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Sample records for heat of adsorption

  1. Differential Heat of Adsorption and Isosteres.

    PubMed

    Tian, Yun; Wu, Jianzhong

    2017-01-31

    Heat of adsorption is a basic thermodynamic property extensively used not only for understanding thermal effects and heat management in industrial gas storage and separation processes but also for development and validation of adsorption models and materials force fields. Despite a long history of theoretical studies and a vast experimental literature, controversies often arise in the thermodynamic analysis of heat effects due to various assumptions used to describe gas adsorption and inconsistencies between direct calorimetric measurements and isosteric heat obtained from various adsorption isotherms. Here we present a rigorous theoretical procedure for predicting isosteric heat without any assumption about the geometry of porous adsorbents or operating conditions. Quantitative relations between the differential heat and various isosteres have been established with the grand-canonical Monte Carlo simulation for gas adsorption in amorphous as well as crystalline porous materials. The inconsistencies and practical issues with conventional methods for the analysis of the heat effect have been clarified in the context of the exact results for model systems. Via the resolution of a number of controversies about heat analysis, we hope that the new theoretical procedure will be adopted for both fundamental research and industrial applications of gas adsorption processes.

  2. Possibility of using adsorption refrigeration unit in district heating network

    NASA Astrophysics Data System (ADS)

    Grzebielec, Andrzej; Rusowicz, Artur; Jaworski, Maciej; Laskowski, Rafał

    2015-09-01

    Adsorption refrigeration systems are able to work with heat sources of temperature starting with 50 °C. The aim of the article is to determine whether in terms of technical and economic issues adsorption refrigeration equipment can work as elements that produce cold using hot water from the district heating network. For this purpose, examined was the work of the adsorption air conditioning equipment cooperating with drycooler, and the opportunities offered by the district heating network in Warsaw during the summer. It turns out that the efficiency of the adsorption device from the economic perspective is not sufficient for production of cold even during the transitional period. The main problem is not the low temperature of the water supply, but the large difference between the coefficients of performance, COPs, of adsorption device and a traditional compressor air conditioning unit. When outside air temperature is 25 °C, the COP of the compressor type reaches a value of 4.49, whereas that of the adsorption device in the same conditions is 0.14. The ratio of the COPs is 32. At the same time ratio between the price of 1 kWh of electric power and 1 kWh of heat is only 2.85. Adsorption refrigeration equipment to be able to compete with compressor devices, should feature COPads efficiency to be greater than 1.52. At such a low driving temperature and even changing the drycooler into the evaporative cooler it is not currently possible to achieve.

  3. Towards an accurate estimation of the isosteric heat of adsorption - A correlation with the potential theory.

    PubMed

    Askalany, Ahmed A; Saha, Bidyut B

    2017-03-15

    Accurate estimation of the isosteric heat of adsorption is mandatory for a good modeling of adsorption processes. In this paper a thermodynamic formalism on adsorbed phase volume which is a function of adsorption pressure and temperature has been proposed for the precise estimation of the isosteric heat of adsorption. The estimated isosteric heat of adsorption using the new correlation has been compared with measured values of prudently selected several adsorbent-refrigerant pairs from open literature. Results showed that the proposed isosteric heat of adsorption correlation fits the experimentally measured values better than the Clausius-Clapeyron equation.

  4. Isosteric heat of hydrogen adsorption on MOFs: comparison between adsorption calorimetry, sorption isosteric method, and analytical models

    NASA Astrophysics Data System (ADS)

    Kloutse, A. F.; Zacharia, R.; Cossement, D.; Chahine, R.; Balderas-Xicohténcatl, R.; Oh, H.; Streppel, B.; Schlichtenmayer, M.; Hirscher, M.

    2015-12-01

    Isosteric heat of adsorption is an important parameter required to describe the thermal performance of adsorptive storage systems. It is most frequently calculated from adsorption isotherms measured over wide ranges of pressure and temperature, using the so-called adsorption isosteric method. Direct quantitative estimation of isosteric heats on the other hand is possible using the coupled calorimetric-volumetric method, which involves simultaneous measurement of heat and adsorption. In this work, we compare the isosteric heats of hydrogen adsorption on microporous materials measured by both methods. Furthermore, the experimental data are compared with the isosteric heats obtained using the modified Dubinin-Astakhov, Tóth, and Unilan adsorption analytical models to establish the reliability and limitations of simpler methods and assumptions. To this end, we measure the hydrogen isosteric heats on five prototypical metal-organic frameworks: MOF-5, Cu-BTC, Fe-BTC, MIL-53, and MOF-177 using both experimental methods. For all MOFs, we find a very good agreement between the isosteric heats measured using the calorimetric and isosteric methods throughout the range of loading studied. Models' prediction on the other hand deviates from both experiments depending on the MOF studied and the range of loading. Under low-loadings of less than 5 mol kg-1, the isosteric heat of hydrogen adsorption decreases in the order Cu-BTC > MIL-53 > MOF-5 > Fe-BTC > MOF-177. The order of isosteric heats is coherent with the strength of hydrogen interaction revealed from previous thermal desorption spectroscopy measurements.

  5. A compact low-temperature single crystal adsorption calorimetry setup for measuring coverage dependent heats of adsorption at cryogenic temperatures.

    PubMed

    Hörtz, Peter; Schäfer, Rolf

    2014-07-01

    Here we present the modification of an already existing Single Crystal Adsorption Calorimetry (SCAC) apparatus which has been extended by a compact cooling system to measure the coverage dependent heats of adsorption of gaseous compounds on thin metal substrates in a temperature range from 80 K to 430 K. The setup is characterized and its performance is tested by studying the adsorption of CO on Pt(111) at 150 K and 300 K. Coverage dependent sticking probabilities and heat of adsorption measurements are compared to previous experimental and theoretical studies proving the reliability of our compact low-temperature-SCAC setup.

  6. Influence of heat treatment of rayon-based activated carbon fibers on the adsorption of formaldehyde.

    PubMed

    Rong, Haiqin; Ryu, Zhenyu; Zheng, Jingtang; Zhang, Yuanli

    2003-05-15

    The influence of heat treatment of rayon-based activated carbon fibers on the adsorption behavior of formaldehyde was studied. Heat treatment in an inert atmosphere of nitrogen for rayon-based activated carbon fibers (ACFs) resulted in a significant increase in the adsorption capacities and prolongation of breakthrough time on removing of formaldehyde. The effect of different heat-treatment conditions on the adsorption characteristics was investigated. The porous structure parameters of the samples under study were investigated using nitrogen adsorption at the low temperature 77.4 K. The pore size distributions of the samples under study were calculated by density functional theory. With the aid of these analyses, the relationship between structure and adsorption properties of rayon-based ACFs for removing formaldehyde was revealed. Improvement of their performance in terms of adsorption selectivity and adsorption rate for formaldehyde were achieved by heat post-treatment in an inert atmosphere of nitrogen.

  7. Initial heats of H{sub 2}S adsorption on activated carbons: Effect of surface features

    SciTech Connect

    Bagreev, A.; Adib, F.; Bandosz, T.J.

    1999-11-15

    The sorption of hydrogen sulfide was studied on activated carbons of various origins by means of inverse gas chromatography at infinite dilution. The conditions of the experiment were dry and anaerobic. Prior to the experiments the surface of some carbon samples was oxidized using either nitric acid or ammonium persulfate. Then the structural parameters of carbons were evaluated from the sorption of nitrogen. From the IGC experiments at various temperatures, heats of adsorption were calculated. The results showed that the heat of H{sub 2}S adsorption under dry anaerobic conditions does not depend on surface chemistry. The dependence of the heat of adsorption on the characteristic energy of nitrogen adsorption calculated from the Dubinin-Raduskevich equation was found. This correlation can be used to predict the heat of H{sub 2}S adsorption based on the results obtained from nitrogen adsorption.

  8. Evaluation of the isosteric heat of adsorption at zero coverage for hydrogen on activated carbons

    NASA Astrophysics Data System (ADS)

    Dohnke, E.; Beckner, M.; Romanos, J.; Olsen, R.; Wexler, C.; Pfeifer, P.

    2011-03-01

    Activated carbons made from corn cob show promise as materials for high-capacity hydrogen storage. As part of our characterization of these materials, we are interested in learning how different production methods affect the adsorption energies. In this talk, we will show how hydrogen adsorption isotherms may be used to calculate these adsorption energies at zero coverage using Henry's law. We will additionally discuss differences between the binding energy and the isosteric heat of adsorption by applying this analysis at different temperatures.

  9. Demonstration of Metabolic Heat Regenerated Temperature Swing Adsorption Technology

    NASA Technical Reports Server (NTRS)

    Paul, Heather; Iacomini, Christine; Powers, Aaron; Dunham, Jonah; Straub-Lopez, Katie; Anerson, Grant; MacCallum, Taber

    2007-01-01

    Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is currently being investigated for removal and rejection of CO2 and heat from a Portable Life Support System (PLSS) to a Martian environment. The metabolically-produced CO2 present in the vent loop gas is collected using a CO2 selective adsorbent that has been cooled via a heat exchanger to near CO2 sublimation temperatures (approx.195K) with liquid CO2 obtained from Martian resources. Once the adsorbent is fully loaded, fresh warm, moist vent loop (approx.300K) is used to heat the adsorbent via another heat exchanger. The adsorbent will then reject the collected CO2 to the Martian ambient. Two beds are used to achieve continuous CO2 removal by cycling between the cold and warm conditions for adsorbent loading and regeneration, respectively. Small experiments have already been completed to show that an adsorbent can be cycled between these PLSS operating conditions to provide adequate conditions for CO2 removal from a simulated vent loop. One of the remaining technical challenges is extracting enough heat from the vent loop to warm the adsorbent in an appreciable time frame to meet the required adsorb/desorb cycle. The other key technical aspect of the technology is employing liquid CO2 to achieve the appropriate cooling. A technology demonstrator has been designed, built and tested to investigate the feasibility of 1) warming the adsorbent using the moist vent loop, 2) cooling the adsorbent using liquid CO2, and 3) using these two methods in conjunction to successfully remove CO2 from a vent loop and reject it to Mars ambient. Both analytical and numerical methods were used to perform design calculations and trades. The demonstrator was built and tested. The design analysis and testing results are presented along with recommendations for future development required to increase the maturity of the technology.

  10. Overall Heat and Mass Transfer Coefficient of Water Vapor Adsorption

    NASA Astrophysics Data System (ADS)

    Hamamoto, Yoshinori; Mori, Hideo; Godo, Masazumi; Miura, Kunio; Watanabe, Yutaka; Ishizawa, Toshihiko; Takatsuka, Takeshi

    A fundamental investigation was performed to develop a compact and simple desiccant ventilation unit which is one of the main components of a novel energy saving air-conditioning system. Water vapor in the air is adsorbed and/or desorbed to be controlled the humidity of supply air through a unit of an adsorbent rotor. A numerical simulation helps to understand the phenomena of heat and mass transfer in the rotor block. Overall transfer coefficients were estimated by performing both experiment and calculation. It was examined that the transient overall equivalent heat and mass transfer coefficient was not constant. It seems that both film fluid and diffusion resistance govern the coefficients in the block, and the influence of air flow on the time averaged coefficients is estimated by a considering the laminar forced convection from a flat plate. There is little difference of the coefficient between adsorption and desorption process. The correlation and fitting parameters are presented for prediction of the overall heat and mass transfer coefficients. The estimation accuracy was improved.

  11. Intraparticle heat and mass transfer characteristics of silica-gel/water vapor adsorption

    SciTech Connect

    Yamamoto, Eri; Watanabe, Fujio; Hasatani, Masanobu

    1999-07-01

    Recently, highly efficient energy utilization systems which extensively employ adsorption phenomena such as pressure swing adsorption, heat storage, adsorption heat pump, etc. are being regarded as one of the countermeasures for environmental issues such as green house effect and ozone layer destruction. An Adsorption Heat Pump (AHP) has been investigated as one of the important techniques via which cold heat energy is obtained from waste thermal energy below 373K without using electricity and CFCs. An AHP normally consists of an adsorber and an evaporator/condenser and cold heat energy is generated by latent heat of evaporation during adsorption process. For realizing the AHP technology, it has been pointed out that the development of an adsorber with optimum heat and mass transfer characteristics is essentially important. In this study, experimental studies were carried out which was based on the data of temperature inside the adsorbent particle and adsorptivity profiles at the adsorption/desorption process by volumetric method. To clarify adsorption mechanism relatively large silica-gel particle (7 mm f) was used. Temperature distribution in the particle is determined at the center, at one half radius in the radial direction and at the surface by using very thin (30 mm f) thermocouples. The temperatures at these points simultaneously increase/decrease as soon as the adsorption/desorption started, reached their respective maximum/minimum values and then return to initial temperature. The temperature profiles for the adsorption process show that the temperature at the surface is initially slightly higher than the other two points. All three points reached their respective maximum temperature at the same time with the temperature at the center point the highest and at the surface the lowest. The temperature profiles during the desorptive process are almost exactly the opposite to that of the adsorption process. This shows that the adsorption phenomena can take

  12. Adsorption of CO{sub 2} on activated carbon: Simultaneous determination of integral heat and isotherm of adsorption

    SciTech Connect

    Berlier, K.; Frere, M.

    1996-09-01

    Simultaneous measurements of isotherms and integral heats of adsorption of carbon dioxide (CO{sub 2}) at temperatures ranging from 278 K to 327 K (seven temperatures) and at pressures up to 110 kPa on activated carbon are presented.

  13. Adsorption Behavior of Heat Modified Soybean Oil via Boundary Lubrication Coefficient of Friction Measurements

    USDA-ARS?s Scientific Manuscript database

    The frictional behaviors of soybean oil and heat modified soybean oils with different Gardner scale viscosities as additives in hexadecane have been examined in a boundary lubrication test regime (steel contacts) using Langmuir adsorption model. The free energy of adsorption (delta-Gads) of various...

  14. Simulated Lunar Testing of Metabolic Heat Regenerated Temperature Swing Adsorption

    NASA Technical Reports Server (NTRS)

    Padilla, Sebastian A.; Bower, Chad E.; Iacomini, Christie S.; Paul, Heather L.

    2012-01-01

    Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. An Engineering Development Unit (EDU) of the MTSA Subassembly (MTSAS) was designed and assembled for optimized Martian operations, but also meets system requirements for lunar operations. For lunar operations the MTSA sorption cycle is driven via a vacuum swing between suit ventilation loop pressure and lunar vacuum. The focus of this effort was testing in a simulated lunar environment. This environment was simulated in Paragon's EHF vacuum chamber. The objective of the testing was to evaluate the full cycle performance of the MTSA Subassembly EDU, and to assess CO2 loading and pressure drop of the wash coated aluminum reticulated foam sorbent bed. Lunar environment testing proved out the feasibility of pure vacuum swing operation, making MTSA a technology that can be tested and used on the Moon prior to going to Mars. Testing demonstrated better than expected CO2 Nomenclature loading on the sorbent and nearly replicates the equilibrium data from the sorbent manufacturer. This exceeded any of the previous sorbent loading tests performed by Paragon. Subsequently, the increased performance of the sorbent bed design indicates future designs will require less mass and volume than the current EDU rendering MTSA as very competitive for Martian PLSS applications.

  15. Adsorption of SO2 onto oxidized and heat-treated activated carbon fibers (ACFs)

    USGS Publications Warehouse

    Daley, M.A.; Mangun, C.L.; DeBarr, J.A.; Riha, S.; Lizzio, A.A.; Donnals, G.L.; Economy, J.

    1997-01-01

    Oxidation of the ACFs, using an aqueous oxidant, decreased their adsorption capacity for SO2 from flue gas due to a decrease in pore volume and repulsion of the SO2 from acidic surface groups. If these samples were heat-treated to desorb the oxygen containing function groups, the amount of SO2 adsorption increased. This increase in adsorption capacity was directly correlated to the amount of CO2 evolved during heat-treatment of the oxidized ACFs. The amount of SO2 adsorbed for these samples was related to the pore size, pore surface chemistry and pore volume. This analysis is explained in more detail in this paper.

  16. Performance monitoring of an adsorption heat pump; Model development and simulation studies

    SciTech Connect

    Meunier, F.; Zanife, T. )

    1990-01-01

    Performance monitoring of an adsorption heat pump has been studied in a case of hot water delivery to a slaughterhouse when heat demand is a very irregular function of time. As the heat delivered by an adsorption heat pump is discontinuous, a heat storage tank has been used. The influence of the heat transfer fluid mass flow rate in the heat pump is very important because: a low mass flow rate yields a high temperature lift but a low efficiency; a high mass flow rate produces instabilities on the condensater and yields a low efficiency, and; an intermediate mass flow rate yields a reasonable efficiency and a correct temperature lift. Nevertheless, after a very large peak demand, the temperature requirement is not satisfied and a 7% dissatisfaction of the needs if obtained. To get 100% satisfaction of the needs, it would probably be necessary to overdesign the heat pump and the boiler.

  17. SO2 gas adsorption by modified kaolin clays: influence of previous heating and time acid treatments.

    PubMed

    Volzone, Cristina; Ortiga, Jose

    2011-10-01

    Modified kaolin clays were used as adsorbents for SO(2) gas adsorptions. The clays were heated up to 900 °C previous to acid treatments with 0.5 N sulfuric acid solutions at boiling temperature during different times up to 1440 min. Equilibrium adsorption at 25 °C and 0.1 MPa was carried out by using a volumetric apparatus. The samples were characterized by chemical analysis, X-ray diffraction and infrared analysis. The heating of the clays followed by acid treatment improved the adsorption capacity of the kaolin clays. The presence of amorphous silica and hydroxyl in the final products improved SO(2) adsorption capacity. Better properties for SO(2) adsorption were found in kaolin rich in not well ordered kaolinite clay mineral.

  18. Effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell initial attachment.

    PubMed

    Kern, Travis; Yang, Yunzhi; Glover, Renee; Ong, Joo L

    2005-03-01

    The clinical success of dental implants is governed in part by surface properties of implants and their interactions with the surrounding tissues. The objective of this study was to investigate the effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell attachment in vitro. Passivated titanium samples used in this study were either non heat treated or heat treated at 750 degrees C for 90 minutes. It was observed that the contact angle on heat-treated titanium surfaces was statistically lower compared with the non-heat-treated titanium surfaces. The non-heat-treated titanium surface was also observed to be amorphous oxide, whereas heat treatment of titanium resulted in the conversion of amorphous oxide to crystalline anatase oxide. No significant difference in albumin and fibronectin adsorption was observed between the heat-treated and non-heat-treated titanium surfaces. In addition, no significant difference in initial cell attachment was observed between the two groups. It was concluded that heat treatment of titanium resulted in significantly more hydrophilic surfaces compared to non-heat-treated titanium surfaces. However, differences in oxide crystallinity and wettability were not observed to affect protein adsorption and initial osteoblast precursor cell attachment.

  19. Equilibrium and heat of adsorption for organic vapors and activated carbons

    SciTech Connect

    David Ramirez; Shaoying Qi; Mark J. Rood; K. James Hay

    2005-08-01

    Determination of the adsorption properties of novel activated carbons is important to develop new air quality control technologies that can solve air quality problems in a more environmentally sustainable manner. Equilibrium adsorption capacities and heats of adsorption are important parameters for process analysis and design. Experimental adsorption isotherms were thus obtained for relevant organic vapors with activated carbon fiber cloth (ACFC) and coal-derived activated carbon adsorbents (CDAC). The Dubinin-Astakhov (DA) equation was used to describe the adsorption isotherms. The DA parameters were analytically and experimentally shown to be temperature independent. The resulting DA equations were used with the Clausius-Clapeyron equation to analytically determine the isosteric heat of adsorption ({Delta}H{sub s}) of the adsorbate-adsorbent systems studied here. ACFC showed higher adsorption capacities for organic vapors than CDAC. {Delta}H{sub s} values for the adsorbates were independent of the temperature for the conditions evaluated. {Delta}H{sub s} values for acetone and benzene obtained in this study are comparable with values reported in the literature. This is the first time that {Delta}H{sub s} values for organic vapors and these adsorbents are evaluated with an expression based on the Polanyi adsorption potential and the Clausius-Clapeyron equation. 28 refs., 5 figs., 5 tabs., 3 appends.

  20. Effects of heat treatment of calcium hydroxyapatite particles on the protein adsorption behavior.

    PubMed

    Kandori, Kazuhiko; Mizumoto, Saki; Toshima, Satoko; Fukusumi, Masao; Morisada, Yoshiaki

    2009-08-06

    The effects of heat treatment of calcium hydroxyapatite (Hap) on the protein adsorption behavior were examined using typical proteins of bovine serum albumin (BSA: isoelectric point (iep) = 4.7, molecular mass (Ms) = 67,200 Da, acidic protein), myoglobin (MGB: iep = 7.0, Ms = 17,800 Da, neutral protein), and lysozyme (LSZ: iep = 11.1, Ms = 14,600 Da, basic protein). The TEM, XRD, and gas adsorption measurements ascertained that all of the Hap particles examined were highly crystallized and nonporous. The Hap single phase was continued up to the heat treatment temperature of 600 degrees C. However, after treatment above 800 degrees C in air, the beta-Ca3(PO4)2 (beta-TCP) phase slightly appeared. TG and ICP-AES measurements suggested that all of the Hap particles are Ca2+-deficient. Also, it was indicated from FTIR and XPS measurements that a partially dehydrated oxyhydroxyapatite (pd-OHap) was formed after treatment at high temperature. The saturated amounts of adsorbed BSA (nsBSA) did not vary on the Hap particles after heat treatment at 200 and 400 degrees C. However, nsBSA values were increased by raising the heat treatment temperature above 600 degrees C. The adsorption coverage of BSA was increased up to ca. 1.4. This adsorption coverage of BSA (thetaBSA) over unity suggests that the BSA molecules densely adsorbed and a part of BSA molecules adsorbed as end-on type on the Hap particle surface or BSA molecules became contracted. Similar adsorption behavior was observed on the LSZ system, but the adsorption coverage of LSZ (thetaLSZ) values are much less than thetaBSA. On the other hand, no effect of the heat treatment of Hap particles was observed on the adsorption of MGB. The increases of nsBSA and nsLSZ were explained by the increase of calcium and phosphate ions in the solutions dissolved from beta-TCP formed after heat treatment of Hap, especially treated at high temperature. The dissolved Ca2+ and PO(4)3 - ions may act as binders between proteins and Hap

  1. Generation of high-temperature steam from unused thermal energy by a novel adsorption heat pump

    NASA Astrophysics Data System (ADS)

    Nakaso, Koichi; Eshima, Shotaro; Fukai, Jun

    2017-01-01

    For the effective utilization of unused thermal energy, the novel adsorption heat pump system for generating high-temperature steam is proposed. This system adopts a direct heat exchange method to the adsorption heat pump to increase heat transfer rate between adsorbent and heat transfer fluid. The heat pump system consists of two processes: steam generation process and regeneration process. In the steam generation process, water is directly introduced to the adsorbent. In the regeneration process, dry gas is introduced to the adsorbent. In this study, the performance of the system is numerically evaluated. The efficiency of the heat pump system is calculated by the ratio of enthalpy of product steam to input energy. To calculate the enthalpy of steam, mass of steam generated is estimated based on the progress of the regeneration process. Input energy of the heat pump system consists of the blower power to introduce dry gas and the thermal energy to heat dry gas. The effect of the operating condition on the performance of the steam generation process is studied. It is found there is the appropriate regeneration time to maximize the efficiency of the heat pump system.

  2. Analysis of combined heat and mass transfer in closed-cycle adsorption cooling systems

    SciTech Connect

    Hajji, A.

    1987-01-01

    A relationship for the solid-vapor adsorption equilibrium is proposed and proved to represent accurately the experimental data and to be convenient for numerical calculations. Formulas describing the process involved in closed-cycle cooling and heating systems are also derived. These formulas are first applied in a dynamic analysis of a closed-cycle solar adsorption refrigerator. A computer program was written to study the effect of the design parameters and operating conditions on the system performance. A second application concerns the simulation of the regenerative adsorption cooling systems which were recently introduced to increase the performance of adsorption machines. A computer program was developed to analyze the dynamic behavior of such systems. An analytical investigation of the vapor-liquid absorption is presented. Closed-form solution were obtained where the depth of the absorbing solution is taken into account. The effect of interfacial instability on heat and mass transfer is also modeled by introducing constant heat and mass transfer coefficients. An analysis of the fully developed natural convection heat and mass transfer between two inclined parallel plates is presented. Solvability conditions are determined and closed-form expressions for the temperature and concentration obtained.

  3. Adsorption of chloridazon from aqueous solution on heat and acid treated sepiolites.

    PubMed

    González-Pradas, E; Socías-Viciana, M; Ureña-Amate, M D; Cantos-Molina, A; Villafranca-Sánchez, M

    2005-05-01

    The adsorption of chloridazon on heat treated sepiolite samples at 110 degrees C (S-110), 200 degrees C (S-200), 400 degrees C (S-400), 600 degrees C (S-600) and acid treated samples with H2SO4 solutions of two different concentrations (0.25 and 1.0M) (S-0.25 and S-1.0, respectively) from pure water at 25 degrees C has been studied by using batch experiments. In addition, column experiments were carried out with the natural (S-110) and 600 degrees C (S-600) heat treated samples, using a 10.30 mg l-1 aqueous solution of chloridazon. The adsorption experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (Kf) of the samples; Kf values range from 2.89 mg kg-1 for the S-1.0 sample up to 164 mg kg-1 for the S-600 sample; so, the heat treatment given to the sepiolite greatly increases its adsorption capacity for the herbicide chloridazon whereas the acid treatment produces a clear decrease in the amount of chloridazon adsorbed. The removal efficiency (R) has also been calculated; R values ranging from 5.08% for S-1.0 up to 60.9% for S-600. The batch experiments showed that the strongest heat treatment is more effective than the natural and acid treated sepiolite in relation to adsorption of chloridazon. The column experiments also showed that 600 degrees C heat treated sepiolite might be reasonably used in removing chloridazon from water. Thus, as this type of clay is relatively plentiful, these activated samples might be reasonably used in order to remove chloridazon from water.

  4. On the microscopic origin of the temperature evolution of isosteric heat for methane adsorption on graphite.

    PubMed

    Liu, Lumeng; Zhang, Han; Do, D D; Nicholson, D; Liu, Junjie

    2017-10-02

    Understanding methane adsorption is fundamental to understanding gas storage and gas separation technologies. Detailed analyses of methane adsorption on non-porous substrates are pivotal for understanding the intrinsic interactions between the methane molecule and the adsorbent. In this paper, we particularly address the isosteric heat, which is a crucial parameter that characterizes the energetics of such systems. We have used grand canonical Monte Carlo simulations to study methane adsorption on graphite over a range of temperatures (from 50 K to 110 K). Our simulation results show good agreement with experimental data for the 2D phase transition, the 2D triple and critical points in the first layer obtained from low energy electron diffraction, neutron scattering and heat capacity measurements. On the basis of this agreement, we present a detailed microscopic picture of isosteric heat and its evolution with temperature. Our results show that the origin of the cusp and spike in the isosteric heat curve and their shift with temperature are associated with the balance of entropic and enthalpic contributions between the first and second layer.

  5. Preparation of modified semi-coke by microwave heating and adsorption kinetics of methylene blue.

    PubMed

    Wang, Xin; Peng, Jin-Hui; Duan, Xin-Hui; Srinivasakannan, Chandrasekar

    2013-01-01

    Preparation of modified semi-coke has been achieved, using phosphoric acid as the modifying agent, by microwave heating from virgin semi-coke. Process optimization using a Central Composite Design (CCD) design of Response Surface Methodology (RSM) technique for the preparation of modifies semi-coke is presented in this paper. The optimum conditions for producing modified semi-coke were: concentration of phosphoric acid 2.04, heating time 20 minutes and temperature 587 degrees C, with the optimum iodine of 862 mg/g and yield of 47.48%. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy (SEM) and nitrogen adsorption isotherm. The BET surface area of modified semi-coke was estimated to be 989.60 m2/g, with the pore volume of 0.74 cm3/g and a pore diameter of 3.009 nm, with micro-pore volume contributing to 62.44%. The Methylene Blue monolayer adsorption capacity was found to be mg/g at K. The adsorption capacity of the modified semi-coke highlights its suitability for liquid phase adsorption application with a potential usage in waste water treatment.

  6. Dynamic model of heat and mass transfer in rectangular adsorber of a solar adsorption machine

    NASA Astrophysics Data System (ADS)

    Chekirou, W.; Boukheit, N.; Karaali, A.

    2016-10-01

    This paper presents the study of a rectangular adsorber of solar adsorption cooling machine. The modeling and the analysis of the adsorber are the key point of such studies; because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. The adsorber is heated by solar energy and contains a porous medium constituted of activated carbon AC-35 reacting by adsorption with methanol. To study the solar collector type effect on system's performances, the used model takes into account the variation of ambient temperature and solar intensity along a simulated day, corresponding to a total daily insolation of 26.12 MJ/m2 with ambient temperature average of 27.7 °C, which is useful to know the daily thermal behavior of the rectangular adsorber.

  7. Testing, Modeling and System Impact of Metabolic Heat Regenerated Temperature Swing Adsorption

    NASA Technical Reports Server (NTRS)

    Lacomini, Christine S.; Powers, Aaron; Lewis, Matthew; Linrud, Christopher; Waguespack, Glenn; Conger, Bruce; Paul, Heather L.

    2008-01-01

    Metabolic heat regenerated temperature swing adsorption (MTSA) technology is being developed for removal and rejection of carbon dioxide (CO2) and heat from a portable life support system (PLSS) to the Martian environment. Previously, hardware was built and tested to demonstrate using heat from simulated, dry ventilation loop gas to affect the temperature swing required to regenerate an adsorbent used for CO2 removal. New testing has been performed using a moist, simulated ventilation loop gas to demonstrate the effects of water condensing and freezing in the heat exchanger during adsorbent regeneration. In addition, thermal models of the adsorbent during regeneration were modified and calibrated with test data to capture the effect of the CO2 heat of desorption. Finally, MTSA impact on PLSS design was evaluated by performing thermal balances assuming a specific PLSS architecture. Results using NASA s Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT), a PLSS system evaluation tool, are presented.

  8. Analysis of Adsorbate-Adsorbate and Adsorbate-Adsorbent Interactions to Decode Isosteric Heats of Gas Adsorption.

    PubMed

    Madani, S Hadi; Sedghi, Saeid; Biggs, Mark J; Pendleton, Phillip

    2015-12-21

    A qualitative interpretation is proposed to interpret isosteric heats of adsorption by considering contributions from three general classes of interaction energy: fluid-fluid heat, fluid-solid heat, and fluid-high-energy site (HES) heat. Multiple temperature adsorption isotherms are defined for nitrogen, T=(75, 77, 79) K, argon at T=(85, 87, 89) K, and for water and methanol at T=(278, 288, 298) K on a well-characterized polymer-based, activated carbon. Nitrogen and argon are subjected to isosteric heat analyses; their zero filling isosteric heats of adsorption are consistent with slit-pore, adsorption energy enhancement modelling. Water adsorbs entirely via specific interactions, offering decreasing isosteric heat at low pore filling followed by a constant heat slightly in excess of water condensation enthalpy, demonstrating the effects of micropores. Methanol offers both specific adsorption via the alcohol group and non-specific interactions via its methyl group; the isosteric heat increases at low pore filling, indicating the predominance of non-specific interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Performance Investigation of a Solar Heat Driven Adsorption Chiller under Two Different Climatic Conditions

    NASA Astrophysics Data System (ADS)

    Choudhury, Biplab; Chatterjee, Pradip Kumar; Habib, Khairul; Saha, Bidyut Baran

    2017-05-01

    The demand for cooling, especially in the developing economies, is rising at a fast rate. Fast-depleting sources of fossil fuel and environmental concerns necessitate looking for alternative cooling solutions. Solar heat driven adsorption based cooling cycles are environmentally friendly due to their use of natural refrigerants and the thermal compression process. In this paper, a performance simulation study of a basic two-bed solar adsorption chiller has been performed through a transient model for two different climatic locations in India. Effect of operating temperatures and cycle time on the chiller performance has been studied. It is observed that the solar hot water temperature obtained in the composite climate of Delhi (28.65°N, 77.25°E) can run the basic adsorption cooling cycle efficiently throughout the year. Whereas, the monsoon months of July and August in the warm and humid climate of Durgapur (23.48°N, 87.32°E) are unable to supply the required driving heat.

  10. Performance investigation of a waste heat driven pressurized adsorption refrigeration cycle

    NASA Astrophysics Data System (ADS)

    Habib, K.

    2015-12-01

    This article presents performance investigation of a waste heat driven two bed pressurised adsorption refrigeration system. In this study, highly porous activated carbon (AC) of type Maxsorb III has been selected as adsorbent while n-butane, R-134a, R410a, R507a and carbon dioxide (CO2) are chosen as refrigerants. All the five refrigerants work at above atmospheric pressure. Among the five pairs studied, the best pairs will be identified which will be used to provide sufficient cooling capacity for a driving heat source temperature above 60°C. Results indicate that for a driving source temperature above 60°C, AC-R410a pair provides highest cooling capacity while AC-CO2 pairs works better when the heat source temperature falls below 60°C.

  11. Adsorption of organic substances with different physicochemical properties 2. The heats of adsorption of freon 13B1 on active carbons

    SciTech Connect

    Baikova, T.V.; Gubkina, M.L.; Larin, A.V.; Polyakov, N.S.

    1995-03-01

    Toxic organic compounds which cause danger to the ozone layer must be removed from air. Adsorption processes are finding increasingly wide use. The linear regions of the adsorption isotherms of freon 13B1 (CF{sub 3}Br) on active carbons with different porous structures were studied by gas chromatography at 343-573 K. The Henry`s constants were determined, and the isosteric heats of adsorption (Q) were calculated in the region of zero filling. It was established that the Q values for active carbons with different pore size distributions are almost the same and vary within 38-41 kJ mol{sup -1}. This coincidence can be explained assuming that the interaction between the adsorbed molecules and the active carbons occurs in the pores whose sizes are comparable with those of the adsorbed molecules.

  12. Modeling Of Metabolic Heat Regenerated Temperature Swing Adsorption (MTSA) Subassembly For Prototype Design

    NASA Technical Reports Server (NTRS)

    Bower, Chad E.; Padilla, Sebastian A.; Iacomini, Christie S.; Paul, Heather L.

    2010-01-01

    This paper describes modeling methods for the three core components of a Metabolic heat regenerated Temperature Swing Adsorption (MTSA) subassembly: a sorbent bed, a sublimation (cooling) heat exchanger (SHX), and a condensing icing (warming) heat exchanger (CIHX). The primary function of the MTSA, removing carbon dioxide from a space suit Portable Life Support System (PLSS) ventilation loop, is performed via the sorbent bed. The CIHX is used to heat the sorbent bed for desorption and to remove moisture from the ventilation loop while the SHX is alternately employed to cool the sorbent bed via sublimation of a spray of water at low pressure to prepare the reconditioned bed for the next cycle. This paper describes subsystem heat a mass transfer modeling methodologies relevant to the description of the MTSA subassembly in Thermal Desktop and SINDA/FLUINT. Several areas of particular modeling interest are discussed. In the sorbent bed, capture of the translating carbon dioxide (CO2) front and associated local energy and mass balance in both adsorbing and desorbing modes is covered. The CIHX poses particular challenges for modeling in SINDA/FLUINT as accounting for solids states in fluid submodels are not a native capability. Methods for capturing phase change and latent heat of ice as well as the transport properties across a layer of low density accreted frost are developed. This extended modeling capacity is applicable to temperatures greater than 258 K. To extend applicability to the minimum device temperature of 235 K, a method for a mapped transformation of temperatures from below the limit temperatures to some value above is given along with descriptions for associated material property transformations and the resulting impacts to total heat and mass transfer. Similar considerations are given for the SHX along with functional relationships for areal sublimation rates as limited by flow mechanics in t1he outlet duct.

