hanford 300A, Washington State. Simulations using a 2D reactive transport model under field-relevant hydrogeochemical conditions revealed a complex distribution of calcite concentration as a result of dynamic groundwater-river interactions. The calcite concentration distribution in turn affected the spatial and temporal changes in aqueous carbonate, calcium, and pH, which subsequently influenced U(VI) mobility and discharge rates into the river. The results implied that calcite distribution and its concentration dynamics is an important consideration for field characterization, monitoring, and reactive transport prediction.

  7. Flavor chemistry of lemon-lime carbonated beverages.

    PubMed

    Hausch, Bethany J; Lorjaroenphon, Yaowapa; Cadwallader, Keith R

    2015-01-14

    The most potent aroma-active components of Sprite (SP), Sierra Mist (SM), and 7UP (7UP) were identified. Aroma extracts were prepared by liquid–liquid continuous extraction/solvent-assisted flavor evaporation (LLCE/SAFE). Twenty-eight compounds were detected by gas chromatography–olfactometry (GC-O) with linalool (floral, lavender), octanal (pungent orange), and 2,3-dehydro-1,8-cineole (minty) determined to be predominant aroma compounds based on their high flavor dilution (FD) factors by aroma extract dilution analysis (AEDA). The data indicate that lemon-lime flavor is composed of a small number of compounds (22 at the most in SM), and only a subset of these may be important because many compounds were detected only at low FD factors. Predominant aroma compounds (23) were quantified using static headspace solid phase microextraction (SPME) combined with stable isotope dilution assays (SIDA). In contrast to FD factors, the calculated odor-activity values (OAVs) indicate that octanal and limonene make the greatest contribution to the overall aroma of lemon-lime carbonated beverages, followed by nonanal, decanal, linalool, 1,8-cineole, and geranyl acetate. The results demonstrate that lemon-lime carbonated beverages share many of the same compounds but the relative abundance of these compounds varies by brand. PMID:25494537

  8. Energy reduction in beet sugar processing by cossette liming

    SciTech Connect

    Randall, J.M.; Camirand, W.M.; Neumann, H.J.

    1981-01-01

    Under appropriate conditions of temperature and fresh Ca(OH)/sub 2/ application, demethylation occurs in the pectin in the cell walls of sugar beet cossettes, allowing Ca/sup 2 +/ to precipitate the pectin as calcium pectate. The calcium pectate will not degrade and pass into solution during subsequent hot extraction of sugar from the cossettes. This retention of pectin in the pulp was shown by 10 to 20% increases in solids weight in the pulp for a number of processing conditions. The toughened pulp produced by retention of calcium pectate allowed easier mechanical dewatering of the pulp which could save considerably on the heat normally required to dry the pulp for cattle feed. Beyond data reported in this paper, there are qualitative indications that the sugar juice extracted from limed cossettes is purer than standard juice, for pectin and colloidal materials remain in the pulp. Thus, much less purification of the juice with lime would be necessary than is required in standard beet-sugar processing, and the current 2% CaO used for purification may be cut almost in half. This represents another energy saving, for production of CaO at the factory is a major consumer of energy. These, along with other possible energy savings resulting from cossette liming (such as less water used for extraction, cold extraction, ion exchange of the purer juice), could produce an overall saving up to 20% of the energy currently used in beet-sugar processing. Some of these possibilities will be further investigated.

  9. Flavor chemistry of lemon-lime carbonated beverages.

    PubMed

    Hausch, Bethany J; Lorjaroenphon, Yaowapa; Cadwallader, Keith R

    2015-01-14

    The most potent aroma-active components of Sprite (SP), Sierra Mist (SM), and 7UP (7UP) were identified. Aroma extracts were prepared by liquid–liquid continuous extraction/solvent-assisted flavor evaporation (LLCE/SAFE). Twenty-eight compounds were detected by gas chromatography–olfactometry (GC-O) with linalool (floral, lavender), octanal (pungent orange), and 2,3-dehydro-1,8-cineole (minty) determined to be predominant aroma compounds based on their high flavor dilution (FD) factors by aroma extract dilution analysis (AEDA). The data indicate that lemon-lime flavor is composed of a small number of compounds (22 at the most in SM), and only a subset of these may be important because many compounds were detected only at low FD factors. Predominant aroma compounds (23) were quantified using static headspace solid phase microextraction (SPME) combined with stable isotope dilution assays (SIDA). In contrast to FD factors, the calculated odor-activity values (OAVs) indicate that octanal and limonene make the greatest contribution to the overall aroma of lemon-lime carbonated beverages, followed by nonanal, decanal, linalool, 1,8-cineole, and geranyl acetate. The results demonstrate that lemon-lime carbonated beverages share many of the same compounds but the relative abundance of these compounds varies by brand.

  10. Hydration rind dates rhyolite flows.

    PubMed

    Friedman, I

    1968-02-23

    Hydration of obsidian has been used to date rhyolite flows, containing obsidian or porphyritic glass, at Glass Mountain (Medicine Lake Highlands) and Mono Lake, California. The method is simple and rapid and can be used to date flows that erupted between 200 and approximately 200,000 years ago. PMID:17768978

  11. Attraction between hydrated hydrophilic surfaces

    NASA Astrophysics Data System (ADS)

    Kanduč, Matej; Schneck, Emanuel; Netz, Roland R.

    2014-08-01

    According to common knowledge, hydrophilic surfaces repel via hydration forces while hydrophobic surfaces attract, but mounting experimental evidence suggests that also hydrophilic surfaces can attract. Using all-atom molecular dynamics simulations at prescribed water chemical potential we study the crossover from hydration repulsion to hydrophobic attraction for planar polar surfaces of varying stiffness and hydrogen-bonding capability. Rescaling the partial charges of the polar surface groups, we cover the complete spectrum from very hydrophobic surfaces (characterized by contact angles θ ≃ 135°) to hydrophilic surfaces exhibiting complete wetting (θ = 0°). Indeed, for a finite range θadh < θ < 90°, we find a regime where hydrophilic surfaces attract at sub-nanometer separation and stably adhere without intervening water. The adhesive contact angle θadh depends on surface type and lies in the range 65° < θadh < 80°, in good agreement with experiments. Analysis of the total number of hydrogen bonds (HBs) formed by water and surface groups rationalizes this crossover between hydration repulsion and hydrophilic attraction in terms of a subtle balance: Highly polar surfaces repel because of strongly bound hydration water, less polar hydrophilic surfaces attract because water-water HBs are preferred over surface-water HBs. Such solvent reorganization forces presumably underlie also other important phenomena, such as selective ion adsorption to interfaces as well as ion pair formation.

  12. Strong covalent hydration of terephthalaldehyde.

    PubMed

    Baymak, Melek S; Vercoe, Kellie L; Zuman, Petr

    2005-11-24

    Spectrophotometric and electroanalytical studies indicate that one of the formyl groups of terephthalaldehyde in aqueous solution is present in about 23% as a geminal diol. Stronger covalent hydration of CHO in terephthalaldehyde than in p-nitrobenzaldehyde is attributed to a strong resonance interaction between the two formyl groups.

  13. Hydration rind dates rhyolite flows.

    PubMed

    Friedman, I

    1968-02-23

    Hydration of obsidian has been used to date rhyolite flows, containing obsidian or porphyritic glass, at Glass Mountain (Medicine Lake Highlands) and Mono Lake, California. The method is simple and rapid and can be used to date flows that erupted between 200 and approximately 200,000 years ago.

  14. Hydration rind dates rhyolite flows

    USGS Publications Warehouse

    Friedman, I.

    1968-01-01

    Hydration of obsidian has been used to date rhyolite flows, containing obsidian or porphyritic glass, at Glass Mountain (Medicine Lake Highlands) and Mono Lake, California. The method is simple and rapid and can be used to date flows that erupted between 200 and approximately 200,000 years ago.

  15. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained "solubility product" of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  16. Interactions of arsenic with calcite surfaces revealed by in situ nanoscale imaging

    NASA Astrophysics Data System (ADS)

    Renard, François; Putnis, Christine V.; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hovelmann, Jörn; Sarret, Géraldine

    2015-06-01

    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in situ study of the evolution of the (10-14) calcite cleavage surface morphology during dissolution and growth in the presence of solutions with various amounts of As(III) or As(V) at room temperature and pH range 6-11 using a flow-through cell connected to an atomic force microscope (AFM). Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  17. Diel cycles in calcite production and dissolution in a eutrophic basin

    SciTech Connect

    Cicerone, D.S.; Stewart, A.J.; Roh, Y.

    1999-10-01

    Calcite production is understood largely as a longer-term phenomenon (e.g., seasonal whitings) that can occur in hardwater lakes, and is significant ecologically because it can slow the rate of eutrophication by reducing, through adsorption, the availability of nutrients to primary producers. In this study the authors show that rapid changes in concentration of dissolved CO{sub 2} by photosynthesis and respiration within a eutrophic basin generated strong day-to-night cycles in calcite production and dissolution. Diel cycles in calcite production and dissolution were large enough that they could drive secondary diel cycles in the availability of metals that strongly sorb to the surfaces of calcite particles. They explored the possibility of the secondary diel cycling of metals by intensive 7-d in situ monitoring of water-quality conditions in a shallow, eutrophic spill-control basin near an industrial facility in eastern Tennessee; inspecting data from a 7-year record of water-quality parameters for this basin; analyzing physicochemical characteristics and mineralogic composition of sediments in the basin; and conducting laboratory experiments to characterize the interaction of calcite with Cd, under solid-liquid nonequilibrium conditions. The authors found that the basin accumulated and stored calcite. In situ monitoring showed that calcite was produced during daylight, and tended to dissolve again at night; the calcite production and dissolution processes seemed to be modulated by dissolved-phase CO{sub 2} dynamics, in concert with large diel fluctuations in pCa, pH, and Po{sub 2}. Laboratory experiments showed a rapid interaction ({lt}6 h) of Cd with calcite, in response to dissolved CO{sub 2} changes. Thus, concentrations of dissolved Cd can vary over daily cycles, mediated by diel changes in calcite production and dissolution. Thermodynamic considerations suggest that other metals, such as Zn, Sr, Ni, and Ba, may demonstrate this behavior as well.

  18. Retrofit costs for lime/limestone FGD and lime spray drying at coal-fired utility boilers

    SciTech Connect

    Emmel, T.E.; Jones, J.W.

    1990-01-01

    The paper gives results of a research program the objective of which was to significantly improve engineering cost estimates currently being used to evaluate the economic effects of applying SO2 controls to existing coal-fired utility boilers. The costs of retrofitting conventional lime/limestone wet flue gas desulfurization (L/LS FGD) and lime spray drying (LSD) FGD at 100-200 coal-fired power plants are being estimated under this program. The retrofit capital cost estimating procedures used for L/LS FGD and LSD FGD make two cost adjustments to current procedures used to estimate FGD costs: cost adders (for items not normally included in FGD system costs; e.g., demolition and relocation of existing facilities) and cost multipliers (to adjust capital costs for site access, congestion, and underground obstructions).

  19. Thermal properties of methane gas hydrates

    USGS Publications Warehouse

    Waite, William F.

    2007-01-01

    Gas hydrates are crystalline solids in which molecules of a “guest” species occupy and stabilize cages formed by water molecules. Similar to ice in appearance (fig. 1), gas hydrates are stable at high pressures and temperatures above freezing (0°C). Methane is the most common naturally occurring hydrate guest species. Methane hydrates, also called simply “gas hydrates,” are extremely concentrated stores of methane and are found in shallow permafrost and continental margin sediments worldwide. Brought to sea-level conditions, methane hydrate breaks down and releases up to 160 times its own volume in methane gas. The methane stored in gas hydrates is of interest and concern to policy makers as a potential alternative energy resource and as a potent greenhouse gas that could be released from sediments to the atmosphere and ocean during global warming. In continental margin settings, methane release from gas hydrates also is a potential geohazard and could cause submarine landslides that endanger offshore infrastructure. Gas hydrate stability is sensitive to temperature changes. To understand methane release from gas hydrate, the U.S. Geological Survey (USGS) conducted a laboratory investigation of pure methane hydrate thermal properties at conditions relevant to accumulations of naturally occurring methane hydrate. Prior to this work, thermal properties for gas hydrates generally were measured on analog systems such as ice and non-methane hydrates or at temperatures below freezing; these conditions limit direct comparisons to methane hydrates in marine and permafrost sediment. Three thermal properties, defined succinctly by Briaud and Chaouch (1997), are estimated from the experiments described here: - Thermal conductivity, λ: if λ is high, heat travels easily through the material. - Thermal diffusivity, κ: if κ is high, it takes little time for the temperature to rise in the material. - Specific heat, cp: if cp is high, it takes a great deal of heat to

  20. Mesoscale texture of cement hydrates.

    PubMed

    Ioannidou, Katerina; Krakowiak, Konrad J; Bauchy, Mathieu; Hoover, Christian G; Masoero, Enrico; Yip, Sidney; Ulm, Franz-Josef; Levitz, Pierre; Pellenq, Roland J-M; Del Gado, Emanuela

    2016-02-23

    Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water. Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials. PMID:26858450

  1. Physical activity, hydration and health.

    PubMed

    Marcos, Ascensión; Manonelles, Pedro; Palacios, Nieves; Wärnberg, Julia; Casajús, José A; Pérez, Margarita; Aznar, Susana; Benito, Pedro J; Martínez-Gomez, David; Ortega, Francisco B; Ortega, Eduardo; Urrialde, Rafael

    2014-06-01

    Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory disea ses and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences.