  13. Heat transfer to the adsorbent in solar adsorption cooling device

    NASA Astrophysics Data System (ADS)

    Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin

    2014-08-01

    The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.

  14. Estimation of CO heats of adsorption on metal surfaces from vibrational spectra

    SciTech Connect

    Bradford, M.C.J.; Vannice, M.A.

    1996-09-01

    The study of CO chemisorption on metal surfaces is, in general, of extreme fundamental importance for understanding of bonding mechanisms and of practical importance because of the use of CO in NO{sub x} reduction catalysts and Fischer-Tropsch synthesis reactions. An empirical relationship between the bond dissociation energy at 0 K, D{sub 0}, and the force constant, k, was obtained for a series of heteronuclear carbon-containing and homonuclear metal diatomic species, suggesting that the potential wells for these species have similar curvature. This D{sub 0}-k relationship was then used as part of a simple mathematical formalism to calculate the metal-carbon and carbon-oxygen bond strengths of Co adsorbed on metal surfaces directly from experimental values of A{sub 1} vibrational modes. By assuming a rigid metal lattice, whose bonds remain unperturbed as a result of Co adsorption, it was thus possible to directly calculate the heat of adsorption of CO, Q{sub ad}, from the calculated bond strengths. Although calculated values of Q{sub ad} for CO on 3d and 4d transition metals were in reasonable agreement with experimental values reported in the literature, agreement was not satisfactory for the 5d transition metals. Further analysis indicates that the discrepancy is likely due to the assumption of a rigid metal lattice and that Co adsorption on some metal surfaces, particularly those of platinum and iridium, induces some bond relaxation on the metal surface. It is thus suggested that metal surfaces which have both a large curvature of the cohesive function and adsorb CO primarily via 5{sigma} donation to the surface, i.e., little metal back-bonding, are strongly susceptible to bond relaxation and possible reconstruction.

  15. System Modeling of Metabolic Heat Regenerated Temperature Swing Adsorption (MTSA) Subassembly for Prototype Design

    NASA Technical Reports Server (NTRS)

    Bower, Chad; Padilla, Sebastian; Iacomini, Christie; Paul, Heather L.

    2009-01-01

    This paper describes modeling methods for the three core components of a Metabolic heat regenerated Temperature Swing Adsorption (MTSA) subassembly: the sorbent bed, a sublimation (cooling) heat exchanger (SHX), and a condensing icing (warming) heat exchanger (CIHX). The primary function of the MTSA, removing carbon dioxide from a ventilation loop, is performed via the sorbent bed. The CIHX is used to heat the sorbent bed for desorption and to remove moisture from the ventilation loop while the SHX is alternately employed to cool the sorbent bed via sublimation of a spray of water at low pressure to prepare the reconditioned bed for the next cycle. This paper describes a system level model of the MTSA as developed in Thermal Desktop and SINDA/FLUINT including assumptions on geometry and physical phenomena, modeling methodology and relevant pa ra mete rizatio ns. Several areas of particular modeling interest are discussed. In the sorbent bed, capture of the translating CO2 saturation front and associated local energy and mass balance in both adsorbing and desorbing modes is covered. The CIHX poses particular challenges for modeling in SINDA/FLUINT as accounting for solids states in fluid submodels are not a native capability. Methods for capturing phase change and latent heat of ice as well as the transport properties across a layer of low density accreted frost are developed. This extended modeling capacity is applicable to temperatures greater than 258 K. To extend applicability to the minimum device temperature of 235 K, a method for a mapped transformation of temperatures from below the limit temperatures to some value above is given along with descriptions for associated material property transformations and the resulting impacts to total heat and mass transfer. Similar considerations are shown for the SHX along with assumptions for flow mechanics and resulting model methods for sublimation in a flow.

  16. System Modeling of Metabolic Heat Regenerated Temperature Swing Adsorption (MTSA) Subassembly for Prototype Design

    NASA Technical Reports Server (NTRS)

    Bower, Chad; Padilla, Sebastian; Iacomini, Christie; Paul, Heather L.

    2009-01-01

    This paper describes modeling methods for the three core components of a Metabolic heat regenerated Temperature Swing Adsorption (MTSA) subassembly: the sorbent bed, a sublimation (cooling) heat exchanger (SHX), and a condensing icing (warming) heat exchanger (CIHX). The primary function of the MTSA, removing carbon dioxide from a ventilation loop, is performed via the sorbent bed. The CIHX is used to heat the sorbent bed for desorption and to remove moisture from the ventilation loop while the SHX is alternately employed to cool the sorbent bed via sublimation of a spray of water at low pressure to prepare the reconditioned bed for the next cycle. This paper describes a system level model of the MTSA as developed in Thermal Desktop and SINDA/FLUINT including assumptions on geometry and physical phenomena, modeling methodology and relevant pa ra mete rizatio ns. Several areas of particular modeling interest are discussed. In the sorbent bed, capture of the translating CO2 saturation front and associated local energy and mass balance in both adsorbing and desorbing modes is covered. The CIHX poses particular challenges for modeling in SINDA/FLUINT as accounting for solids states in fluid submodels are not a native capability. Methods for capturing phase change and latent heat of ice as well as the transport properties across a layer of low density accreted frost are developed. This extended modeling capacity is applicable to temperatures greater than 258 K. To extend applicability to the minimum device temperature of 235 K, a method for a mapped transformation of temperatures from below the limit temperatures to some value above is given along with descriptions for associated material property transformations and the resulting impacts to total heat and mass transfer. Similar considerations are shown for the SHX along with assumptions for flow mechanics and resulting model methods for sublimation in a flow.

  17. Enhanced isosteric heat of H2 adsorption by inclusion of crown ethers in a porous metal-organic framework.

    PubMed

    Park, Hye Jeong; Suh, Myunghyun Paik

    2012-04-07

    Inclusion of 18-crown-6 or 15-crown-5 in a porous MOF increased the isosteric heats of H(2) adsorption significantly, which are comparable to MOFs containing open metal sites. This journal is © The Royal Society of Chemistry 2012

  18. Metal-Organic Frameworks in Adsorption-Driven Heat Pumps: The Potential of Alcohols as Working Fluids.

    PubMed

    de Lange, Martijn F; van Velzen, Benjamin L; Ottevanger, Coen P; Verouden, Karlijn J F M; Lin, Li-Chiang; Vlugt, Thijs J H; Gascon, Jorge; Kapteijn, Freek

    2015-11-24

    A large fraction of global energy is consumed for heating and cooling. Adsorption-driven heat pumps and chillers could be employed to reduce this consumption. MOFs are often considered to be ideal adsorbents for heat pumps and chillers. While most published works to date on this topic have focused on the use of water as a working fluid, the instability of many MOFs to water and the fact that water cannot be used at subzero temperatures pose certain drawbacks. The potential of using alcohol-MOF pairs in adsorption-driven heat pumps and chillers is investigated. To this end, 18 different selected MOF structures in combination with either methanol or ethanol as a working fluid are considered, and their potential is assessed on the basis of adsorption measurements and thermodynamic efficiencies. If alcohols are used instead of water, then (1) adsorption occurs at lower relative pressures for methanol and even lower pressure for ethanol, (2) larger pores can be utilized efficiently, as hysteresis is absent for pores smaller than 3.4 nm (2 nm for water), (3) larger pore sizes need to be employed to ensure the desired stepwise adsorption, (4) the effect of (polar/apolar) functional groups in the MOF is far less pronounced, (5) the energy released or taken up per cycle is lower, but heat and mass transfer may be enhanced, (6) stability of MOFs seems to be less of an issue, and (7) cryogenic applications (e.g., ice making) become feasible. From a thermodynamic perspective, UiO-67, CAU-3, and ZIF-8 seem to be the most promising MOFs for both methanol and ethanol as working fluids. Although UiO-67 might not be completely stable, both CAU-3 and ZIF-8 have the potential to be applied, especially in subzero-temperature adsorption chillers (AC).

  19. Emulsifying properties and oil/water (O/W) interface adsorption behavior of heated soy proteins: effects of heating concentration, homogenizer rotating speed, and salt addition level.

    PubMed

    Cui, Zhumei; Chen, Yeming; Kong, Xiangzhen; Zhang, Caimeng; Hua, Yufei

    2014-02-19

    The adsorption of heat-denatured soy proteins at the oil/water (O/W) interface during emulsification was studied. Protein samples were prepared by heating protein solutions at concentrations of 1-5% (w/v) and were then diluted to 0.3% (w/v). The results showed that soy proteins that had been heated at higher concentrations generated smaller droplet size of emulsion. Increase in homogenizer rotating speed resulted in higher protein adsorption percentages and lower surface loads at the O/W interface. Surface loads for both unheated and heated soy proteins were linearly correlated with the unadsorbed proteins' equilibrium concentration at various rotating speeds. With the rise in NaCl addition level, protein adsorption percentage and surface loads of emulsions increased, whereas lower droplet sizes were obtained at the ionic strength of 0.1 M. The aggregates and non-aggregates displayed different adsorption behaviors when rotating speed or NaCl concentration was varied.

  20. New Carbon-Based Porous Materials with Increased Heats of Adsorption for Hydrogen Storage

    SciTech Connect

    Snurr, Randall Q.; Hupp, Joseph T.; Kanatzidis, Mercouri G.; Nguyen, SonBinh T.

    2014-11-03

    . Only after modeling suggested record-breaking hydrogen uptake at 77 K did we proceed to synthesize, characterize, and test the material, ultimately yielding experimental results that agreed closely with predictions that were made before the material was synthesized. We also synthesized, characterized, and computationally simulated the behavior of two new materials displaying the highest experimental Brunauer$-$Emmett$-$Teller (BET) surface areas of any porous materials reported to date (~7000 m2/g). Key to evacuating the initially solvent-filled materials without pore collapse, and thereby accessing the ultrahigh areas, was the use of a supercritical CO2 activation technique developed by our team. In our efforts to increase the hydrogen binding energy, we developed the first examples of “zwitterionic” metal-organic frameworks (MOFs). The two structures feature zwitterionic characteristics arising from N-heterocyclic azolium groups in the linkers and negatively charged Zn2(CO2)5 nodes. These groups interact strongly with the H2 quadrupole. High initial isosteric heats of adsorption for hydrogen were measured at low H2 loading. Simulations were used to determine the H2 binding sites, and results were compared with inelastic neutron scattering. In addition to MOFs, the project produced a variety of related materials known as porous organic frameworks (POFs), including robust catechol-functionalized POFs with tunable porosities and degrees of functionalization. Post-synthesis metalation was readily carried out with a wide range of metal precursors (CuII, MgII, and MnII salts and complexes), resulting in metalated POFs with enhanced heats of hydrogen adsorption compared to the starting nonmetalated materials. Isosteric heats of adsorption as high as 9.6 kJ/mol were observed, compared to typical values around 5 kJ/mol in unfunctionalized MOFs and POFs

  1. Correlations and adsorption mechanisms of aromatic compounds on a high heat temperature treated bamboo biochar.

    PubMed

    Yang, Kun; Yang, Jingjing; Jiang, Yuan; Wu, Wenhao; Lin, Daohui

    2016-03-01

    Adsorption of aromatic compounds, including polycyclic aromatic hydrocarbons, nitrobenzenes, phenols, and anilines, on a bamboo biochar produced at 700 °C (Ba700) was investigated with the mechanism discussion by isotherm fitting using the Polanyi-theory based Dubinin-Ashtakhov (DA) model. Correlations of adsorption capacity (Q(0)) of organic compounds with their molecular sizes and melting points, as well as correlations of adsorption affinity (E) with their solvatochromic parameters (i.e., π* and αm), on the biochar, were developed and indicating that adsorption is captured by the pore filling mechanism and derived from the hydrophobic effects of organic compounds and the forming of π-π electron donor-acceptor (EDA) interactions and hydrogen bonding interactions of organic molecules with surface sites of the biochar. The effects of organic molecular sizes and melting points on adsorption capacity are ascribed to the molecular sieving effect and the packing efficiency of the organic molecules in the biochar pores, respectively. These correlations can be used to quantitatively estimate the adsorption of organic compounds on biochars from their commonly physicochemical properties including solvatochromic parameters, melting points and molecular cross-sectional area. The prediction using these correlations is important for assessing the unknown adsorption behaviors of new organic compounds and also helpful to guide the surface modification of biochars and make targeted selection in the environmental applications of biochars as adsorbents.

  2. On the isosteric heat of adsorption of non-polar and polar fluids on highly graphitized carbon black.

    PubMed

    Horikawa, Toshihide; Zeng, Yonghong; Do, D D; Sotowa, Ken-Ichiro; Alcántara Avila, Jesús Rafael

    2015-02-01

    Isosteric heat of adsorption is indispensable in probing the energetic behavior of interaction between adsorbate and solid, and it can shed insight into how molecules interact with a solid by studying the dependence of isosteric heat on loading. In this study, we illustrated how this can be used to explain the difference between adsorption of non-polar (and weakly polar) fluids and strong polar fluids on a highly graphitized carbon black, Carbopack F. This carbon black has a very small quantity of functional group, and interestingly we showed that no matter how small it is the analysis of the isosteric heat versus loading can identify its presence and how it affects the way polar molecules adsorb. We used argon and nitrogen as representatives of non-polar fluid and weakly polar fluid, and methanol and water for strong polar fluid. The pattern of the isosteric heat versus loading can be regarded as a fingerprint to determine the mechanism of adsorption for strong polar fluids, which is very distinct from that for non-polar fluids. This also allows us to estimate the interplay between the various interactions: fluid-fluid, fluid-basal plane and fluid-functional group.

  3. The effect of pre-adsorption of OVA or WPC on subsequent OVA or WPC fouling on heated stainless steel surface.

    PubMed

    Lv, Huiting; Huang, Song; Mercadé-Prieto, Ruben; Wu, Xue E; Chen, Xiao Dong

    2015-05-01

    Fouling on the heat exchanger surface during food processing has been researched extensively due to its great importance in energy efficiency, product quality and food safety. The nature of heat exchanger surface has an effect on the initial deposition behavior and deposit removal behavior to some degree. Protein adsorption on surface is considered to be the initial stage in fouling. In the current study, protein 'pre-adsorption' at room temperature on stainless steel has been investigated as a means to influence the behavior of protein fouling at pasteurization temperatures. Pre-adsorption was carried out with whey protein concentrate (WPC) and ovalbumin (OVA), respectively, which reduced the fouling of OVA (∼20-30% energy saving in the processing time examined). However, the pre-adsorption had little effect on fouling of whey protein concentrate. Contact angles were measured to show the surface change due to protein pre-adsorption. Protein pre-adsorption made the surfaces more hydrophilic.

  4. Adsorption and dilatational rheology of heat-treated soy protein at the oil-water interface: relationship to structural properties.

    PubMed

    Wang, Jin-Mei; Xia, Ning; Yang, Xiao-Quan; Yin, Shou-Wei; Qi, Jun-Ru; He, Xiu-Ting; Yuan, De-Bao; Wang, Li-Juan

    2012-03-28

    We evaluated the influence of heat treatment on interfacial properties (adsorption at the oil-water interface and dilatational rheology of interfacial layers) of soy protein isolate. The related structural properties of protein affecting these interfacial behaviors, including protein unfolding and aggregation, surface hydrophobicity, and the state of sulfhydryl group, were also investigated. The structural and interfacial properties of soy protein depended strongly on heating temperature (90 and 120 °C). Heat treatment at 90 °C induced an increase in surface hydrophobicity due to partial unfolding of protein, accompanied by the formation of aggregates linked by disulfide bond, and lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native protein. Contrastingly, heat treatment at 120 °C led to a higher surface activity of the protein and rapid development of intermolecular interactions in the adsorbed layer, as evidenced by a faster increase of surface pressure and dilatational modulus. The interfacial behaviors of this heated protein may be mainly associated with more flexible conformation and high free sulfhydryl group, even if some exposed hydrophobic groups are involved in the formation of aggregates. These results would be useful to better understand the structure dependence of protein interfacial behaviors and to expand utilization of heat-treated protein in the formulation and production of emulsions.

  5. Simulated Lunar Testing of Metabolic Heat Regenerated Temperature Swing Adsorption Technology

    NASA Technical Reports Server (NTRS)

    Padilla, Sebastian A.; Bower, Chad; Iacomini, Christie S.; Paul, H.

    2011-01-01

    Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. An Engineering Development Unit (EDU) of the MTSA subassembly was designed and assembled for optimized Martian operations, but also meets system requirements for lunar operations. For lunar operations the MTSA sorption cycle is driven via a vacuum swing between suit ventilation loop pressure and lunar vacuum. The focus of this effort is operations and testing in a simulated lunar environment. This environment was simulated in Paragon s EHF vacuum chamber. The objective of this testing was to evaluate the full cycle performance of the MTSA Subassembly EDU, and to assess CO2 loading and pressure drop of the wash coated aluminum reticulated foam sorbent bed. The lunar testing proved out the feasibility of pure vacuum swing operation, making MTSA a technology that can be tested and used on the Moon prior to going to Mars. Testing demonstrated better than expected CO2 loading on the sorbent and nearly replicates the equilibrium data from the sorbent manufacturer. This had not been achieved in any of the previous sorbent loading tests performed by Paragon. Subsequently, the increased performance of the sorbent bed design indicates future designs will require less mass and volume than the current EDU rendering MTSA as very competitive for Martian PLSS applications.

  6. Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

    SciTech Connect

    Zhang, W.M.; Xu, Z.W.; Pan, B.C.; Hong, C.H.; Jia, K.; Jiang, P.J.; Zhang, Q.J.; Pan, B.J.

    2008-09-15

    Removal of phthalate esters from water has been of considerable concern recently. In the present study, the adsorptive removal performance of diethyl phthalate (DEP) from water was investigated with the aminated polystyrene resin (NDA-101) and oxidized polystyrene resin (NDA-702). In addition, the commercial homogeneous polystyrene resin (XAD-4) and acrylic ester resin (Amberlite XAD-7) as well as coal-based granular activated carbon (AC-750) were chosen for comparison. The corresponding equilibrium isotherms are well described by the Freundlich equation and the adsorption capacities for DEP followed the order NDA-702 > NDA-101 > AC-750 > XAD-4 > XAD-7. Analysis of adsorption mechanisms suggested that these adsorbents spontaneously adsorb DEP molecules driven mainly by enthalpy change, and the adsorption process was derived by multiple adsorbent-adsorbate interactions such as hydrogen bonding, {pi}-{pi} stacking, and micropore filling. The information related to the adsorbent surface heterogeneity and the adsorbate-adsorbate interaction was obtained by Do's model. All the results indicate that heterogeneous resins NDA-702 and NDA-101 have excellent potential as an adsorption material for the removal of DEP from the contaminated water.

  7. Transient Modeling and Analysis of a Metabolic Heat-Regenerated Temperature Swing Adsorption (MTSA) System for a PLSS

    NASA Technical Reports Server (NTRS)

    Iacomini, Christie; Powers, Aaron; Speight, Garland; Padilla, Sebastian; Paul, Heather L.

    2009-01-01

    A Metabolic heat-regenerated Temperature Swing Adsorption (MTSA) system is being developed for carbon dioxide, water and thermal control in a lunar and martian portable life support system (PLSS). A previous system analysis was performed to evaluate the impact of MTSA on PLSS design. That effort was Mars specific and assumed liquid carbon dioxide (LCO2) coolant made from martian resources. Transient effects were not considered but rather average conditions were used throughout the analysis. This effort takes into further consideration the transient effects inherent in the cycling MTSA system as well as assesses the use of water as coolant. Standard heat transfer, thermodynamic, and heat exchanger methods are presented to conduct the analysis. Assumptions and model verification are discussed. The tool was used to perform various system studies. Coolant selection was explored and takes into account different operational scenarios as the minimum bed temperature is driven by the sublimation temperature of the coolant (water being significantly higher than LCO2). From this, coolant mass is sized coupled with sorbent bed mass because MTSA adsorption performance decreases with increasing sublimation temperature. Reduction in heat exchanger performance and even removal of certain heat exchangers, like a recuperative one between the two sorbent beds, is also investigated. Finally, the coolant flow rate is varied over the cycle to determine if there is a more optimal means of cooling the bed from a mass perspective. Results of these studies and subsequent recommendations for system design are presented.

  8. Transient Modeling and Analysis of a Metabolic Heat-Regenerated Temperature Swing Adsorption (MTSA) System for a PLSS

    NASA Technical Reports Server (NTRS)

    Iacomini, Christie; Powers, Aaron; Speight, Garland; Padilla, Sebastian; Paul, Heather L.

    2009-01-01

    A Metabolic heat-regenerated Temperature Swing Adsorption (MTSA) system is being developed for carbon dioxide, water and thermal control in a lunar and martian portable life support system (PLSS). A previous system analysis was performed to evaluate the impact of MTSA on PLSS design. That effort was Mars specific and assumed liquid carbon dioxide (LCO2) coolant made from martian resources. Transient effects were not considered but rather average conditions were used throughout the analysis. This effort takes into further consideration the transient effects inherent in the cycling MTSA system as well as assesses the use of water as coolant. Standard heat transfer, thermodynamic, and heat exchanger methods are presented to conduct the analysis. Assumptions and model verification are discussed. The tool was used to perform various system studies. Coolant selection was explored and takes into account different operational scenarios as the minimum bed temperature is driven by the sublimation temperature of the coolant (water being significantly higher than LCO2). From this, coolant mass is sized coupled with sorbent bed mass because MTSA adsorption performance decreases with increasing sublimation temperature. Reduction in heat exchanger performance and even removal of certain heat exchangers, like a recuperative one between the two sorbent beds, is also investigated. Finally, the coolant flow rate is varied over the cycle to determine if there is a more optimal means of cooling the bed from a mass perspective. Results of these studies and subsequent recommendations for system design are presented.

  9. Effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing yellow zein.

    PubMed

    Sessa, D J; Palmquist, D E

    2008-09-01

    The Freundlich model was evaluated for use to assess the effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing corn zein. Because zein protein and its color/odor components are all adsorbed by activated carbon, a method to monitor their removal was needed. Yellow color is due to xanthophylls; a contributor to off-odor is diferuloylputrescine. The off-odor component absorbs ultraviolet (UV) light at about 325 nm and its removal coincides with removal of yellow color. A spectrophotometric method based on UV absorbances 280 nm for protein and 325 nm for the off-odor component was used to monitor their adsorptions onto activated carbon. Equilibrium studies were performed over temperature range from 25 to 60 degrees C for zein dissolved in 70% aqueous ethanol. Runs made at 55 degrees C adsorbed significantly more of the color/odor components than the protein.

  10. High Efficiency Adsorption Chillers: High Efficiency Adsorption Cooling Using Metal Organic Heat Carriers

    SciTech Connect

    2010-10-01

    BEETIT Project: PNNL is incorporating significant improvements in materials that adsorb liquids or gases to design more efficient adsorption chillers. An adsorption chiller is a type of air conditioner that is powered by heat, solar or waste heat, or combustion of natural gas. Unlike typical chillers, this type has few moving parts and uses almost no electricity to operate. PNNL is designing adsorbent materials at the molecular level with at least 3 times higher refrigerant capacity and up to 20 times faster kinetics than adsorbents used in current chillers. By using the new adsorbent, PNNL is able to create a chiller that is significantly smaller, has twice the energy efficiency, and lower costs for materials and assembly time compared to conventional adsorption chillers.

  11. New composite sorbents of water and ammonia for chemical and adsorption heat pumps

    NASA Astrophysics Data System (ADS)

    Aristov, Yu. I.; Vasiliev, L. L.

    2006-11-01

    New sorbents of water and ammonia — “salt in porous matrix” composites and “salt on fiber” composites — have been reviewed. The possibility of “constructing” the sorption properties of the composites at the nanophase level by varying their composition, the size of the host-matrix pores, and synthesis conditions has been shown. The application of the new materials in adsorption refrigerating devices has been considered.

  12. Gas adsorption/absorption heat switch, phase 1

    NASA Technical Reports Server (NTRS)

    Chan, C. K.

    1987-01-01

    The service life and/or reliability of far-infrared sensors on surveillance satellites is presently limited by the cryocooler. The life and/or reliability, however, can be extended by using redundant cryocoolers. To reduce parasitic heat leak, each stage of the inactive redundant cryocooler must be thermally isolated from the optical system, while each stage of the active cryocooler must be thermally connected to the system. The thermal break or the thermal contact can be controlled by heat switches. Among different physical mechanisms for heat switching, mechanically activated heat switches tend to have low reliability and, furthermore, require a large contact force. Magnetoresistive heat switches are, except at very low temperatures, of very low efficiency. Heat switches operated by the heat pipe principle usually require a long response time. A sealed gas gap heat switch operated by an adsorption pump has no mechanical motion and should provide the reliability and long lifetime required in long-term space missions. Another potential application of a heat switch is the thermal isolation of the optical plane during decontamination.

  13. A continuous heat regenerative adsorption refrigerator using spiral plate heat exchanger as adsorbers: improvements

    SciTech Connect

    Wang, R.Z.; Wu, J.Y.; Xu, Y.X.

    1999-02-01

    Spiral plate heat exchangers as adsorbers have been proposed, and a prototype heat regenerative adsorption refrigerator using activated carbon-methanol pair has been developed and tested. Various improvements have been made, the authors get a specific cooling power for 2.6 kg-ice/day-kg adsorbent at the condition of generation temperature lower than 100 C. Discussions on the arrangements of thermal cycles and influences of design are shown.

  14. Design and Assembly of an Integrated Metabolic Heat Regenerated Temperature Swing Adsorption (MTSA) Subassembly Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Padilla, Sebastian A.; Powers, Aaron; Iacomini, Christie S.; Bower, Chad E.; Paul, Heather L.

    2012-01-01

    Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. The core of the MTSA technology is a sorbent bed that removes CO2 from the PLSS ventilation loop gas via a temperature swing. A Condensing Icing Heat eXchanger (CIHX) is used to warm the sorbent while also removing water from the ventilation loop gas. A Sublimation Heat eXchanger (SHX) is used to cool the sorbent. Research was performed to explore an MTSA designed for both lunar and Martian operations. Previously the sorbent bed, CIHX, and SHX had been built and tested individually on a scale relevant to PLSS operations, but they had not been done so as an integrated subassembly. Design and analysis of an integrated subassembly was performed based on this prior experience and an updated transient system model. Focus was on optimizing the design for Martian operations, but the design can also be used in lunar operations. An Engineering Development Unit (EDU) of an integrated MTSA subassembly was assembled based on the design. Its fabrication is discussed. Some details on the differences between the as-assembled EDU and the future flight unit are considered.

  15. Design and Assembly of an Integrated Metabolic Heat Regenerated Temperature Swing Adsorption (MTSA) Subassembly Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Padilla, Sebastian A.; Powers, Aaron; Iacomini, Christie S.; Paul, Heather L.

    2011-01-01

    Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. The core of the MTSA technology is a sorbent bed that removes CO2 from the PLSS ventilation loop gas via a temperature swing. A Condensing Ice Heat eXchanger (CIHX) is used to warm the sorbent while also removing water from the ventilation loop gas. A Sublimation Heat eXchanger (SHX) is used to cool the sorbent. Research was performed to explore an MTSA designed for both lunar and Martian operations. Previously each the sorbent bed, CIHX, and SHX had been built and tested individually on a scale relevant to PLSS operations, but they had not been done so as an integrated subassembly. Design and analysis of an integrated subassembly was performed based on this prior experience and an updated transient system model. Focus was on optimizing the design for Martian operations, but the design can also be used in lunar operations. An Engineering Development Unit (EDU) of an integrated MTSA subassembly was assembled based on the design. Its fabrication is discussed. Some details on the differences between the as-assembled EDU to the future flight unit are considered.

  16. Electric Adsorption Heat Pump for Electric Vehicles: Electric-Powered Adsorption Heat Pump for Electric Vehicles

    SciTech Connect

    2011-11-21

    HEATS Project: PNNL is developing a new class of advanced nanomaterial called an electrical metal organic framework (EMOF) for EV heating and cooling systems. The EMOF would function similar to a conventional heat pump, which circulates heat or cold to the cabin as needed. However, by directly controlling the EMOF's properties with electricity, the PNNL design is expected to use much less energy than traditional heating and cooling systems. The EMOF-based heat pumps would be light, compact, efficient, and run using virtually no moving parts.

  17. Effect of heat treatment on the efficient adsorption of Cd2+ ions by nanosized SiO2, TiO2 and their composite

    NASA Astrophysics Data System (ADS)

    Waseem, M.; Muntha, S. T.; Nawaz, M.; Rehman, W.; Rehman, M. A.; Shah, K. H.

    2017-01-01

    In this study nanosized SiO2, TiO2 and their composite were synthesized via the oil in water (o/w) microemulsion method and their thermal treatment was performed at 378, 573, 973 and 1273 K. The physicochemical properties of the samples were studied by surface area measurements, scanning electron microscopy, Fourier transform infra-red spectroscopy and x-ray diffraction analysis. The Brunauer, Emmett and Teller surface area of all the adsorbents increases from 378 to 573 K, while it decreases upon further heat treatment. The average crystallite size decreases by heating the samples from 378 to 573 K while it increases when the adsorbents were thermally heat treated at 973 and 1273 K. The intensity of a few IR bands was reduced along with the disappearance of most of the bands at higher temperatures. The appearance of the beta-cristobalite phase in SiO2 and the rutile phase in TiO2 was confirmed from the diffraction data. The heat treated samples were subjected to preliminary adsorption of Cd2+ ions from aqueous solution at 293 K. Based on the preliminary adsorption experiments, SiO2, TiO2 and their composite heat treated at 573 K were selected for further adsorption studies. The Langmuir model was found to be fitted to the sorption data of TiO2 and the nanocomposite while the adsorption of Cd2+ ions by the SiO2 nanoparticles was explained well based on the Freundlich model. In the present study, the maximum Cd2+ adsorption capacity of SiO2, TiO2 and their composite was found to be 79.72, 98.55 and 107.17 mg g‑1, respectively. The q m and K f values obtained in the present study were found to be far better than those reported in the literature. The negative values of ΔG confirm the feasibility of an adsorption process at higher temperatures. The positive values of ΔH and ΔS represent the endothermic and physical nature of the adsorption process with the increased randomness of Cd2+ ions at the solid/solution interface.

  18. Bounding Limitations in the Practical Design of Adsorption Heat Pump Water Heaters

    SciTech Connect

    Ally, Moonis Raza; Sharma, Vishaldeep; Gluesenkamp, Kyle R

    2016-01-01

    The boundary temperatures for any sorption-based technology can be estimated on the basis of Trouton s hypothesis that isosteres, extrapolated to infinite pressure (or analogously to infinite temperature) meet at a single point. In this paper we discuss the consequences of this hypothesis for many sorption devices that are thermally operated, suitable for exploiting renewable energy resources, or making better use of high or low level thermal energy. Trouton s hypothesis is independent of the working fluids making it particularly useful to both liquid-vapor and solid-vapor systems. We exemplify the use of the derived boundary temperatures derived from Trouton s hypothesis to important processes such as ice making, space cooling in hot climates, deep freezing, and residential hot water production. The boundary temperatures help determine which sorption or solar heating technology may be better suited to serve the given application, or whether it is beyond the scope of sorption systems.

  19. Equilibrium and Heat of Adsorption for Organic Vapors and Activated Carbons

    DTIC Science & Technology

    2005-05-01

    Technol. 2005, 39, 5864-5871 5864 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 15, 2005 10.1021/es048144r CCC: $30.25  2005 American Chemical...0.654 VOL. 39, NO. 15, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 5865 have due to the drag force on the sample pan. In addition, the N2 flow prevented...results are provided as lines. 5866 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 15, 2005 Increasing the adsorption temperature from 20 to 60 °C

  20. Magnetic carbon composites with a hierarchical structure for adsorption of tetracycline, prepared from sugarcane bagasse via hydrothermal carbonization coupled with simple heat treatment process.

    PubMed

    Rattanachueskul, Natthanan; Saning, Amonrada; Kaowphong, Sulawan; Chumha, Nawapong; Chuenchom, Laemthong

    2017-02-01

    Sugarcane bagasse, an agricultural waste, was successfully converted into novel magnetic carbon composites by low temperature hydrothermal carbonization at 230°C for 24h, followed by heat treatment at 400°C for only 1h in air. Effects of NaOH and iron loading on the chemical properties of the composites were studied. In addition, various techniques were employed to investigate the physicochemical properties of the composites. Adsorption kinetics and isotherms were investigated with tetracycline (TC) for the magnetic composites. The magnetic carbon composite exhibited 48.35mg/g maximum adsorption capacity and was highly stable chemically and mechanically, with also good magnetic properties. The adsorption of TC by the magnetic adsorbent was mainly attributed to H-bonds and π-π interactions. The results indicate that waste sugarcane bagasse from the sugar industries can be efficiently transformed to a magnetic adsorbent for TC removal via a facile environmentally friendly method.

  1. Improving the Performance of an Adsorption Heat Converter in Condensation and Evaporation of the Adsorbate in Sorbent Pores

    NASA Astrophysics Data System (ADS)

    Lyakh, M. Yu.; Rabinovich, O. S.; Vasiliev, L. L.; Tsitovich, A. P.

    2013-11-01

    The possibilities of raising the specific refrigerating capacity and the cooling temperature of an adsorption refrigerator through the phase transition of the adsorbate in low-temperature-sorbent pores have been investigated by the computer-modeling method. Using an adsorption refrigerator with busofite-based MnCl2 and BaCl2 sorbents (in the high-temperature and low-temperature adsorbers respectively) as an example, it has been shown that the operating regime of the refrigerator with adsorbate condensation and evaporation enables one to raise the specific capacity of the apparatus by 20% and to double the average cooling temperature.

  2. Differential heat of adsorption of water vapor on silicified microcrystalline cellulose (SMCC): an investigation using isothermal microcalorimetry.

    PubMed

    Qian, Ken K; Bogner, Robin H

    2011-01-01

    A novel dual-shaft configuration in isothermal microcalorimetry was developed to study the interaction of water vapor with pharmaceutical excipients. An instrument performance test is suggested to validate the experimental data. Reliable experimental results can be collected using a single perfusion shaft; however, there was limitation of the dual-shaft configuration, which resulted deviation in the experimental results. A periodic performance test is recommended. Silicified microcrystalline cellulose (SMCC) was used as a model system to study the interaction using the dual-shaft method. Enthalpy of water vapor adsorption on SMCC was determined and compared to literature data. The data collected using the dual-shaft configuration did not reflect the actual physical system. The deviation was most likely due to the lack of flow control caused by viscous resistance. The enthalpy of adsorption was then calculated using isothermal microcalorimetry coupled with a dynamic vapor sorption apparatus. The results, -55 kJ/mol at low relative humidity (RH) to -22 kJ/mol at high RH, were consistent with the physical phenomenon of water vapor adsorption. Enthalpy of adsorption showed surface heterogeneity of SMCC and suggested multilayer condensation of water at approximately 60% RH. However, at high RH, the results showed the moisture-excipient interaction can be more complex than the proposed mechanism.

  3. ADSORPTION OF OXYGEN BY HEAT-TREATED GRANULAR AND FIBROUS ACTIVATED CARBONS. (R828157)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  4. ADSORPTION OF OXYGEN BY HEAT-TREATED GRANULAR AND FIBROUS ACTIVATED CARBONS. (R828157)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  5. Adsorption and molecular heat exchange ion the gas-solid system

    SciTech Connect

    Borisov, S.F.; Balakhonov, N.F.; Zak, D.I.; Shestakov, A.M.; Shveikin, G.P.

    1987-03-01

    The purpose of this paper was to determine, in terms of the energy accomodation coefficient, the efficiency of energy exchange between rarefied gas molecules and atoms and an adsorptive surface coating during adsorption and heat transfer. To this end the authors investigated the contribution of adsorption to the energy accomodation coefficient of helium on the surface of tungsten at different temperatures and the dependence of this coefficient on temperature and kinetics using a quantum harmonic oscillator model and a thermal phonon approximation. Experimental data for purposes of verifying the model were obtained by mass and Auger electron spectroscopy.

  6. Part II: Quantum mechanical prediction of heats of adsorption for C2-C4 hydrocarbons in MOF-74-Mg/Zn periodic structures

    NASA Astrophysics Data System (ADS)

    Degaga, Gemechis D.; Valenzano, Loredana

    2017-08-01

    Periodic boundary condition models are used to investigate the interaction of small hydrocarbons (C2-C4) with MOF-74-Mg/Zn. In contrast to other studies where molecular cluster approaches are used, the complete chemical environment of the framework is included. This allows correcting the binding energies for basis-set superposition error, molecular lateral interaction, zero-point energy, and thermal contributions. As such, the presented results are directly comparable to experimental calorimetric values. This work discusses, for the first time, the origin of the fictitious agreement between binding energies obtained with molecular clusters and experimental heats of adsorption, identifying its origin as due to compensation of errors.

  7. Analysis of the adsorption process and of desiccant cooling systems: a pseudo- steady-state model for coupled heat and mass transfer. [DESSIM, DESSIM2, DESSIM4

    SciTech Connect

    Barlow, R.S.

    1982-12-01

    A computer model to simulate the adiabatic adsorption/desorption process is documented. Developed to predict the performance of desiccant cooling systems, the model has been validated through comparison with experimental data for single-blow adsorption and desorption. A literature review on adsorption analysis, detailed discussions of the adsorption process, and an initial assessment of the potential for performance improvement through advanced component development are included.

  8. Adsorption of oxygen on W/100/ - Adsorption kinetics and structure

    NASA Technical Reports Server (NTRS)

    Bauer, E.; Poppa, H.; Viswanath, Y.

    1976-01-01

    The adsorption of oxygen on W(100) single-crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED), and retarding-field work-function measurements. The AES results reveal stepwise changes in the sticking coefficients in the coverage range 0 to 1 and activated adsorption at higher coverages. Upon room-temperature adsorption, a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the p(2 x 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room-temperature adsorbates changes their structure irreversibly. At temperatures below 750 K, some new structures are observed.

  9. Adsorption of oxygen on W/100/ - Adsorption kinetics and structure

    NASA Technical Reports Server (NTRS)

    Bauer, E.; Poppa, H.; Viswanath, Y.

    1976-01-01

    The adsorption of oxygen on W(100) single-crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED), and retarding-field work-function measurements. The AES results reveal stepwise changes in the sticking coefficients in the coverage range 0 to 1 and activated adsorption at higher coverages. Upon room-temperature adsorption, a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the p(2 x 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room-temperature adsorbates changes their structure irreversibly. At temperatures below 750 K, some new structures are observed.

  10. Henry constant and isosteric heat at zero-loading for gas adsorption in carbon nanotubes.

    PubMed

    Do, D D; Do, H D; Wongkoblap, A; Nicholson, D

    2008-12-28

    The Henry constant and the isosteric heat of adsorption at zero loading in a carbon nanotube bundle are studied with Monte Carlo integration for the adsorption of gases over a range of temperatures. The spacing between nanotubes in a bundle is determined from the minimization of potential energy of interaction between these tubes. We study different tube configurations with bundles of 2, 3, 4 and 7 tubes. Depending on the configuration it is found that the spacing is of between 0.31 to 0.333 nm, and this falls within the range reported in the literature. The Henry constant has been carefully defined so that it will not become negative at high temperatures. This is done with the aid of accessible volume, rather than the usual absolute void volume. We show that linearity of the van't Hoff plot for the Henry constant is not strictly followed. Furthermore the slope of this plot is not equal to the isosteric heat of adsorption at zero loading, which is found to be a strong function of temperature. From the results we find that the Henry constant and the heat of adsorption depend on the tube configuration. In general the adsorption in the cusp interstices is strongest followed by that inside the tube and finally on the outer surface. However for very small tubes adsorption occurs inside the tube first. For molecules with orientation, the behaviour is even more interesting and the shape of the isosteric heat versus temperature depends on the degree of orientation, tube configuration and the domain of adsorption (interstices, inside the tube and on the outer surface).

  11. On the Henry constant and isosteric heat at zero loading in gas phase adsorption.

    PubMed

    Do, D D; Nicholson, D; Do, H D

    2008-08-01

    The Henry constant and the isosteric heat of adsorption at zero loading are commonly used as indicators of the strength of the affinity of an adsorbate for a solid adsorbent. It is assumed that (i) they are observable in practice, (ii) the Van Hoff's plot of the logarithm of the Henry constant versus the inverse of temperature is always linear and the slope is equal to the heat of adsorption, and (iii) the isosteric heat of adsorption at zero loading is either constant or weakly dependent on temperature. We show in this paper that none of these three points is necessarily correct, first because these variables might not be observable since they are outside the range of measurability; second that the linearity of the Van Hoff plot breaks down at very high temperature, and third that the isosteric heat versus loading is a strong function of temperature. We demonstrate these points using Monte Carlo integration and Monte Carlo simulation of adsorption of various gases on a graphite surface. Another issue concerning the Henry constant is related to the way the adsorption excess is defined. The most commonly used equation is the one that assumes that the void volume is the volume extended all the way to a boundary passing through the centres of the outermost solid atoms. With this definition the Henry constant can become negative at high temperatures. Although adsorption at these temperatures may not be practical because of the very low value of the Henry constant, it is more useful to define the Henry constant in such a way that it is always positive at all temperatures. Here we propose the use of the accessible volume; the volume probed by the adsorbate when it is in nonpositive regions of the potential, to calculate the Henry constant.

  12. Effect of Heat Treatment on the Nitrogen Content and Its Role on the Carbon Dioxide Adsorption Capacity of Highly Ordered Mesoporous Carbon Nitride.

    PubMed

    Lakhi, Kripal S; Park, Dae-Hwan; Joseph, Stalin; Talapaneni, Siddulu N; Ravon, Ugo; Al-Bahily, Khalid; Vinu, Ajayan

    2017-03-02

    Mesoporous carbon nitrides (MCNs) with rod-shaped morphology and tunable nitrogen contents have been synthesized through a calcination-free method by using ethanol-washed mesoporous SBA-15 as templates at different carbonization temperatures. Carbon tetrachloride and ethylenediamine were used as the sources of carbon and nitrogen, respectively. The resulting MCN materials were characterized with low- and high-angle powder XRD, nitrogen adsorption, high-resolution (HR) SEM, HR-TEM, elemental analysis, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure techniques. The carbonization temperature plays a critical role in controlling not only the crystallinity, but also the nitrogen content and textural parameters of the samples, including specific surface area and specific pore volume. The nitrogen content of MCN decreases with a concomitant increase in specific surface area and specific pore volume, as well as the crystallinity of the samples, as the carbonization temperature is increased. The results also reveal that the structural order of the materials is retained, even after heat treatment at temperatures up to 900 °C with a significant reduction of the nitrogen content, but the structure is partially damaged at 1000 °C. The carbon dioxide adsorption capacity of these materials is not only dependent on the textural parameters, but also on the nitrogen content. The MCN prepared at 900 °C, which has an optimum BET surface area and nitrogen content, registers a carbon dioxide adsorption capacity of 20.1 mmol g(-1) at 273 K and 30 bar, which is much higher than that of mesoporous silica, MCN-1, activated carbon, and multiwalled carbon nanotubes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Effects of aging and heat treatment on whole yeast cells and yeast cell walls and on adsorption of ochratoxin A in a wine model system.

    PubMed

    Nunez, Y P; Pueyo, E; Carrascosa, A V; Martínez-Rodríguez, A J

    2008-07-01

    A wine model was evaluated to determine the influence of aging on the ability of whole yeast cells (WY) and yeast cell walls (YCW) to remove ochratoxin A (OTA). Aging and autolysis were monitored for 214 h in the model wine. The original concentration of OTA in the model wine was 10 microg/liter, and WY and YCW were added at a final concentration of 1 g/liter. YCW mannoproteins were involved in the removal of OTA from the model wine through adsorption mechanisms. Aging affected the capacity of WY to remove OTA, but YCW removal capacity remained constant during aging. A previous heat treatment (85 degrees C for 10 min) of WY and YCW increased their removal capacity and increased the efficiency of the decontamination process.

  14. Adsorption of xenon and krypton on shales

    NASA Technical Reports Server (NTRS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    1981-01-01

    A method that uses a mass spectrometer as a manometer is employed in the measurement of Xe and Kr adsorption parameters on shales and related samples, where gas partial pressures were lower than 10 to the -11th atm, corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Results show heats of adsorption in the 2-7 kcal/mol range, and Henry constants at 0-25 C of 1 cu cm STP/g per atmosphere are extrapolated. Although the adsorption properties obtained are variable by sample, the range obtained suggests that shales may be capable of an equilibrium adsorption with modern air high enough to account for a significant fraction of the atmospheric inventory of Xe, and perhaps even of Kr. This effect will nevertheless not account for the factor-of-25 defficiency of atmospheric Xe, in comparison with the planetary gas patterns observed in meteorites.

  15. Adsorption of xenon and krypton on shales

    NASA Technical Reports Server (NTRS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    1981-01-01

    A method that uses a mass spectrometer as a manometer is employed in the measurement of Xe and Kr adsorption parameters on shales and related samples, where gas partial pressures were lower than 10 to the -11th atm, corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Results show heats of adsorption in the 2-7 kcal/mol range, and Henry constants at 0-25 C of 1 cu cm STP/g per atmosphere are extrapolated. Although the adsorption properties obtained are variable by sample, the range obtained suggests that shales may be capable of an equilibrium adsorption with modern air high enough to account for a significant fraction of the atmospheric inventory of Xe, and perhaps even of Kr. This effect will nevertheless not account for the factor-of-25 defficiency of atmospheric Xe, in comparison with the planetary gas patterns observed in meteorites.

  16. Control synthesis of PbS-TiO₂ hollow hybrid structures through ion adsorption-heating progress and their photocatalytic activity.

    PubMed

    Xia, Hongbo; Wu, Suli; Zhang, Shufen

    2017-08-31

    Hollow hybrid nanostructure has received significant attention because of its unique structural features. This study reports a facile "ion adsorption-heating" method to fabricate PbS-TiO₂ hybrid hollow particles. In this method, the TiO₂ spheres used as substrate material to grow PbS are aggregates of many small amorphous TiO₂ particles, and each of the small particles is covered by thioglycollic acid ligands through Ti4+-carboxyl coordination. When the Pb2+ ions were added into the TiO₂ spheres colloidal solution, these ions can be adsorbed by sulfydryl (-SH) groups to form metal thiolate, and the C-S bond will be dissociated by heating to release S2-. Then, the S2- will react with Pb2+ ions to form PbS without additives as sulfur sources. Meanwhile, the amorphous TiO₂ spheres were transformed into anatase phase during the heating process. As a result, the crystallization of TiO₂ spheres along with the formation of PbS was simultaneously carried out by heating. During the heating process, owing to the Kirkendall effect of S2- diffusion and Ostwald ripening effect of the crystallization of amorphous TiO₂ spheres, PbS-TiO₂ hollow hybrid structure can be obtained. The XRD and XPS characterizations proved the formation of anatase TiO₂ and PbS. The characterization of TEM confirmed the formation of the hollow structure of PbS-TiO₂ hybrid sample. The photocatalytic activity of the PbS-TiO₂ hollow hybrid spheres have been investigated by the degradation of Cr6+ under visible light. The results show that PbS-TiO₂ hollow hybrid spheres exhibited highest photocatalytic activity, in which almost all the Cr6+ were degraded after 140 min. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Thermodynamic features of dioxins' adsorption.

    PubMed

    Prisciandaro, Marina; Piemonte, Vincenzo; di Celso, Giuseppe Mazziotti; Ronconi, Silvia; Capocelli, Mauro

    2017-02-15

    In this paper, the six more poisonous species among all congeners of dioxin group are taken into account, and the P-T diagram for each of them is developed. Starting from the knowledge of vapour tensions and thermodynamic parameters, the theoretical adsorption isotherms are calculated according to the Langmuir's model. In particular, the Langmuir isotherm parameters (K and wmax) have been validated through the estimation of the adsorption heat (ΔHads), which varies in the range 20-24kJ/mol, in agreement with literature values. This result will allow to put the thermodynamical basis for a rational design of different process units devoted to dioxins removal. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. A feasible way to remove the heat during adsorptive methane storage.

    PubMed

    Gütlein, Stefan; Burkard, Christoph; Zeilinger, Johannes; Niedermaier, Matthias; Klumpp, Michael; Kolb, Veronika; Jess, Andreas; Etzold, Bastian J M

    2015-01-06

    Methane originating from biogas or natural gas is an attractive and environmentally friendly alternative to gasoline. Adsorption is seen as promising storage technology, but the heat released limits fast filling of these systems. Here a lab scale adsorptive methane storage tank, capable to study the temperature increase during fast filling, was realized. A variation of the filling time from 1 h to 31 s, showed a decrease of the storage capacity of 14% and temperature increase of 39.6 °C. The experimental data could be described in good accordance with a finite element simulation solving the transient mass, energy, and impulse balance. The simulation was further used to extrapolate temperature development in real sized car tanks and for different heat pipe scenarios, resulting in temperature rises of approximately 110 °C. It could be clearly shown, that with heat conductivity as solei mechanism the heat cannot be removed in acceptable time. By adding an outlet to the tank a feed flow cooling with methane as heat carrier was realized. This setup was proofed in simulation and lab scale experiments to be a promising technique for fast adsorbent cooling and can be crucial to leverage the full potential of adsorptive methane gas storage.

  19. Adsorption of star polymers

    NASA Astrophysics Data System (ADS)

    Halperin, A.; Joanny, J. F.

    1991-06-01

    The adsorption of star polymers on a flat solid surface is analyzed by means of scalling arguments based on the Daoud-Cotton blob model. For the adsorption of a single star, consisting of f arms comprising each N monomers, we distinguish three regimes determined by the adsorption energy of a monomer at the surface, δ kT. 1) Strong adsorption characterized by the full adsorption of all arms occurs for δ > (f/N)^{3/5}. 2) A “Sombrero” like structure comprising f_ads fully adsorbed arms and f{-}f_ads free arms is obtained for (f/N)^{3/5}> δ > f^{9/20}/N^{3/5}. 3) Weakly adsorbed stars retain, essentially, the structure of a free star. This regime occurs for δ < f^{9/20}/N^{3/5}. The weakly adsorbed structure may also exist as a metastable state if δ > f^{9/5}/N^{3/5}. Nous étudions l'adsorption de polymères en étoile sur une surface solide en utilisant une approche de lois d'échelles basée sur le modèle de blobs de Daoud et Cotton. Pour une étoile formée de f bras contenant chacun N monomères, nous distinguons trois régimes suivant la valeur de l'énergie d'adsorption d'un monomère sur la surface δ kT. 1) L'adsorption forte caractérisée par une adsorption complète de tous les bras se produit lorsque δ > (f/N)^{3/5}. 2) Une structure en “sombrero” avec f_ads bras adsorbés et f{-}f_ads bras libres est obtenue si f^{9/20}/N^{3/5}δ < (f/N)^{3/5}. 3) Les étoiles faiblement adsorbées gardent une structure très similaire à celle des étoiles libres en solution. Ce régime existe si δ < f^{9/20}/N^{3/5}. La structure correspondant aux étoiles faiblement adsorbées peut aussi exister comme un état métastable si δ > f^{9/5}/N^{3/5}.

  20. Parametric study of a silica gel-water adsorption refrigeration cycle -- The influence of thermal capacitance and heat exchanger UA-values on cooling capacity, power density, and COP

    SciTech Connect

    Boelman, E.C.; Saha, B.B.; Kashiwagi, Takao

    1997-12-31

    The influence of heat exchanger UA-values (adsorber/desorber, evaporator, and condenser) is investigated for an adsorption chiller, with consideration given to the thermal capacitance of the adsorber/desorber by means of a lumped-parameter cycle simulation model developed by the authors and co-workers for the single-stage silica gel-water adsorption chiller. The closed-cycle-type chiller, for use in air conditioning, is driven by low-grade waste heat (85 C [185 F]) and cooled by water at 31 C (88 F) and operates on relatively short cycle times (420 seconds adsorption/desorption; 30 second adsorber/desorber sensible cooling and heating). The results showed cycle performance to be considerably affected by the thermal capacitance and UA-value of the adsorber/desorber, which is attributed to the severe sensible cooling/heating requirements resulting from batched cycle operation. The model is also sensitive to the evaporator UA-value--but to a lesser extent. The condenser UA-value is the least sensitive parameter due to the working pair adsorption behavior in the temperature range defined for desorption and condensation.

  1. Adsorption Behavior of Nonplanar Phthalocyanines: Competition of Different Adsorption Conformations

    PubMed Central

    2016-01-01

    Using density functional theory augmented with state-of-the-art van der Waals corrections, we studied the geometric and electronic properties of nonplanar chlorogallium-phthalocyanine GaClPc molecules adsorbed on Cu(111). Comparing these results with published experimental data for adsorption heights, we found indications for breaking of the metal–halogen bond when the molecule is heated during or after the deposition process. Interestingly, the work-function change induced by this dissociated geometry is the same as that computed for an intact adsorbate layer in the “Cl-down” configuration, with both agreeing well with the experimental photoemission data. This is unexpected, as the chemical natures of the adsorbates and the adsorption distances are markedly different in the two cases. The observation is explained as a consequence of Fermi-level pinning due to fractional charge transfer at the interface. Our results show that rationalizing the adsorption configurations on the basis of electronic interface properties alone can be ambiguous and that additional insight from dispersion-corrected DFT simulations is desirable. PMID:27066160

  2. Adsorption Behavior of Nonplanar Phthalocyanines: Competition of Different Adsorption Conformations.

    PubMed

    Wruss, Elisabeth; Hofmann, Oliver T; Egger, David A; Verwüster, Elisabeth; Gerlach, Alexander; Schreiber, Frank; Zojer, Egbert

    2016-03-31

    Using density functional theory augmented with state-of-the-art van der Waals corrections, we studied the geometric and electronic properties of nonplanar chlorogallium-phthalocyanine GaClPc molecules adsorbed on Cu(111). Comparing these results with published experimental data for adsorption heights, we found indications for breaking of the metal-halogen bond when the molecule is heated during or after the deposition process. Interestingly, the work-function change induced by this dissociated geometry is the same as that computed for an intact adsorbate layer in the "Cl-down" configuration, with both agreeing well with the experimental photoemission data. This is unexpected, as the chemical natures of the adsorbates and the adsorption distances are markedly different in the two cases. The observation is explained as a consequence of Fermi-level pinning due to fractional charge transfer at the interface. Our results show that rationalizing the adsorption configurations on the basis of electronic interface properties alone can be ambiguous and that additional insight from dispersion-corrected DFT simulations is desirable.

  3. Pore with gate: enhancement of the isosteric heat of adsorption of dihydrogen via postsynthetic cation exchange in metal-organic frameworks.

    PubMed

    Yang, Sihai; Martin, Gregory S B; Titman, Jeremy J; Blake, Alexander J; Allan, David R; Champness, Neil R; Schröder, Martin

    2011-10-03

    Three isostructural anionic frameworks {[(Hdma)(H(3)O)][In(2)(L(1))(2)]·4DMF·5H(2)O}(∞) (NOTT-206-solv), {[H(2)ppz][In(2)(L(2))(2)]·3.5DMF·5H(2)O}(∞) (NOTT-200-solv), and {[H(2)ppz][In(2)(L(3))(2)]·4DMF·5.5H(2)O}(∞) (NOTT-208-solv) (dma = dimethylamine; ppz = piperazine) each featuring organic countercations that selectively block the channels and act as pore gates have been prepared. The organic cations within the as-synthesized frameworks can be replaced by Li(+) ions to yield the corresponding Li(+)-containing frameworks {Li(1.2)(H(3)O)(0.8)[In(2)(L(1))(2)]·14H(2)O}(∞) (NOTT-207-solv), {Li(1.5)(H(3)O)(0.5)[In(2)(L(2))(2)]·11H(2)O}(∞) (NOTT-201-solv), and {Li(1.4)(H(3)O)(0.6)[In(2)(L(3))(2)]·4acetone·11H(2)O}(∞) (NOTT-209-solv) in which the pores are now unblocked. The desolvated framework materials NOTT-200a, NOTT-206a, and NOTT-208a display nonporous, hysteretic and reversible N(2) uptakes, respectively, while NOTT-206a and NOTT-200a provide a strong kinetic trap showing adsorption/desorption hysteresis with H(2). Single crystal X-ray analysis confirms that the Li(+) ions are either tetrahedrally (in NOTT-201-solv and NOTT-209-solv) or octahedrally (in NOTT-207-solv) coordinated by carboxylate oxygen atoms and/or water molecules. This is supported by (7)Li solid-state NMR spectroscopy. NOTT-209a, compared with NOTT-208a, shows a 31% enhancement in H(2) storage capacity coupled to a 38% increase in the isosteric heat of adsorption to 12 kJ/mol at zero coverage. Thus, by modulating the pore environment via postsynthetic cation exchange, the gas adsorption properties of the resultant MOF can be fine-tuned. This affords a methodology for the development of high capacity storage materials that may operate at more ambient temperatures.

  4. Adsorption of water vapor by poly(styrenesulfonic acid), sodium salt: isothermal and isobaric adsorption equilibria.

    PubMed

    Toribio, F; Bellat, J P; Nguyen, P H; Dupont, M

    2004-12-15

    Air conditioning and dehumidifying systems based on sorption on solids are of great interest, especially in humid climates, because they allow reduction of thermal loads and use of chlorofluorocarbons. Previous studies have shown that hydrophilic polymers such as sulfonic polymers can have very high performance in water adsorption from air. The aim of this study was to characterize the water vapor adsorption properties of fully sulfonated and monosulfonated poly(styrenesulfonic acid), sodium salt, and to elucidate the mechanism of adsorption on these materials. Adsorption isotherms have been determined by TGA between 298 and 317 K for pressures ranging from 0.1 to 45 hPa. They have type II of the IUPAC classification and a small hysteresis loop between adsorption and desorption processes was observed only for the monosulfonated sample. Water content is up to 80% weight at 80% relative humidity. Adsorption isotherms have been well fitted with the FHH model. Adsorption-desorption isobars have been determined by TGA under 37 hPa in the temperature range 298-373 K. They show that these polymers can be completely regenerated by heating at 313 K under humidified air. No degradation of the adsorption properties has been observed after several regenerations. Adsorption enthalpies and entropies have been deduced from the Clapeyron equation and from DSC measurements. A good agreement was found. A mechanism of adsorption is proposed considering two kinds of adsorbate: bounded water in electrostatic interaction with functional groups and free water resulting from condensation.

  5. Analysis of the use of adsorption processes in trigeneration systems

    NASA Astrophysics Data System (ADS)

    Grzebielec, Andrzej; Rusowicz, Artur

    2013-12-01

    The trigeneration systems for production of cold use sorption refrigeration machines: absorption and adsorption types. Absorption systems are characterized namely by better cooling coefficient of performance, while the adsorptive systems are characterized by the ability to operate at lower temperatures. The driving heat source temperature can be as low as 60-70 °C. Such temperature of the driving heat source allows to use them in district heating systems. The article focuses on the presentation of the research results on the adsorption devices designed to work in trigeneration systems.

  6. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  7. Adsorption of selected volatile organic vapors on multiwall carbon nanotubes.

    PubMed

    Shih, Yang-hsin; Li, Mei-syue

    2008-06-15

    Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. This study examines the adsorption behaviors of volatile organic compounds (VOCs), n-hexane, benzene, trichloroethylene and acetone on two multiwall carbon nanotubes (MWCNTs), CNT1 and CNT2. Among these VOCs, acetone exhibits the highest adsorption capacity. The highest adsorption enthalpies and desorption energies of acetone were also observed. The strong chemical interactions between acetone and both MWCNTs may be the result from chemisorption on the topological defects. The adsorption heats of trichloroethylene, benzene, and n-hexane are indicative of physisorption on the surfaces of both MWCNTs. CNT2 presents a higher adsorption capacity than CNT1 due to the existence of an exterior amorphous carbon layer on CNT2. The amorphous carbon enhances the adsorption capacity of organic chemicals on carbon nanotubes. The morphological and structure order of carbon nanotubes are the primary affects on the adsorption process of organic chemicals.

  8. Adsorption of Gases on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mbaye, Mamadou Thiao

    2014-01-01

    This research focus in studying the interaction between various classical and quantum gases with novel carbon nanostructures, mainly carbon nanotubes (CNTs). Since their discovery by the Japanese physicist Sumio Iijima [1] carbon nanotubes have, experimentally and theoretically, been subjected to many scientific investigation. Studies of adsorption on CNTs are particularly directed toward their better usage in gas storage, gas separation, catalyst, drug delivery, and water purification. We explore the adsorption of different gases entrapped in a single, double, or multi-bundles of CNTs using computer simulations. The first system we investigate consists of Ar and Kr films adsorbed on zigzag or armchair nanotubes. Our simulations revealed that Kr atoms on intermediate size zigzag NTs undergo two phase transitions: A liquid-vapor (L→V), and liquid-commensurate (L→CS) with a fractional coverage of one Kr atoms adsorbed for every four carbon atoms. For Ar on zigzag and armchair NTs, the only transition observed is a L→V. In the second problem, we explore the adsorption of CO2 molecules in a nanotube bundle and calculate the isosteric heat of adsorption of the entrapped molecules within the groove. We observed that the lower the temperature, the higher the isosteric of adsorption. Last, we investigate the adsorption of hydrogen, Helium, and Neon gases on the groove site of two parallel nanotubes. At low temperature, the transverse motion on the plane perpendicular to the tubes' axis is frozen out and as a consequence, the heat capacity is reduced to 1/2. At high temperature, the atoms gain more degree of freedom and as a consequence the heat capacity is 5/2.

  9. Adsorption analysis of ammonia in an aqueous solution

    SciTech Connect

    Arman, B.; Panchal, C.B.

    1993-08-01

    An analysis is carried out to determine the effects of the diffusional resistance on the rate of the adsorption of ammonia in an aqueous solution. A performance prediction model is developed to calculate the local rate of heat and mass transfer, including physical and thermodynamic property calculations of the mixture. An algorithm is developed for calculating the interfacial conditions. The local heat- and mass-transfer calculation is then incorporated into the performance prediction method for adsorption for a given geometry.

  10. Preparation of tamarind fruit seed activated carbon by microwave heating for the adsorptive treatment of landfill leachate: A laboratory column evaluation.

    PubMed

    Foo, K Y; Lee, L K; Hameed, B H

    2013-04-01

    The preparation of tamarind fruit seed granular activated carbon (TSAC) by microwave induced chemical activation for the adsorptive treatment of semi-aerobic landfill leachate has been attempted. The chemical and physical properties of TSAC were examined. A series of column tests were performed to determine the breakthrough characteristics, by varying the operational parameters, hydraulic loading rate (5-20 mL/min) and adsorbent bed height (15-21 cm). Ammonical nitrogen and chemical oxygen demand (COD), which provide a prerequisite insight into the prediction of leachate quality was quantified. Results illustrated an encouraging performance for the adsorptive removal of ammonical nitrogen and COD, with the highest bed capacity of 84.69 and 55.09 mg/g respectively, at the hydraulic loading rate of 5 mL/min and adsorbent bed height of 21 cm. The dynamic adsorption behavior was satisfactory described by the Thomas and Yoon-Nelson models. The findings demonstrated the applicability of TSAC for the adsorptive treatment of landfill leachate.

  11. Kinetics of a gas adsorption compressor

    NASA Technical Reports Server (NTRS)

    Chan, C. K.; Tward, E.; Elleman, D. D.

    1984-01-01

    Chan (1981) has suggested that a process based on gas adsorption could be used as a means to drive a Joule-Thomson (J-T) device. The resulting system has several advantages. It is heat powered, it has no sealing, there are no mechanical moving parts, and no active control is required. In the present investigation, a two-phase model is used to analyze the transients of a gas adsorption compressor. The modeling of the adsorption process is based on a consideration of complete thermal and mechanical equilibrium between the gaseous phase and the adsorbed gas phase. The experimental arrangement for two sets of kinetic tests is discussed, and data regarding the experimental results are presented in graphs. For a theoretical study, a two-phase model was developed to predict the transient behavior of the compressor. A computer code was written to solve the governing equations with the aid of a standard forward marching predictor-corrector method.

  12. Kinetics and mechanism of dye adsorption on WO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Adhikari, Sangeeta; Mandal, Sandip; Sarkar, Debasish; Kim, Do-Heyoung; Madras, Giridhar

    2017-10-01

    Monoclinic WO3 nanoparticles were synthesized by a simple acid catalyzed co-precipitation reaction. Spherical particles with average size ∼55 nm were confirmed from electron microscopy followed by functional, structural and optical characterizations. The adsorption of methylene blue was examined by using WO3 nanoparticles and the capacity was higher than most of the reported studies. The effect of pH and material loading on adsorption was determined. The mechanism of adsorption was examined by XPS and a detailed explanation of surface phenomena was proposed. Regeneration study was carried and a high stability of heat treated WO3 towards adsorption of methylene blue was observed.

  13. Microcalorimetry of oxygen adsorption on fcc Co{110}.

    PubMed

    Liao, Kristine; Fiorin, Vittorio; Jenkins, Stephen J; King, David A

    2012-05-28

    The coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage. The initial heat of adsorption of 633 kJ mol(-1) is similar to heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. As the coverage increases, the heat of adsorption and sticking probability drop very rapidly up to the onset of oxidation. As already observed for other oxygen-metal surface systems, strong lateral adatom repulsions are responsible for the transition from the chemisorption regime to oxide film formation at higher coverage. The heat of oxide formation at the onset is 475 kJ mol(-1), which is consistent with the formation of CoO crystallites. The oxide film formation is discussed in terms of nucleation and island growth, and the Mott-Cabrera mechanisms, the latter being evidenced by the relatively constant heat of adsorption and sticking probability in contrast to the nickel and iron oxidation cases.

  14. NOM removal by adsorption and membrane filtration using heated aluminum oxide particles.

    PubMed

    Cai, Zhenxiao; Kim, Jaeshin; Benjamin, Mark M

    2008-01-15

    Heated aluminum oxide particles (HAOPs) are a newly synthesized adsorbent with attractive properties for use in hybrid adsorption/membrane filtration systems. This study compared removal of natural organic matter (NOM) from water by adsorption onto HAOPs with that by adsorption onto powdered activated carbon (PAC) or coagulation with alum or ferric chloride (FeCl3); explored the overlap between the NOM molecules that preferentially adsorb to HAOPs and those that are removed by the more conventional approaches; and evaluated NOM removal and fouling in hybrid adsorbent/membrane systems. For equivalent molar doses of the trivalent metals, HAOPs remove more NOM, and NOM with higher SUVA254, than alum or FeCl3. Most of the HAOPs-nonadsorbable fraction of the NOM can be adsorbed by PAC; in fact, that fraction appears to be preferentially adsorbed compared to the average NOM in untreated water. Predeposition of the adsorbents on a microfiltration membrane improves system performance. For the water tested, at a flux of 100 L/m2-hr, predeposition of 11 mg/L PAC and 5 mg/L HAOPs (as Al3+) allowed the system to operate 5 times as long before the transmembrane pressure increased by 1 psi and to remove 10-20 times as much NOM as when no adsorbents were added.

  15. Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

    NASA Astrophysics Data System (ADS)

    Lazarevic, Natasa; Adnadjevic, Borivoj; Jovanovic, Jelena

    2011-07-01

    The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.

  16. Metabolic Heat Regenerated Temperature Swing Adsorption for CO(sub 2) and Heat Removal/Rejection in a Martian PLSS

    NASA Technical Reports Server (NTRS)

    Iacomini, Christine; Powers, Aaron; Bowers, Chad; Straub-Lopez, Katie; Anderson, Grant; MacCallum, Taber; Paul, Heather

    2007-01-01

    Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of CO2 in an environment with a ppCO2 of 0.4-0.9 kPa. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address both these challenges. The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (195K) removes metabolically-produced CO2 in the vent loop. Once fully loaded, the adsorbent is then warmed externally by the vent loop (approx. 300K), rejecting the captured CO2 to Mars ambient. Two beds are used to effect a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the vent loop. Any cryogenic fluid can be used in the application; however, since CO2 is readily available at Mars and can be easily produced and stored on the Martian surface, the solution is rather elegant and less complicated when employing liquid CO2. As some metabolic heat will need to be rejected anyway, finding a practical use for metabolic heat is also an overall benefit to the PLSS. To investigate the feasibility of the technology, a series of experiments was conducted which lead to the selection and partial characterization of an appropriate adsorbent. The adsorbent NaX successfully removed CO2 from a simulated vent loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no show stoppers to the development of MTSA technology and allow its development to focus on other design challenges as listed in the conclusions.

  17. Metabolic Heat Regenerated Temperature Swing Adsorption for CO(sub 2) and Heat Removal/Rejection in a Martian PLSS

    NASA Technical Reports Server (NTRS)

    Iacomini, Christine; Powers, Aaron; Bowers, Chad; Straub-Lopez, Katie; Anderson, Grant; MacCallum, Taber; Paul, Heather

    2007-01-01

    Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of CO2 in an environment with a ppCO2 of 0.4-0.9 kPa. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address both these challenges. The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (195K) removes metabolically-produced CO2 in the vent loop. Once fully loaded, the adsorbent is then warmed externally by the vent loop (approx. 300K), rejecting the captured CO2 to Mars ambient. Two beds are used to effect a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the vent loop. Any cryogenic fluid can be used in the application; however, since CO2 is readily available at Mars and can be easily produced and stored on the Martian surface, the solution is rather elegant and less complicated when employing liquid CO2. As some metabolic heat will need to be rejected anyway, finding a practical use for metabolic heat is also an overall benefit to the PLSS. To investigate the feasibility of the technology, a series of experiments was conducted which lead to the selection and partial characterization of an appropriate adsorbent. The adsorbent NaX successfully removed CO2 from a simulated vent loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no show stoppers to the development of MTSA technology and allow its development to focus on other design challenges as listed in the conclusions.

  18. Water adsorption on goethite: Application of multilayer adsorption models

    NASA Astrophysics Data System (ADS)

    Hatch, C. D.; Tumminello, R.; Meredith, R.

    2016-12-01

    Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

  19. Dynamic adsorption of ammonia: apparatus, testing conditions, and adsorption capacities

    NASA Astrophysics Data System (ADS)

    Amid, Hooman; Mazé, Benoît; Flickinger, Michael C.; Pourdeyhimi, Behnam

    2017-04-01

    There is a growing need for adsorbents with high capacities for adsorption of toxic gas molecules. Methods and conditions to test these materials introduce large discrepancies and overestimates (~90%) in the reported literature. This study describes a simple apparatus utilizing hand-held inexpensive gas sensors for testing adsorbents and hybrid adsorbent materials, explains possible sources for the observed discrepancies based on how the measurements are made, and provides guidelines for accurate measurements of adsorption capacity. Ammonia was the model gas and Ammonasorb™ activated carbon was the model commercial adsorbent. Inlet ammonia concentration, residence time, adsorbent pre-treatment (baking) and humidity, affected the measured adsorption capacities. Results suggest that the time lag in gas detection sensors leads to overestimated capacities. Monitoring both inlet and outlet concentrations using two calibrated sensors solved this issue. There was a direct relationship between adsorption capacity and residence time and capacities were higher at higher inlet concentrations. The size of the adsorbent particles did not show a significant effect on adsorption breakthrough, and the apparatus was able to quantify how humidity reduced the adsorption capacity.

  20. Fractional statistical theory of adsorption of polyatomics.

    PubMed

    Riccardo, J L; Ramirez-Pastor, A J; Romá, F

    2004-10-29

    A new theoretical description of fractional statistical theory of adsorption (FSTA) phenomena is presented based on Haldane's statistics. Thermodynamic functions for adsorption of polyatomics are analytically developed. The entropy is characterized by an exclusion parameter g, which relates to the configuration of the admolecules and surface geometry. FSTA provides a simple framework to address a large class of complex adsorption systems. Comparisons of theoretical adsorption isotherms with experiments and simulations indicate that adsorption configuration and adsorption energy can accurately be assessed from this theory.