  2. Mesoscale texture of cement hydrates

    PubMed Central

    Ioannidou, Katerina; Krakowiak, Konrad J.; Bauchy, Mathieu; Hoover, Christian G.; Masoero, Enrico; Yip, Sidney; Ulm, Franz-Josef; Levitz, Pierre; Pellenq, Roland J.-M.; Del Gado, Emanuela

    2016-01-01

    Strength and other mechanical properties of cement and concrete rely upon the formation of calcium–silicate–hydrates (C–S–H) during cement hydration. Controlling structure and properties of the C–S–H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water. Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C–S–H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C–S–H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C–S–H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C–S–H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials. PMID:26858450

  3. Physical activity, hydration and health.

    PubMed

    Marcos, Ascensión; Manonelles, Pedro; Palacios, Nieves; Wärnberg, Julia; Casajús, José A; Pérez, Margarita; Aznar, Susana; Benito, Pedro J; Martínez-Gomez, David; Ortega, Francisco B; Ortega, Eduardo; Urrialde, Rafael

    2014-01-01

    Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory disea ses and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences. PMID:24972459

  4. Gas hydrate reservoir characteristics and economics

    SciTech Connect

    Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.

    1992-06-01

    The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

  5. Gas hydrate reservoir characteristics and economics

    SciTech Connect

    Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.

    1992-01-01

    The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

  6. Acidic deposition: State of science and technology. Report 15. Liming acidic surface waters. Final report

    SciTech Connect

    Olem, H.; Thornelof, E.; Sandoy, S.; Schreiber, R.K.

    1990-09-01

    The document describes the science and technology of aquatic liming--a method for improving the water quality of acidic surface waters to restore or enhance fisheries. The report is a comprehensive compilation of years of research in North America and Europe by dozens of scientists. Several mitigation technologies--including those that have only been proposed--are critically evaluated along with the effects of liming on water chemistry and aquatic biota. Through these evaluations, the state of the science and technology of aquatic liming is identified for the reader. Whole-lake liming is now recognized as a valuable management tool for acidic surface waters and their fisheries. However, some liming technologies are considered experimental and will need further evaluation. Distinctions between technologies are included--as is the distinction between liming acidic surface waters and reducing acidifying emissions.

  7. [Study on the traditional lime mortar from the memorial archway in the southern Anhui province].

    PubMed

    Wei, Guo-Feng; Sun, Sheng; Wang, Cheng-Xing; Zhang, Bing-Jian; Chen, Xi-Min

    2013-07-01

    The traditional lime mortar was investigated by means of scanning electron microscope (SEM), X-ray diffractometry and Fourier transform infrared spectrometry (FTIR). The results show that the mortar from the memorial archway in the southern Anhui province was the organic-inorganic composite materials composed of lime with tung oil or sticky rice. It was found that the excellent performance of the tung oil-lime mortar can be explained by the compact lamellar organic-inorganic composite structure that was produced by carbonization reaction of lime, cross-linking reactions of tung oil and oxygen and complexing reaction of Ca2+ and -COO-. The compact micro-structure of sticky rice-lime mortar, which was produced due to carbonation process of lime controlled by amylopectin, should be the cause of the good performance of this kind of organic-inorganic mortar.

  8. Advanced mineral calciner for regeneration of lime. Topical technical report, May 1992-August 1993

    SciTech Connect

    Namazian, M.; Kelly, J.T.; Woodworth, R.

    1994-10-01

    Pulp and paper market growth and process changes require low cost incremental capacity lime regeneration units. Existing rotary kiln lime regeneration technology is costly to install and operate, especially at the lower capacity needed for the pulp and paper growth market. If this capacity need is not met by a cost effective and environmentally clean system, an 8 BCF potential gas market could move off-shore. The Advanced Mineral Calciner (AMC) is an environmentally clean, low capital and low operating cost lime regeneration system that is well suited to meeting this projected market. To quantify the benefits of the AMC, in small-scale a 100 lb/hr test system was built and operated. The product lime was subjected to standard industry tests to evaluate the extent of reaction and level of reactivity. The results showed that the lime produced by AMC has low unreacted core and good reactivity, compared to lime produced by rotary kilns.

  9. [Study on the traditional lime mortar from the memorial archway in the southern Anhui province].

    PubMed

    Wei, Guo-Feng; Sun, Sheng; Wang, Cheng-Xing; Zhang, Bing-Jian; Chen, Xi-Min

    2013-07-01

    The traditional lime mortar was investigated by means of scanning electron microscope (SEM), X-ray diffractometry and Fourier transform infrared spectrometry (FTIR). The results show that the mortar from the memorial archway in the southern Anhui province was the organic-inorganic composite materials composed of lime with tung oil or sticky rice. It was found that the excellent performance of the tung oil-lime mortar can be explained by the compact lamellar organic-inorganic composite structure that was produced by carbonization reaction of lime, cross-linking reactions of tung oil and oxygen and complexing reaction of Ca2+ and -COO-. The compact micro-structure of sticky rice-lime mortar, which was produced due to carbonation process of lime controlled by amylopectin, should be the cause of the good performance of this kind of organic-inorganic mortar. PMID:24059213

  10. Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes.

    PubMed

    Wällstedt, Teresia; Borg, Hans

    2003-01-01

    In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.

  11. STRONTIUM ISOTOPE EVOLUTION OF PORE WATER AND CALCITE IN THE TOPOPAH SPRING TUFF, YUCCA MOUNTAIN , NEVADA

    SciTech Connect

    B.D. Marshall; K. Futa

    2001-02-07

    Yucca Mountain, a ridge of Miocene volcanic rocks in southwest Nevada, is being characterized as a site for a potential high-level radioactive waste repository. One issue of concern for the future performance of the potential repository is the movement of water in and around the potential repository horizon. Past water movement in this unsaturated zone is indicated by fluid inclusions trapped in calcite coatings on fracture footwall surfaces and in some lithophysal cavities. Some of the fluid inclusions have homogenization temperatures above the present-day geotherm (J.F. Whelan, written communication), so determining the ages of the calcite associated with those fluid inclusions is important in understanding the thermal history of the potential repository site. Calcite ages have been constrained by uranium-lead dating of silica polymorphs (opal and chalcedony) that are present in most coatings. The opal and chalcedony ages indicate that deposition of the calcite and opal coatings in the welded part of the Topopah Spring Tuff (TSw hydrogeologic unit) spanned nearly the entire history of the 12.8-million-year-old rock mass at fairly uniform overall long-term rates of deposition (within a factor of five). Constraining the age of a layer of calcite associated with specific fluid inclusions is complicated. Calcite is commonly bladed with complex textural relations, and datable opal or chalcedony may be millions of years older or younger than the calcite layer or may be absent from the coating entirely. Therefore, a more direct method of dating the calcite is presented in this paper by developing a model for strontium evolution in pore water in the TSw as recorded by the strontium coprecipitated with calcium in the calcite. Although the water that precipitated the calcite in fractures and cavities may not have been in local isotopic equilibrium with the pore water, the strontium isotope composition of all water in the TSw is primarily controlled by water

  12. Well log evaluation of gas hydrate saturations

    USGS Publications Warehouse

    Collett, T.S.

    1998-01-01

    The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative due to the lack of previous quantitative studies. Gas volumes that may be attributed to a gas hydrate accumulation within a given geologic setting are dependent on a number of reservoir parameters; one of which, gas-hydrate saturation, can be assessed with data obtained from downhole well logging devices. The primary objective of this study was to develop quantitative well-log evaluation techniques which will permit the calculation of gas-hydrate saturations in gas-hydrate-bearing sedimentary units. The "standard" and "quick look" Archie relations (resistivity log data) yielded accurate gas-hydrate and free-gas saturations within all of the gas hydrate accumulations assessed in the field verification phase of the study. Compressional wave acoustic log data have been used along with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate accurate gas-hydrate saturations in all of the gas hydrate accumulations assessed in this study. The well log derived gas-hydrate saturations calculated in the field verification phase of this study, which range from as low as 2% to as high as 97%, confirm that gas hydrates represent a potentially important source of natural gas.

  13. Short-term responses of wetland vegetation after liming of an Adirondack watershed

    SciTech Connect

    Mackun, I.R.; Leopold, D.J.; Raynal, D.J. )

    1994-08-01

    Watershed liming has been suggested as a long-term mitigation strategy for lake acidity, particularly in areas subject to high levels of acidic deposition. However, virtually no information has been available on the impacts of liming on wetland vegetation. In 1989, 1100 Mg of limestone (83.5% CaCO[sub 3]) were aerially applied to 48% (100 ha) of the Woods Lake watershed in the west-central Adirondack region of New York as part of the first comprehensive watershed liming study in North America. We inventoried wetland vegetation in 1.0-m[sup 2] plots before liming and during the subsequent 2 yr. Within this period liming influenced the cover, frequency, or importance values of only 6 of 64 wetland taxa. The cover of Sphagnum spp. and of the cespitose sedge Carex interior decreased in control relative to limed plots, and cover of the rhizomatous sedge Cladium mariscoides increased nearly threefold in limed areas. These two sedges, which are relatively tall, are characteristic of more calcareous habitats. Cover of the grass Muhlenbergia uniflora, cover and importance were adversely affected or inhibited by lime. It is unclear whether liming directly inhibited the growth of these three small-statured species, or whether the adverse effects of lime were mediated through shifts in competitive interactions with other species. The limited responses that we observed to liming, along with changes that occurred in control plots over the study period, may indicate that in the short term watershed liming was no more of a perturbation than the environmental factors responsible for natural annual variation in wetland communities.

  14. Handbook of gas hydrate properties and occurrence

    SciTech Connect

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  15. Uranium isotope fractionation during coprecipitation with aragonite and calcite

    NASA Astrophysics Data System (ADS)

    Chen, Xinming; Romaniello, Stephen J.; Herrmann, Achim D.; Wasylenki, Laura E.; Anbar, Ariel D.

    2016-09-01

    Natural variations in 238U/235U of marine calcium carbonates might provide a useful way of constraining redox conditions of ancient environments. In order to evaluate the reliability of this proxy, we conducted aragonite and calcite coprecipitation experiments at pH ∼7.5 and ∼8.5 to study possible U isotope fractionation during incorporation into these minerals. Small but significant U isotope fractionation was observed in aragonite experiments at pH ∼8.5, with heavier U isotopes preferentially enriched in the solid phase. 238U/235U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007 + 0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ∼7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca2UO2(CO3)3(aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca2UO2(CO3)3(aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism. These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, PCO2 , Ca2+, or Mg2+ concentrations. In general, these effects are likely to be small (<0.13‰), but are nevertheless potentially significant because of the small natural range of

  16. Thermal conductivity of hydrate-bearing sediments

    USGS Publications Warehouse

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

  17. Well log characterization of natural gas hydrates

    USGS Publications Warehouse

    Collett, Timothy S.; Lee, Myung W.

    2011-01-01

    In the last 25 years we have seen significant advancements in the use of downhole well logging tools to acquire detailed information on the occurrence of gas hydrate in nature: From an early start of using wireline electrical resistivity and acoustic logs to identify gas hydrate occurrences in wells drilled in Arctic permafrost environments to today where wireline and advanced logging-while-drilling tools are routinely used to examine the petrophysical nature of gas hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. The most established and well known use of downhole log data in gas hydrate research is the use of electrical resistivity and acoustic velocity data (both compressional- and shear-wave data) to make estimates of gas hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. New downhole logging tools designed to make directionally oriented acoustic and propagation resistivity log measurements have provided the data needed to analyze the acoustic and electrical anisotropic properties of both highly inter-bedded and fracture dominated gas hydrate reservoirs. Advancements in nuclear-magnetic-resonance (NMR) logging and wireline formation testing have also allowed for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids (i.e., free-water along with clay and capillary bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms controlling the formation and occurrence of gas hydrate in nature along with data on gas hydrate reservoir properties (i.e., permeabilities) needed to accurately predict gas production rates for various gas hydrate

  18. Speciation of heavy metals during co-composting of sewage sludge with lime.

    PubMed

    Wong, J W C; Selvam, A

    2006-05-01

    During composting the humification of organic matter will have a significant effect on the physicochemical form of existence of heavy metals. Therefore the present study was conducted to investigate the effect of co-composting sewage sludge with lime on heavy metal speciation and the changes in DTPA extractable metals. Metal speciation was conducted to evaluate the redistribution of Cu, Mn, Ni, Pb and Zn in sewage sludge composted with lime. Sewage sludge was mixed with sawdust in 2:1 (w/w fresh weight) and then composted with lime at 0%, 0.63%, 1% or 1.63% (dry weight) for 100 days. The lime addition did not cause any changes in the different forms of Cu and Mn, but the composting process caused transformations of residual form of Cu and Mn into oxidizable and reducible form, respectively. For Ni, the reducible form was mainly transformed into residual form and lime addition decreased this transformation. Major transformation of different forms of Pb was not found, however the residual form of Pb increased with lime addition. The predominant residual form of Zn was mainly transformed into oxidizable form and the lime addition reduced this transformation. Addition of lime to sewage sludge during composting resulted in lower DTPA extractable metal contents. Therefore, lime is a suitable material to co-compost with sewage sludge to reduce the availability of heavy metals.