  1. Electrokinetic investigation of surfactant adsorption.

    PubMed

    Bellmann, C; Synytska, A; Caspari, A; Drechsler, A; Grundke, K

    2007-05-15

    Fuerstenau [D.W. Fuerstenau, in: M.L. Hair (Ed.), Dekker, New York, 1971, p. 143] has already discussed the role of hydrocarbon chain of surfactants, the effect of alkyl chain length, chain structure and the pH of the solution on the adsorption process of surfactants. Later Kosmulski [M. Kosmulski, Chemical Properties of Material Surfaces, Surfactant Science Series, vol. 102, Dekker, New York, Basel, 2001] included the effect of surfactant concentration, equilibration time, temperature and electrolyte in his approaches. Certainly, the character of the head groups of the surfactant and the properties of the adsorbent surface are the basis for the adsorption process. Different surfactants and adsorbents cause different adsorption mechanisms described firstly by Rosen [M.J. Rosen, Surfactants and Interfacial Phenomena, second ed., Wiley, New York, 1989]. These adsorption mechanisms and their influencing factors were studied by electrokinetic investigations. Here only changes of the charges at the surfaces could be detected. To control the results of electrokinetic investigations they were compared with results from ellipsometric measurements. In the case of surfactant adsorption the chain length was vitally important. It could be shown by the adsorption of alkyl trimethyl ammonium bromides onto polymer films spin coated at wafer surfaces. The influence of the chain length depending on surface properties of the polymer film was studied. Streaming potential measurements were applied for these investigations. The obtained results enabled us to calculate the molar cohesive free energy per mol of CH2-group in the alkaline chain of the surfactant if all other specific adsorption effects were neglected.

  2. Adsorption of citric acid from dilute aqueous solutions by hydroxyapatite.

    PubMed

    Vega, Enrique D; Narda, Griselda E; Ferretti, Ferdinando H

    2003-12-01

    The role of citric acid in the demineralization of dental enamel, which is mainly constituted by hydroxyapatite, is important for periodontal regeneration and in the conditioning of enamel or dentin for bonding restorative resins. The adsorption of citric acid from aqueous solutions onto synthetic hydroxyapatite at 278, 288, 298, and 308 K and pH 4.8 has been studied by means of UV spectroscopy. The adsorption reaction, which takes place by an interaction between phosphate groups and citrate anions at the solid-solution interface, yields an adsorbate-adsorbent complex of high stability. The adsorption isotherms fit the Langmuirian shape. The proposed adsorption model, where citrate species interact in a bidentate manner (one citrate ion links two phosphate sites), is coherent with the experimental data. The activation standard heat and activation standard entropy were calculated. All the thermodynamic and kinetic parameters were in concordance with the adsorption reaction proposed in this work.

  3. Adsorption of organic vapors on polar surfaces- Recent advances.

    PubMed

    Goss, K U

    1994-01-01

    This paper summarizes recent research on the adsorption of organic vapors on surfaces. Since the low gas phase concentration range is typical for environmental situations, this review is restricted to these adsorption coefficients.Two environmental parameters have a strong influence on the adsorption of organic vapors on polar surfaces:temperature andrelative humidity (which is the most suitable parameter for describing the influence of ambient moisture). An exponential relationship was found for the adsorption coefficientversus relative humidity and the reciprocal temperature, respectively. Comparing the heats of adsorption, two different groups of substances emerged: polar chemicals exhibited heats of sorption which were higher than their corresponding heats of condensation due to their ability to form hydrogen bonds, while for the nonpolar compounds the opposite was true. Sorption takes place on the surface of an adsorbed water film when the relative humidity exceeds the value which is necessary to form a monomolecular layer of water on the surface of the adsorbent (≥ 30 % relative humidity). Therefore, at temperature below 0 °C, a change in the adsorption behavior might be expected due to a change of properties of the adsorbed water film. However, no alterations were observed at temperatures from -12 °C to + 4 °C (adsorption on quartz sand). The results were comparable to those at much higher temperatures (50 - 80 °C).A statistical approach for the prediction of the adsorption coefficients from physico-chemical parameters of the substances (vapor pressure, polarizability, and electron-donating capability) was developed and good agreement was found with experimental results and independent data from the literature. Finally, two special cases, the adsorption on bulk water and ice, are discussed.

  4. Martian Liquid CO2 and Metabolic Heat Regenerated Temperature Swing Adsorption for Portable Life Support Systems

    NASA Astrophysics Data System (ADS)

    Iacomini, Christine; MacCallum, Taber; Morin, Tom; Straub-Lopez, Kathrine; Paul, Heather

    2007-01-01

    Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of CO2 in an environment with a ppCO2 of 0.4-0.9 kPa. This paper presents a conceptual system for CO2 collection, compression, and cooling to produce sub-critical (liquid) CO2. A first order estimate of the system mass and energy to condense and store liquid CO2 outside at Mars ambient temperature at 600 kPa is discussed. No serious technical hurdles were identified and it is likely that better overall performance would be achieved if the system were part of an integrated ISRU strategy rather than a standalone system. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology for CO2 removal from a PLSS vent loop, where the Martian liquid CO2 is used as the heat sink is developed to utilize the readily available liquid CO2. This paper will describe the technology and present data in support of its design.

  5. Adsorption and Gas Separation of Molecules by Carbon Nanohorns.

    PubMed

    Gatica, Silvina M; Nekhai, Anton; Scrivener, Adam

    2016-05-19

    In this paper, we report the results of Monte Carlo simulations of the adsorption of neon, argon, methane and carbon dioxide in carbon nanohorns. We model the nanohorns as an array of carbon cones and obtained adsorption isotherms and isosteric heats. The main sites of adsorption are inside the cones and in the interstices between three cones. We also calculated the selectivity of carbon dioxide/methane, finding that nanohorns are a suitable substrate for gas separation. Our simulations are compared to available experimental data.

  6. Adsorption of cadmium by sulphur dioxide treated activated carbon.

    PubMed

    Macías-García, A; Gómez-Serrano, V; Alexandre-Franco, M F; Valenzuela-Calahorro, C

    2003-10-01

    Merck carbon (1.5 mm) was treated in three ways: heating from ambient temperature to 900 degrees C in SO(2); treatment at ambient temperature in SO(2); or successive treatments in SO(2) and H(2)S at ambient temperature. All samples were then characterised and tested as adsorbents of Cd(2+) from aqueous solution. The characterisation was in terms of composition by effecting ultimate and proximate analyses and also of textural properties by N(2) adsorption at -196 degrees C. Kinetics and extent of the adsorption process of Cd(2+) were studied at 25 and 45 degrees C at pH of the Cd(2+) solution (i.e., 6.2) and at 25 degrees C also at pH 2.0. The various treatments of the starting carbon had no significant effect on the kinetics of the adsorption of Cd(2+), but increased its adsorption capacity. The most effective treatment was heating to 900 degrees C, the adsorption in this case being 70.3% more than that of the starting carbon. The adsorption increased at 45 degrees C but decreased at pH 2.0 when compared to adsorption at 25 degrees C and pH 6.2, respectively.

  7. Demonstration of a Solar Thermal Combined Heating, Cooling and Hot Water System Utilizing an Adsorption Chiller for DoD Installations

    DTIC Science & Technology

    2013-12-01

    PAGE U 83 19b. TELEPHONE NUMBER (include area code) 919-282-1050 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 ii...1.00 $ 8,370 changes to mechanical room specific to accommodating larger frame size of adsorption chiller Chiller $ 191,000...Outlet Chilled .. . ···1 4" 4" Condenser!-· _ _:6:,"-+_..:6:,"--1 Hot. ... .. . L----𔃾’-"_.....__4.;..’_’ ___, *All are ANSI f langed connections

  8. Adsorption isotherms of charged nanoparticles.

    PubMed

    Dos Santos, Alexandre P; Bakhshandeh, Amin; Diehl, Alexandre; Levin, Yan

    2016-10-19

    We present theory and simulations which allow us to quantitatively calculate the amount of surface adsorption excess of charged nanoparticles onto a charged surface. The theory is very accurate for weakly charged nanoparticles and can be used at physiological concentrations of salt. We have also developed an efficient simulation algorithm which can be used for dilute suspensions of nanoparticles of any charge, even at very large salt concentrations. With the help of the new simulation method, we are able to efficiently calculate the adsorption isotherms of highly charged nanoparticles in suspensions containing multivalent ions, for which there are no accurate theoretical methods available.

  9. Linear adsorption of nonionic organic compounds from water onto hydrophilic minerals: Silica and alumina

    USGS Publications Warehouse

    Su, Y.-H.; Zhu, Y.-G.; Sheng, G.; Chiou, C.T.

    2006-01-01

    To characterize the linear adsorption phenomena in aqueous nonionic organic solute-mineral systems, the adsorption isotherms of some low-molecular- weightnonpolar nonionic solutes (1,2,3-trichlorobenzene, lindane, phenanthrene, and pyrene) and polar nonionic solutes (1,3-dinitrobenzene and 2,4-dinitrotoluene) from single-and binary-solute solutions on hydrophilic silica and alumina were established. Toward this objective, the influences of temperature, ionic strength, and pH on adsorption were also determined. It is found that linear adsorption exhibits low exothermic heats and practically no adsorptive competition. The solute-solid configuration and the adsorptive force consistent with these effects were hypothesized. For nonpolar solutes, the adsorption occurs presumably by London (dispersion) forces onto a water film above the mineral surface. For polar solutes, the adsorption is also assisted by polar-group interactions. The reduced adsorptive forces of solutes with hydrophilic minerals due to physical separation by the water film and the low fractions of the water-film surface covered by solutes offer a theoretical basis for linear solute adsorption, low exothermic heats, and no adsorptive competition. The postulated adsorptive forces are supported by observations that ionic strength or pH poses no effect on the adsorption of nonpolar solutes while it exhibits a significant effect on the uptake of polar solutes. ?? 2006 American Chemical Society.

  10. Adsorption of Organics from Domestic Water Supplies.

    ERIC Educational Resources Information Center

    McGuire, Michael J.; Suffet, Irwin H.

    1978-01-01

    This article discusses the current state of the art of organics removal by adsorption. Various theoretical explanations of the adsorption process are given, along with practical results from laboratory, pilot-scale, and full-scale applications. (CS)

  11. Second law analysis of adsorption cycles with thermal regeneration

    SciTech Connect

    Pons, M.

    1996-09-01

    Adsorption processes can be used for operating environment-friendly refrigeration cycles. When combined with the thermal regeneration process, these cycles can have quite high performance. The second law analysis of the adsorption cycles with thermal regeneration is fully developed. The different heat transports between heat transfer fluid and adsorbent, between adsorbate and condenser/evaporator heat sources, and between heat transfer fluid and heat sources are analyzed. The entropy balance is then completely established. Consistency between the first law and second law analysis is verified by the numerical values of the entropy productions. The optimal operation of an adsorber is then described, and the study of those optimal conditions lead to some correlation between the different internal entropy productions.

  12. Metabolic Heat Regenerated Temperature Swing Adsorption for CO2 and Heat Removal/Rejection in a Martian PLSS

    NASA Technical Reports Server (NTRS)

    Iacomini, Christine; Powers, Aaron; Bower, Chad; Straub-Lopez, Kathrine; Anderson, Grant; MacCallum, Taber; Paul, Heather L.

    2007-01-01

    Two of the fundamental problems facing the development of a Portable Life Support System (PLSS) for use on Mars, are (i) heat rejection (because traditional technologies use sublimation of water, which wastes a scarce resource and contaminates the premises), and (ii) rejection of carbon dioxide (CO2) in an environment with a CO2 partial pressure (ppCO2) of 0.4-0.9 kPa. Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address both these challenges. The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (195K) removes metabolically-produced CO2 in the ventilation loop. Once fully loaded, the adsorbent is then warmed externally by the ventilation loop (300K), rejecting the captured CO2 to Mars ambient. Two beds are used to provide a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the ventilation loop. Any cryogenic fluid can be used in the application; however, since CO2 is readily available on Mars and can be easily produced and stored on the Martian surface, the solution is rather elegant and less complicated when employing liquid CO2. As some metabolic heat will need to be rejected anyway, finding a practical use for metabolic heat is also an overall benefit to the PLSS. To investigate the feasibility of the technology, a series of experiments were conducted which lead to the selection and partial characterization of an appropriate adsorbent. The Molsiv Adsorbents 13X 8x12 (also known as NaX zeolite) successfully removed CO2 from a simulated ventilation loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no show stoppers to the development of MTSA technology and allow its development to focus on other design

  13. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  14. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  15. Adsorption of pesticides on resins.

    PubMed

    Kyriakopoulos, Grigorios; Hourdakis, Adamadia; Doulia, Danae

    2003-03-01

    The objective of this work was to assess the capability of organic hydrophobic polymeric resins Amberlite XAD-4 and XAD-7 to remove the pesticides alachlor and amitrole from water. The pesticides adsorption on the two different adsorbents was measured by batch equilibrium technique and isotherm types and parameters were estimated. Two theoretical models were applied based on a Freundlich and a Langmuir isotherms. The effect of pesticides chemical composition and structure as well as the nature of solid surface on the efficiency of adsorption was evaluated. The influence of pH also was studied. In low pH solutions adsorption of amitrole was higher upon the nonionic aliphatic acrylic ester copolymer XAD-7 in comparison to the nonionic, crosslinked macroreticular copolymer of styrene divinylbenzene XAD-4. In neutral and intermediate pH solutions the polar acrylic ester copolymer XAD-7 was more effective to the retention of alachlor. The acrylic ester copolymer showed at pH 3 the lower effectiveness in alachlor removal from water. The data of the adsorption isotherms of pesticides upon the examined polymeric resins seemed to conform to both the Freundlich and the Langmuir isotherm models.

  16. High pressure adsorption isotherms of nitrogen onto granular activated carbon for a single bed pressure swing adsorption refrigeration system

    NASA Astrophysics Data System (ADS)

    Palodkar, Avinash V.; Anupam, Kumar; Roy, Zunipa; Saha, B. B.; Halder, G. N.

    2017-10-01

    Adsorption characteristics of nitrogen onto granular activated carbon for the wide range of temperature (303-323 K) and pressure (0.2027-2.0265 MPa) have been reported for a single bed pressure swing adsorption refrigeration system. The experimental data were fitted to Langmuir, Dubinin-Astakhov and Dubinin-Radushkevich (D-R) isotherms. The Langmuir and D-R isotherm models were found appropriate in correlating experimental adsorption data with an average relative error of ±2.0541% and ±0.6659% respectively. The isosteric heat of adsorption data were estimated as a function of surface coverage of nitrogen and temperature using D-R isotherm. The heat of adsorption was observed to decrease from 12.65 to 6.98 kJ.mol-1 with an increase in surface concentration at 303 K and it followed the same pattern for other temperatures. It was found that an increase in temperature enhances the magnitude of the heat of adsorption.

  17. Sub-ambient carbon dioxide adsorption properties of nitrogen doped graphene

    SciTech Connect

    Tamilarasan, P.; Ramaprabhu, Sundara

    2015-04-14

    Carbon dioxide adsorption on carbon surface can be enhanced by doping the surface with heterogeneous atoms, which can increase local surface affinity. This study presents the carbon dioxide adsorption properties of nitrogen doped graphene at low pressures (<100 kPa). Graphene was exposed to nitrogen plasma, which dopes nitrogen atoms into carbon hexagonal lattice, mainly in pyridinic and pyrrolic forms. It is found that nitrogen doping significantly improves the CO{sub 2} adsorption capacity at all temperatures, due to the enrichment of local Lewis basic sites. In general, isotherm and thermodynamic parameters suggest that doped nitrogen sites have nearly same adsorption energy of surface defects and residual functional groups. The isosteric heat of adsorption remains in physisorption range, which falls with surface coverage, suggesting the distribution of magnitude of adsorption energy. The absolute values of isosteric heat and entropy of adsorption are slightly increased upon nitrogen doping.

  18. [Adsorption characteristics of ciprofloxacin in ustic cambosols].

    PubMed

    Cui, Hao; Wang, Shu-ping

    2012-08-01

    In order to understand the adsorption characteristics of ciprofloxacin in ustic cambosols, static adsorption experiments were used to investigate dynamic and isothermal adsorption characteristics of ciprofloxacin in ustic cambosols, influence of pH on the adsorption process. Results showed that the absorption process of ciprofloxacin can be divided into two stages: fast adsorption and slow balance. The adsorption processes followed the pseudo-second-order kinetics, with adsorption rate of 1.138 x 10(-3) - 2.849 x 10(-2) kg x (min x mg)(-1). Adsorption isotherms of ciprofloxacin in ustic cambosols were well described by the Freundlich and Langmuir equation, Freundlich equation is more applicable than Langmuir equation, with the adsorption capacity (lgKf) of 2.725. Moreover, at the tested pH interval of 4-9, lgKd values of ciprofloxacin increased and then decreased with the increase of pH in ustic cambosols; the maximum adsorption of ciprofloxacin in ustic cambosols can be obtained when the pH value was 5 with lgKd value was 3.11; strong acid or alkali conditions were unfavorable to ciprofloxacin adsorption. It could be deduced that cationic adsorptions was one of the significant sorption mechanisms for ciprofloxacin in ustic cambosols.

  19. Probing the mechanism of water adsorption in carbon micropores with multitemperature isotherms and water preadsorption experiments.

    PubMed

    Rutherford, S W

    2006-11-21

    The phenomenon of water adsorption in carbon micropores is examined through the study of water adsorption equilibrium in molecular sieving carbon. Adsorption and desorption isotherms are obtained over a wide range of concentrations from less than 0.1% to beyond 80% of the vapor pressure. Evidence is provided in support of a proposed bimodal water adsorption mechanism that involves the interaction of water molecules with functional groups at low relative pressures and the adsorption of water molecules between graphene layers at higher pressures. Decomposition of the equilibrium isotherm data through application of the extended cooperative multimolecular sorption theory, together with favorable quantitative comparison, provides support for the proposed adsorption mechanism. Additional support is obtained from a multitemperature study of water equilibrium. Temperatures of 20, 50, and 60 degrees C were probed in this investigation in order to provide isosteric heat of adsorption data for water interaction with the carbon molecular sieve. At low loading, the derived isosteric heat of adsorption is estimated to be 69 kJ/mol. This value is indicative of the adsorption of water to functional groups. At higher loading, the isosteric heat of adsorption decreases with increasing loading and approaches the heat of condensation, indicative of adsorption between graphene layers. Further support for the proposed adsorption mechanism is derived from carbon dioxide adsorption experiments on carbon molecular sieve that is preadsorbed with various amounts of water. Significant exclusion of carbon dioxide occurs, and a quantitative analysis that is based on the proposed bimodal water adsorption mechanism is employed in this investigation.

  20. Dye adsorption behavior of Luffa cylindrica fibers.

    PubMed

    Demir, H; Top, A; Balköse, D; Ulkü, S

    2008-05-01

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m(2)/g.

  1. Adsorption of organic chemicals in soils.

    PubMed Central

    Calvet, R

    1989-01-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described. PMID:2695323

  2. Structure and adsorption properties of a porous cooper hexacyanoferrate polymorph

    NASA Astrophysics Data System (ADS)

    Roque-Malherbe, R.; Carballo, E.; Polanco, R.; Lugo, F.; Lozano, C.

    2015-11-01

    The key questions addressed here were: the structure elucidation and the investigation of the adsorption space and framework expansion effect of a Cu(II) hexacyanoferrate (III) polymorph (labeled Cu-PBA-I). The structural analysis was performed with a broad set of characterization methods. Additionally, a low and high pressure carbon dioxide adsorption investigation was performed, assuming, to comprehend the adsorption experiments, that the adsorbent plus the adsorbed phase were a solid solution. We concluded: that the Cu-PBA-I presented the following composition, K1/4 Cu (II)[ Fe (III)(CN)6 ] 3 / 4⋄1/4 nH2 O , exhibited an antiferromagnetic behavior and displayed a thermally stable I 4 bar m 2 space group lattice in the degassed state. Moreover, the low pressure adsorption study allowed the calculation of the micropore volume, W=0.09 cm3/g and the isosteric heat of adsorption, qiso=19 kJ/mol; further, the high pressure adsorption data revealed an extremely high adsorption capacity owing to a framework expansion effect. Finally, the DRIFTS spectrum of adsorbed CO2 displayed peaks corresponding to carbon dioxide physically adsorbed and interacting with electron accepting Lewis acid sites. Hence, was produced an excellent adsorbent which combine porosity and anti-ferromagnetism, antagonist properties rarely found together.

  3. Modification of a magnetic carbon composite for ciprofloxacin adsorption.

    PubMed

    Mao, Haixin; Wang, Shikui; Lin, Jian-Ying; Wang, Zengshuang; Ren, Jun

    2016-11-01

    A magnetic carbon composite, Fe3O4/C composite, was fabricated by one-step hydrothermal synthesis, modified by heat treatment under an inert atmosphere (N2), and then used as an adsorbent for ciprofloxacin (CIP) removal. Conditions for the modification were optimized according to the rate of CIP removal. The adsorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction measurements, vibrating-sample magnetometry, scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption isotherm measurements. The results indicate that the modified adsorbent has substantial magnetism and has a large specific area, which favor CIP adsorption. The effects of solution pH, adsorbent dose, contact time, initial CIP concentration, ion strength, humic acid and solution temperature on CIP removal were also studied. Our results show that all of the above factors influence CIP removal. The Langmuir adsorption isotherm fits the adsorption process well, with the pseudo second-order model describing the adsorption kinetics accurately. The thermodynamic parameters indicate that adsorption is mainly physical adsorption. Recycling experiments revealed that the behavior of adsorbent is maintained after recycling for five times. Overall, the modified magnetic carbon composite is an efficient adsorbent for wastewater treatment. Copyright © 2016. Published by Elsevier B.V.

  4. REMOVAL OF CESIUM FROM AQUEOUS SOLUTIONS BY ADSORPTION

    DOEpatents

    Knoll, K.C.

    1963-07-16

    A process of removing microquantities of cesium from aqueous solutions also containing macroquantities of other ions by adsorption on clinoptilolite is described. The invention resides in the pretreatment of the clinoptilolite by heating at 400 deg C and cooling prior to use. (AEC)

  5. Adsorption of Gemini surfactants onto clathrate hydrates.

    PubMed

    Salako, O; Lo, C; Couzis, A; Somasundaran, P; Lee, J W

    2013-12-15

    This work addresses the adsorption of two Gemini surfactants at the cyclopentane (CP) hydrate-water interface. The Gemini surfactants investigated here are Dowfax C6L and Dowfax 2A1 that have two anionic head groups and one hydrophobic tail group. The adsorption of these surfactants was quantified using adsorption isotherms and the adsorption isotherms were determined using liquid-liquid titrations. Even if the Gemini surfactant adsorption isotherms show multi-layer adsorption, they possess the first Langmuir layer with the second adsorption layer only evident in the 2A1 adsorption isotherm. Zeta potentials of CP hydrate particles in the surfactant solution of various concentrations of Dowfax C6L and Dowfax 2A1 were measured to further explain their adsorption behavior at the CP hydrate-water interface. Zeta potentials of alumina particles as a model particle system in different concentrations of sodium dodecyl sulfate (SDS), Dowfax C6L and Dowfax 2A1 were also measured to confirm the configuration of all the surfactants at the interface. The determination of the isotherms and zeta-potentials provides an understanding framework for the adsorption behavior of the two Gemini surfactants at the hydrate-water interface. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Adsorption Refrigeration System

    SciTech Connect

    Wang, Kai; Vineyard, Edward Allan

    2011-01-01

    Adsorption refrigeration is an environmentally friendly cooling technology which could be driven by recovered waste heat or low-grade heat such as solar energy. In comparison with absorption system, an adsorption system has no problems such as corrosion at high temperature and salt crystallization. In comparison with vapor compression refrigeration system, it has the advantages of simple control, no moving parts and less noise. This paper introduces the basic theory of adsorption cycle as well as the advanced adsorption cycles such as heat and mass recovery cycle, thermal wave cycle and convection thermal wave cycle. The types, characteristics, advantages and drawbacks of different adsorbents used in adsorption refrigeration systems are also summarized. This article will increase the awareness of this emerging cooling technology among the HVAC engineers and help them select appropriate adsorption systems in energy-efficient building design.

  7. Adsorption of goethite onto quartz and kaolinite

    USGS Publications Warehouse

    Goldberg, M.C.; Weiner, Eugene R.; Boymel, P.M.

    1984-01-01

    The adsorption of colloidal goethite onto quartz and kaolinite substrates has been studied as a function of pH and NaCl concentration. Goethite adsorption was measured quantitatively by Fourier-transform infrared spectroscopy. The results indicate that adsorption onto both substrates is due primarily to coulombic forces; however, the pH dependence of adsorption is very different for the two substrates. This is explained by the fact that the surface charge on quartz is entirely pH-dependent, while kaolinite has surface faces which carry a permanent negative charge. Adsorption of goethite on to kaolinite increases markedly with increasing NaCl concentration, while adsorption onto quartz is relatively independent of NaCl concentration. This can be explained by the influence of NaCl concentration upon the development of surface charge on the substrates. A method is described for separating surface-bound goethite from free goethite.

  8. Adsorption of radon and water vapor on commercial activated carbons

    SciTech Connect

    Hassan, N.M.; Ghosh, T.K.; Hines, A.L.; Loyalka, S.K.

    1995-02-01

    Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of the isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer`s classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.

  9. Computational studies of methane adsorption in nanoporous carbon

    NASA Astrophysics Data System (ADS)

    Ortiz, Lindsey

    In this thesis we have completed computational studies on the adsorption of methane into nanoporous carbon. We identified multi-layer adsorption at supercritical temperatures with excess amount even at large distances from the pore walls. We also determined that results could be used successfully to model methane adsorption from PSD’s coming from N 2. This works for both the adsorption isotherms and isosteric heats. A future direction would be to analyze lower temperature adsorption. Simulations at 195 K, the temperature of dry ice, would be of interest since dry ice is deemed of possible importance for storage. Another future direction is to study more varied pore geometries. In this thesis, we have only studied slit shaped pores. As can be seen in Figure 36, AC contains more varied pore geometries. Analysis of more varied pore geometries would offer a greater understanding of adsorption in AC and is therefore of interest. Figure 37 shows a possible model that may be used to run simulations on multiple pore sizes at the same time.

  10. Adsorption of water vapor on reservoir rocks

    SciTech Connect

    Not Available

    1993-07-01

    Progress is reported on: adsorption of water vapor on reservoir rocks; theoretical investigation of adsorption; estimation of adsorption parameters from transient experiments; transient adsorption experiment -- salinity and noncondensible gas effects; the physics of injection of water into, transport and storage of fluids within, and production of vapor from geothermal reservoirs; injection optimization at the Geysers Geothermal Field; a model to test multiwell data interpretation for heterogeneous reservoirs; earth tide effects on downhole pressure measurements; and a finite-difference model for free surface gravity drainage well test analysis.

  11. Adsorption and isotopic fractionation of Xe

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.

    1986-01-01

    A theoretical description of the mechanisms of isotopic fractionation arising during adsorption of noble gases in a Henry's Law pressure regime is given. Experimental data on the isotopic composition of Xe adsorbed on activated charcoal in the temperature range 220 K to 350 K are presented. Both theoretical considerations and the experimental data indicate that equilibrium adsorption does not significantly alter the isotopic structure of adsorbed structure of adsorbed noble gases. Therefore, if adsorption is responsible for the elemental noble gas pattern in meteorites and the earth, the heavy noble gas isotopic fractionation between them must have been produced prior to and by a different process than equilibrium adsorption.

  12. Adsorption and isotopic fractionation of Xe

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.

    1986-01-01

    A theoretical description of the mechanisms of isotopic fractionation arising during adsorption of noble gases in a Henry's Law pressure regime is given. Experimental data on the isotopic composition of Xe adsorbed on activated charcoal in the temperature range 220 K to 350 K are presented. Both theoretical considerations and the experimental data indicate that equilibrium adsorption does not significantly alter the isotopic structure of adsorbed structure of adsorbed noble gases. Therefore, if adsorption is responsible for the elemental noble gas pattern in meteorites and the earth, the heavy noble gas isotopic fractionation between them must have been produced prior to and by a different process than equilibrium adsorption.

  13. Kinetic and thermodynamic control of protein adsorption

    PubMed Central

    Satulovsky, J.; Carignano, M. A.; Szleifer, I.

    2000-01-01

    Control of nonspecific protein adsorption is very important for the design of biocompatible and biomimetic materials as well as drug carriers. Grafted polymer layers can be used to prevent protein adsorption. We have studied the molecular factors that determine the equilibrium and kinetic control of protein adsorption by grafted polymer layers. We find that polymers that are not attracted to the surface are very effective for kinetic control but not very good for equilibrium reduction of protein adsorption. Polymers with attractions to the surface show exactly the opposite behavior. The implications for molecular design of biocompatible materials also are discussed in this paper. PMID:10908651

  14. The adsorption of nicotine from aqueous solutions on different zeolite structures.

    PubMed

    Rakić, Vesna; Damjanović, Ljiljana; Rac, Vladislav; Stosić, Dusan; Dondur, Vera; Auroux, Aline

    2010-03-01

    The present work is focused on the adsorption of nicotine from aqueous solutions. Based on the data available in the literature, serious concern is claimed regarding the appearance of nicotine in ground, surface and municipal wastewaters. In order to investigate the possibility of abatement by adsorption, three different types of zeolites (BEA, MFI and HEU) have been applied as adsorbents. In addition, the adsorption was performed on activated carbon, a solid customarily used for removal of pollutants from water. The adsorption of nicotine was studied by isothermal microcalorimetry, which provided the heats evolved as a result of adsorption. The values of these heats revealed that the investigated solids are energetically heterogeneous for the adsorption of nicotine from aqueous solution. Additionally, the amounts of adsorbed pollutant were determined and presented in the form of adsorption isotherms. The obtained adsorption isotherms were interpreted using Langmuir, Freundlich, and Sips equations; the latter was found to express high level of agreement with experimental data of nicotine adsorption on the investigated solids. The possibilities to regenerate the adsorbents were examined by means of thermogravimetry coupled with mass spectrometry. From all obtained results, it was possible to distinguish zeolite BEA as a material which possesses the capacity for adsorption of nicotine comparable to that of activated carbon.

  15. Adsorption of acid dye onto organobentonite.

    PubMed

    Baskaralingam, P; Pulikesi, M; Elango, D; Ramamurthi, V; Sivanesan, S

    2006-02-06

    Removal of Acid Red 151 from aqueous solution at different dye concentrations, adsorbent doses and pH has been studied. The bentonite clay has been modified using cationic surfactants, which has been confirmed using XRD and FT-IR analyses. Experimental result has shown that the acidic pH favours the adsorption. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. The adsorption capacity has been found to be 357.14 and 416.66 mg g(-1) for the cetyldimethylbenzylammonium chloride-bentonite (CDBA-bent) and cetylpyridinium chloride-bentonite (CP-bent), respectively. Kinetic studies show that the adsorption followed second-order kinetics.

  16. The influence of protein aggregation on adsorption kinetics

    NASA Astrophysics Data System (ADS)

    Rovner, Joel; Roberts, Christopher; Furst, Eric; Hudson, Steven

    2015-03-01

    When proteins adsorb to an air-water interface they lower the surface tension and may form an age-dependent viscoelastic film. Protein adsorption to surfaces is relevant to both commercial uses and biological function. The rate at which the surface tension decreases depends strongly on temperature, solution pH, and protein structure. These kinetics also depend on the degree to which the protein is aggregated in solution. Here we explore these differences using Chymotrypsinogen as a model protein whose degree of aggregation is adjusted through controlled heat treatment and measured by chromatography. To study these effects we have used a micropipette tensiometer to produce a spherical-cap bubble whose interfacial pressure was controlled - either steady or oscillating. Short heat treatment produced small soluble aggregates, and these adsorbed faster than the original protein monomer. Longer heat treatment produced somewhat larger soluble aggregates which adsorbed more slowly. These results point to complex interactions during protein adsorption.

  17. Optimization of adsorption processes for climate control and thermal energy storage

    SciTech Connect

    Narayanan, S; Yang, S; Kim, H; Wang, EN

    2014-10-01

    Adsorption based heat-pumps have received significant interest owing to their promise of higher efficiencies and energy savings when coupled with waste heat and solar energy compared to conventional heating and cooling systems. While adsorption systems have been widely studied through computational analysis and experiments, general design guidelines to enhance their overall performance have not been proposed. In this work, we identified conditions suitable for the maximum utilization of the adsorbent to enhance the performance of both intermittent as well as continuously operating adsorption systems. A detailed computational model was developed based on a general framework governing adsorption dynamics in a single adsorption layer and pellet. We then validated the computational analysis using experiments with a model system of zeolite 13X-water for different operating conditions. A dimensional analysis was subsequently carried out to optimize adsorption performance for any desired operating condition, which is determined by the choice of adsorbent-vapor pair, adsorption duration, operational pressure, intercrystalline porosity, adsorbent crystal size, and intracrystalline vapor diffusivity. The scaling analysis identifies the critical dimensionless parameters and provides a simple guideline to determine the most suitable geometry for the adsorbent particles. Based on this selection criterion, the computational model was used to demonstrate maximum utilization of the adsorbent for any given operational condition. By considering a wide range of parametric variations for performance optimization, these results offer important insights for designing adsorption beds for heating and cooling systems. (C) 2014 Elsevier Ltd. All rights reserved.

  18. Development of equations for differential and integral enthalpy change of adsorption for simulation studies.

    PubMed

    Do, D D; Nicholson, D; Fan, Chunyan

    2011-12-06

    We present equations to calculate the differential and integral enthalpy changes of adsorption for their use in Monte Carlo simulation. Adsorption of a system of N molecules, subject to an external potential energy, is viewed as one of transferring these molecules from a reference gas phase (state 1) to the adsorption system (state 2) at the same temperature and equilibrium pressure (same chemical potential). The excess amount adsorbed is the difference between N and the hypothetical amount of gas occupying the accessible volume of the system at the same density as the reference gas. The enthalpy change is a state function, which is defined as the difference between the enthalpies of state 2 and state 1, and the isosteric heat is defined as the negative of the derivative of this enthalpy change with respect to the excess amount of adsorption. It is suitable to determine how the system behaves for a differential increment in the excess phase adsorbed under subcritical conditions. For supercritical conditions, use of the integral enthalpy of adsorption per particle is recommended since the isosteric heat becomes infinite at the maximum excess concentration. With these unambiguous definitions we derive equations which are applicable for a general case of adsorption and demonstrate how they can be used in a Monte Carlo simulation. We apply the new equations to argon adsorption at various temperatures on a graphite surface to illustrate the need to use the correct equation to describe isosteric heat of adsorption. © 2011 American Chemical Society

  19. Thermodynamic characteristics of the adsorption of organic molecules on modified MCM-41 adsorbents

    NASA Astrophysics Data System (ADS)

    Gus'kov, V. Yu.; Sukhareva, D. A.; Salikhova, G. R.; Karpov, S. I.; Kudasheva, F. Kh.; Roessner, F.; Borodina, E. V.

    2017-07-01

    The adsorption of a number of organic molecules on samples of MCM-41 adsorbent modified with dichloromethylphenylsilane and subsequently treated with sulfuric acid (MDCS) and N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride (MNM) is studied. Specific retention volumes equal to the Henry constant are determined by means of inverse gas chromatography at infinite dilution. The thermodynamic characteristics of adsorption, the dispersive and specific components of the Helmholtz energy of adsorption, and the increment of the methyl group to the heat of adsorption are calculated. It is shown that the grafting of aminosilane and phenylsilane groups enhances the forces of dispersion and reduces specific interactions. A greater drop in polarity is observed for MDCS than for MNM, due to the stronger polarity of amoinosilane; the enthalpy factor makes the main contribution to the adsorption of organic compounds on the investigated adsorbents. It is found that the MNM sample is capable of the irreversible adsorption of alcohols.

  20. Ion Exchange and Adsorption of Inorganic Contaminants

    EPA Science Inventory

    In the first part of the chapter, the fundamentals of ion exchange and adsorption processes are explained, with the goal of demonstrating how these principles influence process design for inorganic contaminant removal. In the second part, ion exchange and adsorption processes th...

  1. Ion Exchange and Adsorption of Inorganic Contaminants

    EPA Science Inventory

    In the first part of the chapter, the fundamentals of ion exchange and adsorption processes are explained, with the goal of demonstrating how these principles influence process design for inorganic contaminant removal. In the second part, ion exchange and adsorption processes th...

  2. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

    PubMed

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg(2+) ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, (27)Al/(29)Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2(nd) law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

  3. Zeolite Y adsorbents with high vapor uptake capacity and robust cycling stability for potential applications in advanced adsorption heat pumps

    SciTech Connect

    Li, XS; Narayanan, S; Michaelis, VK; Ong, TC; Keeler, EG; Kim, H; Mckay, IS; Griffin, RG; Wang, EN

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N-2 sorption, Al-27/Si-29 MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N-2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. (C) 2014 Elsevier Inc. All rights reserved.

  4. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps

    PubMed Central

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K.; Ong, Ta-Chung; Keeler, Eric G.; Kim, Hyunho; McKay, Ian S.; Griffin, Robert G.; Wang, Evelyn N.

    2014-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, 27Al/29Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick’s 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. PMID:25395877

  5. Adsorption of beta blockers to environmental surfaces.

    PubMed

    Kibbey, Tohren C G; Paruchuri, Rajiv; Sabatini, David A; Chen, Lixia

    2007-08-01

    Beta-adrenergic blocking agents (beta blockers) are widely used pharmaceuticals which have been detected in the environment. Predicting the transport and ultimate fate of beta blockers in the environment requires understanding their adsorption to soils and sediments, something for which little information is currently available. The objective of this work was to examine the adsorption of three beta blockers, propranolol, metoprolol and nadolol, to a natural alluvial material, as well as to six minerals present as components of the alluvial material. Batch adsorption experiments indicate that, for most of the minerals studied, compound hydrophobicity is an important predictor of adsorption, with propranolol,the most hydrophobic compound studied, adsorbing to the greatest extent. Results further suggest that, for the minerals studied, electrostatic effects are not a good predictor of adsorption; adsorption extent was not well-predicted by either surface zeta potential or by the difference between experiment pH and point of zero charge, despite the cationic nature af the three beta blockers at experiment pH values. Experiments were conducted to examine the effect of an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), on adsorption. Results indicate that SDBS significantly increases the adsorption of propranolol to two different sorbents. This result is potentially important because surfactants such as SDBS are likely to be present in wastewater effluents with beta blockers and could influence their mobility in the environment.

  6. Moisture adsorption isotherms and glass transition temperature of pectin.

    PubMed

    Basu, Santanu; Shivhare, U S; Muley, S

    2013-06-01

    The moisture adsorption isotherms of low methoxyl pectin were determined at 30-70°C and water activity ranging from 0.11 to 0.94. The moisture adsorption isotherms revealed that the equilibrium moisture content increased with water activity. Increase in temperature, in general, resulted in decreased equilibrium moisture content. However in some cases, equilibrium moisture content values increased with temperature at higher water activities. Selected sorption models (GAB, Halsey, Henderson, Oswin, modified Oswin) were tested for describing the adsorption isotherms. Parameters of each sorption models were determined by nonlinear regression analysis. Oswin model gave the best fit for pectin sorption behaviour. Isosteric heat of sorption decreased with increase in moisture content and varied between 14.607 and 0.552 kJ/mol. Glass transition temperature decreased with increase in moisture content of pectin.

  7. Caffeine adsorption of montmorillonite in coffee extracts.

    PubMed

    Shiono, Takashi; Yamamoto, Kenichiro; Yotsumoto, Yuko; Yoshida, Aruto

    2017-08-01

    The growth in health-conscious consumers continues to drive the demand for a wide variety of decaffeinated beverages. We previously developed a new technology using montmorillonite (MMT) in selective decaffeination of tea extract. This study evaluated and compared decaffeination of coffee extract using MMT and activated carbon (AC). MMT adsorbed caffeine without significant adsorption of caffeoylquinic acids (CQAs), feruloylquinic acids (FQAs), dicaffeoylquinic acids (di-CQAs), or caffeoylquinic lactones (CQLs). AC adsorbed caffeine, chlorogenic acids (CGAs) and CQLs simultaneously. The results suggested that the adsorption selectivity for caffeine in coffee extract is higher in MMT than AC. The caffeine adsorption isotherms of MMT in coffee extract fitted well to the Langmuir adsorption model. The adsorption properties in coffee extracts from the same species were comparable, regardless of roasting level and locality of growth. Our findings suggest that MMT is a useful adsorbent in the decaffeination of a wide range of coffee extracts.

  8. Adsorption and desorption of reversible supramolecular polymers

    NASA Astrophysics Data System (ADS)

    Zweistra, Henk J. A.; Besseling, N. A. M.

    2006-08-01

    We report numerical mean-field results on the quasichemical level of approximation that describe adsorption of reversible supramolecular polymers at a flat interface. Emphasis is laid on the regime of strong adsorption from a dilute solution. There are two differences with respect to macromolecular polymer adsorption: (i) adsorption sets in at relatively high monomer concentrations of the surrounding solution, and (ii) the surface is filled within a much narrower concentration range. Contrary to macromolecular polymers, supramolecular polymers can therefore be desorbed by dilution of the equilibrium solution by solvent within an experimentally accessible concentration window. Based on simple thermodynamic arguments, we provide a quantitative explanation why supramolecular polymers adsorb at relatively high concentrations. Moreover, we discuss the (by comparison) narrow concentration window wherein filling of the surface occurs. This is attributed to the cooperative nature of supramolecular polymer adsorption. The degree of cooperativity is quantified by means of the Hill parameter n .

  9. Quantum Monte Carlo studies of surface adsorptions

    NASA Astrophysics Data System (ADS)

    Wei, Ching-Ming; Hsing, Cheng-Rong

    2012-02-01

    Surface adsorption is the first step to the study of surface catalytic reaction. The most common used tool is the Density Functional Theory (DFT) based on exchange-correlation approximations and the accuracy usually has not been checked carefully by highly accurate quantum many-body approaches. We have performed calculations of the surface adsorptions using the state-of-the-art diffusion quantum Monte Carlo (QMC) method to examine the accuracy of LDA and GGA (PBE) functionals in the study of surface adsorptions. The systems examined include the H2O and OH adsorptions on various types of surfaces such as NaCl(100), MgO(100), TiO2(110), graphene, Si(100)-(2x2) and Al(100). By comparing GGA (PBE) results with DMC, our results indicate that (i) for the H2O adsorption, PBE predicts the correct adsorption energies; (ii) for the OH adsorption, PBE has predicted a large over-binding effect except on graphene and Si(100) surfaces. This fact indicates that one needs to be cautious when using DFT to study the surface adsorptions of OH free radical.

  10. Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks.

    PubMed

    Kim, Hyunho; Cho, H Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M; Wang, Evelyn N

    2016-01-22

    Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes.

  11. Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Kim, Hyunho; Cho, H. Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M.; Wang, Evelyn N.

    2016-01-01

    Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes.

  12. Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks

    PubMed Central

    Kim, Hyunho; Cho, H. Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M.; Wang, Evelyn N.

    2016-01-01

    Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes. PMID:26796523

  13. On the physical adsorption of vapors by microporous carbons

    SciTech Connect

    Bradley, R.H. . Inst. of Surface Science and Technology); Rand, B. . Division of Ceramics)

    1995-01-01

    The physical adsorption of nonpolar and polar vapors by active carbons is discussed in relation to pore structure and pore wall chemistry. For nonpolar vapors the Dubinin-Radushkevich equation is used to derive micropore volumes (W[sub 0]), average adsorption energies (E[sub 0]), and micropore widths (L) for a number of systems. These parameters are used to interpret the adsorption behavior of nitrogen which, because it is a relatively small molecule, is frequently used at 77 K to probe porosity and surface area. Results are presented for three carbons from differing precursors, namely, coal, coconut shells, and polyvinylidene chloride (PVDC) to illustrate the applicability of the technique. For the latter carbon increases in micropore size, induced by activation in carbon dioxide, and reductions in accessible pore volume caused by heat treatment in argon are also characterized and related to structural changes. The approach is then extended to the adsorption of larger hydrogen vapors, where the resulting W[sub 0] values may require correction for molecular packing effects which occur in the lower relative pressure regions of the isotherms, i.e., during the filling of ultramicropores. These packing effects are shown to limit the use of the Polanyi characteristic curve for correlating isotherm data for several vapors, of differing molecular size, by one adsorbent. Data for the adsorption of water, which is a strongly polar liquid, have been interpreted using the Dubinin-Serpinsky equation.

  14. Ethane adsorption on aggregates of dahlia-like nanohorns: experiments and computer simulations.

    PubMed

    Russell, Brice A; Migone, Aldo D; Petucci, Justin; Mercedes Calbi, M; Yudasaka, Masako; Iijima, Sumio

    2016-06-01

    This is a report on a study of the adsorption characteristics of ethane on aggregates of unopened dahlia-like carbon nanohorns. This sorbent presents two main groups of adsorption sites: the outside surface of individual nanohorns and deep, interstitial spaces between neighbouring nanohorns towards the interior of the aggregates. We have explored the equilibrium properties of the adsorbed ethane films by determining the adsorption isotherms and isosteric heat of adsorption. Computer simulations performed on different model structures indicate that the majority of ethane adsorption occurs on the outer region of the aggregates, near the ends of the nanohorns. We have also measured the kinetics of adsorption of ethane on this sorbent. The measurements and simulations were conducted along several isotherms spanning the range between 120 K and 220 K.

  15. Adsorption equilibria of chlorinated organic solvents onto activated carbon

    SciTech Connect

    Yun, J.H.; Choi, D.K.; Kim, S.H.

    1998-04-01

    Adsorption equilibria of dichloromethane, 1,1,1-trichloroethane, and trichloroethylene on activated carbon were obtained by a static volumetric technique. Isotherms were measured for the pure vapors in the temperature range from 283 to 363 K and pressures up to 60 kPa for dichloromethane, 16 kPa for 1,1,1-trichloroethane, and 7 kPa for trichloroethylene, respectively. The Toth and Dubinin-Radushkevich equations were used to correlate experimental isotherms. Thermodynamic properties such as the isosteric heat of adsorption and the henry`s constant were calculated. It was found that the values of isosteric heat of adsorption were varied with surface loading. Also, the Henry`s constant showed that the order of adsorption affinity is 1,1,1-trichloroethane, trichloroethylene, and dichloromethane. By employing the Dubinin-Radushkevich equation, the limiting volume of the adsorbed space, which equals micropore volume, was determined, and its value was found to be approximately independent of adsorbates.

  16. Adsorption of ciprofloxacin on surface-modified carbon materials.

    PubMed

    Carabineiro, S A C; Thavorn-Amornsri, T; Pereira, M F R; Figueiredo, J L

    2011-10-01

    The adsorption capacity of ciprofloxacin (CPX) was determined on three types of carbon-based materials: activated carbon (commercial sample), carbon nanotubes (commercial multi-walled carbon nanotubes) and carbon xerogel (prepared by the resorcinol/formaldehyde approach at pH 6.0). These materials were used as received/prepared and functionalised through oxidation with nitric acid. The oxidised materials were then heat treated under inert atmosphere (N2) at different temperatures (between 350 and 900°C). The obtained samples were characterised by adsorption of N2 at -196 °C, determination of the point of zero charge and by temperature programmed desorption. High adsorption capacities ranging from approximately 60 to 300 mgCPxgC(-1) were obtained (for oxidised carbon xerogel, and oxidised thermally treated activated carbon Norit ROX 8.0, respectively). In general, it was found that the nitric acid treatment of samples has a detrimental effect in adsorption capacity, whereas thermal treatments, especially at 900 °C after oxidation, enhance adsorption performance. This is due to the positive effect of the surface basicity. The kinetic curves obtained were fitted using 1st or 2nd order models, and the Langmuir and Freundlich models were used to describe the equilibrium isotherms obtained. The 2nd order and the Langmuir models, respectively, were shown to present the best fittings. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    minutes to >60 hours, and this in turn, led to a ˜300 fold increase in capacity, convergence of capacities at similar reduced temperatures (critical temperature being the reducing parameter), discontinuities in the isotherms, lowering of gate-opening pressures, changes in the isotherm shapes as well as width of hysteresis loops. Although an experimental time effect was also seen for H2 adsorption at 77K, H2 showed no discontinuity in the adsorption isotherm, adsorption-desorption hysteresis was much less pronounced, and equilibration required significantly less time. The significant difference in rates of adsorption by different gases was attributed to an activated configurational diffusion regime in which the diffusing species moves through a corrugated surface potential when the diameter of the adsorbate approaches that of the pore. A concentration-dependent diffusion model coupled with insufficient equilibration time provides an alternate explanation to describe the stepwise adsorption behavior in GO-MOFs and the changes in capacities. A sigmoid shape of adsorption rate data at cryogenic temperatures is atypical of simple Fickian diffusion, suggesting a more complex mechanistic explanation is required to explain adsorption kinetics to GO-MOFs. Extending the unreacted shrinking core model from the field of catalyst deactivation suggests that relaxation will be much faster relative to diffusion when temperature is increased even by just 10K. From a thermodynamic perspective, adsorption isotherms on (2) demonstrate universality when pressure and temperature are scaled/reduced according to those at critical conditions. At similar reduced conditions, isotherms of gases on (2) converged and both capacity and pressure points of discontinuities showed a predictive behavior. Discrete levels of capacities were found which decrease in temperature. Existence of a universal parameter of heat of gate-opening is calculated and the heats of adsorption and structural expansion are

  18. How Surface Heterogeneity Affects Protein Adsorption: Annealing of OTS Patterns and Albumin Adsorption Kinetics*

    PubMed Central

    Hodgkinson, Gerald N.; Hlady, Vladimir

    2009-01-01

    Fluorescence microscopy and intensity histogram analysis techniques were used to monitor spatially-resolved albumin adsorption kinetics to model heterogeneous surfaces on sub-μm scales. Several distinct protein subpopulations were resolved, each represented by a normal distribution of adsorption densities on the adsorbent surface. Histogram analyses provided dynamic information of mean adsorption density, spread in adsorption density, and surface area coverage for each distinct protein subpopulation. A simple adsorption model is proposed in which individual protein binding events are predicted by the summation of multiple protein's surface sub-site interactions with different binding energy sub-sites on adsorbent surfaces. This model is predictive of the albumin adsorption on the patterns produced by one step μ-contact printing (μCP) of octadecyltrichlorosilane (OTS) on glass but fails to describe adsorption once the same patterns are altered by a thermal annealing step. PMID:19746205

  19. The Accelerated Late Adsorption of Pulmonary Surfactant

    PubMed Central

    2011-01-01

    Adsorption of pulmonary surfactant to an air−water interface lowers surface tension (γ) at rates that initially decrease progressively, but which then accelerate close to the equilibrium γ. The studies here tested a series of hypotheses concerning mechanisms that might cause the late accelerated drop in γ. Experiments used captive bubbles and a Wilhelmy plate to measure γ during adsorption of vesicles containing constituents from extracted calf surfactant. The faster fall in γ reflects faster adsorption rather than any feature of the equation of state that relates γ to surface concentration (Γ). Adsorption accelerates when γ reaches a critical value rather than after an interval required to reach that γ. The hydrophobic surfactant proteins (SPs) represent key constituents, both for reaching the γ at which the acceleration occurs and for producing the acceleration itself. The γ at which rates of adsorption increase, however, is unaffected by the Γ of protein in the films. In the absence of the proteins, a phosphatidylethanolamine, which, like the SPs, induces fusion of the vesicles with the interfacial film, also causes adsorption to accelerate. Our results suggest that the late acceleration is characteristic of adsorption by fusion of vesicles with the nascent film, which proceeds more favorably when the Γ of the lipids exceeds a critical value. PMID:21417351

  20. Activation thermodynamics of virus adsorption to solids.

    PubMed Central

    Preston, D R; Farrah, S R

    1988-01-01

    The kinetics of bacteriophage MS2, T2, and f2 adsorption to powdered nitrocellulose and disrupted Seitz S1 filters at pH 7 were determined as a function of temperature. Data from these studies were combined with data produced in a previous study on MS2 adsorption to clay by Stagg et al. (Appl. Environ. Microbiol. 33:385-391, 1977). These workers studied the adsorption of MS2 to bentonite clay as a function of temperature. Data from both this previous study and the current one were used to calculate the thermodynamic parameters of virus adsorption. The results show that adsorption of bacteriophages to the solids tested is a physical process (energy of activation, less than 40 kcal [168 J]/mol) rather than a chemical process (energy of activation, greater than 40 kcal/mol). The free energy of activation showed a high negative correlation (r = -0.904, r2 = 0.817) with the percentage of virus adsorption to the solids tested. The energy of activation was highly negatively correlated with the percentage of virus adsorption to nitrocellulose and clay (r = -0.913, r2 = 0.834) but poorly correlated with the percentage of virus adsorption to disrupted Seitz S1 filters (r = -0.348, r2 = 0.121). In general, under conditions in which the percentage of virus adsorption was low, the energy of activation, the free energy of activation, and the entropy of activation were high. Increasing the percentage of virus adsorbed by changing the adsorbing conditions or changing the adsorbing solid decreased the energy of activation, the free energy of activation, and the entropy of activation. PMID:3214152

  1. Monte Carlo simulations of Protein Adsorption

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Kumar, Sanat K.; Belfort, Georges

    2008-03-01

    Amyloidogenic diseases, such as, Alzheimer's are caused by adsorption and aggregation of partially unfolded proteins. Adsorption of proteins is a concern in design of biomedical devices, such as dialysis membranes. Protein adsorption is often accompanied by conformational rearrangements in protein molecules. Such conformational rearrangements are thought to affect many properties of adsorbed protein molecules such as their adhesion strength to the surface, biological activity, and aggregation tendency. It has been experimentally shown that many naturally occurring proteins, upon adsorption to hydrophobic surfaces, undergo a helix to sheet or random coil secondary structural rearrangement. However, to better understand the equilibrium structural complexities of this phenomenon, we have performed Monte Carlo (MC) simulations of adsorption of a four helix bundle, modeled as a lattice protein, and studied the adsorption behavior and equilibrium protein conformations at different temperatures and degrees of surface hydrophobicity. To study the free energy and entropic effects on adsorption, Canonical ensemble MC simulations have been combined with Weighted Histogram Analysis Method(WHAM). Conformational transitions of proteins on surfaces will be discussed as a function of surface hydrophobicity and compared to analogous bulk transitions.

  2. Adsorption of lead over graphite oxide.

    PubMed

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water. Published by Elsevier B.V.

  3. Adsorption of lead over Graphite Oxide

    PubMed Central

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M.; Oki, Aderemi

    2014-01-01

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb2+ was found to be 98, 91 and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water. PMID:24152870

  4. Adsorption of lead over graphite oxide

    NASA Astrophysics Data System (ADS)

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M.; Oki, Aderemi

    2014-01-01

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb2+ was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water.

  5. Investigation of uranium (VI) adsorption by polypyrrole.

    PubMed

    Abdi, S; Nasiri, M; Mesbahi, A; Khani, M H

    2017-06-15

    The purpose of this study was to investigate the adsorption of uranium (VI) ions on the polypyrrole adsorbent. Polypyrrole was synthesized by a chemical method using polyethylene glycol, sodium dodecylbenzenesulfonate, and cetyltrimethylammonium bromide as the surfactant and iron (III) chloride as an oxidant in the aqueous solution. The effect of various surfactants on the synthesized polymers and their performance as the uranium adsorbent were investigated. Adsorbent properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of different parameters such as pH, contact time, initial metal ion concentrations, adsorbent dose, and the temperature was investigated in the batch system for uranium adsorption process. It has been illustrated that the adsorption equilibrium time is 7min. The results showed that the Freundlich model had the best agreement and the maximum adsorption capacity of polypyrrole for uranium (VI) was determined 87.72mg/g from Langmuir isotherm. In addition, the mentioned adsorption process was fast and the kinetic data were fitted to the Pseudo first and second order models. The adsorption kinetic data followed the pseudo-second-order kinetic model. Moreover, the thermodynamic parameters ΔG(0), ΔH(0) and ΔS(0) showed that the uranium adsorption process by polypyrrole was endothermic and spontaneous. Copyright © 2017. Published by Elsevier B.V.

  6. [Mechanism study of fluoride adsorption by hydrous metal oxides].

    PubMed

    Guo, Hui-Chao; Li, Wen-Jun; Chang, Zhi-Dong; Wang, Huan-Ying; Zhou, Yue

    2011-08-01

    Hydrous oxides of cerium, aluminum, nickel and copper were prepared by alkaline precipitation method. Langmuir adsorption isotherm was studied and specific surface area was measured by BET method through N2 adsorption-desorption process. IR characterization of hydrous metal oxides before and after fluoride adsorption was also studied. Results show that different hydrous metal oxides have different specific surface areas and their pore size distributions also are not all the same. Adsorption capacity is not directly dependent on the specific surface area. Isotherm study indicates that the adsorption follows Langmuir model and shows the feature of monolayer adsorption. IR study before and after fluoride adsorption shows that different hydrous metal oxides have similar adsorption sites in the same IR region as well as adsorption sites in the different IR region. The comprehensive interaction of these adsorption sites with fluoride ions results in the different adsorption capacity of different hydrous metal oxides.

  7. Apparatus for the study of macromolecular adsorption

    NASA Astrophysics Data System (ADS)

    Mayo, C. S.; Hallock, R. B.

    1989-04-01

    A surface plasmon adsorbate monitor (SPAM) is described which allows the adsorption of macromolecules or other adsorbates to a metal surface to be monitored. Surface plasmons are employed and the apparatus has no moving parts. The kinetics of adsorption may be studied on a time scale of seconds rather than the more common time scale of minutes; a simple improvement in computer memory access should allow temporal studies in the millisecond range. As an illustration, the adsorption of carboxyl-terminated polystyrene from a solution with acetone onto a silver surface is measured.

  8. Mechanisms of fibrinogen adsorption at solid substrates.

    PubMed

    Adamczyk, Zbigniew; Barbasz, Jakub; Cieśla, Michał

    2011-06-07

    Adsorption of fibrinogen, modeled as a linear chain of touching beads of various sizes, was theoretically studied using the random sequential adsorption (RSA) model. The adsorption process was assumed to consist of two steps: (i) formation of an irreversibly bound fibrinogen monolayer under the side-on orientation, which is independent of the bulk protein concentration and (ii) formation of the reversibly bound, end-on monolayer, whose coverage was dependent on the bulk concentration. Calculation based on the RSA model showed that the maximum surface concentration of the end-on (reversible) monolayer equals N(⊥∞) = 6.13 × 10(3) μm(-2) which is much larger than the previously found value for the side-on (irreversible) monolayer, equal to N(∞) = 2.27 × 10(3) μm(-2). Hence, the maximum surface concentration of fibrinogen in both orientations is determined to be 8.40 × 10(3) μm(-2) corresponding to the protein coverage of 5.70 mg m(-2) assuming 20% hydration. Additionally, the surface blocking function (ASF) was determined for the end-on fibrinogen adsorption, approximated for the entire range of coverage by the interpolating polynomial. For the coverage approaching the jamming limit, the surface blocking function (ASF) was shown to vanish proportionally to (θ(⊥∞) - θ(⊥))(2). These calculation allowed one to theoretically predict adsorption isotherms for the end-on regime of fibrinogen and adsorption kinetics under various transport conditions (diffusion and convection). Using these theoretical results, a quantitative interpretation of experimental data obtained by TIRF and ellipsometry was successfully performed. The equilibrium adsorption constant for the end-on adsorption regime was found to be 8.04 × 10(-3) m. On the basis of this value, the depth of the adsorption energy minimum, equal to -17.4 kT, was predicted, which corresponds to ΔG = -41.8 kJ mol(-1). This is in accordance with adsorption energy derived as the sum of the van der Waals

  9. Adsorption of normal pentane on the surface of rutile. Experimental results and simulations.

    PubMed

    Rakhmatkariev, G U; Carvalho, A J Palace; Ramalho, J P Prates

    2007-07-03

    Adsorption isotherms and differential heats of normal pentane adsorption on microcrystalline rutile were measured at 303 K. The heat of adsorption of n-pentane on rutile at zero occupancy is 64 kJ/mol. The differential heats have three descending segments, corresponding to the adsorption of n-pentane on three types of surfaces. At low coverage (first segment), the adsorption is restricted to the rows A of the (110) faces along the 5-fold coordinatively unsaturated (cus) Ti(4+) ions with differential heat showing a linear decrease with increasing occupancy. The second segment is attributed to bonding with atoms of the rows along the remaining faces exposed, (101) and (100). The third segment is related to a multilayer adsorption. The mean molar adsorption entropy of n-pentane is ca. -25 J/mol K less than the entropy of the bulk liquid, thus revealing a hindered state of motion of the n-pentane molecules on the surface of rutile. Simulations of the adsorption of n-pentane on the three most abundant crystallographic faces of rutile were also performed. The adsorption isotherm obtained from the combination of each face's isotherm weighted by the respective abundance was found to be in a good agreement with the experimental data. A structural characterization of n-pentane near the surface was also conducted, and it was found that the substrate, especially for the (110) face, strongly perturbs the distribution of n-pentane conformations, compared to those found for the gas phase. Adsorbed molecules are predominantly oriented with their long axes and their backbone zigzag planes parallel to the surface and are also characterized by fewer gauche conformations than observed in the bulk phase.

  10. Adsorption of amylase enzyme on ultrafiltration membranes.

    PubMed

    Beier, Søren Prip; Enevoldsen, Ann Dorrit; Kontogeorgis, Georgios M; Hansen, Ernst B; Jonsson, Gunnar

    2007-08-28

    A method to measure the static adsorption on membrane surfaces has been developed and described. The static adsorption of amylase-F has been measured on two different ultrafiltration membranes, both with a cutoff value of 10 kDa (a PES membrane and the ETNA10PP membrane, which is a surface-modified PVDF membrane). The adsorption follows the Langmuir adsorption theory. Thus, the static adsorption consists of monolayer coverage and is expressed both as a permeability drop and an adsorption resistance. From the adsorption isotherms, the maximum static permeability drops and the maximum static adsorption resistances are determined. The maximum static permeability drop for the hydrophobic PES membrane is 75%, and the maximum static adsorption resistance is 0.014 m2.h.bar/L. The maximum static permeability drop for the hydrophilic surface-modified PVDF membrane (ETNA10PP) is 23%, and the maximum static adsorption resistance is 0.0046 m2.h.bar/L. The difference in maximum static adsorption, by a factor of around 3, affects the performance during the filtration of a 5 g/L amylase-F solution at 2 bar. The two membranes behave very similarly during filtration with almost equal fluxes and retentions even though the initial water permeability of the PES membrane is around 3 times larger than the initial water permeability of the ETNA10PP membrane. This is mainly attributed to the larger maximum static adsorption of the PES membrane. The permeability drop during filtration exceeds the maximum static permeability drop, indicating that the buildup layer on the membranes during filtration exceeds monolayer coverage, which is also seen by the increase in fouling resistance during filtration. The accumulated layer on the membrane surface can be described as a continually increasing cake-layer thickness, which is independent of the membrane type. At higher concentrations of enzyme, concentration polarization effects cannot be neglected. Therefore, stagnant film theory and the osmotic

  11. Formation of titanosilicate precursors of an active adsorption phase

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T. F.; Ivanets, A. I.; Katsoshvili, L. L.

    2017-04-01

    Micro-mesoporous titanosilicate precursors of the active absorption phase of a composite ceramic membrane are synthesized, and their textural and adsorption properties are investigated by means of low-temperature nitrogen adsorption/desorption. Low-temperature isotherms of nitrogen adsorption/desorption are analyzed using the BET, Langmuir, comparative t-plot, Barrett-Joyner-Halenda, and density functional theory methods. It is found that at high contents of silicon(IV) oxide, the resulting xerogels have surface areas of 656 and 890 m2/g according to the BET and Langmuir approaches, respectively, while the micropores' inner and outer surfaces are 453 and 466 m2/g, respectively, according to the t-plot. According to the DFT distributions, the mesopore diameters of a sample can be adjusted in the range of 3-9 nm. By analyzing the type of capillary condensation hysteresis in the adsorption/desorption isotherms, it is shown that the pores in the samples are very bottle-like, even though their shape may be different in reality. It is found that in samples with high contents of titanium(IV) oxide, the pore throats are blocked during adsorbate desorption, due to the percolation effect. It is assumed that the stabilization of particles of titanium(IV) oxide by amorphous layers of silica protects the texture of titanosilicate xerogels from full contraction and the coalescence of particles during heat treatment ranging from 393 to 923 K.

  12. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  13. Capillary condensation and adsorption of binary mixtures.

    PubMed

    Weinberger, B; Darkrim-Lamari, F; Levesque, D

    2006-06-21

    The adsorption of equimolar binary mixtures of hydrogen-carbon dioxide, hydrogen-methane, and methane-carbon dioxide in porous material models is determined by grand canonical Monte Carlo simulations. The material models have an adsorbent surface similar to that of nanofibers with a herringbone structure. Our main result, which is relevant for hydrogen purification and carbon dioxide capture, is that the adsorption selectivities calculated for the mixtures can differ significantly from those deduced from simulations of the adsorption of pure gases, in particular, when one of the adsorbed gases presents a capillary condensation induced by confinement within the pore network. A comparison of our data is also made with theoretical models used in the literature for predicting the properties of the mixture adsorption.

  14. Ionic Adsorption and Desorption of CNT Nanoropes

    PubMed Central

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-01-01

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment. PMID:28335306

  15. Ionic Adsorption and Desorption of CNT Nanoropes.

    PubMed

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-09-28

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment.

  16. Modeling the adsorption of mixed gases based on pure gas adsorption properties

    NASA Astrophysics Data System (ADS)

    Tzabar, N.; Holland, H. J.; Vermeer, C. H.; ter Brake, H. J. M.

    2015-12-01

    Sorption-based Joule-Thomson (JT) cryocoolers usually operate with pure gases. A sorption-based compressor has many benefits; however, it is limited by the pressure ratios it can provide. Using a mixed-refrigerant (MR) instead of a pure refrigerant in JT cryocoolers allows working at much lower pressure ratios. Therefore, it is attractive using MRs in sorption- based cryocoolers in order to reduce one of its main limitations. The adsorption of mixed gases is usually investigated under steady-state conditions, mainly for storage and separation processes. However, the process in a sorption compressor goes through various temperatures, pressures and adsorption concentrations; therefore, it differs from the common mixed gases adsorption applications. In order to simulate the sorption process in a compressor a numerical analysis for mixed gases is developed, based on pure gas adsorption characteristics. The pure gas adsorption properties have been measured for four gases (nitrogen, methane, ethane, and propane) with Norit-RB2 activated carbon. A single adsorption model is desired to describe the adsorption of all four gases. This model is further developed to a mixed-gas adsorption model. In future work more adsorbents will be tested using these four gases and the adsorption model will be verified against experimental results of mixed-gas adsorption measurements.

  17. Visualization and Measurement of Adsorption/Desorption Process of Ethanol in Activated Carbon Adsorber

    NASA Astrophysics Data System (ADS)

    Asano, Hitoshi; Murata, Kenta; Takenaka, Nobuyuki; Saito, Yasushi

    Adsorption refrigerator is one of the efficient tools for waste heat recovery, because the system is driven by heat at relative low temperature. However, the coefficient of performance is low due to its batch operation and the heat capacity of the adsorber. In order to improve the performance, it is important to optimize the configuration to minimize the amount of driving heat, and to clarify adsorption/desorption phenomena in transient conditions. Neutron radiography was applied to visualize and measure the adsorption amount distribution in an adsorber. The visualization experiments had been performed at the neutron radiography facility of E-2 port of Kyoto University Research Reactor. Activated carbon and ethanol were used as the adsorbent and refrigerant. From the acquired radiographs, adsorption amount was quantitatively measured by applying the umbra method using a checkered neutron absorber with boron powder. Then, transient adsorption and desorption processes of a rectangular adsorber with 84 mm in width, 50 mm in height and 20 mm in depth were visualized. As the result, the effect of fins in the adsorbent layer on the adsorption amount distribution was clearly visualized.

  18. Adsorption of nisin and pediocin on nanoclays.

    PubMed

    Meira, Stela Maris Meister; Jardim, Arthur Izé; Brandelli, Adriano

    2015-12-01

    Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) were studied as potential carriers for the antimicrobial peptides nisin and pediocin. Adsorption occurred from peptide solutions in contact with nanoclays at room temperature. Higher adsorption of nisin and pediocin was obtained on bentonite. The antimicrobial activity of the resultant bacteriocin-nanoclay systems was analyzed using skimmed milk agar as food simulant and the largest inhibition zones were observed against Gram-positive bacteria for halloysite samples. Bacteriocins were intercalated into the interlayer space of montmorillonites as deduced from the increase of the basal spacing measured by X-ray diffraction (XRD) assay. Infrared spectroscopy suggested non-electrostatic interactions, such as hydrogen bonding between siloxane groups from clays and peptide molecules. Transmission electron microscopy did not show any alteration in morphologies after adsorption of antimicrobial peptides on bentonite and halloysite. These results indicate that nanoclays, especially halloysite, are suitable nanocarriers for nisin and pediocin adsorption.

  19. Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp).

    PubMed

    Sun, Xiuquan; Wick, Collin D; Thallapally, Praveen K; McGrail, B Peter; Dang, Liem X

    2011-03-31

    Enhancing the efficiency of the Rankine cycle, which is utilized for multiple renewable energy sources, requires the use of a working fluid with a high latent heat of vaporization. To further enhance its latent heat, a working fluid can be placed in a metal organic heat carrier (MOHC) with a high heat of adsorption. One such material is Ni\\DOBDC, in which linear alkanes have a higher heat of adsorption than cyclic alkanes. We carried out molecular dynamics simulations to investigate the structural, diffusive, and adsorption properties of n-hexane and cyclohexane in Ni\\DOBDC. The strong binding for both n-hexane and cyclohexane with Ni\\DOBDC is attributed to the increase of the heat of adsorption observed in experiments. Our structural results indicate the organic linkers in Ni\\DOBDC are the primary binding sites for both n-hexane and cyclohexane molecules. However, at all temperatures and loadings examined in present work, n-hexane clearly showed stronger binding with Ni\\DOBDC than cyclohexane. This was found to be the result of the ability of n-hexane to reconfigure its structure to a greater degree than cyclohexane to gain more contacts between adsorbates and adsorbents. The geometry and flexibility of guest molecules were also related to their diffusivity in Ni\\DOBDC, with higher diffusion for flexible molecules. Because of the large pore sizes in Ni\\DOBDC, energetic effects were the dominant force for alkane adsorption and selectivity.

  20. Interfacial thermodynamics of protein adsorption and ion co-adsorption. III. Electrochemistry of bovine serum albumin adsorption on silver iodide.

    PubMed

    Fraaije, J G; Norde, W; Lyklema, J

    1991-12-01

    An experimental analysis of charge regulation in protein adsorption is presented. The model system consists of colloidal particles of the slightly water soluble salt silver iodide as the adsorbent and the protein bovine serum albumin as the adsorbate. Protein adsorption experiments corroborate earlier findings that albumin adsorbs maximally close to the isoelectric point of the protein. The adsorption is reversible with respect to protein-protein exchange. The charge regulation is studied by novel potentiometric titrations. The Galvani potential of the adsorbent, partially covered with protein, is varied by the addition of AgNO3/KI while the pH is kept constant by means of a pH-stat. It is shown that the ion co-adsorption is a linear decreasing function of the blank surface charge density. The results are consistent with thermodynamics: for the first time a few phenomenological linkage relations between the ion co-adsorptions and chemical potentials are verified experimentally. The charge regulation is interpreted in terms of a contact layer model, which explains the ion co-adsorption by compounded ion exchange equilibria in the small layer of atomic contact between adsorbed protein and surface.