  19. The effect of liming on antibacterial and hormone levels in wastewater biosolids.

    PubMed

    Olszewski, Jennifer M; Lozano, Nuria; Haines, Christine; Rice, Clifford P; Ramirez, Mark; Torrents, Alba

    2013-01-01

    This study analyzes the effect of liming on levels of triclocarban (TCC), triclosan (TCS), estrone (E1), and progesterone (P), two antimicrobial agents and two natural hormones, respectively. Factors studied include lime particle size, mixing time, and overall lime contact time. The study results suggest that coarse lime may be more active than fine lime due to less interaction with surrounding air. Both TCS and TCC concentrations were lower in coarse limed samples versus unlimed samples and the decrease was a function of time. A similar, but statistically insignificant trend in TCC and TCS levels was observed in fine lime samples with respect to unlimed samples. Liming was also found to decrease apparent E1 levels, with more notable decreases in samples amended with coarse lime. P-levels significantly increased after 1-day of contact time, stabilizing over the next 14 days of the study period. This increase and stabilization of P-levels was attributed to the pH and moisture-driven conversion of more chemically complex steroids into P. PMID:23485235

  20. The role of soda lime during administration of inhaled nitric oxide.

    PubMed

    Pickett, J A; Moors, A H; Latimer, R D; Mahmood, N; Ghosh, S; Oduro, A

    1994-06-01

    We have studied the ability of three commercially available preparations of soda lime to act as nitrogen dioxide scavengers during administration of inhaled nitric oxide. Soda lime, with a green to brown colour change (indicator = potassium permanganate), markedly reduced concentrations of nitrogen dioxide, but also markedly reduced inhaled concentrations of nitric oxide. The other varieties of soda lime, with colour changes from pink to white (indicator = kenazol yellow) or white to violet (indicator = ethyl violet), produced little effect on concentrations of nitrogen dioxide. None of the above soda limes can be recommended for use as a nitrogen dioxide scavenger during administration of inhaled nitric oxide.

  1. [Causes for the reaction between dry soda lime and halogenated inhalation anesthetics].

    PubMed

    Förster, H; Dudziak, R

    1997-12-01

    All volatile anesthetics undergo chemical breakdown to multiple, partly identified degradation products in the presence of dry soda lime. These chemical reactions are highly exothermic, ranging from 100 degrees C for halothane to 120 degrees C for sevoflurane. The increase in temperature correlates with the moisture content of the soda lime, being maximal below 5%. Sevoflurane and isoflurane were exposed to dry soda lime in a circle system. The anaesthetic gas was condensed in a series of cold temperature traps and the degradation products of the volatile anesthetics were analysed using GC/MS. Surprisingly, neither sevoflurane nor its degradation products could be measured in the gas-flow emerging from the soda lime during the first 15-20 min of exposure. After 20 minutes, larger quantities of methanol, compounds C and D as well as compounds A and B were detected. After 40-60 min of exposure, sevoflurane's degradation markedly decreased and unaltered sevoflurane emerged from the soda lime canister. Additionally, using isoflurane in the same experimental set-up resulted in various degradation products due to its reaction with dry soda lime. Obviously, all volatile anesthetics are prone to such a reaction. In conclusion, sevoflurane and isoflurane react with dry soda lime. These reactions are caused by the presence of two components of soda lime, sodium hydroxide and potassium hydroxide. A modification of soda lime to prevent its reaction with volatile anaesthetics is discussed.

  2. The effect of hydrate saturation on water retention curves in hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Mahabadi, Nariman; Zheng, Xianglei; Jang, Jaewon

    2016-05-01

    The experimental measurement of water retention curve in hydrate-bearing sediments is critically important to understand the behavior of hydrate dissociation and gas production. In this study, tetrahydrofuran (THF) is selected as hydrate former. The pore habit of THF hydrates is investigated by visual observation in a transparent micromodel. It is confirmed that THF hydrates are not wetting phase on the quartz surface of the micromodel and occupy either an entire pore or part of pore space resulting in change in pore size distribution. And the measurement of water retention curves in THF hydrate-bearing sediments with hydrate saturation ranging from Sh = 0 to Sh = 0.7 is conducted for excess water condition. The experimental results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Based on the experimental results, fitting parameters for van Genuchten equation are suggested for different hydrate saturation conditions.

  3. Fabrication of porous calcite using chopped nylon fiber and its evaluation using rats.

    PubMed

    Ishikawa, Kunio; Tram, Nguyen Xuan Thanh; Tsuru, Kanji; Toita, Riki

    2015-02-01

    Although porous calcite has attracted attention as bone substitutes, limited studies have been made so far. In the present study, porous calcite block was fabricated by introducing chopped nylon fiber as porogen. Ca(OH)2 powder containing 10 wt% chopped nylon fiber was compacted at 150 MPa, and sintered to burn out the fiber and to carbonate the Ca(OH)2 under stream of 1:2 O2-CO2. Sintering of Ca(OH)2 at 750 °C or lower temperature resulted in incomplete burning out of the fiber whereas sintering at 800 °C or higher temperature resulted in the formation of CaO due to the thermal decomposition of Ca(OH)2. However, sintering at 770 °C resulted in complete burning out of the fiber and complete carbonation of Ca(OH)2 to calcite without forming CaO. Macro- and micro-porosities of the porous calcite were approximately 23 and 16%, respectively. Diameter of the macropores was approximately 100 μm which is suitable for bone tissue penetration. Porous calcite block fabricated by this method exhibited good tissue response when implanted in the bone defect in femur of 12-weeks-old rat. Four weeks after implantation, bone bonded on the surface of calcite. Furthermore, bone tissue penetrated interior to the macropore at 8 weeks. These results demonstrated the good potential value of porous calcite as artificial bone substitutes.

  4. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum.

    PubMed

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

    2014-01-01

    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

  5. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum

    PubMed Central

    Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

    2014-01-01

    Summary In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

  6. Influence of surface conductivity on the apparent zeta potential of calcite.

    PubMed

    Li, Shuai; Leroy, Philippe; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe

    2016-04-15

    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength ⩽ 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted the corrected zeta potential by assuming that the zeta potential is located at the outer Helmholtz plane, i.e. without considering a stagnant diffuse layer at the calcite-water interface. The surface conductivity of calcite crystals was inferred from electrical conductivity measurements and computed using our basic Stern model. Surface conductivity was also successfully predicted by our surface complexation model. PMID:26852350

  7. Influence of surface conductivity on the apparent zeta potential of calcite.

    PubMed

    Li, Shuai; Leroy, Philippe; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe

    2016-04-15

    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength ⩽ 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted the corrected zeta potential by assuming that the zeta potential is located at the outer Helmholtz plane, i.e. without considering a stagnant diffuse layer at the calcite-water interface. The surface conductivity of calcite crystals was inferred from electrical conductivity measurements and computed using our basic Stern model. Surface conductivity was also successfully predicted by our surface complexation model.

  8. Controls of carbonate mineralogy and solid-solution of Mg in calcite: evidence from spelean systems

    SciTech Connect

    Gonzalez, L.A.; Lohmann, K.C.

    1985-01-01

    Precipitation of carbonate minerals in spelean systems occurs under a wide range of fluid chemistry, Mg-Ca ratios, alkalinities, pH and temperatures; thus, spelean systems provide ideal settings to determine factors controlling the mineralogy of precipitated carbonates and solid-solution of Mg in calcite. Cave waters and actively-precipitating carbonate speleothems were collected from Carlsbad Caverns National Park, New Mexico and the Mammoth-Flint Cave System, Kentucky. Carbonate mineralogy of precipitated phases was determined by x-ray diffraction, and major and minor element composition of waters and accompanying minerals were determined by Atomic Absorption Spectrophotometry. Results demonstrate that at a constant CO3 concentration the precipitation threshold for calcite to aragonite is controlled dominantly by the Mg/Ca ratio of the ambient fluid. Aragonite precipitation is favored by high Mg/Ca ratios. Conversely, with increasing CO3 concentration at constant fluid Mg/Ca ratios, calcite is preferentially precipitated. Solid-solution of Mg in calcite is positively correlated with both increased Mg/Ca ratios and CO3 concentrations. These data suggest that Mg contents of calcite can not be defined solely in terms of a homogeneous distribution coefficient. Rather, Mg concentrations can be also be affected by the CO3 concentration and degree of calcite saturation, suggesting that the rate of crystal growth also plays and important role in Mg solid-solution in calcites.

  9. Calcite Formation in Soft Coral Sclerites Is Determined by a Single Reactive Extracellular Protein*

    PubMed Central

    Rahman, M. Azizur; Oomori, Tamotsu; Wörheide, Gert

    2011-01-01

    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called “calcite and aragonite seas.” Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that –OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature. PMID:21768106

  10. Effect of Second-phase Particles on Static Adjustment of Calcite Grain Boundaries in Carbonate Mylonites

    NASA Astrophysics Data System (ADS)

    Ree, J.; Lee, S.; Jung, H.

    2010-12-01

    Static adjustment of grain boundaries during the waning stage of deformation with sustained heat (e.g. at the end of an orogeny) has not been studied much, although it is important for the interpretation of microstructural status during the main stage of deformation. We report here that static adjustment of calcite grain boundaries is dependent on second-phase particles in carbonate mylonites from the Geounri Shear Zone in the Taebaeksan Basin of South Korea. The carbonate mylonites consist of relic (porphyroclastic) calcites (120-400 μm) and dynamically recrystallized calcites (30-35 μm) with second-phase particles (15-20 μm) of quartz and phyllosilicates. Both calcite grains contain mechanical twins and the twins are wider (10-20 μm thick) in the relic calcites than in the dynamically recrystallized ones (1-3 μm thick). In the layers of carbonate mylonite with less than 3% of second phases, grain boundaries of calcites are straight with triple junctions. In contrast, calcite grain boundaries are lobate to wavy in the layers with more than 3% of second phases, suggesting dynamic grain boundary migration. Calcite grains in both layers show a strong lattice preferred orientation indicating dominant slip system of basal with minor one of rhomb . We interpret that the foam texture of calcite in the mylonite layers with less than 3% of second phases was produced during the waning stage of the main deformation with a sustained heat since both syntectonic and posttectonic chloritoid porphyroblasts occur in adjacent phyllonite layers in the shear zone. 3% volume fraction of second-phase particles might be a critical value above which deformation microstructures of the main phase were ‘frozen’ without static adjustment in our carbonate mylonites.

  11. Hydration of blended cement pastes containing waste ceramic powder as a function of age

    NASA Astrophysics Data System (ADS)

    Scheinherrová, Lenka; Trník, Anton; Kulovaná, Tereza; Pavlík, Zbyšek; Rahhal, Viviana; Irassar, Edgardo F.; Černý, Robert

    2016-07-01

    The production of a cement binder generates a high amount of CO2 and has high energy consumption, resulting in a very adverse impact on the environment. Therefore, use of pozzolana active materials in the concrete production leads to a decrease of the consumption of cement binder and costs, especially when some type of industrial waste is used. In this paper, the hydration of blended cement pastes containing waste ceramic powder from the Czech Republic and Portland cement produced in Argentina is studied. A cement binder is partially replaced by 8 and 40 mass% of a ceramic powder. These materials are compared with an ordinary cement paste. All mixtures are prepared with a water/cement ratio of 0.5. Thermal characterization of the hydrated blended pastes is carried out in the time period from 2 to 360 days. Simultaneous DSC/TG analysis is performed in the temperature range from 25 °C to 1000 °C in an argon atmosphere. Using this thermal analysis, we identify the temperature, enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates gels dehydration, portlandite, vaterite and calcite decomposition and their changes during the curing time. Based on thermogravimetry results, we found out that the portlandite content slightly decreases with time for all blended cement pastes.