  1. Defluoridation of drinking water using adsorption processes.

    PubMed

    Loganathan, Paripurnanda; Vigneswaran, Saravanamuthu; Kandasamy, Jaya; Naidu, Ravi

    2013-03-15

    Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Mechanisms of fibrinogen adsorption at solid substrates.

    PubMed

    Adamczyk, Zbigniew; Bratek-Skicki, Anna; Żeliszewska, Paulina; Wasilewska, Monika

    2014-01-01

    The aim of this work was to critically review recent results pertinent to fibrinogen adsorption at solid/electrolyte interfaces with the emphasis focused on a quantitative analysis of these processes in terms of the electrostatic interactions. Accordingly, in the first part, the primary chemical structure of fibrinogen is analyzed. Physicochemical data pertinent to the bulk properties derived from hydrodynamic, dynamic light scattering and micro-electrophoretic measurements aided by theoretical modeling are discussed. Possible conformations and the effective charge distribution over the fibrinogen molecule for various pH an ionic strength are defined, especially the semi-collapsed conformation prevailing at physiological conditions. Adsorption kinetics of fibrinogen at hydrophilic and hydrophobic (polymer modified) substrates determined by various techniques is described. Adsorption at polymeric carrier particles, pertinent to immunological assays, studied in terms of electrokinetic and concentration depletion methods, are also considered. The reversibility of adsorption, fibrinogen molecule orientations and maximum coverages are thoroughly discussed. The stability of fibrinogen monolayers formed at these carrier particles in respect to pH and ionic strength cyclic changes is also discussed. In the final section interactions and deposition of model colloid particles on fibrinogen monolayers are analyzed which allows one to derive valuable information about molecule orientations. Based on the physicochemical data, adsorption kinetics and colloid particle deposition measurements, probable adsorption mechanisms of fibrinogen on solid/electrolyte interfaces are defined.

  3. Gas adsorption capacity of wood pellets

    DOE PAGES

    Yazdanpanah, F.; Sokhansanj, Shahabaddine; Lim, C. Jim; ...

    2016-02-03

    In this paper, temperature-programmed desorption (TPD) analysis was used to measure and analyze the adsorption of off-gases and oxygen by wood pellets during storage. Such information on how these gases interact with the material helps in the understanding of the purging/stripping behavior of off-gases to develop effective ventilation strategies for wood pellets. Steam-exploded pellets showed the lowest carbon dioxide (CO2) uptake compared to the regular and torrefied pellets. The high CO2 adsorption capacity of the torrefied pellets could be attributed to their porous structure and therefore greater available surface area. Quantifying the uptake of carbon monoxide by pellets was challengingmore » due to chemical adsorption, which formed a strong bond between the material and carbon monoxide. The estimated energy of desorption for CO (97.8 kJ/mol) was very high relative to that for CO2 (7.24 kJ/mol), demonstrating the mechanism of chemical adsorption and physical adsorption for CO and CO2, respectively. As for oxygen, the strong bonds that formed between the material and oxygen verified the existence of chemical adsorption and formation of an intermediate material.« less

  4. Gas adsorption capacity of wood pellets

    SciTech Connect

    Yazdanpanah, F.; Sokhansanj, Shahabaddine; Lim, C. Jim; Lau, A.; Bi, X. T.

    2016-02-03

    In this paper, temperature-programmed desorption (TPD) analysis was used to measure and analyze the adsorption of off-gases and oxygen by wood pellets during storage. Such information on how these gases interact with the material helps in the understanding of the purging/stripping behavior of off-gases to develop effective ventilation strategies for wood pellets. Steam-exploded pellets showed the lowest carbon dioxide (CO2) uptake compared to the regular and torrefied pellets. The high CO2 adsorption capacity of the torrefied pellets could be attributed to their porous structure and therefore greater available surface area. Quantifying the uptake of carbon monoxide by pellets was challenging due to chemical adsorption, which formed a strong bond between the material and carbon monoxide. The estimated energy of desorption for CO (97.8 kJ/mol) was very high relative to that for CO2 (7.24 kJ/mol), demonstrating the mechanism of chemical adsorption and physical adsorption for CO and CO2, respectively. As for oxygen, the strong bonds that formed between the material and oxygen verified the existence of chemical adsorption and formation of an intermediate material.

  5. Toward understanding reactive adsorption of ammonia on Cu-MOF/graphite oxide nanocomposites.

    PubMed

    Petit, Camille; Huang, Liangliang; Jagiello, Jacek; Kenvin, Jeffrey; Gubbins, Keith E; Bandosz, Teresa J

    2011-11-01

    The adsorption of ammonia on HKUST-1 (a metal-organic framework, MOF) and HKUST-1/graphite oxide (GO) composites was investigated in two different experimental conditions. From the isotherms, the isosteric heats of adsorption were calculated from the Clausius-Clapeyron equation following the virial approach. The results on HKUST-1 were compared with those obtained using molecular simulation studies. All materials exhibit higher ammonia adsorption capacities than those reported in the literature. The ammonia adsorption on the composites is higher than that measured separately on the MOF component and on GO. The strong adsorption of ammonia caused by chemical interactions on different adsorption sites is evidenced by the trends in the isosteric heats of adsorption. The molecular simulations conducted on HKUST-1 support the trends observed experimentally. In particular, the strong chemisorption of ammonia on the metallic centers of HKUST-1 is confirmed. Nevertheless, higher adsorption capacities are predicted compared with the experimental results. This discrepancy is mainly assigned to the partial collapse of the MOF structure upon exposure to ammonia, which is not accounted for in the simulation study.

  6. Adsorption mechanism of cadmium on juniper bark and wood

    Treesearch

    Eun Woo Shin; K. G. Karthikeyan; Mandla A. Tshabalala

    2007-01-01

    In this study the capacity of sorbents prepared from juniper wood (JW) and bark (JB) to adsorb cadmium (Cd) from aqueous solutions at different pH values was compared. Adsorption behavior was characterized through adsorption kinetics, adsorption isotherms, and adsorption edge experiments. Results from kinetics and isotherm experiments showed that JB (76.3–91.6 lmol Cd...

  7. Albumin (BSA) Adsorption over Graphene in Aqueous Environment: Influence of Orientation, Adsorption Protocol, and Solvent Treatment.

    PubMed

    Vilhena, J G; Rubio-Pereda, Pamela; Vellosillo, Perceval; Serena, P A; Pérez, Rubén

    2016-02-23

    We report 150 ns explicit solvent MD simulations of the adsorption on graphene of albumin (BSA) in two orientations and using two different adsorption protocols, i.e., free and forced adsorption. Our results show that free adsorption occurs with little structural rearrangements. Even taking adsorption to an extreme, by forcing it with a 5 nN downward force applied during the initial 20 ns, we show that along a particular orientation BSA is able to preserve the structural properties of the majority of its binding sites. Furthermore, in all the cases considered in this work, the ibuprofen binding site has shown a strong resilience to structural changes. Finally, we compare these results with implicit solvent simulations and find that the latter predicts an extreme protein unfolding upon adsorption. The origin of this discrepancy is attributed to a poor description of the water entropic forces at interfaces in the implicit solvent methods.

  8. Assessing the Adsorption Properties of Shales

    NASA Astrophysics Data System (ADS)

    Pini, R.

    2014-12-01

    Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity through the mechanism of adsorption. The current ability to extract natural gas that is adsorbed in the rock's matrix is limited and current technology focuses primarily on the free gas in the fractures, thus leading to very low recovery efficiencies. Shales constitute also a great portion of so-called caprocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing leakage phenomena. Whether it is a reservoir or a caprock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm. The data are analyzed by using thermodynamically rigorous measures of adsorption and a graphical method is applied for their interpretation. The density of the adsorbed phase is estimated and compared to data reported in the literature; the latter is key to disclose gas-reserves and/or potential storage capacity estimates. When evaluated against classic adsorbent materials, the adsorption mechanism in shales is further complicated by

  9. Adsorption of aqueous copper on peanut hulls

    NASA Astrophysics Data System (ADS)

    Davis, Kanika Octavia

    A method was established for measuring the adsorption of Cu(II) from aqueous solution to unmodified and modified peanut hulls at constant temperature and pH. Modification of the hulls was performed by oxidation with alkaline hydrogen peroxide. During the modification process, the hydrogen peroxide solubilizes the lignin component, making the surface more porous which increases the availability of binding sites, while simultaneously oxidizing the cellulose. The oxidation of alcohol groups creates more binding sites by creating functional groups such as COO-, which increases chelation to metal ions. Fourier transform infrared spectroscopy confirms delignification of the peanut hulls by the disappearance of carboxyl peaks of the modified hulls, which were originally produced from the lignin content. Although, oxidation is not fully confirmed, it is not ruled out because the expected carboxylate peak (1680 cm-1) maybe overshadowed by a broad peak due to OH bending of water adsorbed to the hulls. Hulls adsorbed copper from solutions in the concentration range of 50-1000 ppm of CuCl2. Concentrations of pre- and post-adsorption solutions were determined using inductively coupled plasma optical emission spectroscopy. The adsorption isotherms were fit to known two and three-parameter models, evaluated and the binding mechanism was inferred. Maximum surface coverage was 3.5 +/- 0.6 mg Cu2+ /g hull for unmodified hulls and 11 +/- 1 mg Cu2+/g hull for modified hulls. The adsorption for the hulls is best described by the Langmuir model, suggesting monolayer, homogeneous adsorption. With a free energy of adsorption of 10.5 +/- 0.9 kJ/mol for unmodified hulls and 14.5 +/-0.4 kJ/mol for modified hulls, the process is categorized as chemisorption for both types of hulls. The adsorption for both hulls is also described by the Redlich-Peterson model, giving beta nearer to 1 than 0, which further suggests homogeneous adsorption described by the Langmuir model. After rinsing the hulls

  10. Methane adsorption on aggregates of fullerenes: site-selective storage capacities and adsorption energies.

    PubMed

    Kaiser, Alexander; Zöttl, Samuel; Bartl, Peter; Leidlmair, Christian; Mauracher, Andreas; Probst, Michael; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2013-07-01

    Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118-281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane-methane and fullerene-methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes.

  11. Methane Adsorption on Aggregates of Fullerenes: Site-Selective Storage Capacities and Adsorption Energies

    PubMed Central

    Kaiser, Alexander; Zöttl, Samuel; Bartl, Peter; Leidlmair, Christian; Mauracher, Andreas; Probst, Michael; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2013-01-01

    Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118–281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane–methane and fullerene–methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes. PMID:23744834

  12. Kinetic modelling of cytochrome c adsorption on SBA-15.

    PubMed

    Yokogawa, Yoshiyuki; Yamauchi, Rie; Saito, Akira; Yamato, Yuta; Toma, Takeshi

    2017-01-01

    The adsorption capacity of mesoporous silicate (MPS) materials as an adsorbent for protein adsorption from the aqueous phase and the mechanism of the adsorption processes by comparative analyses of the applicability of five kinetic transfer models, pseudo-first-order model, pseudo-second-order model, Elovich kinetic model, Bangham's equation model, and intraparticle diffusion model, were investigated. A mixture of tetraethyl orthosilicate (TEOS) and triblock copolymer as a template was stirred, hydrothermally treated to form the mesoporous SBA-15 structure, and heat-treated at 550°C to form the MPS material, SBA-15. The synthesized SBA-15 was immersed in a phosphate buffered saline (PBS) solution containing cytochrome c for 2, 48, and 120 hours at 4°C. The TEM observations of proteins on/in mesoporous SBA-15 revealed the protein behaviors. The holes of the MPS materials were observed to overlap those of the stained proteins for the first 2 hours of immersion. The stained proteins were observed between primary particles and partly inside the mesoporous channels in the MPS material when it had been immersed for 48 hours. For MPS when it had been immersed for 120 hours, stained proteins were observed in almost all meso-scale channels of MPS. The time profiles for adsorption of proteins can be described well by Bangham's equation model and the intraparticle diffusion model. The Bangham's equation model is based on the assumption that pore diffusion was the only rate controlling step during adsorption, whose contribution to the overall mechanism of cytochrome c adsorption on SBA-15 should not be neglected. The kinetic curves obtained from the experiment for cytochrome c adsorption on SBA-15 could show the three steps: the initial rapid increase of the adsorbed amount of cytochrome c, the second gradual increase, and the final equilibrium stage. These three adsorption steps can be interpreted well by the multi-linearity of the intraparticle diffusion model

  13. A FOURIER TRANSFORM INFRARED PHOTOACOUSTIC SPECTROSCOPY (FTIR-PAS) STUDY OF THE ADSORPTION OF ORGANOPHOSPHORUS COMPOUNDS ON HEAT-TREATED MAGNESIUM OXIDE. (R825549C015)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Effect of pyrolysis temperatures and times on the adsorption of cadmium onto orange peel derived biochar.

    PubMed

    Tran, Hai Nguyen; You, Sheng-Jie; Chao, Huan-Ping

    2016-02-01

    The mechanism and capacity of adsorption of cadmium (Cd) on orange peel (OP)-derived biochar at various pyrolysis temperatures (400, 500, 600, 700 and 800°C) and heating times (2 and 6 h) were investigated. Biochar was characterized using proximate analysis, point of zero charge (PZC) analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Equilibrium and kinetic experiments of Cd adsorption on biochar were performed. The results indicated that the pH value at PZC of biochar approached 9.5. Equilibrium can be reached rapidly (within 1 min) in kinetic experiments and a removal rate of 80.6-96.9% can be generated. The results fitted the pseudo-second-order model closely. The adsorption capacity was estimated using the Langmuir model. The adsorption capacity of Cd on biochar was independent of the pyrolysis temperature and heating time (p>0.01). The maximum adsorption capacity of Cd was 114.69 (mg g(-1)). The adsorption of Cd on biochar was regarded as chemisorption. The primary adsorption mechanisms were regarded as Cπ-cation interactions and surface precipitation. Cadmium can react with calcite to form the precipitation of (Ca,Cd)CO3 on the surface of biochar. The OP-derived biochar can be considered a favourable alternative and a new green adsorbent for removing Cd(2+) ions from an aqueous solution.

  15. INFLUENCE OF THE KRAMER EFFECT ON ADSORPTION ON METALS.

    DTIC Science & Technology

    ADSORPTION, *ALLOYS, *FILMS, *METALS, *PROCESSING, ACIDS, ALCOHOLS , CYCLOHEXANES, EXCHANGE REACTIONS , FATTY ACIDS, HEAT TREATMENT , LEAD ALLOYS...LINOLENIC ACID, MACHINING , MEASUREMENT, MONOMOLECULAR FILMS, OLEIC ACID, SURFACES, TIN ALLOYS, WATER

  16. Thermodynamic formalism of water uptakes on solid porous adsorbents for adsorption cooling applications

    NASA Astrophysics Data System (ADS)

    Sun, Baichuan; Chakraborty, Anutosh

    2014-05-01

    This Letter presents a thermodynamic formulation to calculate the amount of water vapor uptakes on various adsorbents such as zeolites, metal organic frameworks, and silica gel for the development of an advanced adsorption chiller. This formalism is developed from the rigor of the partition distribution function of each water vapor adsorptive site on adsorbents and the condensation approximation of adsorptive water molecules and is validated with experimental data. An interesting and useful finding has been established that the proposed model is thermodynamically connected with the pore structures of adsorbent materials, and the water vapor uptake highly depends on the isosteric heat of adsorption at zero surface coverage and the adsorptive sites of the adsorbent materials. Employing the proposed model, the thermodynamic trends of water vapor uptakes on various adsorbents can be estimated.

  17. Adsorption of carbon dioxide, methane and nitrogen on an ultramicroporous copper metal-organic framework.

    PubMed

    Wu, Xiaofei; Yuan, Bin; Bao, Zongbi; Deng, Shuguang

    2014-09-15

    An ultramicroporous copper metal-organic framework (Cu-MOF), Cu(hfipbb)(H2hfipbb)0.5 [H2hfipbb=4,4'-(hexafluoro-isopropylidene) bis(benzoic acid)] was successfully synthesized by a microwave-assisted method (1) with a shorter reaction time and higher MOFs yield. The obtained Cu-MOF sample was characterized with scanning electron microscopy for crystal structure, powder X-ray diffraction for phase structure, and carbon dioxide adsorption at 273 K for pore textural properties. Single-component adsorption (adsorption equilibrium and kinetics) of CO2, CH4, and N2 on 1 was measured using a Micromeritics ASAP 2020 adsorption porosimeter at 278, 298 and 318 K, and pressures up to 1 bar. Isosteric heats of adsorption, Henry's constants, and diffusion time constants were calculated and carefully analyzed. Adsorption equilibrium selectivity (α), adsorbent selection parameter for pressure swing adsorption processes (S), kinetic selectivity and combined separation selectivity (β) for CO2/CH4, CO2/N2 and CH4/N2 binary mixtures were estimated based on the single-component adsorption data. The relative high values of the adsorption selectivities suggest that Cu-MOF is a promising adsorbent for separating CO2/CH4, CO2/N2 and CH4/N2 gas pairs. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Adsorption and diffusion of carbon dioxide on metal-organic framework (MOF-5)

    SciTech Connect

    Zhao, Z.X.; Li, Z.; Lin, Y.S.

    2009-11-15

    Adsorption equilibrium and diffusion of CO{sub 2} on microporous metal-organic frameworks (MOF-5, or IRMOF-1) crystals were experimentally studied by the gravimetric method in the pressure range up to 1 atm. The MOF-5 crystal cubes of about 40-60 {mu} m in sizes were synthesized by the solvothermal method. Freundlich adsorption isotherm equation can fit well CO{sub 2} adsorption isotherms on MOF-5, with isosteric heat of adsorption of about 34 kJ/mol. Diffusion coefficient of CO{sub 2} in the MOF-5 is in the range of 8.1-11.5 x 10{sup -9} cm{sup 2}/s in 295-331K with activation energy of 7.61 kJ/mol. MOF-5 offers attractive adsorption properties as an adsorbent for separation of CO{sub 2} from flue gas.

  19. Preparation of narrow pores carbon suitable for hydrogen sulfide adsorption

    SciTech Connect

    Tanada, S.; Kita, T.; Boki, K.; Kozaki, Y.

    1985-01-01

    Microporous N-containing activated carbon (N-CAC) suitable for hydrogen sulfide adsorption was prepared by impregnating raw activated carbon with a 25% methylol melamine urea solution and then heating it at different temperatures from 100 to 1000/sup 0/C. The structures of raw activated carbon and N-CAC No. 8 carbonized at the most suitable temperature 850/sup 0/C have been discussed based on applying the Dubinin-Radushkevich equation to adsorption isotherm of hydrogen sulfide. The 12.2% increase in micropore volume of N-CAC No.8 result from the numerical increase of micropores rather than radial expansion of micropores. The relation of q and ..delta..S could be consistently explained by the interaction of hydrogen sulfide with micropores of adsorbents.

  20. Investigation of Microgranular Adsorptive Filtration System

    NASA Astrophysics Data System (ADS)

    Cai, Zhenxiao

    Over the past few decades, enormous advances have been made in the application of low-pressure membrane filtration to both drinking water and wastewater treatment. Nevertheless, the full potential of this technology has not been reached, due primarily to limitations imposed by membrane fouling. In drinking water treatment, much of the fouling is caused by soluble and particulate natural organic matter (NOM). Efforts to overcome the problem have focused on removal of NOM from the feed solution, usually by addition of conventional coagulants like alum and ferric chloride (FeCl3) or adsorbents like powdered activated carbon (PAC). While coagulants and adsorbents can remove a portion of the NOM, their performance with respect to fouling control has been inconsistent, often reducing fouling but sometimes having no effect or even exacerbating fouling. This research investigated microgranular adsorptive filtration (muGAF), a process that combines three existing technologies---granular media filtration, packed bed adsorption, and membrane filtration---in a novel way to reduce membrane fouling while simultaneously removing NOM from water. In this technology, a thin layer of micron-sized adsorbent particles is deposited on the membrane prior to delivering the feed to the system. The research reported here represents the first systematic study of muGAF, and the results demonstrate the promising potential of this process. A new, aluminum-oxide-based adsorbent---heated aluminum oxide particles (HAOPs)---was synthesized and shown to be very effective for NOM removal as well as fouling reduction in muGAF systems. muGAF has also been demonstrated to work well with powdered activated carbon (PAC) as the adsorbent, but not as well as when HAOPs are used; the process has also been successful when used with several different membrane types and configurations. Experiments using a wide range of operational parameters and several analytical tools lead to the conclusion that the fouling

  1. Adsorption of plutonium oxide nanoparticles.

    PubMed

    Schmidt, Moritz; Wilson, Richard E; Lee, Sang Soo; Soderholm, L; Fenter, P

    2012-02-07

    Adsorption of monodisperse cubic plutonium oxide nanoparticles ("Pu-NP", [Pu(38)O(56)Cl(x)(H(2)O)(y)]((40-x)+), with a fluorite-related lattice, approximately 1 nm in edge size) to the muscovite (001) basal plane from aqueous solutions was observed in situ (in 100 mM NaCl background electrolyte at pH 2.6). Uptake capacity of the surface quantified by α-spectrometry was 0.92 μg Pu/cm(2), corresponding to 10.8 Pu per unit cell area (A(UC)). This amount is significantly larger than that of Pu(4+) needed for satisfying the negative surface charge (0.25 Pu(4+) for 1 e(-)/A(UC)). The adsorbed Pu-NPs cover 17% of the surface area, determined by X-ray reflectivity (XR). This correlates to one Pu-NP for every 14 unit cells of muscovite, suggesting that each particle compensates the charge of the unit cells onto which it adsorbs as well as those in its direct proximity. Structural investigation by resonant anomalous X-ray reflectivity distinguished two different sorption states of Pu-NPs on the surface at two different regimes of distance from the surface. A fraction of Pu is distributed within 11 Å from the surface. The distribution width matches the Pu-NP size, indicating that this species represents Pu-NPs adsorbed directly on the surface. Beyond the first layer, an additional fraction of sorbed Pu was observed to extend more broadly up to more than 100 Å from the surface. This distribution is interpreted as resulting from "stacking" or aggregation of the nanoparticles driven by sorption and accumulation of Pu-NPs at the interface although these Pu-NPs do not aggregate in the solution. These results are the first in situ observation of the interaction of nanoparticles with a charged mineral-water interface yielding information important to understanding the environmental transport of Pu and other nanophase inorganic species.

  2. Adsorption of Benzoic Acid in Aqueous Solution by Bagasse Fly Ash

    NASA Astrophysics Data System (ADS)

    Suresh, S.

    2012-09-01

    This paper reports the studies on the benzoic acid (BA) onto bagasse fly ash (BFA) was studied in aqueous solution in a batch system. Physico-chemical properties including surface area, surface texture of the GAC before and after BA adsorption onto BFA were analysed using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The optimum initial pH for the adsorption of BA was found to be 5.56. The adsorbent dose was 10 g/l for BFA and the equilibrium time 8 h of reaction. Pseudo first and second order models were used to find the adsorption kinetics. It was found that intraparticle diffusion played important role in the adsorption mechanisms of BA and the adsorption kinetics followed pseudo-second order kinetic model rather than the pseudo first order kinetic model. Isotherm data were generated for BA solution having initial concentrations of BA in the range of 10-200 mg/l for the BFA dosage of 10 g/l at temperatures of 288, 303, and 318 K. The adsorption of BA onto BFA was favorably influenced by an increase in temperature. Equilibrium data were well represented by the Redlich-Peterson isotherm model. Values of the change in entropy ( ΔS 0), heat of adsorption ( ΔH 0) for adsorption of BA on BFA was found to be 120.10 and 19.61 kJ/mol respectively. The adsorption of BA onto BFA was an endothermic reaction. Desorption of BA from BFA was studied by various solvents method. Acetic acid was found to be a better eluant for desorption of BA with a maximum desorption efficiency of 55.2 %. Owing to its heating value, spent BFA can be used as a co-fuel for the production of heat in boiler furnaces.

  3. Adsorption equilibrium of organic vapors on single-walled carbon nanotubes

    USGS Publications Warehouse

    Agnihotri, S.; Rood, M.J.; Rostam-Abadi, M.

    2005-01-01

    Gravimetric techniques were employed to determine the adsorption capacities of commercially available purified electric arc and HiPco single-walled carbon nanotubes (SWNTs) for organic compounds (toluene, methyl ethyl ketone (MEK), hexane and cyclohexane) at relative pressures, p/p0, ranging from 1 ?? 10-4 to 0.95 and at isothermal conditions of 25, 37 and 50 ??C. The isotherms displayed both type I and type II characteristics. Adsorption isotherm modeling showed that SWNTs are heterogeneous adsorbents, and the Freundlich equation best describes the interaction between organic molecules and SWNTs. The heats of adsorption were 1-4 times the heats of vaporization, which is typical for physical adsorption of organic vapors on porous carbons. ?? 2005 Elsevier Ltd. All rights reserved.

  4. Adsorption of reovirus by minerals and soils.

    PubMed Central

    Moore, R S; Taylor, D H; Reddy, M M; Sturman, L S

    1982-01-01

    Adsorption of [35S]methionine-labeled reovirus by 30 dry soils, minerals, and finely ground rocks suspended in synthetic freshwater at pH 7 was investigated to determine the conditions necessary for optimum virus removal during land application of wastewaters. All of the minerals and soils studied were excellent adsorbents of reovirus, with greater than 99% of the virus adsorbed after 1 h at 4 degrees C. Thereafter, virus remaining in suspension was significantly inactivated, and within 24 h a three to five log10 reduction in titer occurred. The presence of divalent cations, i.e., Ca2+ and Mg2+, in synthetic freshwater enhanced removal, whereas soluble organic matter decreased the amount of virus adsorbed in secondary effluent. The amount of virus adsorbed by these substrates was inversely correlated with the amount of organic matter, capacity to adsorb cationic polyelectrolyte, and electrophoretic mobility. Adsorption increased with increasing available surface area, as suspended infectivity was reduced further by the more finely divided substrates. However, the organic content of the soils reduced the level of infectious virus adsorbed below that expected from surface area measurements alone. The inverse correlation between virus adsorption and substrate capacity for cationic polyelectrolyte indicates that the adsorption of infectious reovirus particles is predominately a charged colloidal particle-charged surface interaction. Thus, adsorption of polyelectrolyte may be useful in predicting the fate of viruses during land application of sewage effluents and sludges. PMID:7149717

  5. Predicting neopentane isosteric enthalpy of adsorption at zero coverage in MCM-41.

    PubMed

    Herdes, Carmelo; Ferreiro-Rangel, Carlos Augusto; Düren, Tina

    2011-06-07

    The isosteric enthalpy of adsorption for neopentane at relative pressures down to 3 × 10(-8) in MCM-41 was predicted for the temperature range from -15 to 0 °C. At such low pressures and temperatures, experimental measurements become problematic for this system. We used an atomistic model for MCM-41 obtained by means of a kinetic Monte Carlo method mimicking the synthesis of the material. The model was parametrized to represent experimental nitrogen adsorption isotherms at 77 K using grand canonical Monte Carlo simulations. The simulated isosteric enthalpy of adsorption shows very good agreement with available experimental data, demonstrating that GCMC simulations can predict heats of adsorption for conditions that are challenging for experimental measurements. Additional insights into the adsorption mechanisms, derived from energetic analysis at the molecular level, are also presented.

  6. Adsorption of surfactants and polymers at interfaces

    NASA Astrophysics Data System (ADS)

    Rojas, Orlando Jose

    Surface tension and high-resolution laser light scattering experiments were used to investigate the adsorption of isomeric sugar-based surfactants at the air/liquid interface in terms of surfactant surface packing and rheology. Soluble monolayers of submicellar surfactant solutions exhibited a relatively viscous behavior. It was also proved that light scattering of high-frequency thermally-induced capillary waves can be utilized to study surfactant exchange between the surface and the bulk solution. Such analysis revealed the existence of a diffusional relaxation mechanism. A procedure based on XPS was developed for quantification, on an absolute basis, of polymer adsorption on mica and Langmuir-Blodgett cellulose films. The adsorption of cationic polyelectrolytes on negatively-charged solid surfaces was highly dependent on the polymer ionicity. It was found that the adsorption process is driven by electrostatic mechanisms. Charge overcompensation (or charge reversal) of mica occurred after adsorption of polyelectrolytes of ca. 50% charge density, or higher. It was demonstrated that low-charge-density polyelectrolytes adsorb on solid surfaces with an extended configuration dominated by loops and tails. In this case the extent of adsorption is limited by steric constraints. The conformation of the polyelectrolyte in the adsorbed layer is dramatically affected by the presence of salts or surfactants in aqueous solution. The phenomena which occur upon increasing the ionic strength are consistent with the screening of the electrostatic attraction between polyelectrolyte segments and solid surface. This situation leads to polyelectrolyte desorption accompanied by both an increase in the layer thickness and the range of the steric force. Adsorbed polyelectrolytes and oppositely charged surfactants readily associate at the solid/liquid interface. Such association induces polyelectrolyte desorption at a surfactant concentration which depends on the polyelectrolyte charge

  7. Adsorption behavior of heavy metals on biomaterials.

    PubMed

    Minamisawa, Mayumi; Minamisawa, Hiroaki; Yoshida, Shoichiro; Takai, Nobuharu

    2004-09-08

    We have investigated adsorption of Cd(II) and Pb(II) at pH 2-6.7 onto the biomaterials chitosan, coffee, green tea, tea, yuzu, aloe, and Japanese coarse tea, and onto the inorganic adsorbents, activated carbon and zeolite. High adsorptive capabilities were observed for all of the biomaterials at pH 4 and 6.7. In the adsorption of Cd(II), blend coffee, tea, green tea, and coarse tea have comparable loading capacities to activated carbon and zeolite. Although activated carbon, zeolite, and chitosan are utilized in a variety of fields such as wastewater treatment, chemical and metallurgical engineering, and analytical chemistry, these adsorbents are costly. On the other hand, processing of the test biomaterials was inexpensive, and all the biomaterials except for chitosan were able to adsorb large amounts of Pb(II) and Cd(II) ions after a convenient pretreatment of washing with water followed by drying. The high adsorption capability of the biomaterials prepared from plant materials is promising in the development of a novel, low-cost adsorbent. From these results, it is concluded that heavy metal removal using biomaterials would be an effective method for the economic treatment of wastewater. The proposed adsorption method was applied to the determination of amounts of Cd(II) and Pb(II) in water samples.

  8. Adsorption of Wine Constituents on Functionalized Surfaces.

    PubMed

    Mierczynska-Vasilev, Agnieszka; Smith, Paul A

    2016-10-18

    The adsorption of macromolecules on solid surfaces is of great importance in the field of nanotechnology, biomaterials, biotechnological, and food processes. In the field of oenology adsorption of wine macromolecules such as polyphenols, polysaccharides, and proteins is much less desirable on membrane materials because of fouling and reduced filtering performance. On the other hand, adsorption of these molecules on processing aids is very beneficial for achieving wine clarity and stability. In this article, the effect of surface chemical functionalities on the adsorption of white, rosé, and red wine constituents was evaluated. Allylamine, acrylic acid, and ethanol were selected as precursors for plasma polymerization in order to generate coatings rich in amine, carboxyl, and hydroxyl chemical groups, respectively. The surface chemical functionalities were characterized by X-ray photoelectron spectroscopy (XPS) and the ability of different surface chemical functionalities to adsorb wine constituents were characterized by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). The results demonstrated that the amine and carboxyl modified surfaces encourage adsorption of constituents from white wine. The hydroxyl modified surfaces have the ability to preferentially adsorb rosé wine constituents, whereas red wine adsorbed to the highest extent on acrylic acid surface.

  9. Surface characterization of titanium and adsorption of bovine serum albumin

    SciTech Connect

    Feng, B.; Weng, J.; Yang, B.C.; Chen, J.Y.; Zhao, J.Z.; He, L.; Qi, S.K.; Zhang, X.D

    2002-09-15

    The surface oxide films on titanium were characterized and the relationship between the characterization and the adsorption of bovine serum albumin (BSA) on titanium was studied. The surface oxide films on titanium were obtained by heat-treatment in different oxidizing atmospheres, such as air and water vapor. The surface roughness, energy, morphology, chemical composition and crystal structure were used to characterize the titanium surfaces. The characterization was performed using a profilometer, scanning electronic microscopy (SEM), a sessile drop method, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Percentages of surface hydroxyl groups were determined by XPS analysis for the titanium plates and the densities were measured by a chemical method for titanium powders. After heat-treatment, the titanium surfaces were uniformly roughened and the surface titanium oxide was predominantly rutile TiO{sub 2}. The crystal planes in the rutile films were preferentially orientated in the (110) plane with the highest density of titanium ions. Heat-treatment increased the surface energy and the amount of surface hydroxyl groups on the titanium. The different oxidizing atmospheres resulted in different percentages of oxygen species in the TiO{sub 2}, in the physisorbed water and acidic hydroxyl groups and in the basic hydroxyl groups on the titanium surfaces. The analysis for the adsorption of BSA on titanium confirmed that the surface characterization of titanium has a strong effect on the bioactivity of titanium. The BSA chemically adsorbed onto the titanium surfaces. The adsorption of BSA on the titanium surfaces was positively related with the amounts of their surface hydroxyl groups, including basic hydroxyl groups and acidic hydroxyl groups, and the values of the polar component of the total surface energy.

  10. Adsorption of H2, Ne, and N2 on Activated Charcoal

    NASA Technical Reports Server (NTRS)

    Chang, C. K.; Tward, E.; Boudaie, K. I.

    1986-01-01

    9-page report presents measured adsorption isotherms of hydrogen, neon, and nitrogen on activated charcoal for temperatures from 77 to 400 K and pressures from 1 to 80 atmospheres (0.1 to 8.1 MPa). Heats of adsorption calculated from isotherms also presented. Report gives expressions, based on ideal-gas law, which show relationship between different definitions of volume of gas adsorbed and used in describing low-pressure isotherms.

  11. Adsorption of aniline and toluidines on montmorillonite

    SciTech Connect

    Essington, M.E. )

    1994-09-01

    Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. In order to assess the ability of clay liner material to restrict the mobility of amine compounds under a variety of chemical conditions and to further elucidate amine adsorption characteristics, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+]- and K[sup +]-saturated Wyoming bentonite (SWy-1) was investigated. Adsorption experiments were performed under conditions of varied pH and ionic environment. Amine adsorption on montmorillonite is pH dependent. Maximum amine adsorption occurs when solution pH is approximately equal to the pK[sub a] of the anilinium ion deprotonation reaction (pH 4.45-5.08). An amine adsorption envelope results from the combined influence of increasing anilinium ion and anilinium-aniline complex formation (as pH decreases to the pK[sub a]) and amine competition with H[sup +] for surface sites, decreasing anilinium-aniline complex concentration, and decreasing aniline available for water bridging with exchangeable Ca[sup 2+] and K[sup +] (as solution pH decreases below the pK[sub a]). For any given amine, maximum adsorption increases with decreasing ionic strength. Maximum amine adsorption is greater in the Ca[sup 2+] systems than in the K[sup +] systems at equivalent cation charge and reflects the formation of an amine water bridge with the exchangeable Ca[sup 2+]. Amine adsorption is also greater in chloride systems compared with sulfate systems at comparable cation concentrations, possibly due to the formation of aqueous anilinium-sulfate complexes. The amine compounds are retained mainly by bentonite through a cation exchange process, the capacity of the clay to adsorb the amine compounds being a significant percentage of the exchange capacity at the pK[sub a]. However, amine retention decreases with increasing pH and is minimal at solution pH values greater than 7. 19 refs., 6 figs.

  12. Adsorption of phenanthrene on natural snow.

    PubMed

    Domine, Florent; Cincinelli, Alessandra; Bonnaud, Elodie; Martellini, Tania; Picaud, Sylvain

    2007-09-01

    The snowpack is a reservoir for semivolatile organic compounds (SVOCs) and, in particular, for persistent organic pollutants (POPs), which are sequestered in winter and released to the atmosphere or hydrosphere in the spring. Modeling these processes usually assumes that SVOCs are incorporated into the snowpack by adsorption to snow surfaces, but this has never been proven because the specific surface area (SSA) of snow has never been measured together with snow composition. Here we expose natural snow to phenanthrene vapors (one of the more volatile POPs) and measure for the first time both the SSA and the chemical composition of the snow. The results are consistent with an adsorption equilibrium. The measured Henry's law constant is H(Phen)(T) = 2.88 x 10(22) exp(-10660/7) Pa m2 mol(-1), with Tin Kelvin. The adsorption enthalpy is delta H(ads) = -89 +/- 18 kJ mol(-1). We also perform molecular dynamics calculations of phenanthrene adsorption to ice and obtain AHads = -85 +/- 8 kJ mol(-1), close to the experimental value. Results are applied to the adsorption of phenanthrene to the Arctic and subarctic snowpacks. The subarctic snowpack, with a low snow area index (SAI = 1000), is a negligible reservoir of phenanthrene, butthe colder Arctic snowpack, with SAI = 2500, sequesters most of the phenanthrene present in the (snow + boundary layer) system.

  13. Functionalization of delaminated zeolite ITQ-6 for the adsorption of carbon dioxide

    SciTech Connect

    Zukal, A.; Dominguez, I.; Mayerova, J.; Cejka, J.

    2009-09-15

    Novel functionalized adsorbents for CO{sub 2} separation were synthesized by grafting 3-aminopropyl, 3-(methylamino) propyl, or 3-(phenylamino)propyl ligands in the delaminated zeolite ITQ-6. On the basis of the texture parameters determined from nitrogen adsorption isotherms recorded at 77 K and the results of chemical analysis, physicochemical properties of functionalized ITQ-6 were evaluated and compared with those of mesoporous SBA-15 silica functionalized with the same ligands. To examine carbon dioxide adsorption on functionalized materials, adsorption isotherms at 293 K were measured. To obtain information on the surface energetics of CO{sub 2} adsorption on selected samples, isotherms were taken in the temperature range front 273 to 333 K and adsorption isosteres were calculated. Isosteric adsorption heats determined from the slope of adsorption isosteres proved that all of the 3-aminopropyl ligands in ITQ-6 take part in CO{sub 2} adsorption. It was found that in the whole region of CO{sub 2} pressures the efficiency of the amine ligand, defined as the number of adsorbed CO{sub 2} molecules per one airline ligand, is higher for functionalized ITQ-6 than for functionalized SBA-15 silica.

  14. Single-molecule imaging of protein adsorption mechanisms to surfaces.

    PubMed

    Zareh, Shannon Kian; Wang, Yan Mei

    2011-07-01

    Protein-surface interactions cause the desirable effect of controlled protein adsorption onto biodevices as well as the undesirable effect of protein fouling. The key to controlling protein-surface adsorptions is to identify and quantify the main adsorption mechanisms: adsorptions that occur (1) while depositing a protein solution onto dry surfaces and (2) after the deposition onto wet surfaces. Bulk measurements cannot reveal the dynamic protein adsorption pathways and thus cannot differentiate between the two adsorption mechanisms. We imaged the interactions of single streptavidin molecules with hydrophobic fused-silica surfaces in real-time. We observed both adsorbed proteins on surfaces and diffusing proteins near surfaces and analyzed their adsorption kinetics. Our analysis shows that the protein solution deposition process is the primary mechanism of streptavidin adsorption onto surfaces at the subnanomolar to nanomolar protein concentrations. Furthermore, we found that hydrophilic fused-silica surfaces can prevent the adsorption of streptavidin molecules. Copyright © 2010 Wiley-Liss, Inc.

  15. Optimal design of gas adsorption refrigerators for cryogenic cooling

    NASA Technical Reports Server (NTRS)

    Chan, C. K.

    1983-01-01

    The design of gas adsorption refrigerators used for cryogenic cooling in the temperature range of 4K to 120K was examined. The functional relationships among the power requirement for the refrigerator, the system mass, the cycle time and the operating conditions were derived. It was found that the precool temperature, the temperature dependent heat capacities and thermal conductivities, and pressure and temperature variations in the compressors have important impacts on the cooling performance. Optimal designs based on a minimum power criterion were performed for four different gas adsorption refrigerators and a multistage system. It is concluded that the estimates of the power required and the system mass are within manageable limits in various spacecraft environments.

  16. Adsorption of phenolic compound by aged-refuse.

    PubMed

    Xiaoli, Chai; Youcai, Zhao

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

  17. Effect of polymer adsorption on mobility ratio

    SciTech Connect

    Omar, A.E.

    1983-03-01

    Several properties of two of the viscous polymer fluids used in rheological control were investigated. Polymer adsorption on the rock surfaces of porous sandstones and its effect on permeability of producing formation was studied. A naturally occurring polymer, a Guar gum, was found greatly to reduce the permeability of the producing formation, although the use of a breaker solution was found to restore the permeability lost through polymer plugging. Use of appropriate breaker solution was found to reduce the permeability loss to only one or two per cent of the original value. Adsorption of the synthetic polymer, acrylamide, was found to be directly related to the shaliness of the porous sand. Deactivation of polymer due to adsorption was found to be significant in formations having large surface areas. The results indicate that polymer loss eventually results in a water bank ahead of the polymer solution and thus greatly reduces the polymer's effectiveness in water-flooding.

  18. Adsorption properties of thermally sputtered calcein film

    NASA Astrophysics Data System (ADS)

    Kruglenko, I.; Burlachenko, J.; Kravchenko, S.; Savchenko, A.; Slabkovska, M.; Shirshov, Yu.

    2014-05-01

    High humidity environments are often found in such areas as biotechnology, food chemistry, plant physiology etc. The controlling of parameters of such ambiences is vitally important. Thermally deposited calcein films have extremely high adsorptivity at exposure to water vapor of high concentration. This feature makes calcein a promising material for humidity sensing applications. The aim of this work is to explain high sensitivity and selectivity of calcein film to high humidity. Quartz crystal microbalance sensor, AFM and ellipsometry were used for calcein film characterization and adsorption properties investigation. The proposed model takes into account both the molecular properties of calcein (the presence of several functional groups capable of forming hydrogen bonds, and their arrangement) and the features of structure of thermally deposited calcein film (film restructuring due to the switching of bonds "calcein-calcein" to "calcein-water" in the course of water adsorption).

  19. Molecular simulation of adsorption and diffusion in VPI-5 and other aluminophosphates

    SciTech Connect

    Cracknell, R.F.; Gubbins, K.E. )

    1993-03-01

    Adsorption isotherms for argon in AlPO[sub 4]-5, AlPO[sub 4]-8, and VPI-5 were simulated at 77 and 87 K using the grand canonical Monte Carlo method. The shapes of the isotherms were found to be in qualitative agreement with published experimental data; however, the maximum predicted values of the adsorption were higher than the experimental values. Only an unphysical choice of parameters could bring about agreement. Possible causes of this discrepancy are discussed. We also report isosteric heats of adsorption obtained from the GCMC results and diffusion coefficients for VPI-5 obtained from molecular dynamics. 36 refs., 13 figs., 1 tab.

  20. Adsorption of gases on carbon molecular sieves

    SciTech Connect

    Vyas, S.N.; Patwardhan, S.R.; Vijayalakshmi, S. . Dept. of Chemical Engineering); Ganesh, K.S. )

    1994-12-01

    Adsorption on carbon molecular sieves (CMS) prepared by coke deposition has become an interesting area of adsorption due to its microporous nature and favorable separation factor on size and shape selectivity basis for many gaseous systems. In the present work CMS was synthesized from coconut shell through three major steps, namely, carbonization, activation, and coke deposition by hydrocarbon cracking. The crushed, washed, and sieved granules of coconut shell (particle size 2--3 mm) were pretreated with sodium silicate solution and oven-dried at 150 C to create the inorganic sites necessary for coke deposition. Carbonization and activation of the dried granules were carried out at 800 C, for 30 min each. The activated char thus produced was subjected to hydrocarbon cracking at 600 C for periods varying from 30 to 180 min. The product samples were characterized in terms of adsorption isotherm, kinetic adsorption curve, surface area, pore volume, pore size distribution, and characteristic energy for adsorption by using O[sub 2], N[sub 2], C[sub 2]H[sub 2], CO[sub 2], C[sub 3]H[sub 6], and CH[sub 4].

  1. Adsorption of cadmium ions on oxygen surface sites in activated carbon

    SciTech Connect

    Jia, Y.F.; Thomas, K.M.

    2000-02-08

    Various types of oxygen functional groups were introduced onto the surface of coconut shell derived activated carbon by oxidation using nitric acid. Fourier-transform infrared spectroscopy (FTIR), temperature-programmed desorption (TPD), and selective neutralization were used to characterize the surface oxygen functional groups. The oxidized carbons were also heat treated to provide a suite of carbons where the oxygen functional groups of various thermal stabilities were varied progressively. The adsorption of cadmium ions was enhanced dramatically by oxidation of the carbon. The ratio of released protons to adsorbed cadmium ions on oxidized carbon was approximately 2, indicating cation exchange was involved in the process of adsorption. Na{sup +} exchange studies with the oxidized carbon gave a similar ratio. After heat treatment of the oxidized carbons to remove oxygen functional groups, the ratio of H{sup +} released to Cd{sup 2+} adsorbed and the adsorption capacity decreased significantly. Both reversible and irreversible processes were involved in cadmium ion adsorption with reversible adsorption having higher enthalpy. The irreversible adsorption resulted from cation exchange with carboxylic acid groups, whereas the reversible adsorption probably involved physisorption of the partially hydrated cadmium ion.

  2. Adsorption of tetrahydrothiophene (THT) onto soils

    NASA Astrophysics Data System (ADS)

    Juriga, Martin; Kubinec, Róbert; Rajzinger, Ján; Jelemenský, Karol; Gužela, Štefan

    2014-08-01

    Adsorption is one of the major industrial separation technique nowadays. Although adsorption is most commonly used as a separation method, in some cases cause harmful and undesirable effects such as capture odorant from natural gas onto soil. In the event of an accident, the gas can leak from pipes in two ways - either directly into the surrounding air, or the soil where the odorant can be mostly absorbed depending of type of soil, water content and temperature. Design of experimental apparatus for measurement of breakthrough curves is studied in detail. Alternative arrangement of experimental apparatus, calibration of measuring devices, method of measurement and processing the data are narrowly discussed. Moreover, experimental measurements of breakthrough curves are presented. The actual measurement was made to identify the equilibrium adsorption capacity of THT (tetrahydrothiophene) onto soils. Experimental data were evaluated using Linear, Freundlich, Langmuir and Koble-Corrigan model.

  3. Adsorption of biopolymers at hydrophilic cellulose-water interface.

    PubMed

    Halder, Ebrahim; Chattoraj, D K; Das, K P

    2005-04-05

    The extent of adsorption (Gamma2(1)) of bovine serum albumin (BSA), beta-lactoglobulin, lysozyme, gelatin, and DNA from aqueous solution onto the hydrophilic surface of cellulose has been measured as function of biopolymer concentration at different temperatures, pHs, and ionic strengths, and in the presence of a high concentration of inorganic salts and denaturants. In all cases, the value of Gamma2(1) increases with the increase of biopolymer concentration (X2) in bulk and it attains a maximum value at a critical mole fraction concentration X2m. The value of Gamma2m depends upon the nature of protein, temperature, pH, and ionic strength, as well as the nature of neutral salts present in excess. Gamma2m for proteins at a fixed physicochemical condition stands in the following order: Gelatin>betalactoglobulin>lysozyme>BSA. The isotherms for adsorption of DNA nucleotides on cellulose surface at pH 4.0 have been compared at different temperatures and ionic strengths, and in the presence of high concentration of inorganic salts LiCl, NaCl, KCl, and Na2SO4. Values of Gamma2m for different systems have been evaluated and critically compared. At pH 6.0 and 8.0, Gamma2(1) values of DNA nucleotides on cellulose are all negative due to the excess positive hydration of cellulose. At pH 4.0, adsorption of nucleotides of acid, alkali, and heat-denatured DNA widely differ from each other and in the presence of excess concentration of urea becomes negative. The probable mechanisms of biopolymer-cellulose adsorption in terms of polymer hydration, steric interaction, London-van der Waals, hydrophobic, and other types of interactions have been discussed qualitatively. The standard free energy change for the adsorption of protein and DNA nucleotides on the cellulose surface at the state of adsorption saturation has been calculated in kJ per kg of cellulose using an integrated form of the Gibbs adsorption equation. The relation between DeltaG degrees and maximum affinities between

  4. Adsorption of monoclonal antibodies to glass microparticles.

    PubMed

    Hoehne, Matthew; Samuel, Fauna; Dong, Aichun; Wurth, Christine; Mahler, Hanns-Christian; Carpenter, John F; Randolph, Theodore W

    2011-01-01

    Microparticulate glass represents a potential contamination to protein formulations that may occur as a result of processing conditions or glass types. The effect of added microparticulate glass to formulations of three humanized antibodies was tested. Under the three formulation conditions tested, all three antibodies adsorbed irreversibly at near monolayer surface coverages to the glass microparticles. Analysis of the secondary structure of the adsorbed antibodies by infrared spectroscopy reveal only minor perturbations as a result of adsorption. Likewise, front-face fluorescence quenching measurements reflected minimal tertiary structural changes upon adsorption. In contrast to the minimal effects on protein structure, adsorption of protein to suspensions of glass microparticles induced significant colloidal destabilization and flocculation of the suspension.

  5. Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption.

    PubMed

    Song, Guanling; Cao, Lijing; Chen, Xiao; Hou, Wenhua; Wang, Qunhui

    2012-01-01

    A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

  6. Adsorption kinetics of silicic acid on akaganeite.

    PubMed

    Naren, Gaowa; Ohashi, Hironori; Okaue, Yoshihiro; Yokoyama, Takushi

    2013-06-01

    As part of a series of studies on the interaction between ferric ions and silicic acid in the hydrosphere, the adsorption of silicic acid on akaganeite was investigated kinetically at various pH values. The adsorption of silicic acid increased with increasing pH over an initial pH range of 4-11.5. In the kinetic experiment, the Cl(-) was released from akaganeite much faster than silicic acid was adsorbed. From this result, we concluded that chloride ions bound on the surface of akaganeite are released and Fe-OH or Fe-O(-) sites are formed, which then acts as an adsorption site for silicic acid. The uptake mechanism of silicic acid by akaganeite is significantly different from that by schwertmannite, despite the presence of the same tunnel structure.

  7. Preliminary investigation of the capillary adsorption for a hollow waveguide based laser ammonia analyzer

    NASA Astrophysics Data System (ADS)

    Du, Zhenhui; Wang, Ruixue; Li, Jinyi

    2016-10-01

    Hollow Waveguide (HWG) is usually used as a gas cell in an infrared gas sensor feathered with low-volume and high-sensitivity. However, the measured concentration is often distorted by the interference of the adsorption of gas molecules on the inner wall surface of the HWG. This adsorption is a type of physical absorption called capillary adsorption. In order to correct this distortion, the characteristics of HWG adsorption of ammonia were investigated by using the laser analyzer itself under HWG heating-cooling process and various ammonia flow rate in the HWG. The results showed that the readout of ammonia concentration increased by 17.8% when heating the HWG for no-flowing ammonia in the HWG, and the readout undergone a process of increase to fast decrease to slow increase when heating the HWG for flowing ammonia in the HWG at various flow rate. These surely come from the adsorption and desorption of ammonia on the inner wall surface of the HWG. The preliminary investigation provides a quantitative readout distortion and a creditable evidence for further study about the adsorption of HWG.

  8. Adsorption of lipids on silicalite-1

    NASA Astrophysics Data System (ADS)

    Atyaksheva, L. F.; Ivanova, I. I.; Ivanova, M. V.; Tarasevich, B. N.; Fedosov, D. A.

    2017-05-01

    The adsorption of egg lecithin and cholesterol from chloroform solutions onto silicalite-1 (hydrophobic silica with MFI zeolite structure) is investigated. Adsorption isotherms of the L-type for lecithin and the S-type for cholesterol are obtained in the 0.05-4.5 mg/mL range of equilibrium lipid concentrations. The maximum adsorption for lecithin is 30 mg/g; for cholesterol it is 70 mg/g. Chloroform treatment results in the desorption of no more than 10% of the lecithin and up to 50% of the cholesterol from the silicalite-1 surface. The lecithin molecules in the monolayer on the silicalite-1 are oriented such that their hydrophobic tails are oriented toward the surface and are partially inside the pores of the adsorbent.

  9. Adsorption of arsenate on untreated dolomite powder.

    PubMed

    Ayoub, G M; Mehawej, M

    2007-09-05

    Raw dolomite powder was evaluated for its efficiency in adsorbing As(V) from water. An experimental setup comprised of a fluidized dolomite powder bed was used to assess the impact of various test variables on the efficiency of removal of As(V). Test influents including distilled water (DW), synthetic groundwater (SGW) and filtered sewage effluent (FSE) were employed to assess the effect of influent parameters on the adsorption process and the quality of the effluent generated. Dolomite exhibited good As(V) removal levels for distilled water (>92%) and synthetic ground water (>84%) influents at all initial As(V) concentrations tested (0.055-0.600 ppm). Breakthrough of dolomite bed occurred after 45 bed volumes for DW and 20 bed volumes for SGW influents with complete breakthrough taking place at more than 300 bed volumes. As(V) removal from FSE influents was relatively unsuccessful as compared to the DW and SGW influents. Partial removal in the order of 32% from filtered sewage effluent at initial concentration of 0.6 mg/L started at 75 bed volumes and gradually stopped at 165 bed volumes. Varying degrees of As(V) adsorption capacities were observed by the different test influents employed, which indicate that the adsorption of As(V) is adversely affected by competing species, mainly sulfates and phosphates present in the influent. The adsorptive behavior of dolomite was described by fitting data generated from the study into the Langmuir and Freundlich isotherm models. Both models described well the adsorption of dolomite. The average isotherm adsorptive capacity was determined at 5.02 mug/g. Regeneration of the dolomite bed can be achieved with the use of caustic soda solution at a pH of 10.5.

  10. Utilisation of chitinous materials in pigment adsorption.

    PubMed

    Wang, San-Lang; Chen, Yan-Cheng; Yen, Yue-Horng; Liang, Tzu-Wen

    2012-12-01

    The effect of adding the cells of four lactobacilli to a squid pen powder (SPP)-containing medium on prodigiosin (PG) production by Serratia marcescens TKU011 is examined. The best increase in PG productivity was shown by strain TKU012. Among the samples of strain TKU012 and the chitinous materials of cicada casting powder (CCP), shrimp shell powder (SSP), squid pen powder (SPP), α-chitin, and β-chitin, TKU012 cells displayed the best adsorption rate (84%) for PG, followed by CCP, SSP, SPP, α-chitin, and β-chitin. As for the water-soluble food colourants, Allura Red AC (R40) and Tartrazne (Y4), SPP and SSP had better adsorptive powers than pure chitin preparations, strain TKU012, and CCP. Treatment with organic solvents, hot alkali, or proteases (papain, bromelain) diminished the adsorption rates of the biosorbents.

  11. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyan, M.; Lafferty, C.; Kimber, G.

    1996-10-01

    This work describes development of a series of novel activated carbon materials and their testing for possible water treatment applications by studying the adsorption of sodium pentachlorphenolate, PCP (a common herbicide/wood preservative). Although the application of activated carbons is an established technology for the treatment of public water supplies, there is a growing need for materials with higher selectivity and adsorptive capacities as well as high abrasion resistance. The materials that will be discussed include extruded wood-derived carbons with novel pore size distributions and high hardness, as well as activated carbon fiber composites. Comparisons will be made with commercial granular water treatment carbons.

  12. Controlling the adsorption enthalpy of CO(2) in zeolites by framework topology and composition.

    PubMed

    Grajciar, Lukáš; Čejka, Jiří; Zukal, Arnošt; Otero Areán, Carlos; Turnes Palomino, Gemma; Nachtigall, Petr

    2012-10-01

    Zeolites are often investigated as potential adsorbents for CO(2) adsorption and separation. Depending on the zeolite topology and composition (Si/Al ratio and extra-framework cations), the CO(2) adsorption heats at low coverages vary from -20 to -60 kJ mol(-1), and with increasing surface coverage adsorption heats either stay approximately constant or they quickly drop down. Experimental adsorption heats obtained for purely siliceous porous solids and for ion-exchanged zeolites of the structural type MFI, FER, FAU, LTA, TUN, IMF, and -SVR are discussed in light of results of periodic density functional theory calculations corrected for the description of dispersion interactions. Key factors influencing the stability of CO(2) adsorption complexes are identified and discussed at the molecular level. A general model for CO(2) adsorption in zeolites and related materials is proposed and data reported in literature are evaluated with regard to the proposed model. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Adsorption of Lead ions onto Activated Carbon derived from Sugarcane bagasse

    NASA Astrophysics Data System (ADS)

    Salihi, I. U.; Kutty, S. R. M.; Isa, M. H.

    2017-05-01

    In this study, activated carbon was developed from sugarcane bagasse and its effectiveness in adsorbing lead (Pb2+) ions from synthetic aqueous solution was examined. Sugarcane bagasse activated carbon (SCBA) was developed in a tube furnace at a temperature of 900 °C, a heating rate of 10 °C/min, residence time of 3 hours, and at a nitrogen flow rate of 100 mL/min. Batch adsorption experiments were carried out to investigate the effects of pH and SCBA dosages on the adsorption process. The batch adsorption test showed that extent of Pb2+ adsorption by SCBA was dependent upon pH and SCBA dosage. The optimum pH for Pb2+ adsorption was found to be at pH 5.0. Maximum Pb2+ removal efficiency obtained from the batch studies was 87.3 % at SCBA dosage of 10 g/L. Equilibrium adsorption data was described by Langmuir model with a coefficient of determination (R2) of 0.9508. Maximum adsorption capacity according to Langmuir model was evaluated to be 23.4 mg/g. The adsorption capacity of the SCBA was compared with that of other plant-based adsorbents. SCBA is an effective adsorbent for the removal of Pb2+ from aqueous solution.

  14. Adsorption of polyampholytes on charged surfaces.

    PubMed

    Ozon, F; di Meglio, J-M; Joanny, J-F

    2002-06-01

    We have studied the adsorption of neutral polyampholytes on model charged surfaces that have been characterized by contact angle and streaming current measurements. The loop size distributions of adsorbed polymer chains have been obtained using atomic-force microscopy (AFM) and compared to recent theoretical predictions. We find a qualitative agreement with theory; the higher the surface charge, the smaller the number of monomers in the adsorbed layer. We propose an original scenario for the adsorption of polyampholytes on surfaces covered with both neutral long-chain and charged short-chain thiols.

  15. Adsorption of SO2 on bituminous coal char and activated carbon fiber

    USGS Publications Warehouse

    DeBarr, Joseph A.; Lizzio, Anthony A.; Daley, Michael A.

    1997-01-01

    The SO2 adsorption behaviors of activated carbons produced from Illinois coal and of commercially prepared activated carbon fibers (ACFs) were compared. There was no relation between surface area of coal-based carbons and SO2 adsorption, whereas adsorption of SO2 on the series of ACFs was inversely proportional to N2 BET surface area. Higher surface area ACFs had wider pores and adsorbed less SO2; thus, pore size distribution is thought to play a significant role in SO2 adsorption for these materials. Oxidation with HNO3 and/or H2SO4, followed by heat treatment at 700−925°C to remove carbon−oxygen complexes, resulted in increased SO2 adsorption for both coal chars and ACFs. This behavior was explained by an increase in the available number of free sites, previously occupied by oxygen and now available for SO2 adsorption. The use of nitrogen-containing functional groups on ACFs of proper pore size shows promise for further increasing SO2 adsorption capacities. Knowledge of the relationship among the number of free sites, pore size, and surface chemistry on corresponding SO2 adsorption should lead to the development of more efficient adsorbents prepared from either coal or ACFs.

  16. Applications and limits of theoretical adsorption models for predicting the adsorption properties of adsorbents.

    PubMed

    Park, Hyun Ju; Nguyen, Duc Canh; Na, Choon-Ki; Kim, Chung-il

    2015-01-01

    The objective of this study is to evaluate the applicability of adsorption models for predicting the properties of adsorbents. The kinetics of the adsorption of NO3- ions on a PP-g-AA-Am non-woven fabric have been investigated under equilibrium conditions in both batch and fixed bed column processes. The adsorption equilibrium experiments in the batch process were carried out under different adsorbate concentration and adsorbent dosage conditions and the results were analyzed using adsorption isotherm models, energy models, and kinetic models. The results of the analysis indicate that the adsorption occurring at a fixed adsorbate concentration with a varying adsorbent dosage occur more easily compared to those under a fixed adsorbent dosage with a varying adsorbate concentration. In the second part of the study, the experimental data obtained using fixed bed columns were fit to Bed Depth Service Time, Bohart-Adams, Clark, and Wolborska models, to predict the breakthrough curves and determine the column kinetic parameters. The adsorption properties of the NO3- ions on the PP-g-AA-Am non-woven fabric were differently described by different models for both the batch and fixed bed column process. Therefore, it appears reasonable to assume that the adsorption properties were dominated by multiple mechanisms, depending on the experimental conditions.

  17. Thermodynamic and kinetic investigations of PO3-4 adsorption on blast furnace slag.

    PubMed

    Oguz, Ensar

    2005-01-01

    The kinetics of adsorption of PO(3-)(4) by blast furnace slag were found to be fast, reaching equilibrium in 20 min and following a pseudo-second-order rate equation. The adsorption behavior of PO(3-)(4) on blast furnace slag has been studied as a function of the solution agitation speed, pH, and temperature. Results have been analyzed by Freundlich, Langmuir, BET, and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption, 10.31 kJ mol(-1), was calculated from the D-R adsorption isotherm. The rate constants were calculated for 293, 298, 303, and 308 K using a pseudo-second-order rate equation and the activation energy (E(a)) was derived using the Arrhenius equation. Thermodynamic parameters such as DeltaH(0), DeltaS(0), and DeltaG(0) were calculated from the slope and intercept of linear plot of lnK(D) against 1/T. The DeltaH(0) and DeltaG(0) values of PO(3-)(4) adsorption on the blast furnace slag show endothermic heat of adsorption. But there is a negative free energy value, indicating that the process of PO(3-)(4) adsorption is favored at high temperatures.

  18. Separation of helium-methane mixtures by pressure swing adsorption

    SciTech Connect

    Cheng, H.C.; Hill, F.B.

    1985-01-01

    The separation of mixtures of helium and methane using a single column of activated carbon in a pressure swing adsorption process was studied experimentally. Process performance was predicted with an average error of 10% or less by a local-equilibrium well-stirred cell model in which dead volumes at the feed and product ends of the column were accounted for. Systematic differences between experiment and model were ascribed to omission from the model of flow resistance and heat release. 17 references, 8 figures, 1 table.

  19. Reversible alteration of CO2 adsorption upon photochemical or thermal treatment in a metal-organic framework.

    PubMed

    Park, Jinhee; Yuan, Daqiang; Pham, Khanh T; Li, Jian-Rong; Yakovenko, Andrey; Zhou, Hong-Cai

    2012-01-11

    A metal-organic framework (MOF) for reversible alteration of guest molecule adsorption, here carbon dioxide, upon photochemical or thermal treatment has been discovered. An azobenzene functional group, which can switch its conformation upon light irradiation or heat treatment, has been introduced to the organic linker of a MOF. The resulting MOF adsorbs different amount of CO(2) after UV or heat treatment. This remarkable stimuli-responsive adsorption effect has been demonstrated through experiments. © 2011 American Chemical Society

  20. Initial stages of CO2 adsorption on CaO: a combined experimental and computational study.

    PubMed

    Solis, Brian H; Cui, Yi; Weng, Xuefei; Seifert, Jan; Schauermann, Swetlana; Sauer, Joachim; Shaikhutdinov, Shamil; Freund, Hans-Joachim

    2017-02-08

    Room temperature adsorption of carbon dioxide (CO2) on monocrystalline CaO(001) thin films grown on a Mo(001) substrate was studied by infrared reflection-absorption spectroscopy (IRAS) and quantum chemical calculations. For comparison, CO2 adsorption was examined on poorly ordered, nanoparticulate CaO films prepared on Ru(0001). For both systems, CO2 readily adsorbs on the clean CaO surface. However, additional bands were observable on the CaO/Ru(0001) films compared with CaO/Mo(001), because the stricter IRAS surface selection rules do not apply to adsorption on the disordered thin films grown on Ru(0001). Spectral evolution with increasing exposure of the IRA bands suggested the presence of several adsorption sites which are consecutively populated by CO2. Density functional calculations showed that CO2 adsorption occurs as monodentate surface carbonate (CO3(2-)) species at monatomic step sites and other low-coordinated sites, followed by formation of carbonates on terraces, which dominate at increasing CO2 exposure. To explain the coverage-dependent IRAS results, we propose CO2 surface islanding from the onset, most likely in the form of pairs and other chain-like species, which were calculated as thermodynamically favorable. The calculated adsorption energy for isolated CO2 on the terrace sites (184 ± 10 kJ mol(-1)) is larger than the adsorption energy obtained by temperature programmed desorption (∼120-140 kJ mol(-1)) and heat of adsorption taken from microcalorimetry measurements at low coverage (∼125 kJ mol(-1)). However, the calculated adsorption energies become less favorable when carbonate chains intersect on CaO terraces, forming kinks. Furthermore, our assignments of the initial stages of CO2 adsorption are consistent with the observed coverage effect on the CO2 adsorption energy measured by microcalorimetry and the IRAS results.

  1. The adsorption of HCl on volcanic ash

    NASA Astrophysics Data System (ADS)

    Gutiérrez, Xochilt; Schiavi, Federica; Keppler, Hans

    2016-03-01

    Understanding the interaction between volcanic gases and ash is important to derive gas compositions from ash leachates and to constrain the environmental impact of eruptions. Volcanic HCl could potentially damage the ozone layer, but it is unclear what fraction of HCl actually reaches the stratosphere. The adsorption of HCl on volcanic ash was therefore studied from -76 to +150 °C to simulate the behavior of HCl in the dilute parts of a volcanic plume. Finely ground synthetic glasses of andesitic, dacitic, and rhyolitic composition as well as a natural obsidian from Vulcano (Italy) served as proxies for fresh natural ash. HCl adsorption is an irreversible process and appears to increase with the total alkali content of the glass. Adsorption kinetics follow a first order law with rate constants of 2.13 ṡ10-6 s-1 to 1.80 ṡ10-4 s-1 in the temperature range investigated. For dacitic composition, the temperature and pressure dependence of adsorption can be described by the equation ln ⁡ c = 1.26 + 0.27 ln ⁡ p - 715.3 / T, where c is the surface concentration of adsorbed HCl in mg/m2, T is temperature in Kelvin, and p is the partial pressure of HCl in mbar. A comparison of this model with a large data set for the composition of volcanic ash suggests that adsorption of HCl from the gas phase at relatively low temperatures can quantitatively account for the majority of the observed Cl concentrations. The model implies that adsorption of HCl on ash increases with temperature, probably because of the increasing number of accessible adsorption sites. This temperature dependence is opposite to that observed for SO2, so that HCl and SO2 are fractionated by the adsorption process and the fractionation factor changes by four orders of magnitude over a temperature range of 250 K. The assumption of equal adsorption of different species is therefore not appropriate for deriving volcanic gas compositions from analyses of adsorbates on ash. However, with the experimental

  2. IMPACT OF OXYGEN MEDIATED OXIDATIVE COUPLING ON ADSORPTION KINETICS

    EPA Science Inventory

    The presence of molecular oxygen in the test environment promotes oxidative coupling (polymer formation) of phenolic compounds on the surface of granular activated carbon (GAC). Both adsorption equilibria and adsorption kinetics are affected by these chemical reactions. Lack of...

  3. IMPACT OF OXYGEN MEDIATED OXIDATIVE COUPLING ON ADSORPTION KINETICS

    EPA Science Inventory

    The presence of molecular oxygen in the test environment promotes oxidative coupling (polymer formation) of phenolic compounds on the surface of granular activated carbon (GAC). Both adsorption equilibria and adsorption kinetics are affected by these chemical reactions. Lack of...

  4. Assessing the adsorption properties of shales

    NASA Astrophysics Data System (ADS)

    Pini, Ronny

    2015-04-01

    Physical adsorption refers to the trapping of fluid molecules at near liquid-like densities in the pores of a given adsorbent material. Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity. As a matter of fact, the current ability to extract natural gas that is adsorbed in the rock's matrix is limited, and current technology focuses primarily on the free gas in the fractures (either natural or stimulated), thus leading to recovery efficiencies that are very low. Shales constitute also a great portion of so-called cap-rocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing the impact of leakage on the whole operation. Whether it is an unconventional reservoir or a cap-rock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals (a major component in mudrocks) and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm in heterogeneous materials. The data are analyzed by using thermodynamically rigorous measures of adsorption, such as the net- and excess adsorbed amounts and a recently developed methodology is

  5. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons.

    PubMed

    Dai, Xiaodong; Zou, Linda; Yan, Zifeng; Millikan, Mary

    2009-08-30

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N(2) adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO(2) particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  6. Adsorption of Ions at Uncharged Insoluble Monolayers

    NASA Astrophysics Data System (ADS)

    Peshkova, T. V.; Minkov, I. L.; Tsekov, R.; Slavchov, R. I.

    2016-08-01

    A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3–30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na+ is specifically adsorbed, while Cl– remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na+ seems to be the interaction of the ion with the dipole moment of the monolayer.

  7. Adsorption of Ions at Uncharged Insoluble Monolayers.

    PubMed

    Peshkova, Tatyana V; Minkov, Ivan L; Tsekov, Roumen; Slavchov, Radomir I

    2016-09-06

    A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3-30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na(+) is specifically adsorbed, while Cl(-) remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na(+) seems to be the interaction of the ion with the dipole moment of the monolayer.

  8. Adsorption of arsenic from aqueous solution using magnetic graphene oxide

    NASA Astrophysics Data System (ADS)

    Sherlala, A. I. A.; Raman, A. A.; Bello, M. M.

    2017-06-01

    A binary of graphene oxide (GO) and iron oxide (IO) was prepared and used for the removal of arsenic from aqueous solution. The synthesized compound was characterized using XRD analysis. The prepared composite was used for the adsorption of arsenic from aqueous solution. Central Composite Design was used to design the adsorption experiments and to investigate the effects of operational parameters (initial concentration of arsenic, adsorbent dosage, pH and time) on the adsorption capacity and efficiency. The adsorbent shows a high adsorption capacity for the arsenic. The adsorption efficiency ranges between 33.2 % and 99.95 %. The most significant factors affecting the adsorption capacity were found to be the initial concentration of arsenic and the adsorbent dosage. The initial pH of the solution slightly affects the adsorption capacity, with the maximum adsorption capacity occurring around pH 6 - 7. Thus, the developed adsorbent has a potential for effective removal of arsenic from aqueous solution.

  9. In vitro adsorption of tilidine HCl by activated charcoal.

    PubMed

    Cordonnier, J A; Van den Heede, M A; Heyndrickx, A M

    In vitro studies were carried out in order to determine the adsorption of tilidine HCl, a narcotic analgesic, by activated charcoal (max. adsorption capacity 185.5 mg/g of charcoal). The path of the adsorption isotherms at pH 1.2 and 7.5 suggests that the in vivo adsorption of tilidine HCl may be increased when the drug passes from the stomach to the intestine, unless the intestinal content exerts a displacing effect. Nevertheless, the adsorption was dependent on the quantity of activated charcoal used, becoming more complete when the quantity of activated charcoal was increased. The effects of additives on the adsorption capacity of activated charcoal were also investigated in vitro. Ethanol, sorbitol and sucrose significantly reduced drug adsorption, while cacao powder, milk and starch had no effect on tilidine adsorption. At an acid pH, Federa Activated Charcoal significantly adsorbed more drug than either Norit A or Activated Charcoal Merck.