  12. The effectiveness of surface liming in ameliorating the phytotoxic effects of soil contaminated by copper acid leach pad solution in an arid ecosystem

    NASA Astrophysics Data System (ADS)

    Golos, Peter

    2016-04-01

    Revegetation of sites following soil contamination can be challenging especially in identifying the most effective method for ameliorating phytotoxic effects in arid ecosystems. This study at a copper mine in the Great Sandy Desert of Western Australia investigated vegetation restoration of a site contaminated by acid (H2SO4) leach pad solution. Elevated soil copper at low soil pH is phytotoxic to plant roots inhibiting root elongation. In arid ecosystems where rapid root growth is crucial for seedling survival post germination physical or chemical barriers to root growth need to be identified and ameliorated. Initial attempt at rehabilitation of contaminated site with hydrated lime (CaOH2) at 2 tonnes/ha followed by ripping to 30 cm depth then seeding was ineffective as successful seedling emergence was followed by over 90% seedling mortality which was 10-fold greater than seedling mortality in an uncontaminated reference site. High mortality was attributed to seedling roots being impededed as soil water was more than 3-fold greater at 5 to 40 cm depth in contaminated site than reference site. In response to high seedling mortality after emergence test pits were dug to 1 m deep to collect soil samples at 10 cm intervals for phytotoxicity testing and to measure soil pH-CaCl2, copper (DPTA ion extraction), electrical conductivity and gravimetric water content in three replicate pits at three replicate sites. Also, soil impedance was measured down the soil profile at 5 cm intervals at six replicate points/pit. For phytotoxicity testing soil samples were placed into three replicate plastic pots/sample and seeded with 10 seeds of Avena sativa and watered daily. Seedlings were harvested after at least two weeks after seedling emergence and rooting depth in pots measured. There was no difference in seedling emergence and survival of seedlings between contaminated and uncontaminated soil samples however mean seedling root growth was significantly lower in soil samples

  13. The influence of impurities on the growth rate of calcite

    NASA Astrophysics Data System (ADS)

    Meyer, H. J.

    1984-05-01

    The effects of 34 different additives on the growth rate of calcite were investigated. An initial growth rate of about one crystal monolayer (3 × 10 -8 cm) per minute was adjusted at a constant supersaturation which was maintained by a control circuit. Then the impurity was added step by step and the reduction of the growth rate was measured. The impurity concentration necessary to reduce the initial growth rate by a certain percentage increased in the order Fe 2+, ATP, P 3O 5-10, P 2O 4-7, (PO 3) 6-6, Zn 2+, ADP, Ce 3+, Pb 2+, carbamyl phosphate, Fe 3+, PO 3-4, Co 2+, Mn 2+, Be 2+, β-glycerophosphate, Ni 2+, Cd 2+, "Tris", phenylphosphate, chondroitine sulphate, Ba 2+, citrate, AMP, Sr 2+, tricarballylate, taurine, SO 2-4, Mg 2+ by 4 orders of magnitude. The most effective additives halved the initial growth rate in concentrations of 2 × 10 -8 mol/1. For Fe 2+ the halving concentration was nearly proportional to the initial rate. The mechanism of inhibition by adsorption of the impurities at growth sites (kinks) is discussed.

  14. Microbiologically Induced Calcite Precipitation Mediated by Sporosarcina pasteurii.

    PubMed

    Bhaduri, Swayamdipta; Debnath, Nandini; Mitra, Sushanta; Liu, Yang; Kumar, Aloke

    2016-04-16

    The particular bacterium under investigation here (S. pasteurii) is unique in its ability, under the right conditions, to induce the hydrolysis of urea (ureolysis) in naturally occurring environments through secretion of an enzyme urease. This process of ureolysis, through a chain of chemical reactions, leads to the formation of calcium carbonate precipitates. This is known as Microbiologically Induced Calcite Precipitation (MICP). The proper culture protocols for MICP are detailed here. Finally, visualization experiments under different modes of microscopy were performed to understand various aspects of the precipitation process. Techniques like optical microscopy, Scanning Electron Microscopy (SEM) and X-Ray Photo-electron Spectroscopy (XPS) were employed to chemically characterize the end-product. Further, the ability of these precipitates to clog pores inside a natural porous medium was demonstrated through a qualitative experiment where sponge bars were used to mimic a pore-network with a range of length scales. A sponge bar dipped in the culture medium containing the bacterial cells hardens due to the clogging of its pores resulting from the continuous process of chemical precipitation. This hardened sponge bar exhibits superior strength when compared to a control sponge bar which becomes compressed and squeezed under the action of an applied external load, while the hardened bar is able to support the same weight with little deformation.

  15. Calcite-forming bacteria for compressive strength improvement in mortar.

    PubMed

    Park, Sung-Jin; Park, Yu-Mi; Chun, Woo-Young; Kim, Wha-Jung; Ghim, Sa-Youl

    2010-04-01

    Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of concrete mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of concrete mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and x-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the CaCO3 crystals. We used the isolates to improve the compressive strength of concrete mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

  16. Alkaline flocculation of Phaeodactylum tricornutum induced by brucite and calcite.

    PubMed

    Vandamme, Dries; Pohl, Philip I; Beuckels, Annelies; Foubert, Imogen; Brady, Patrick V; Hewson, John C; Muylaert, Koenraad

    2015-11-01

    Alkaline flocculation holds great potential as a low-cost harvesting method for marine microalgae biomass production. Alkaline flocculation is induced by an increase in pH and is related to precipitation of calcium and magnesium salts. In this study, we used the diatom Phaeodactylum tricornutum as model organism to study alkaline flocculation of marine microalgae cultured in seawater medium. Flocculation started when pH was increased to 10 and flocculation efficiency reached 90% when pH was 10.5, which was consistent with precipitation modeling for brucite or Mg(OH)2. Compared to freshwater species, more magnesium is needed to achieve flocculation (>7.5mM). Zeta potential measurements suggest that brucite precipitation caused flocculation by charge neutralization. When calcium concentration was 12.5mM, flocculation was also observed at a pH of 10. Zeta potential remained negative up to pH 11.5, suggesting that precipitated calcite caused flocculation by a sweeping coagulation mechanism.

  17. Alkaline flocculation of Phaeodactylum tricornutum induced by brucite and calcite

    DOE PAGESBeta

    Vandamme, Dries; Pohl, Philip I.; Beuckels, Annelies; Foubert, Imogen; Brady, Patrick Vane; Muylaert, Koenraad; Hewson, John C.

    2015-08-20

    Alkaline flocculation holds great potential as a low-cost harvesting method for marine microalgae biomass production. Alkaline flocculation is induced by an increase in pH and is related to precipitation of calcium and magnesium salts. In this study, we used the diatom Phaeodactylum tricornutum as model organism to study alkaline flocculation of marine microalgae cultured in seawater medium. Flocculation started when pH was increased to 10 and flocculation efficiency reached 90% when pH was 10.5, which was consistent with precipitation modeling for brucite or Mg(OH)2. Compared to freshwater species, more magnesium is needed to achieve flocculation (>7.5 mM). Zeta potential measurementsmore » suggest that brucite precipitation caused flocculation by charge neutralization. When calcium concentration was 12.5 mM, flocculation was also observed at a pH of 10. Furthermore, zeta potential remained negative up to pH 11.5, suggesting that precipitated calcite caused flocculation by a sweeping coagulation mechanism.« less

  18. Thin-film-induced morphological instabilities over calcite surfaces

    PubMed Central

    Vesipa, R.; Camporeale, C.; Ridolfi, L.

    2015-01-01

    Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite–water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view. PMID:27547086

  19. Calcium bilirubinate intercalated calcite single crystal: evidence for microstructure of pigment gallstones

    NASA Astrophysics Data System (ADS)

    Liu, H. Z.; Xu, D. J.; Soloway, Roger D.; Zhang, Y. Z.; Xu, Duan-Fu; Wu, JinGuang

    1994-01-01

    During the preparation of calcium bilirubinate (CaBR) single crystals, brown crystals were grown in a gel solution of CaCl2/Sodium bilirubinate. X-ray diffraction analysis proved that the crystal was calcite. FTIR investigations support this result. However, the subtracted spectra revealed that the CaBR dispersed in the crystals and interacted with calcite on the molecular level, since the maximum band shift of the CaBR in calcite from the correspond bands of CaBR was ca. 20 cm-1. It was confirmed that microstructure also by x- ray diffraction and photoacoustic Fourier transform infrared spectroscopy.

  20. Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy

    USGS Publications Warehouse

    Pedone, V.A.; Cercone, K.R.; Burruss, R.C.

    1990-01-01

    Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

  1. Distribution of Minor Elements in Calcite From the Unsaturated Zone at Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Marshall, B. D.; Whelan, J. F.

    2001-12-01

    Calcite is sporadically distributed in fractures and cavities in the volcanic rocks that form the 500- to 700-m-thick unsaturated zone at Yucca Mountain. Previous work has shown that the calcite precipitated from water moving downward through the unsaturated zone since the volcanic rocks were emplaced approximately 13 Ma. Calcite thus serves as a proxy for the chemistry and amounts of past percolation, two parameters that are important in predictions of the future behavior of the potential radioactive waste repository at Yucca Mountain. Latest calcite, which began forming between approximately 5 and 2 Ma, typically displays fine-scale growth zoning defined by distributions of Mn (inferred from cathodoluminescence), Mg, and Sr. Electron microprobe (EPMA) mapping of outermost calcite reveals Mg growth zoning1 and higher overall concentrations of Mg in late calcite than in older calcite. Micro X-ray fluorescence (micro-XRF) maps were obtained by slow rastering of the samples over a 100-watt X-ray source collimated through a final aperture of 100 μ m. Although the spatial resolution of the micro-XRF mapping is much less than that of EPMA, this technique reveals distributions of some elements to which EPMA is less sensitive. Micro-XRF maps show that Sr is spatially correlated with Mg; Sr concentrations range to 500 μ g/g at the resolution of the 100-μ m collimator. Because both Mg and Sr have similar calcite-water distribution coefficients much less than one, the Mg/Sr in calcite reflects the Mg/Sr of the water that precipitated the calcite. The distribution coefficient for Mn is greater than one and variations in Mn are not correlated with Mg and Sr. Covariation of Mg and Sr in the percolating water may be explained by reactions that affect the rate of uptake of chemical constituents from the overlying rock and soil, and/or evaporation. Late calcite has lower δ 13C values, probably due to a regional change from wetter to drier climate conditions. The higher Mg and

  2. Recurrent Pure Calcite Urolithiasis Confirmed by Endoscopic Removal and Infrared Spectroscopy in a Malnourished Anorectic Female

    PubMed Central

    Andreassen, Kim Hovgaard; Sloth Osther, Palle Jörn

    2016-01-01

    Abstract Often when calcite is found as a component of urinary calculi, they are considered false calculi or artifacts. We present a case of true calcite urolithiasis. The stone material was removed percutaneously from a severely malnourished anorectic woman and analyzed by infrared spectroscopy (IRS). In addition, calcite urolithiasis was confirmed in several recurrent stone events by IRS. Laxative abuse with magnesium oxide was believed to be the underlying cause of stone formation, and ammonium chloride given as one weekly dose turned out to be effective for stone prevention. PMID:27579419

  3. Recurrent Pure Calcite Urolithiasis Confirmed by Endoscopic Removal and Infrared Spectroscopy in a Malnourished Anorectic Female.

    PubMed

    Christiansen, Frederikke Eichner; Andreassen, Kim Hovgaard; Sloth Osther, Palle Jörn

    2016-01-01

    Often when calcite is found as a component of urinary calculi, they are considered false calculi or artifacts. We present a case of true calcite urolithiasis. The stone material was removed percutaneously from a severely malnourished anorectic woman and analyzed by infrared spectroscopy (IRS). In addition, calcite urolithiasis was confirmed in several recurrent stone events by IRS. Laxative abuse with magnesium oxide was believed to be the underlying cause of stone formation, and ammonium chloride given as one weekly dose turned out to be effective for stone prevention. PMID:27579419

  4. Experimental study on the reuse of spent rapidly hydrated sorbent for circulating fluidized bed flue gas desulfurization.

    PubMed

    Li, Yuan; Zheng, Kai; You, Changfu

    2011-11-01

    Rapidly hydrated sorbent, prepared by rapidly hydrating adhesive carrier particles and lime, is a highly effective sorbent for moderate temperature circulating fluidized bed flue gas desulfurization (CFB-FGD) process. The residence time of fine calcium-containing particles in CFB reactors increases by adhering on the surface of larger adhesive carrier particles, which contributes to higher sorbent calcium conversion ratio. The circulation ash of CFB boilers (α-adhesive carrier particles) and the spent sorbent (β and γ-adhesive carrier particles) were used as adhesive carrier particles for producing the rapidly hydrated sorbent. Particle physical characteristic analysis, abrasion characteristics in fluidized bed and desulfurization characteristics in TGA and CFB-FGD systems were investigated for various types of rapidly hydrated sorbent (α, β, and γ-sorbent). The adhesion ability of γ-sorbent was 50.1% higher than that of α-sorbent. The abrasion ratio of β and γ-sorbent was 16.7% lower than that of α-sorbent. The desulfurization abilities of the three sorbent in TGA were almost same. The desulfurization efficiency in the CFB-FGD system was up to 95% at the bed temperature of 750 °C for the β-sorbent. PMID:21928832

  5. Santaclaraite, a new calcium-manganese silicate hydrate from California.

    USGS Publications Warehouse

    Erd, Richard C.; Ohashi, Y.

    1984-01-01

    Santaclaraite, ideally CaMn4(Si5O14(OH))(OH).H2O, occurs as pink and tan veins and masses in Franciscan chert in the Diablo Range, Santa Clara and Stanislaus counties, California. It is associated with four unidentified Mn silicates, Mn-howieite, quartz, braunite, calcite, rhodochrosite, kutnahorite, baryte, harmotome, chalcopyrite and native copper. Santaclaraite is triclinic, space group B1, a 15.633(1), b 7.603(1) , c 12.003(1) A, alpha 109.71(1)o, beta 88.61(1)o, gamma 99.95(1) o, V 1322.0(3) A3; Z = 4. The strongest lines of the X-ray pattern are 7.04(100), 3.003(84), 3.152(80), 7.69(63), 3.847(57) A. Crystals are lamellar to prismatic (flattened on (100)), with good cleavage on (100) and (010); H. 61/2 Dcalc. 3.398 g/cm3, Dmeas. 3.31 (+ or -0.01); optically biaxial negative, alpha 1.681, beta 1.696, gamma 1.708 (all + or - 0.002), 2Valpha 83 (+ or -1)o. Although chemically a hydrated rhodonite, santaclaraite dehydrates to Mn-bustamite at approx 550oC (in air) . Santaclaraite is a five-tetrahedral-repeat single-chain silicate and has structural affinities with rhodonite, nambulite, marsturite, babingtonite and inesite.-J.A.Z.

  6. Control of carbonate alkalinity on Mg incorporation in calcite: Insights on the occurrence of high Mg calcites in diagenetic environments

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Dietzel, Martin

    2015-04-01

    High Mg calcites (HMC), with up to 25 mol % of Mg, are common features in early diagenetic environments and are frequently associated with bio-induced anaerobic oxidation of methane (AOM). Such archives hold valuable information about the biogeochemical processes occurring in sedimentary environments in the geological past. Despite the frequency AOM-induced HMC observed in marine diagenetic settings and their potential role in dolomitization, only a minor number of experimental studies has been devoted on deciphering their formation conditions. Thus, in order to improve our understanding on the formation mechanism of HMC induced by elevated carbonate ion concentrations, we precipitated HMC by computer controlled titration of a (Mg,Ca)Cl2 solution at different Mg/Ca ratios into a NaHCO3 solution under precisely defined physicochemical conditions (T = 25.00 ±0.03°C; pH = 8.3 ±0.1). The formation of carbonates was monitored at a high temporal resolution using in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. We identified two distinct mechanisms of HMC formation. In solutions with molar Mg/Ca ratios ≤ 1/8 calcium carbonate was precipitated as crystalline phases directly from homogeneous solution. In contrast, higher Mg/Ca ratios induced the formation of Mg-rich ACC (up to 10 mol % of Mg), which was subsequently transformed to HMC with up 20 mol % of Mg. Our experimental results highlight that the finally formed HMC has a higher Mg content than the ACC precursor phase. Considering experimental data for Mg containing ACC transformation to crystalline calcium carbonate from literature, the continuous enrichment of Mg in the precipitate throughout transformation of amorphous to crystalline CaCO3 most likely occurs due to the high carbonate alkalinity (DIC about 0.1 M) of our reactive solutions. The Mg incorporation into calcite lattice seems to be favored by intensive supply of carbonate ions as

  7. Gas hydrate cool storage system

    DOEpatents

    Ternes, Mark P.; Kedl, Robert J.

    1985-01-01

    This invention is a process for formation of a gas hydrate to be used as a cool storage medium using a refrigerant in water. Mixing of the immiscible refrigerant and water is effected by addition of a surfactant and agitation. The difficult problem of subcooling during the process is overcome by using the surfactant and agitation and performance of the process significantly improves and approaches ideal.

  8. Multiple stage multiple filter hydrate store

    DOEpatents

    Bjorkman, Jr., Harry K.

    1983-05-31

    An improved hydrate store for a metal halogen battery system is disclosed which employs a multiple stage, multiple filter means or separating the halogen hydrate from the liquid used in forming the hydrate. The filter means is constructed in the form of three separate sections which combine to substantially cover the interior surface of the store container. Exit conduit means is provided in association with the filter means for transmitting liquid passing through the filter means to a hydrate former subsystem. The hydrate former subsystem combines the halogen gas generated during the charging of the battery system with the liquid to form the hydrate in association with the store. Relief valve means is interposed in the exit conduit means for controlling the operation of the separate sections of the filter means, such that the liquid flow through the exit conduit means from each of the separate sections is controlled in a predetermined sequence. The three separate sections of the filter means operate in three discrete stages to provide a substantially uniform liquid flow to the hydrate former subsystem during the charging of the battery system. The separation of the liquid from the hydrate causes an increase in the density of the hydrate by concentrating the hydrate along the filter means.

  9. Gas hydrate resources of northern Alaska

    USGS Publications Warehouse

    Collett, T.S.

    1997-01-01

    Large amounts of natural gas, composed mainly of methane, can occur in arctic sedimentary basins in the form of gas hydrates under appropriate temperature and pressure conditions. Gas hydrates are solids, composed of rigid cages of water molecules that trap molecules of gas. These substances are regarded as a potential unconventional source of natural gas because of their enormous gas-storage capacity. Most published gas hydrate resource estimates are highly simplified and based on limited geological data. The gas hydrate resource assessment for northern Alaska presented in this paper is based on a "play analysis" scheme, in which geological factors controlling the accumulation and preservation of gas hydrates are individually evaluated and risked for each hydrate play. This resource assessment identified two gas hydrate plays; the in-place gas resources within the gas hydrates of northern Alaska are estimated to range from 6.7 to 66.8 trillion cubic metres of gas (236 to 2,357 trillion cubic feet of gas), at the 0.50 and 0.05 probability levels respectively. The mean in-place hydrate resource estimate for northern Alaska is calculated to be 16.7 trillion cubic metres of gas (590 trillion cubic feet of gas). If this assessment is valid, the amount of natural gas stored as gas hydrates in northern Alaska could be almost seven times larger then the estimated total remaining recoverable conventional natural gas resources in the entire United States.

  10. Well log evaluation of gas hydrate saturations

    USGS Publications Warehouse

    Collett, Timothy S.

    1998-01-01

    The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative due to the lack of previous quantitative studies. Gas volumes that may be attributed to a gas hydrate accumulation within a given geologic setting are dependent on a number of reservoir parameters; one of which, gas-hydrate saturation, can be assessed with data obtained from downhole well logging devices. The primary objective of this study was to develop quantitative well-log evaluation techniques which will permit the calculation of gas-hydrate saturations in gas-hydrate-bearing sedimentary units. The `standard' and `quick look' Archie relations (resistivity log data) yielded accurate gas-hydrate and free-gas saturations within all of the gas hydrate accumulations assessed in the field verification phase of the study. Compressional wave acoustic log data have been used along with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate accurate gas-hydrate saturations in this study. The well log derived gas-hydrate saturations calculated in the field verification phase of this study, which range from as low as 2% to as high as 97%, confirm that gas hydrates represent a potentially important source of natural gas.

  11. Multiple stage multiple filter hydrate store

    DOEpatents

    Bjorkman, H.K. Jr.

    1983-05-31

    An improved hydrate store for a metal halogen battery system is disclosed which employs a multiple stage, multiple filter means for separating the halogen hydrate from the liquid used in forming the hydrate. The filter means is constructed in the form of three separate sections which combine to substantially cover the interior surface of the store container. Exit conduit means is provided in association with the filter means for transmitting liquid passing through the filter means to a hydrate former subsystem. The hydrate former subsystem combines the halogen gas generated during the charging of the battery system with the liquid to form the hydrate in association with the store. Relief valve means is interposed in the exit conduit means for controlling the operation of the separate sections of the filter means, such that the liquid flow through the exit conduit means from each of the separate sections is controlled in a predetermined sequence. The three separate sections of the filter means operate in three discrete stages to provide a substantially uniform liquid flow to the hydrate former subsystem during the charging of the battery system. The separation of the liquid from the hydrate causes an increase in the density of the hydrate by concentrating the hydrate along the filter means. 7 figs.

  12. Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: a micron-scale composite adsorbent of active silicate gel and calcite.

    PubMed

    Chen, Quanyuan; Hills, Colin D; Yuan, Menghong; Liu, Huanhuan; Tyrer, Mark

    2008-05-01

    Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C(3)S, Ca(3)SiO(5)). The Ca/Si ratio of calcium silicate hydrate gel (C-S-H) was determined at 0.12 (DTA/TG), 0.17 ((29)Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals. PMID:17950999

  13. Gas hydrates: Technology status report

    SciTech Connect

    Not Available

    1987-01-01

    In 1983, the US Department of Energy (DOE) assumed the responsibility for expanding the knowledge base and for developing methods to recover gas from hydrates. These are ice-like mixtures of gas and water where gas molecules are trapped within a framework of water molecules. This research is part of the Unconventional Gas Recovery (UGR) program, a multidisciplinary effort that focuses on developing the technology to produce natural gas from resources that have been classified as unconventional because of their unique geologies and production mechanisms. Current work on gas hydrates emphasizes geological studies; characterization of the resource; and generic research, including modeling of reservoir conditions, production concepts, and predictive strategies for stimulated wells. Complementing this work is research on in situ detection of hydrates and field tests to verify extraction methods. Thus, current research will provide a comprehensive technology base from which estimates of reserve potential can be made, and from which industry can develop recovery strategies. 7 refs., 3 figs., 6 tabs.

  14. Energy landscape of clathrate hydrates

    NASA Astrophysics Data System (ADS)

    Desmedt, A.; Bedouret, L.; Pefoute, E.; Pouvreau, M.; Say-Liang-Fat, S.; Alvarez, M.

    2012-11-01

    Clathrate hydrates are nanoporous crystalline materials made of a network of hydrogen-bonded water molecules (forming host cages) that is stabilized by the presence of foreign (generally hydrophobic) guest molecules. The natural existence of large quantities of hydrocarbon hydrates in deep oceans and permafrost is certainly at the origin of numerous applications in the broad areas of energy and environmental sciences and technologies (e.g. gas storage). At a fundamental level, their nanostructuration confers on these materials specific properties (e.g. their "glass-like" thermal conductivity) for which the host-guest interactions play a key role. These interactions occur on broad timescale and thus require the use of multi-technique approach in which neutron scattering brings unvaluable information. This work reviews the dynamical properties of clathrate hydrates, ranging from intramolecular vibrations to Brownian relaxations; it illustrates the contribution of neutron scattering in the understanding of the underlying factors governing chemical-physics properties specific to these nanoporous systems.

  15. [The Analysis of Traditional Lime Mortars from Zhejiang Province, China].

    PubMed

    Liu, Xiao-bin; Cui, Biao; Zhang, Bing-jian

    2016-01-01

    The components of ancient mortars have always been an important research field in historic building conservation. It has been well known that using traditional mortars in conservation projects have many advantages, such as compatibility and stability. So, developing new binding materials based on traditional mortar has become an international study hotspot. With China's economic development, the protection of ancient buildings also began to put on the agenda, but the understanding on Chinese traditional mortar is limited, and rare literatures are reported. In the present work, the authors investigate seven ancient city wall sites in Zhejiang Province in situ, and subsequently laboratory analysis were carried out on collected mortar samples. The characterizations of mortar samples were made by multi-density gauge, XRD, FTIR, TG-DSC and wet chemical analysis. The experimental results showed that: the main component of masonry mortars is calcium carbonate, the content between 75% - 90%, and they should be made from relatively pure lime mortar. The raw materials of mortar samples were mainly calcareous quick lime, and sample from Taizhou city also contained magnesium quick lime. There are four city walls were built by sticky-rice mortars. It suggests that the technology of adding the sticky rice soup into mortar was universal in the Ming Dynasties. These mortars have lower density between 1.2 and 1.9 g x cm(-3); this outcome should be the result of long-term natural erosion. We have also analyzed other chemical and physical characteristics of these masonry mortars. The results can afford the basic data for the future repairmen programs, development of new protective materials, and comparative study of mortars. PMID:27228774

  16. [The Analysis of Traditional Lime Mortars from Zhejiang Province, China].

    PubMed

    Liu, Xiao-bin; Cui, Biao; Zhang, Bing-jian

    2016-01-01

    The components of ancient mortars have always been an important research field in historic building conservation. It has been well known that using traditional mortars in conservation projects have many advantages, such as compatibility and stability. So, developing new binding materials based on traditional mortar has become an international study hotspot. With China's economic development, the protection of ancient buildings also began to put on the agenda, but the understanding on Chinese traditional mortar is limited, and rare literatures are reported. In the present work, the authors investigate seven ancient city wall sites in Zhejiang Province in situ, and subsequently laboratory analysis were carried out on collected mortar samples. The characterizations of mortar samples were made by multi-density gauge, XRD, FTIR, TG-DSC and wet chemical analysis. The experimental results showed that: the main component of masonry mortars is calcium carbonate, the content between 75% - 90%, and they should be made from relatively pure lime mortar. The raw materials of mortar samples were mainly calcareous quick lime, and sample from Taizhou city also contained magnesium quick lime. There are four city walls were built by sticky-rice mortars. It suggests that the technology of adding the sticky rice soup into mortar was universal in the Ming Dynasties. These mortars have lower density between 1.2 and 1.9 g x cm(-3); this outcome should be the result of long-term natural erosion. We have also analyzed other chemical and physical characteristics of these masonry mortars. The results can afford the basic data for the future repairmen programs, development of new protective materials, and comparative study of mortars.

  17. Forest liming increases forest floor carbon and nitrogen stocks in a mixed hardwood forest.

    PubMed

    Melvin, April M; Lichstein, Jeremy W; Goodale, Christine L

    2013-12-01

    In acid-impacted forests, decreased soil pH and calcium (Ca) availability have the potential to influence biotic and abiotic controls on carbon (C) and nitrogen (N) cycling. We investigated the effects of liming on above- and belowground C and N pools and fluxes 19 years after lime addition to the Woods Lake Watershed, Adirondack Park, New York, USA. Soil pH and exchangeable Ca remained elevated in the forest floor and upper mineral soil of limed areas. Forest floor C and N stocks were significantly larger in limed plots (68 vs. 31 Mg C/ha, and 3.0 vs. 1.5 Mg N/ha), resulting from a larger mass of Oa material. Liming reduced soil basal respiration rates by 17% and 43% in the Oe and Oa horizons, respectively. Net N mineralization was significantly lower in the limed soils for both forest floor horizons. Additional measurements of forest floor depth outside of our study plots, but within the treatment and control subcatchments also showed a deeper forest floor in limed areas; however, the mean depth of limed forest floor was 5 cm shallower than that observed in our study plots. Using a differential equation model of forest floor C dynamics, we found that liming effects on C fluxes measured within our study plots could explain the small observed increase in the Oe C stock but were not large enough to explain the increase in the Oa. Our catchment-wide assessment of forest floor depth, however, indicates that our plot analysis may be an overestimate of ecosystem-scale C and N stocks. Our results suggest that the mechanisms identified in our study, primarily liming-induced reduction in decomposition rates, may account for much of the observed increase in forest floor C. These findings emphasize the importance of understanding of the effects of liming in hardwood forests, and the long-term impacts of acid deposition on forest C and N uptake and retention.

  18. Capital costs of lime treatment at the Augusta wastewater treatment plant

    SciTech Connect

    Halverson, N.V.

    1988-08-17

    The capital costs were estimated for the addition of lime treatment facilities to the Augusta sewage treatment plant as a means of reducing the phosphorus loading of L Lake and consequently reducing the algae populations in the lake. Primary lime treatments and tertiary lime treatments were considered. The capital cost of a primary lime treatment addition would be lower than for a tertiary treatment addition. Depending on whether the existing primary settling tank can be utilized for lime treatment or a new clarifier must be built, a primary lime treatment addition would currently cost between $500,000 and $3 million to construct at the Augusta sewage treatment plant. Primary lime treatment coupled with the existing activated sludge biological treatment system would remove approximately 80% of the phosphorus from the sewage entering the sewage treatment plant, resulting in an effluent concentration of about 2 mg/l. To reduce effluent phosphorus concentration to 1 mg/l or less, additional coagulation and effluent filtration facilities would be necessary. One disadvantage of primary lime treatment, however, would be the two-fold or three-fold increase in sludge to be disposed. Tertiary lime treatment usually results in lower effluent phosphorus levels than primary lime treatment, but the capital cost is significantly higher. Costs for tertiary lime treatment for the Augusta sewage treatment plant would range from $5 million to $14 million. The higher estimate would include an additional settling stage and filtration of the effluent, features which would improve the efficiency of phosphorus removal and reduce the effluent phosphorus concentration. 12 refs.

  19. Improvement in hardness of soda-lime-silica glass

    SciTech Connect

    Chakraborty, Riya; De, Moumita; Roy, Sudakshina; Dey, Arjun; Biswas, Sampad K.; Middya, Tapas Ranjan; Mukhopadhyay, Anoop K.

    2012-06-05

    Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vicker's hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s{sup -1}. Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate.

  20. Study of Formation Mechanisms of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  1. Hydration mechanism of a cementitious material prepared with Si-Mn slag

    NASA Astrophysics Data System (ADS)

    Zhang, Xu-Fang; Ni, Wen; Wu, Jun-Yu; Zhu, Li-Ping

    2011-04-01

    A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance (NMR) analysis of 29Si and 27Al and infrared spectroscopy (IR) analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.

  2. Flexible minerals: self-assembled calcite spicules with extreme bending strength.

    PubMed

    Natalio, Filipe; Corrales, Tomas P; Panthöfer, Martin; Schollmeyer, Dieter; Lieberwirth, Ingo; Müller, Werner E G; Kappl, Michael; Butt, Hans-Jürgen; Tremel, Wolfgang

    2013-03-15

    Silicatein-α is responsible for the biomineralization of silicates in sponges. We used silicatein-α to guide the self-assembly of calcite "spicules" similar to the spicules of the calcareous sponge Sycon sp. The self-assembled spicules, 10 to 300 micrometers (μm) in length and 5 to 10 μm in diameter, are composed of aligned calcite nanocrystals. The spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. They scatter x-rays like twinned calcite crystals. Whereas natural spicules evidence brittle failure, the synthetic spicules show an elastic response, which greatly enhances bending strength. This remarkable feature is linked to a high protein content. With nano-thermogravimetric analysis, we measured the organic content of a single spicule to be 10 to 16%. In addition, the spicules exhibit waveguiding properties even when they are bent.

  3. Enhancing mechanical properties of calcite by Mg substitutions: An ab initio study

    NASA Astrophysics Data System (ADS)

    Elstnerova, Pavlina; Friak, Martin; Hickel, Tilmann; Fabritius, Helge Otto; Lymperakis, Liverios; Petrov, Michal; Raabe, Dierk; Neugebauer, Joerg; Nikolov, Svetoslav; Zigler, Andreas; Hild, Sabine

    2011-03-01

    Arthropoda representing a majority of all known animal species are protected by an exoskeleton formed by their cuticle. The cuticle represents a hierarchically structured multifunctional bio-composite based on chitin and proteins. Some groups like Crustacea reinforce the load-bearing parts of their cuticle with calcite. As the calcite sometimes contains Mg it was speculated that Mg may have a stiffening impact on the mechanical properties of the cuticle. We present a theoretical parameter-free quantum-mechanical study of thermodynamic, structural and elastic properties of Mg-substituted calcite. Our results show that substituting Ca by Mg causes an almost linear decrease in the crystal volume with Mg concentration and of substituted crystals. As a consequence the calcite crystals become stiffer giving rise e.g. to substantially increased bulk moduli.

  4. Simulation of calcite dissolution and porosity changes in saltwater mixing zones in coastal aquifers

    USGS Publications Warehouse

    Sanford, W.E.; Konikow, L.F.

    1989-01-01

    Thermodynamic models of aqueous solutions have indicated that the mixing of seawater and calcite-saturated fresh groundwater can produce a water that is undersaturated with respect to calcite. Mixing of such waters in coastal carbonate aquifers could lead to significant amounts of limestone dissolution. The potential for such dissolution in coastal saltwater mixing zones is analyzed by coupling the results from a reaction simulation model (PHREEQE) with a variable density groundwater flow and solute transport model. Idealized cross sections of coastal carbonate aquifers are simulated to estimate the potential for calcite dissolution under a variety of hydrologic and geochemical conditions. Results show that limestone dissolution in mixing zones is strongly dependent on groundwater flux and nearly independent of the dissolution kinetics of calcite. -from Authors

  5. Phase transformation of Mg-calcite to aragonite in active-forming hot spring travertines

    NASA Astrophysics Data System (ADS)

    Greer, Heather F.; Zhou, Wuzong; Guo, Li

    2015-08-01

    A travertine specimen collected from the western part of Yunnan Province of China was subjected to microstructural analysis by powder X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. A new formation mechanism was proposed whereby polycrystalline rhombohedral particles of magnesium-containing calcite underwent a phase transformation into sheaf-like clusters of aragonite microrods. It is proposed that a high concentration of magnesium ions and embedded biological matter poisoned the growth of calcite and therefore instigated the phase transformation of the core of the rhombohedral calcite particles to an aragonite phase with a higher crystallinity. The single crystalline aragonite microrods with a higher density than the Mg-calcite nanocrystallites grew at the expense of the latter to generate sheaf-like clusters. This newly discovered formation mechanism is expected to enhance previous knowledge on this geologically important phase transformation from a morphology point of view.

  6. High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction.

    ERIC Educational Resources Information Center

    Herron, J. Dudley, Ed.; Driscoll, D. R.

    1979-01-01

    Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

  7. In Situ Carbon and Oxygen Isotope Analyses of Calcite in CM1 Chondrites

    NASA Astrophysics Data System (ADS)

    Telus, M.; Alexander, C. M. O.'D.; Wang, J.; Hauri, E. H.

    2016-08-01

    We present results from in situ C and O isotope analyses of calcite from CM1 chondrites. There are large isotope variations on small spatial scales. This provides some insight into the evolution of fluids in chondrite parent bodies.

  8. Development of Alaskan gas hydrate resources

    SciTech Connect

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  9. Fundamentals and applications of gas hydrates.

    PubMed

    Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

    2011-01-01

    Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties.

  10. Geomechanical Modeling of Gas Hydrate Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Sanchez, M. J.; Gai, X., Sr.

    2015-12-01

    This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.

  11. Fundamentals and applications of gas hydrates.

    PubMed

    Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

    2011-01-01

    Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties. PMID:22432618

  12. The calcite → aragonite transformation in low-Mg marble: Equilibrium relations, transformations mechanisms, and rates

    USGS Publications Warehouse

    Hacker, Bradley R.; Rubie, David C.; Kirby, Stephen H.; Bohlen, Steven R.

    2005-01-01

    Experimental transformation of a rather pure natural calcite marble to aragonite marble did not proceed via the expected straightforward polymorphic replacement. Instead, the small amount of Mg in the starting material (0.36 wt %) was excluded from the growing aragonite and diffused preferentially into the remaining calcite grains, producing Mg-rich calcite rods that persisted as relicts. Nucleation of aragonite occurred exclusively on grain boundaries, with aragonite [001] oriented subparallel to calcite [0001]. The aragonite crystals preferentially consumed the calcite crystal on which they nucleated, and the reaction fronts developed preferentially along the {010} and {110} planes of aragonite. Each aragonite neoblast that grew was nearly free of Mg (typically <0.1 wt %). The excess Mg was taken up by the calcite grains in between, stabilizing them and causing a few volume percent rodlike relicts of Mg-enriched calcite (up to 10 wt % MgO) to be left behind by the advancing reaction front. The aragonite growth rates are approximately linear and range from ∼3 × 10−11 m s−1 at 600°C to ∼9 × 10−9 m s−1 at 850°C, with an apparent activation enthalpy of 166 ± 91 kJ mol−1. This reaction mechanism and the resultant texture are akin to cellular precipitation reactions in metals. Similar transformation textures have been reported from high-Mg marbles in Japan and China that disproportionated to low-Mg calcite and dolomite.

  13. Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?

    NASA Astrophysics Data System (ADS)

    Bindschedler, S.; Cailleau, G.; Braissant, O.; Millière, L.; Job, D.; Verrecchia, E. P.

    2014-05-01

    Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in nature. They are very often observed in association with needle fibre calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this paper the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of fungi in CaCO3 biomineralization processes, a role still poorly documented. Moreover, on a global

  14. Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?

    NASA Astrophysics Data System (ADS)

    Bindschedler, S.; Cailleau, G.; Braissant, O.; Millière, L.; Job, D.; Verrecchia, E. P.

    2014-01-01

    Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in nature. They are very often observed in association with Needle Fibre Calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this manuscript the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically-influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of Fungi in CaCO3 biomineralization processes, a role still poorly documented at present

  15. Effects of chitosan on the alignment, morphology and shape of calcite crystals nucleating under Langmuir monolayers

    SciTech Connect

    Kim, Kyungil; Uysal, Ahmet; Kewalramani, Sumit; Stripe, Benjamin; Dutta, Pulak

    2009-04-22

    The growth of calcium carbonate crystals under Langmuir monolayers was investigated in the presence of chitosan, a soluble derivative of chitin added to the subphase to better simulate the polyelectrolyte-containing in vivo environment. Chitosan causes distinct concentration-dependent changes in the orientation, shape and morphology of the calcite crystals nucleating under acid and sulfate monolayers. Our results suggest that polyelectrolytes may play essential roles in controlling the growth of biogenic calcite crystals.

  16. Effects of Chitosan on the Morphology and Alignment of Calcite Crystals Nucleating Under Langmuir Monolayers

    SciTech Connect

    Kim, K.; Uysal, A; Kewalramani, S; Stripe, B; Dutta, P

    2009-01-01

    The growth of calcium carbonate crystals under Langmuir monolayers was investigated in the presence of chitosan, a soluble derivative of chitin added to the subphase to better simulate the polyelectrolyte-containing in vivo environment. Chitosan causes distinct concentration-dependent changes in the orientation, shape and morphology of the calcite crystals nucleating under acid and sulfate monolayers. Our results suggest that polyelectrolytes may play essential roles in controlling the growth of biogenic calcite crystals.

  17. Catalytic Biomineralization of Fluorescent Calcite by the Thermophilic Bacterium Geobacillus thermoglucosidasius▿

    PubMed Central

    Yoshida, Naoto; Higashimura, Eiji; Saeki, Yuichi

    2010-01-01

    The thermophilic Geobacillus bacterium catalyzed the formation of 100-μm hexagonal crystals at 60°C in a hydrogel containing sodium acetate, calcium chloride, and magnesium sulfate. Under fluorescence microscopy, crystals fluoresced upon excitation at 365 ± 5, 480 ± 20, or 545 ± 15 nm. X-ray diffraction indicated that the crystals were magnesium-calcite in calcite-type calcium carbonate. PMID:20851984

  18. Origin of sulfate in barite and calcite cements in the Jebel Madar salt dome (Oman)

    NASA Astrophysics Data System (ADS)

    Vandeginste, V.; John, C. M.; Gilhooly, W. P.

    2012-12-01

    Jebel Madar is a 500-m high mountain rising in the desert at the Oman Foothills. The Jebel consists of Triassic to Cretaceous carbonate host rocks forming the carapace of a salt dome. Halokinesis caused major fracturing and faulting at Jebel Madar, and the resulting structures acted as the main pathways for fluids that generated diagenetic cements composed of both barite and calcite. The spatial distribution of calcite and barite occurrences shows that calcite is formed in large abundance along the three main faults, whereas barite is more concentrated along faults further away from the three main ones. The stable carbon and oxygen isotope composition of calcite and fluid inclusion data from both calcite and barite show a distinct evolution of the fluid with a highly saline component towards more mixing with meteoric water. This is in agreement with clumped isotopes data on calcite cements indicating an evolution towards lower temperatures, consistent with doming of the Jebel and greater input of lower-temperature descending meteoric fluids. Here, we present sulphur and oxygen isotopic data on barite that suggest a link between the barite formation and the Precambrian salt underlying Jebel Madar. The average δ34S measured in barite is 33‰ CDT (1σ = 5‰; n = 33), which falls at the lower end of the δ34S range reported for the Ara Group anhydrite. The average δ18O in the same barite samples is 23‰ VSMOW (1σ = 2‰; n = 33). Data from the barite will be compared with sulphur isotopes from the carbonate-associate sulfate in the calcite cements. The overall goal of our research is to gain a better insight in the formation process of barite and calcite in Jebel Madar and its link with salt tectonics. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and the GSA Laubach fund for this study.

  19. The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters

    NASA Astrophysics Data System (ADS)

    Neal, Colin

    This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate) across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC) to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry) and household contamination (e.g. sewage sources from septic tanks). Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers.

  20. Kinetic and thermodynamic factors controlling the distribution of SO32- and Na+ in calcites and selected aragonites

    USGS Publications Warehouse

    Busenberg, E.; Niel, Plummer L.

    1985-01-01

    Significant amounts of SO42-, Na+, and OH- are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO42-. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na+, but very low concentrations of SO42-. The SO42- content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na+ and SO42- increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO42- beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO42- is the same as that of aragonite. Na+ appears to have very little effect on the solubility product of calcites. The amounts of Na+ and SO42- incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient (D) of SO42- in calcite at 25.0??C and 0.50 molal NaCl is described by the equation D = k0 + k1R where k0 and k1 are constants equal to 6.16 ?? 10-6 and 3.941 ?? 10-6, respectively, and R is the rate of crystal growth of calcite in mg??min-1??g-1 of seed. The data on Na+ are consistent with the hypothesis that a significant amount of Na+ occupies interstitial positions in the calcite structure. The distribution of Na+ follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na+ distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na+ contents of calcites are not very accurate indicators of environmental salinities. ?? 1985.

  1. Effects of liming on forage availability and nutrient content in a forest impacted by acid rain.

    PubMed

    Pabian, Sarah E; Ermer, Nathan M; Tzilkowski, Walter M; Brittingham, Margaret C

    2012-01-01

    Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer.

  2. Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain

    PubMed Central

    Pabian, Sarah E.; Ermer, Nathan M.; Tzilkowski, Walter M.; Brittingham, Margaret C.

    2012-01-01

    Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer. PMID:22761890

  3. Cytotoxic and antibacterial activity of the mixture of olive oil and lime cream in vitro conditions.

    PubMed

    Sumer, Zeynep; Yildirim, Gulay; Sumer, Haldun; Yildirim, Sahin

    2013-01-01

    The mixture of olive oil and lime cream has been traditionally used to treat external burns in the region of Hatay/Antakya and middle Anatolia. Olive oil and lime cream have been employed by many physicians to treat many ailments in the past. A limited number of studies have shown the antibacterial effect of olive oil and that it does not have any toxic effect on the skin. But we did not find any reported studies on the mixture of olive oil and lime cream. The aim of this paper is to investigate the cytotoxic and antibacterial activity of olive oil and lime cream individually or/and in combination in vitro conditions, by using disk-diffusion method and in cell culture. The main purpose in using this mixture is usually to clear burns without a trace. Agar overlay, MTT (Cytotoxicity assay) and antibacterial susceptibility tests were used to investigate the cytotoxic and antibacterial activity of olive oil and lime cream. We found that lime cream has an antibacterial activity but also cytotoxic on the fibroblasts. On the other hand olive oil has limited or no antibacterial effect and it has little or no cytotoxic on the fibroblasts. When we combined lime cream and olive oil, olive oil reduced its cytotoxic impact. These results suggest that mixture of olive oil and lime cream is not cytotoxic and has antimicrobial activity.

  4. 77 FR 45715 - Application of Key Lime Air Corporation for Commuter Authority

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-01

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Office of the Secretary Application of Key Lime Air Corporation for Commuter Authority AGENCY: Department... not issue an order finding Key Lime Air Corporation fit, willing, and able, and awarding it a...

  5. Liming of River Audna, Southern Norway: a large-scale experiment of benthic invertebrate recovery.

    PubMed

    Raddum, Gunnar G; Fjellheim, Arne

    2003-04-01

    This study describes the recovery of sensitive invertebrates after liming of the anadromous part of River Audna in 1985. The river lost its salmon population during 1960-1970. The aim of the liming was to produce a water quality with pH > 6.0 and ANC > 20 microg L(-1) and to reduce the content of labile aluminum. Highly sensitive invertebrates like the mayfly Baetis rhodani were not found in the river before liming. Two years after liming, several sensitive invertebrate species showed a positive response. B. rhodani was then recorded at 2 sites in the lower part of the river. In the following 5 years several species of sensitive invertebrates recolonized the whole limed reach of the river and became numerous. Ten years after liming the snail Lymnaea peregra was recorded in the river. The dispersa of this species was also very fast and after 5 years it was found at all investigated sites in the limed main river covering a reach of 40 km. Reduced sulfur deposition in the area also resulted in water-quality improvements in th unlimed stretches of River Audna. Comparisons between limed and unlimed localities indicated that the water quality and the critical limits of sensitive species are the ma factors determining the fauna composition in River Audna independent of the reason for the change in water quality.

  6. Substrate pH and butterfly bush response to dolomitic lime or steel slag amendment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Steel slag is a fertilizer amendment with a high concentration of calcium oxide, and thus capable of raising substrate pH similar to dolomitic lime. Steel slag, however, contains higher concentrations of some nutrients, such as iron, manganese, and silicon, compared to dolomitic lime. The objectiv...

  7. Effects of liming on forage availability and nutrient content in a forest impacted by acid rain.

    PubMed

    Pabian, Sarah E; Ermer, Nathan M; Tzilkowski, Walter M; Brittingham, Margaret C

    2012-01-01

    Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer. PMID:22761890

  8. Barley seedling growth in soils amended with fly ash or agricultural lime followed by acidification

    SciTech Connect

    Renken, R.R.; McCallister, D.L.; Tarkalson, D.D.; Hergert, G.W.; Marx, D.B.

    2006-05-15

    Calcium-rich coal combustion fly ash can be used as an amendment to neutralize soil acidity because of its oxides and carbonate content, but its aluminum content could inhibit plant growth if soil pH values fall below optimal agronomic levels. This study measured root and shoot growth of an acid-sensitive barley (Hordeum vulgare L. 'Kearney') grown in the greenhouse on three naturally acid soils. The soils were either untreated or amended with various liming materials (dry fly ash, wet fly ash, and agricultural lime) at application rates of 0, .5, 1, and 1.5 times the recommended lime requirement, then treated with dilute acid solutions to simulate management-induced acidification. Plant growth indexes were measured at 30 days after planting. Root mass per plant and root length per plant were greater for the limed treatments than in the acidified check. Root growth in the limed treatments did not differ from root growth in the original nonacidified soils. Top mass per plant in all limed soils was either larger than or not different from that in the original nonacidified soils. Based on top mass per plant, no liming material or application rate was clearly superior. Both fly ash and agricultural lime reduced the impact of subsequent acidification on young barley plants. Detrimental effects of aluminum release on plant growth were not observed. Calcium-rich fly ash at agronomic rates is an acceptable acid-neutralizing material with no apparent negative effects.

  9. Gas hydrates of outer continental margins

    SciTech Connect

    Kvenvolden, K.A. )

    1990-05-01

    Gas hydrates are crystalline substances in which a rigid framework of water molecules traps molecules of gas, mainly methane. Gas-hydrate deposits are common in continental margin sediment in all major oceans at water depths greater than about 300 m. Thirty-three localities with evidence for gas-hydrate occurrence have been described worldwide. The presence of these gas hydrates has been inferred mainly from anomalous lacoustic reflectors seen on marine seismic records. Naturally occurring marine gas hydrates have been sampled and analyzed at about tensites in several regions including continental slope and rise sediment of the eastern Pacific Ocean and the Gulf of Mexico. Except for some Gulf of Mexico gas hydrate occurrences, the analyzed gas hydrates are composed almost exclusively of microbial methane. Evidence for the microbial origin of methane in gas hydrates includes (1) the inverse relation between methane occurence and sulfate concentration in the sediment, (2) the subparallel depth trends in carbon isotopic compositions of methane and bicarbonate in the interstitial water, and (3) the general range of {sup 13}C depletion ({delta}{sub PDB}{sup 13}C = {minus}90 to {minus}60 {per thousand}) in the methane. Analyses of gas hydrates from the Peruvian outer continental margin in particular illustrate this evidence for microbially generated methane. The total amount of methane in gas hydrates of continental margins is not known, but estimates of about 10{sup 16} m{sup 3} seem reasonable. Although this amount of methane is large, it is not yet clear whether methane hydrates of outer continental margins will ever be a significant energy resource; however, these gas hydrates will probably constitute a drilling hazard when outer continental margins are explored in the future.

  10. Natural gas hydrate occurrence and issues

    USGS Publications Warehouse

    Kvenvolden, K.A.

    1994-01-01

    Naturally occurring gas hydrate is found in sediment of two regions: (1) continental, including continental shelves, at high latitudes where surface temperatures are very cold, and (2) submarine outer continental margins where pressures are very high and bottom-water temperatures are near 0??C. Continental gas hydrate is found in association with onshore and offshore permafrost. Submarine gas hydrate is found in sediment of continental slopes and rises. The amount of methane present in gas hydrate is thought to be very large, but the estimates that have been made are more speculative than real. Nevertheless, at the present time there has been a convergence of ideas regarding the amount of methane in gas hydrate deposits worldwide at about 2 x 1016 m3 or 7 x 1017 ft3 = 7 x 105 Tcf [Tcf = trillion (1012) ft3]. The potentially large amount of methane in gas hydrate and the shallow depth of gas hydrate deposits are two of the principal factors driving research concerning this substance. Such a large amount of methane, if it could be commercially produced, provides a potential energy resource for the future. Because gas hydrate is metastable, changes of surface pressure and temperature affect its stability. Destabilized gas hydrate beneath the sea floor leads to geologic hazards such as submarine mass movements. Examples of submarine slope failures attributed to gas hydrate are found worldwide. The metastability of gas hydrate may also have an effect on climate. The release of methane, a 'greenhouse' gas, from destabilized gas hydrate may contribute to global warming and be a factor in global climate change.

  11. Arbuscular Mycorrhizal Fungal Communities in the Roots of Maize Lines Contrasting for Al Tolerance Grown in Limed and Non-Limed Brazilian Oxisoil.

    PubMed

    Gomes, Eliane A; Oliveira, Christiane A; Lana, Ubiraci G P; Noda, Roberto W; Marriel, Ivanildo E; de Souza, Francisco A

    2015-07-01

    Aluminum (Al) toxicity is one of the greatest limitations to agriculture in acid soils, particularly in tropical regions. Arbuscular mycorrhizal fungi (AMF) can supply plants with nutrients and give protection against Al toxicity. The aim of this work was to evaluate the effects of soil liming (i.e., reducing Al saturation) on the AMF community composition and structure in the roots of maize lines contrasting for Al tolerance. To this end, we constructed four 18S rDNA cloning libraries from L3 (Al tolerant) and L22 (Al sensitive) maize lines grown in limed and non-limed soils. A total of 790 clones were sequenced, 69% belonging to the Glomeromycota phylum. The remaining sequences were from Ascomycota, which were more prominent in the limed soil, mainly in the L3 line. The most abundant AM fungal clones were related to the family Glomeraceae represented by the genera uncultured Glomus followed by Rhizophagus and Funneliformis. However, the most abundant operational taxonomic units with 27% of the Glomeromycota clones was affiliated to genus Racocetra. This genus was present in all the four libraries, but it was predominant in the non-limed soils, suggesting that Racocetra is tolerant to Al toxicity. Similarly, Acaulospora and Rhizophagus were also present mostly in both lines in non-limed soils. The community richness of AMF in the non-limed soils was higher than the limed soil for both lines. The results suggest that the soil Al saturation was the parameter that mostly influences the AMF species composition in the soils in this study. PMID:25674805

  12. Arbuscular Mycorrhizal Fungal Communities in the Roots of Maize Lines Contrasting for Al Tolerance Grown in Limed and Non-Limed Brazilian Oxisoil.

    PubMed

    Gomes, Eliane A; Oliveira, Christiane A; Lana, Ubiraci G P; Noda, Roberto W; Marriel, Ivanildo E; de Souza, Francisco A

    2015-07-01

    Aluminum (Al) toxicity is one of the greatest limitations to agriculture in acid soils, particularly in tropical regions. Arbuscular mycorrhizal fungi (AMF) can supply plants with nutrients and give protection against Al toxicity. The aim of this work was to evaluate the effects of soil liming (i.e., reducing Al saturation) on the AMF community composition and structure in the roots of maize lines contrasting for Al tolerance. To this end, we constructed four 18S rDNA cloning libraries from L3 (Al tolerant) and L22 (Al sensitive) maize lines grown in limed and non-limed soils. A total of 790 clones were sequenced, 69% belonging to the Glomeromycota phylum. The remaining sequences were from Ascomycota, which were more prominent in the limed soil, mainly in the L3 line. The most abundant AM fungal clones were related to the family Glomeraceae represented by the genera uncultured Glomus followed by Rhizophagus and Funneliformis. However, the most abundant operational taxonomic units with 27% of the Glomeromycota clones was affiliated to genus Racocetra. This genus was present in all the four libraries, but it was predominant in the non-limed soils, suggesting that Racocetra is tolerant to Al toxicity. Similarly, Acaulospora and Rhizophagus were also present mostly in both lines in non-limed soils. The community richness of AMF in the non-limed soils was higher than the limed soil for both lines. The results suggest that the soil Al saturation was the parameter that mostly influences the AMF species composition in the soils in this study.

  13. The use of a sequential leaching procedure for assessing the heavy metal leachability in lime waste from the lime kiln at a caustizicing process of a pulp mill.

    PubMed

    Pöykiö, Risto; Nurmesniemi, Hannu; Kuokkanen, Toivo; Perämäki, Paavo

    2006-12-01

    A five-stage sequential leaching procedure was used to fractionate 13 heavy metals (Cd, Cu, Pb, Cr, Zn, Fe, Mn, Al, Ni, Co, As, V, Ba) and sulphur (S) in lime waste from the lime kiln at the causticizing plant of Stora Enso Oyj Veitsiluoto Pulp Mills at Kemi, Northern Finland, into the following fractions: (1) water-soluble fraction (H(2)O), (2) exchangeable fraction (CH(3)COOH), (3) easily reduced fraction (HONH(3)Cl), (4) oxidizable fraction (H(2)O(2)+CH(3)COONH(4)), and (5) residual fraction (HF+HNO(3)+HCl). Although metals were leachable in all fractions, the highest concentrations for most of the metals were observed in the residual fraction (stage 5). It was also notable that the total heavy metal concentrations in lime waste did not exceed the maximal allowable heavy metal concentrations for soil conditioner agents set by the ministry of the Agricultural and Forestry in Finland. The heavy metals concentrations in lime waste were also lower than the maximal allowable heavy metals concentrations of the European Union Directive 86/278/EEC on the protection of environment, and in particular of the soil, when sewage sludge is used in agriculture. The Ca concentration (420 g kg(-1); d.w.) was about 262 times higher than the typical value of 1.6 g kg(-1) (d.w.) in arable land in Central Finland. However, the concentration Mg (0.2 g kg(-1); d.w.) in lime waste was equal to the Mg concentration in arable land in the Central Finland. The lime waste has strongly alkaline pH ( approximately 12.8) and a neutralizing value (i.e. liming effect) of 47.9% expressed as Ca equivalents (d.w.). This indicates lime waste to be a potential soil conditioner and improvement as well as a pH buffer.

  14. Use of pulp mill inorganic wastes as alternative liming materials.

    PubMed

    Cabral, F; Ribeiro, H M; Hilário, L; Machado, L; Vasconcelos, E

    2008-11-01

    A laboratory aerobic incubation study was performed during 18 weeks under controlled conditions to assess the effects of applying different doses of pulp mill inorganic wastes on the physical-chemical properties of an acid Dystric Cambissol. Three different inorganic wastes were tested - wood ash, dregs and grits, and an agriculture limestone was used as reference. Results showed that increasing the dose applied of the different inorganic wastes tested always led to significant raises of soil pH at different incubation times demonstrating that its use as alternative-liming materials could be a valid and less expensive option to the use of commercial agricultural limestone. Moreover, no immediate concerns seem to be expected related to soil exchangeable sodium (Na) content, at least for the doses needed to increase soil pH until the targeted value 6.5. Particularly for wood ash a pronounced increase on soil extractable potassium and phosphorous was observed, indicating that besides the liming effect this waste can contribute to improve soil fertility by supplying significant available amounts of these nutrients. Finally, metals do not seem to be a limiting factor for the application to land of these by-products.

  15. Late Mississippian lime mud mounds, Pitkin Formation, northern Arkansas

    SciTech Connect

    Manger, W.L.; Ar, V.P.; Webb, G.E.

    1984-04-01

    Carbonates deposited under shallow, open shelf conditions during the Late Mississippian in northern Arkansas exhibit numerous discrete to coalescing lime mud mounds up to 20 m (65 ft) high and tens of meters in diameter. The mounds are composed of a carbonate mud core, typically with fenestrate texture, entrapped by a loosely organized framework dominated by cystoporate bryozoans and rugose corals in the lower part, and by blue-green algae and cryptostomous bryozoans in the upper part. Disarticulated crinozoan detritus is common throughout the core, suggesting that these organisms also contributed to entrapment of lime mud. During deposition, the mud core was indurated enough to support and preserve vertical burrows. Also, rubble of core mudstone is found on the flanks of some mounds, suggesting some erosion. Intermound lithology is a shoaling-upward sequence dominated by oolitic and bioclastic grainstones and packstones. Shale is also present in minor amounts. The Pitkin mounds, interbedded with these intermound sequences, developed contemporaneously with them. Depositional relief was probably less than 3 m (10 ft). The mounds expanded laterally during periods of quieter water; their growth was impeded during times of higher energy. Contacts of the mound and intermound lithologic characteristics are sharp, truncating surfaces. Mound deposition ended with the onset of high energy conditions throughout the region.

  16. Fabrication of microporous calcite block from calcium hydroxide compact under carbon dioxide atmosphere at high temperature.

    PubMed

    Otsu, Akihiro; Tsuru, Kanji; Maruta, Michito; Munar, Melvin L; Matsuya, Shigeki; Ishikawa, Kunio

    2012-01-01

    Effects of carbonation temperature and compacting pressure on basic properties of calcite block were studied using Ca(OH)2 compact made with 0.2-2.0 MPa and their carbonation at 200-800ºC for 1 h. Microporous calcite was obtained only when carbonated at 600ºC using Ca(OH)2 compact made with 0.2 MPa even though thermogravimetry analysis showed that calcite powder was stable up to 920ºC under CO2 atmosphere. CaO formed by carbonation at 700ºC and 800ºC is thought to be caused by the limited CO2 diffusion interior to the Ca(OH)2 compact. Also, unreacted Ca(OH)2 was found for Ca(OH)2 compact prepared with 0.5 MPa or higher pressure even when carbonated at 600ºC. As a result of high temperature carbonation, crystallite size of the calcite, 58.0 nm, was significantly larger when compared to that of calcite prepared at room temperature, 35.5 nm. Porosity and diametral tensile strength of the microporous calcite were 39.5% and 6.4 MPa. PMID:22864212

  17. Microstructural control of calcite via incorporation of intracrystalline organic molecules in shells

    NASA Astrophysics Data System (ADS)

    Okumura, Taiga; Suzuki, Michio; Nagasawa, Hiromichi; Kogure, Toshihiro

    2013-10-01

    It is widely accepted that organic substances regulate or influence the structure of biominerals, but its direct evidences are not plenty. Here we show that the crystallographic microstructures in biotic calcites arise from incorporated intracrystalline organic molecules (IOMs), through a comparison between biotic calcites in shells and synthetic ones with the IOMs extracted from the shells. Although the prismatic layers of a pearl oyster (Pinctada fucata) and a pen shell (Atrina pectinata) morphologically resemble each other, the crystallographic features of constituent calcites are considerably different; in Pinctada, the IOMs are distributed inhomogeneously to form small-angle grain boundaries and associated crystal defects, whereas in Atrina, the IOMs are distributed almost homogeneously and defects are rare in the calcite crystals. We conducted in vitro calcite syntheses in the presence of the IOMs in EDTA-soluble extracts from the prisms. The IOMs in the extracts from Pinctada and Atrina were incorporated into synthetic calcites in a different manner, exhibiting defect-rich/free features as observed in the natural shells. With regard to amino acid compositions of the IOMs, the extract from Atrina has a higher proportion of acidic amino acids than that from Pinctada, implying that acidic proteins do not correlate directly to their affinity for calcium carbonate crystals.

  18. Sea urchin tooth mineralization: calcite present early in the aboral plumula.

    PubMed

    Stock, Stuart R; Veis, Arthur; Xiao, Xianghui; Almer, Jonathan D; Dorvee, Jason R

    2012-11-01

    In both vertebrate bone, containing carbonated hydroxyapatite as the mineral phase, and in invertebrate hard tissue comprised of calcium carbonate, a popular view is that the mineral phase develops from a long-lived amorphous precursor which later transforms into crystal form. Important questions linked to this popular view are: when and where is the crystallized material formed, and is amorphous solid added subsequently to the crystalline substrate? Sea urchin teeth, in which the earliest mineral forms within isolated compartments, in a time and position dependent manner, allow direct investigation of the timing of crystallization of the calcite primary plates. Living teeth of the sea urchin Lytechinus variegatus, in their native coelomic fluid, were examined by high-energy synchrotron X-ray diffraction. The diffraction data show that calcite is present in the most aboral portions of the plumula, representing the very earliest stages of mineralization, and that this calcite has the same crystal orientation as in the more mature adoral portions of the same tooth. Raman spectroscopy of the aboral plumula confirms the initial primary plate mineral material is calcite and does not detect amorphous calcium carbonate; in the more mature adoral incisal flange, it does detect a broader calcite peak, consistent with two or more magnesium compositions. We hypothesize that some portion of each syncytial membrane in the plumula provides the information for nucleation of identically oriented calcite crystals that subsequently develop to form the complex geometry of the single crystal sea urchin tooth.

  19. NMR characterization of hydrocarbon adsorption on calcite surfaces: a first principles study.

    PubMed

    Bevilaqua, Rochele C A; Rigo, Vagner A; Veríssimo-Alves, Marcos; Miranda, Caetano R

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  20. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    SciTech Connect

    Bevilaqua, Rochele C. A.; Miranda, Caetano R.; Rigo, Vagner A.; Veríssimo-Alves, Marcos

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca{sup 2+}. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO{sub 3} (101{sup ¯}4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for {sup 43}Ca, {sup 13}C, and {sup 17}O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.