  10. Adsorption ability comparison of plasma proteins on amorphous carbon surface

    NASA Astrophysics Data System (ADS)

    Takeda, Aoi; Akasaka, Hiroki; Ohshio, Shigeo; Toda, Ikumi; Nakano, Masayuki; Saitoh, Hidetoshi

    2012-11-01

    To understand why amorphous carbon (a-C:H) film shows antithrombogenicity, an adsorption ability of plasma proteins on a-C:H surface was investigated. Protein adsorption is the initial process of clot formation. The protein adsorption ability on a-C:H film surface was compared by the detection using the surface plasmon resonance (SPR) phenomenon to estimate the protein adsorption. The protein adsorption abilities of a fibrinogen (Fib) and a human γ-globulin (HGG) were estimated by the SPR method using a multilayer structure of a-C:H/Au/Cr/glass. Although the adsorption of HGG for a-C:H was saturated at 32 μM in HGG concentration, the adsorption of Fib was not saturated under the detection limit of this method. These results indicated that the adsorption ability to the a-C:H film surface of Fib was higher than HGG.

  11. Adsorption of thorium from aqueous solutions by perlite.

    PubMed

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

    The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

  12. Adsorption behavior of methylene blue by bone char

    NASA Astrophysics Data System (ADS)

    Jia, Puqi; Tan, Hongwei; Liu, Kuiren; Gao, Wei

    2017-07-01

    This work studies the adsorption behavior of methylene blue (MB) from water by bone char (BC). The effects of pH, initial dye concentration and dosage of adsorbent on the adsorption were investigated. It was found that the adsorption capacity of MB was affected by the mount of OH-, initial concentration gradient driving force of MB, the surface charge and adsorption site of BC.

  13. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite.

    PubMed

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g · L(-1), in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics.

  14. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

    PubMed Central

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

  15. Kinetic and thermodynamic studies of sulforaphane adsorption on macroporous resin.

    PubMed

    Yuanfeng, Wu; Lei, Zhang; Jianwei, Mao; Shiwang, Liu; Jun, Huang; Yuru, You; Lehe, Mei

    2016-08-15

    The adsorption equilibrium, kinetic and thermodynamic of sulforaphane (SF) adsorption onto macroporous resin in aqueous phase were studied. The SP850 resin was screened as the appropriate resin for SF purification. From the equilibrium studies, the Redlich-Peterson model was found to be the best for description of the adsorption behavior of SF onto SP850 resin, followed by the Freundlich model and the Langmuir model. Batch equilibrium experiments demonstrated that, in the examined temperature range, the equilibrium adsorption capacity of SP850 resin decreased with increasing adsorption temperature. Thermodynamics studies indicated that the adsorption of SF was a physical, exothermic, and spontaneous process. The adsorption kinetics revealed that the pseudo-second-order kinetic model was suitable to characterize the kinetics of adsorption of SF onto SP850. Finally, the intra-particle diffusion model demonstrated that SF diffused quickly into macropores, and that diffusion slowed down in the meso- and micropores.

  16. ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS

    EPA Science Inventory

    The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

  17. ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS

    EPA Science Inventory

    The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

  18. Investigating the Heavy Metal Adsorption of Mesoporous Silica Materials Prepared by Microwave Synthesis

    NASA Astrophysics Data System (ADS)

    Zhu, Wenjie; Wang, Jingxuan; Wu, Di; Li, Xitong; Luo, Yongming; Han, Caiyun; Ma, Wenhui; He, Sufang

    2017-05-01

    Mesoporous silica materials (MSMs) of the MCM-41 type were rapidly synthesized by microwave heating using silica fume as silica source and evaluated as adsorbents for the removal of Cu2+, Pb2+, and Cd2+ from aqueous solutions. The effects of microwave heating times on the pore structure of the resulting MSMs were investigated as well as the effects of different acids which were employed to adjust the solution pH during the synthesis. The obtained MCM-41 samples were characterized by nitrogen adsorption-desorption analyses, X-ray powder diffraction, and transmission electron microscopy. The results indicated that microwave heating method can significantly reduce the synthesis time of MCM-41 to 40 min. The MCM-41 prepared using citric acid (c-MCM-41(40)) possessed more ordered hexagonal mesostructure, higher pore volume, and pore diameter. We also explored the ability of c-MCM-41(40) for removing heavy metal ions (Cu2+, Pb2+, and Cd2+) from aqueous solution and evaluated the influence of pH on its adsorption capacity. In addition, the adsorption isotherms were fitted by Langmuir and Freundlich models, and the adsorption kinetics were assessed using pseudo-first-order and pseudo-second-order models. The intraparticle diffusion model was studied to understand the adsorption process and mechanism. The results confirmed that the as-synthesized adsorbent could efficiently remove the heavy metal ions from aqueous solution at pH range of 5-7. The adsorption isotherms obeyed the Langmuir model, and the maximum adsorption capacities of the adsorbent for Cu2+, Pb2+, and Cd2+ were 36.3, 58.5, and 32.3 mg/g, respectively. The kinetic data were well fitted to the pseudo-second-order model, and the results of intraparticle diffusion model showed complex chemical reaction might be involved during adsorption process.

  19. Adsorption of oxygen and 1-butene on magnesium ferrite

    SciTech Connect

    Samuilova, O.K.; Kozlova, M.M.; Yagodovskii, V.D.

    1986-08-01

    The kinetics of the adsorption of oxygen and 1-butene on magnesium ferrite was studied. Conductometry and thermal desorption methods were used to investigate the adsorption of oxygen on magnesium ferrite. Two forms of adsorbed oxygen were found. The formation of these forms affects the kinetics of the adsorption of 1-butene.

  20. Critical analysis of adsorption data statistically

    NASA Astrophysics Data System (ADS)

    Kaushal, Achla; Singh, S. K.

    2016-09-01

    Experimental data can be presented, computed, and critically analysed in a different way using statistics. A variety of statistical tests are used to make decisions about the significance and validity of the experimental data. In the present study, adsorption was carried out to remove zinc ions from contaminated aqueous solution using mango leaf powder. The experimental data was analysed statistically by hypothesis testing applying t test, paired t test and Chi-square test to (a) test the optimum value of the process pH, (b) verify the success of experiment and (c) study the effect of adsorbent dose in zinc ion removal from aqueous solutions. Comparison of calculated and tabulated values of t and χ 2 showed the results in favour of the data collected from the experiment and this has been shown on probability charts. K value for Langmuir isotherm was 0.8582 and m value for Freundlich adsorption isotherm obtained was 0.725, both are <1, indicating favourable isotherms. Karl Pearson's correlation coefficient values for Langmuir and Freundlich adsorption isotherms were obtained as 0.99 and 0.95 respectively, which show higher degree of correlation between the variables. This validates the data obtained for adsorption of zinc ions from the contaminated aqueous solution with the help of mango leaf powder.

  1. Adsorption kinetics of laterally and polarly flagellated Vibrio.

    PubMed Central

    Belas, M R; Colwell, R R

    1982-01-01

    The adsorption of laterally and polarly flagellated bacteria to chitin was measured, and from the data obtained, a modified Langmuir adsorption isotherm was derived. Results indicated that the adsorption of laterally flagellated Vibrio parahaemolyticus follows the Langmuir adsorption isotherm, a type of adsorption referred to as surface saturation kinetics, when conditions are favorable for the production of lateral flagella. When conditions were not favorable for the production of lateral flagella, bacterial adsorption did not follow the Langmuir adsorption isotherm; instead, proportional adsorption kinetics were observed. The adsorption of some polarly flagellated bacteria exhibited surface saturation kinetics. However, the binding index (the product of the number of binding sites and bacterial affinity to the surface) of polarly flagellated bacteria differed significantly from that of laterally flagellated bacteria, suggesting that polarly flagellated bacteria adsorb to chitin by a different mechanism from that used by the laterally flagellated bacteria. From the results of dual-label adsorption competition experiments, in which polarly flagellated V. cholerae competed with increasing concentrations of laterally flagellated V. parahaemolyticus, it was observed that laterally flagellated bacteria inhibited the adsorption of polarly flagellated bacteria. In contrast, polarly flagellated bacteria enhanced the adsorption of V. cholerae. In competition experiments, where V. parahaemolyticus competed against increasing concentrations of other bacteria, polarly flagellated bacteria enhanced V. parahaemolyticus adsorption significantly, whereas laterally flagellated bacteria only slightly enhanced the process. The direct correlation observed between surface saturation kinetics, the production of lateral flagella, and the ability of laterally flagellated bacteria to inhibit the adsorption of polarly flagellated bacteria suggests that lateral flagella represent a

  2. Competitive adsorption of VOCcs and BOM: Oxic and anoxic environments

    SciTech Connect

    Sorial, G.A.; Papadimas, S.P.; Suidan, M.T.; Speth, T.F.

    1994-01-01

    The effect of the presence of molecular oxygen on the adsorption of volatile organic compounds (VOCs) in distilled Milli-Q water and in water supplemented with background organic matter (BOM) is evaluated. Experiments are conducted under conditions where molecular oxygen is present in the test environment (oxic adsorption), and where oxygen is absent from the test environment (anoxic adsorption). Adsorption isotherms for tetrachloroethylene (PCE) and trichloroethylene (TCE) in Milli-Q water showed no impact of the presence of oxygen on their adsorption behavior, while adsorption isotherms for cis-1,2-dichloroethylene (DCE) showed higher capacities under toxic conditions. The Ideal Adsorbed Solution Theory (IAST) successfully predicted the VOCs anoxic adsorption isotherms in BOM. However, the IAST model did not predict the VOCs oxic adsorption isotherms in BOM.

  3. Factors affecting the adsorption of xenon on activated carbon

    SciTech Connect

    Underhill, D.W.; DiCello, D.C.; Scaglia, L.A.; Watson, J.A.

    1986-08-01

    The presence of water vapor was found to interfere strongly with the dynamic adsorption of /sup 133/Xe on coconut-base activated charcoal. The percent loss in the xenon adsorption coefficient was similar to values reported earlier for the adsorption of krypton on humidified charcoal. Attempts to increase the adsorption of xenon by (a) using a petroleum-based adsorbent with an extremely high surface area and (b) by impregnation of the adsorbent with iodine were not successful.

  4. Study on the adsorption feature of rutin aqueous solution on macroporous adsorption resins.

    PubMed

    Chen, Zhenbin; Zhang, Anjie; Li, Jie; Dong, Fang; Di, Duolong; Wu, Youzhi

    2010-04-15

    The adsorption feature of different kinds of polystyrene-based macroporous adsorption resins (MARs) was investigated systemically at constant temperature employing Rutin as the adsorbate. Different from traditional adsorption patterns, Langmuir and Freundlich adsorption, and the results showed interesting aspects: (1) With the increase of the volume of the initial solution, the adsorption capacity increased to the maximum, and then decreased gradually. (2) Experimental results clearly verified the opinion that the adsorption process of MARs could be divided into three stages-macropores, mesopores, and micropores-by the capillary effects occurring at the two intersections, and the adsorption feature for every stage could be described well by the fourth type of Brunauer model. (3) The model that the inductive effect transmitted to the first layer could not interpret our experimental results reasonably. Thus, the model that the inductive effect passed on to a higher layer was proposed by investigating regression of the experimental results and the conclusion that the inductive effect transmitted to the third layer was drawn.

  5. Binary adsorption equilibrium of carbon dioxide and water vapor on activated alumina.

    PubMed

    Li, Gang; Xiao, Penny; Webley, Paul

    2009-09-15

    Adsorption equilibria of a CO2/H2O binary mixture on activated alumina F-200 were measured at several temperatures and over a wide range of concentrations from 4% to around 90% of the saturated water vapor pressure. In comparison with the single-component data, the loading of CO2 was not reduced in the presence of H2O, whereas at low relative humidity the adsorption of H2O was depressed. The binary system was described by a competitive/cooperative adsorption model where the readily adsorbed water layers acted as secondary sites for further CO2 adsorption via hydrogen bonding or hydration reaction. The combination of kinetic models, namely, a Langmuir isotherm for characterizing pure CO2 adsorption and a BET isotherm for H2O, was extended to derive a binary adsorption equilibrium model for the CO2/H2O mixture. Models based on the ideal adsorbed solution theory of Myers and Prausnitz failed to characterize the data over the whole composition range, and a large deviation of binary CO2/H2O equilibrium from ideal solution behavior was observed. The extended Langmuir-BET (LBET) isotherm, analogous to the extended Langmuir equation, drastically underestimated the CO2 loading. By incorporating the interactions between CO2 and H2O molecules on the adsorbent surface and taking into account the effect of nonideality, the realistic interactive LBET (R-LBET) model was found to be in very good agreement with the experimental data. The derived binary isosteric heat of adsorption showed that the heat was reduced by competitive adsorption but promoted by cooperative adsorption.

  6. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    ERIC Educational Resources Information Center

    Neumann, M. G.

    1976-01-01

    Discusses the relationship between adsorption isotherms and elution peak shapes in gas chromatography, and describes a laboratory experiment which involves the adsorption of hexane, cyclohexane, and benzene on alumina at different temperatures. (MLH)

  7. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    ERIC Educational Resources Information Center

    Neumann, M. G.

    1976-01-01

    Discusses the relationship between adsorption isotherms and elution peak shapes in gas chromatography, and describes a laboratory experiment which involves the adsorption of hexane, cyclohexane, and benzene on alumina at different temperatures. (MLH)

  8. Adsorption of dyes on Sahara desert sand.

    PubMed

    Varlikli, Canan; Bekiari, Vlasoula; Kus, Mahmut; Boduroglu, Numan; Oner, Ilker; Lianos, Panagiotis; Lyberatos, Gerasimos; Icli, Siddik

    2009-10-15

    Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.

  9. Adsorption of carboxymethyl cellulose on alumina particles.

    PubMed

    Zhivkov, Alexandar M; Hristov, Rosen P

    2015-06-01

    The polyelectrolyte adsorption on colloid particles is often used for stabilization or flocculation of water suspensions. The aim of this work is to study the adsorption of carboxymethyl cellulose (CMC) on alumina (γ-Al2O3) colloid particles. The particles and polymer are chosen because of the capability of the metal-oxide ampholyte surface and the weak polyelectrolytes to alter their charge by pH. The measurements are done at pH 6.0 where the CMC carboxylic gropes are almost fully dissociated and the alumina surface is positively charged. The high linear charge density of the polyelectrolyte chain provides Na(+) counterions condensation on the COO(-) groups. The main employed method is the electric light scattering based on particle orientation in sinusoidal electric field. The electric polarizability and the relaxation time after field switching off (both depending on the particle charge and size) are used as criteria for polymer adsorption and particle aggregation. Micro-electrophoresis is applied as additional techniques indicating the sign and density of the surface charge. The results obtained give the conditions (time dependence, particle and polymer concentrations) where the CMC adsorption is complete and the suspension is stable.

  10. Adsorption mechanisms and the effect of oxytetracycline on activated sludge.

    PubMed

    Song, Xiancai; Liu, Dongfang; Zhang, Guowei; Frigon, Matthew; Meng, Xianrong; Li, Kexun

    2014-01-01

    The adsorption mechanisms and the effect of Oxytetracycline (OTC) onto activated sludge were studied. The results show that the adsorption of Oxytetracycline (OTC) onto activated sludge was coincident with the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model had the best fit which suggested that chemical adsorption mechanism was dominant. The influences including pH and metal ions on the OTC were examined. It was demonstrated that the adsorption process was highly pH-dependant, which indicate that cationic exchange mechanisms may play an important role in the adsorption process. Na(+), K(+), Ca(2+), Mg(2+) and Cd(2+) ions more or less inhibited the adsorption of OTC on activated sludge while Cu(2+) enhanced the adsorption ability. The phenomenon may reflect the result that a surface complexation mechanism could involved in the adsorption. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. A COMPUTATIONAL AND EXPERIMENTAL STUDY OF METAL AND COVALENT ORGANIC FRAMEWORKS USED IN ADSORPTION COOLING

    SciTech Connect

    Jenks, Jeromy WJ; TeGrotenhuis, Ward E.; Motkuri, Radha K.; Paul, Brian; McGrail, B. Peter

    2015-07-09

    Metal-organic frameworks (MOFs) have recently attracted enormous interest over the past few years due to their potential applications in energy storage and gas separation. However, there have been few reports on MOFs for adsorption cooling applications. Adsorption cooling technology is an established alternative to mechanical vapor compression refrigeration systems. Adsorption cooling is an excellent alternative in industrial environments where waste heat is available. Applications also include hybrid systems, refrigeration, power-plant dry cooling, cryogenics, vehicular systems and building HVAC. Adsorption based cooling and refrigeration systems have several advantages including few moving parts and negligible power consumption. Key disadvantages include large thermal mass, bulkiness, complex controls, and low COP (0.2-0.5). We explored the use of metal organic frameworks that have very high mass loading and relatively low heats of adsorption, with certain combinations of refrigerants to demonstrate a new type of highly efficient adsorption chiller. An adsorption chiller based on MOFs suggests that a thermally-driven COP>1 may be possible with these materials, which would represent a fundamental breakthrough in performance of adsorption chiller technology. Computational fluid dynamics combined with a system level lumped-parameter model have been used to project size and performance for chillers with a cooling capacity ranging from a few kW to several thousand kW. In addition, a cost model has been developed to project manufactured cost of entire systems. These systems rely on stacked micro/mini-scale architectures to enhance heat and mass transfer. Presented herein are computational and experimental results for hydrophyilic MOFs, fluorophilic MOFs and also flourophilic Covalent-organic frameworks (COFs).

  12. Adsorption of diblock polypeptides on polystyrene latex.

    PubMed

    Jain, Ritesh; Forciniti, Daniel

    2012-10-30

    The adsorption of peptides at solid/liquid interfaces is affected by peptide/surface and peptide/peptide hydrophobic and electrostatic forces. Three diblock copolypeptides and two homopeptides were adsorbed on poly(styrene) nanospheres from water, water/methanol, and water/glycerol mixtures at different pH's to study both of these effects. Peptides with one hydrophilic (glutamic acid or lysine) and one nonpolar block (alanine) or with both hydrophilic blocks with opposite charges (glutamic acid and lysine) were chemically synthesized and used as adsorbates in this study. The amount adsorbed was determined, and dynamic light scattering (DLS) was used to measure the adsorbed layer thickness. It was found that peptide/surface and peptide/peptide electrostatic interactions dominate the adsorption process. Hydrophobic forces also play a role, but secondary to electrostatic forces. Positively charged blocks show high affinity for the surface, whereas negatively charged blocks were excluded from it. Poly(Lys) has the highest affinity by the surface, while (Glu)(14)-b-(Ala)(5) has the lowest. Adsorption of all peptides was inhibited by methanol and promoted by glycerol. The adsorption for (Lys)(5)-b-(Glu)(6) was extremely sensitive to pH, irrespective of cosolvent, whereas the thickness for (Lys)(30)-b-(Ala)(41) was sensitive to pH as well as cosolvent. Aggregation was observed in the presence of the nanosurfaces but not in the bulk peptides under some pH and solvent conditions.

  13. Adsorption capacity study of carbon nanopowder produced by laser pyrolisis

    NASA Astrophysics Data System (ADS)

    Sonu, Marcel; Savu, Ion; Pastean, Laurentiu; Voicu, Ion N.; Soare, Iuliana; Morjan, Ion G.; Grigoriu, Constantin

    2004-10-01

    The paper presents the experimental results on adsorption properties of carbon nanopowders which have been obtained by laser pyrolysis of hydrocarbon-based mixtures. We have investigated the adsorption of benzene, n-hexane and ciclohexane. The influence of the nanocarbon morphology (which depends on gaseous precursors and synthesis conditions) on adsorption characteristics is reported.

  14. Adsorption isotherm of non-azeotropic solution onto porous adsorbents

    NASA Astrophysics Data System (ADS)

    Bono, A.; Ramlan, N. A.; Anisuzzaman, S. M.; Chu, C. M.; Farm, Y. Y.

    2016-06-01

    Adsorption isotherm is essential component in the understanding of the adsorption process. Several methods of the measurements, analysis and interpretation of adsorption from solution have been reported in the literature. Most of the measurements of adsorption isotherm from solution were involved the measurement of excess isotherm conducted at low region of sorbates concentration. Direct interpretation of excess adsorption isotherm as adsorption isotherm is always been practice. Therefore, in this work a study on the measurement of the adsorption isotherm from solution of non-azeotropic organic solvent mixture onto porous adsorbents for whole range of liquid concentration was conducted. The study included the measurement of excess adsorption isotherm using conventional technique. Theoretical analysis and interpretation of adsorption isotherm from the excess isotherm were conducted using Pseudo Ideal Adsorption, Gibbs Dividing Plane Model and Langmuir-Fruendlich binary isotherm model. For organic solvents, acetone and propanol were chosen as the adsorbates due to the non-azeotropic properties in the mixture. Activated carbon and silicalite were chosen as adsorbents due to the different in their porosity such as macro porous and micro porous structure. The result of the study has revealed that the adsorption isotherm of non-azeotropic mixture onto activated carbon and silicalite can be interpreted as monolayer type of adsorption.

  15. Capture of formaldehyde by adsorption on nanoporous materials.

    PubMed

    Bellat, Jean-Pierre; Bezverkhyy, Igor; Weber, Guy; Royer, Sébastien; Averlant, Remy; Giraudon, Jean-Marc; Lamonier, Jean-François

    2015-12-30

    The aim of this work is to assess the capability of a series of nanoporous materials to capture gaseous formaldehyde by adsorption in order to develop air treatment process and gas detection in workspaces or housings. Adsorption-desorption isotherms have been accurately measured at room temperature by TGA under very low pressure (p<2 hPa) on various adsorbents, such as zeolites, mesoporous silica (SBA15), activated carbon (AC NORIT RB3) and metal organic framework (MOF, Ga-MIL-53), exhibiting a wide range of pore sizes and surface properties. Results reveal that the NaX, NaY and CuX faujasite (FAU) zeolites are materials which show strong adsorption capacity and high affinity toward formaldehyde. In addition, these materials can be completely regenerated by heating at 200°C under vacuum. These cationic zeolites are therefore promising candidates as adsorbents for the design of air depollution process or gas sensing applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Adsorption of alkyltrimethylammonium bromides at water/alkane interfaces: competitive adsorption of alkanes and surfactants.

    PubMed

    Fainerman, V B; Mucic, N; Pradines, V; Aksenenko, E V; Miller, R

    2013-11-12

    The adsorption of members of the homologous series of alkyl trimethylammonium bromides (C(n)TAB) is studied at water/alkane interfaces by drop profile analysis tensiometry. The results are discussed in terms of a competitive adsorption process of alkane and surfactant molecules. A thermodynamic model, derived originally for the adsorption of surfactant mixtures, is adapted such that it describes a competitive adsorption of the surfactant molecules from the aqueous phase and alkane molecules from the oil phase. This new model involves the interspecies attraction coefficient, which mutually increases the adsorption activities of the alkane and C(n)TAB. The effects of the alkyl chain length n of C(n)TABs and the influence of the number of C atoms in the alkane chain are discussed, and the physical quantities are compared to those determined at the aqueous solution/air interface. The new theoretical model for aqueous solution/oil interfaces is also compared to a theory that does not consider the adsorption of alkane. The proposed new model demonstrates good agreement with the experimental data.

  17. Adsorption of halogenated aliphatic contaminants by graphene nanomaterials.

    PubMed

    Zhou, Yang; Apul, Onur Guven; Karanfil, Tanju

    2015-08-01

    In this study, adsorption of ten environmentally halogenated aliphatic synthetic organic compounds (SOCs) by a pristine graphene nanosheet (GNS) and a reduced graphene oxide (rGO) was examined, and their adsorption behaviors were compared with those of a single-walled carbon nanotube (SWCNT) and a granular activated carbon (GAC). In addition, the impacts of background water components (i.e., natural organic matter (NOM), ionic strength (IS) and pH) on the SOC adsorption behavior were investigated. The results indicated HD3000 and SWCNT with higher microporous volumes exhibited higher adsorption capacities for the selected aliphatic SOCs than graphenes, demonstrating microporosity of carbonaceous adsorbents played an important role in the adsorption. Analysis of adsorption isotherms demonstrated that hydrophobic interactions were the dominant contributor to the adsorption of aliphatic SOCs by graphenes. However, π-π electron donor-acceptor and van der Waals interactions are likely the additional mechanisms contributing to the adsorption of aliphatic SOCs on graphenes. Among the three background solution components examined, NOM showed the most influential effect on adsorption of the selected aliphatic SOCs, while pH and ionic strength had a negligible effects. The NOM competition on aliphatic adsorption was less pronounced on graphenes than SWCNT. Overall, in terms of adsorption capacities, graphenes tested in this study did not exhibit a major advantage over SWCNT and GAC for the adsorption of aliphatic SOCs.

  18. Selenite adsorption using leached residues generated by reduction roasting-ammonia leaching of manganese nodules.

    PubMed

    Randhawa, N S; Das, N N; Jana, R K

    2012-11-30

    This study was carried out to investigate the adsorption characteristics of leached manganese nodule residue (MNR), generated from the reduction roasting-ammonia leaching process, towards aqueous selenite. Physicochemical characterization revealed that the leached residue was a complex mixture of oxides of mainly manganese and iron along with MnCO(3). Adsorption studies of the water washed leached residue (wMNR) at varying the pH, selenite ion concentration, wMNR dosage, heat treatment condition indicated that selenite uptake increased with increasing pH and heat-treatment temperature of wMNR. The maximum value of selenite uptake was obtained at pH ~5.0 with wMNR heat-treated at 400°C and thereafter decreased on increasing the pH and heat-treatment temperature further. The adsorption data were best fitted by the Freundlich isotherm model. The derived monolayer selenite adsorption capacities increased from, X(m)=9.50 mg Se/g (for untreated wMNR) to 15.08 mg Se/g (for wMNR heat-treated at 400°C). The results of the studies may be useful for possible utilization of MNR as an adsorbent for the removal of selenite ions from contaminated water bodies. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Influence of Soil Solution Salinity on Molybdenum Adsorption by Soils

    USDA-ARS?s Scientific Manuscript database

    Molybdenum (Mo) adsorption on five arid-zone soils from California was investigated as a function of equilibrium solution Mo concentration (0-30 mg L-1), solution pH (4-8), and electrical conductivity (EC = 0.3 or 8 dS m-1). Molybdenum adsorption decreased with increasing pH. An adsorption maximum...

  20. In vitro study of the adsorption characteristics of drugs.

    PubMed

    Toyoguchi, Teiko; Ebihara, Mitsutaka; Ojima, Fumiyoshi; Hosoya, Jun; Nakagawa, Yoshito

    2005-05-01

    The adsorption characteristics of eight adsorbents, cholestyramine, colestimide, aluminum silicate, sucralfate, aluminum hydroxide, calcium polystyrene sulfonate, carbon sphere and medicinal carbon, on the drugs such as methotrexate, antidepressants, mizoribine and ciprofloxacin hydrochloride were investigated in vitro. Medicinal carbon showed an excellent adsorption of all the tested drugs while the carbon spheres showed a high but slow adsorption characteristic. Cholestyramine and colestimide showed a higher adsorption in methotrexate than the other adsorbents. Aluminum silicate and calcium polystyrene sulfonate showed higher adsorption in four antidepressants, clomipramine hydrochloride, imipramine hydrochloride, mianserin hydrochloride and trazodone hydrochloride. In mizoribine, there were no adsorbents that showed higher adsorption except for the medicinal carbon. In ciprofloxacin hydrochloride, aluminum preparations and calcium polystyrene sulfonate showed higher adsorption characteristics. It is suggested that several adsorbents are potentially useful treatments for drug overdoses, but that these adsorbents have the possibility of decreasing the effects of the co-administered medicines.

  1. Adsorption of cellulase on cellulose: effect of physicochemical properties of cellulose on adsorption and rate of hydrolysis

    SciTech Connect

    Lee, S.B.; Shin, H.S.; Ryu, D.D.Y.

    1982-11-01

    In the cellulase-cellulose reaction system, the adsorption of cellulase on the solid cellulose substrate was found to be one of the important parameters that govern the enzymatic hydrolysis rate of cellulose. The adsorption of cellulase usually parallels the rate of hydrolysis of cellulose. The affinity for cellulase varies depending on the structural properties of cellulose. Adsorption parameters such as the half-saturation constant, the maximum adsorption constant, and the distribution coefficient for both the cellulase and cellulose have been experimentally determined for several substrates. These adsorption parameters vary with the source of cellulose and the pretreatment methods and are correlated with the crystallinity and the specific surface area of cellulose substrates. The changing pattern of adsorption profile of cellulase during the hydrolysis reaction has also been elucidated. For practical utilization of cellulosic materials, the cellulose structural properties and their effects on cellulase adsorption, and the rate of hydrolysis must be taken into consideration. (Refs. 24).

  2. Evaluation of the adsorption capacity of alkali-treated waste materials for the adsorption of sulphamethoxazole.

    PubMed

    Kurup, Lisha

    2012-01-01

    The present work is to develop potential adsorbents from waste material and employ them for the removal of a hazardous antibacterial, sulphamethoxazole, from the wastewater by the Adsorption technique. The Adsorption technique was used to impound the dangerous antibiotics from wastewater using Deoiled Soya (DOS), an agricultural waste, and Water Hyacinth (WH), a prolific colonizer. The adsorption capacity of these adsorbents was further enhanced by treating them with sodium hydroxide solution and it was seen that the adsorption capacity increases by 10 to 25%. Hence a comparative account of the adsorption studies of all the four adsorbents, i.e. DOS, Alkali-treated DOS, WH and Alkali-treated Water Hyacinth has been discussed in this paper. Different isotherms like Freundlich, Langmuir and Dubinin-Radushkevich were also deduced from the adsorption data. Isotherm studies were in turn used in estimating the thermodynamic parameters. DOS showed sorption capacity of 0.0007 mol g(-1) while Alkali-treated Deoiled Soya exhibited 0.0011 mol g(-1) of sorption capacity, which reveals that the adsorption is higher in case of alkali-treated adsorbent. The mean sorption energy (E) was obtained between 9 and 12 kJ mol, which shows that the reaction proceeds by ion exchange reaction. Kinetic study reveals that the reaction follows pseudo-second-order rate equation. Moreover, mass transfer studies performed for the ongoing processes show that the mass transfer coefficient obtained for alkali-treated moieties was higher than the parent moieties. The breakthrough curves plotted from the column studies show percentage saturation of 90-98%. About 87-97% of sulphamethoxazole was recovered from column by desorption.

  3. Methane adsorption in nanoporous carbon: the numerical estimation of optimal storage conditions

    NASA Astrophysics Data System (ADS)

    Ortiz, L.; Kuchta, B.; Firlej, L.; Roth, M. W.; Wexler, C.

    2016-05-01

    The efficient storage and transportation of natural gas is one of the most important enabling technologies for use in energy applications. Adsorption in porous systems, which will allow the transportation of high-density fuel under low pressure, is one of the possible solutions. We present and discuss extensive grand canonical Monte Carlo (GCMC) simulation results of the adsorption of methane into slit-shaped graphitic pores of various widths (between 7 Å and 50 Å), and at pressures P between 0 bar and 360 bar. Our results shed light on the dependence of film structure on pore width and pressure. For large widths, we observe multi-layer adsorption at supercritical conditions, with excess amounts even at large distances from the pore walls originating from the attractive interaction exerted by a very high-density film in the first layer. We are also able to successfully model the experimental adsorption isotherms of heterogeneous activated carbon samples by means of an ensemble average of the pore widths, based exclusively on the pore-size distributions (PSD) calculated from subcritical nitrogen adsorption isotherms. Finally, we propose a new formula, based on the PSD ensemble averages, to calculate the isosteric heat of adsorption of heterogeneous systems from single-pore-width calculations. The methods proposed here will contribute to the rational design and optimization of future adsorption-based storage tanks.

  4. Adsorption of basic dyes from aqueous solution onto pumice powder.

    PubMed

    Akbal, Feryal

    2005-06-15

    The adsorption of methylene blue and crystal violet on pumice powder samples of varying compositions was investigated using a batch adsorption technique. The effects of various experimental parameters, such as adsorbent dosage, initial dye concentration, and contact time, were also investigated. The extent of dye removal increased with decreased initial concentration of the dye and also increased with increased contact time and amount of adsorbent used. Adsorption data were modeled using the Freundlich adsorption isotherm. The adsorption kinetic of methylene blue and crystal violet could be described by the pseudo-second-order reaction model.

  5. Heterogeneous adsorption of activated carbon nanofibers synthesized by electrospinning polyacrylonitrile solution.

    PubMed

    Lee, Jae-Wook; Kang, Hyun-Chul; Shim, Wang-Geun; Kim, Chan; Yang, Kap-Seung; Moon, Hee

    2006-11-01

    This study focuses on the adsorption properties of activated carbon nanofibers (CNFs) fabricated by electrospinning polyacrylonitrile solutions dissolved in dimethylformamide, followed by heat treatment at high activation temperatures (700, 750, 800 degrees C). The samples were characterized by BET, SEM, and XRD. In addition, the adsorption energy distribution functions of CNFs were analyzed by using the generalized nonlinear regularization method. Comparative analysis of energy distribution functions provided significant information on the energetic and structural heterogeneities of CNFs. Furthermore, an investigation of adsorption equilibrium and kinetics of methylene blue (MB) and congo red (CR) revealed that the adsorption capacity and kinetics of MB are much higher and faster than that of CR on a given sample. Our experimental and theoretical results suggest that the CNFs used in this work may be widely used as an adsorbent.

  6. Short-Cycle Adsorption Refrigerator

    NASA Technical Reports Server (NTRS)

    Chan, C. K.

    1988-01-01

    Modular adsorption/Joule-Thomson-effect refrigerator offers fast regeneration; adsorption/desorption cycle time expected to be 1 minute. Pressurized hydrogen generated by bank of compressor modules during heating phase passes through system of check valves and expands in Joule-Thomson junction as it enters refrigeration chamber. Hydrogen absorbs heat from load before it is sucked out by another bank of compressor modules in cooling phase.

  7. Simultaneous description of strong and weak H2 adsorption sites coexisting in MOFs

    NASA Astrophysics Data System (ADS)

    Cha, Moon-Hyun; Kim, Kyung-Suk; Ihm, Jisoon

    2012-02-01

    In designing hydrogen-storage materials, it is a wide-spread practice to introduce transition-metal atoms into the MOF structures in order to increase the binding energy of H2. In such systems, it is necessary to understand and describe the H2 binding behaviors at both strong and weak binding sites. Here, we propose a model that quantitatively characterizes the hydrogen gas adsorption in the presence of different kinds of adsorption sites. Based on equilibrium thermodynamics, this model enables us to figure out the number of H2 molecules adsorbed to each adsorbing site and the corresponding heat of adsorption. When the present model is applied to real experimental data, different binding sites are identified and the contribution of each term to the storage capacity is obtained. While the virial equation gives the isosteric heat of adsorption averaged over the system, our model gives the heat of adsorption at each adsorbed site. Furthermore, by analyzing the results of fitting, we can estimate the volume occupied by adsorbed H2 molecules.

  8. Microstructure-Dependent Gas Adsorption: Accurate Predictions of Methane Uptake in Nanoporous Carbons

    SciTech Connect

    Ihm, Yungok; Cooper, Valentino R; Gallego, Nidia C; Contescu, Cristian I; Morris, James R

    2014-01-01

    We demonstrate a successful, efficient framework for predicting gas adsorption properties in real materials based on first-principles calculations, with a specific comparison of experiment and theory for methane adsorption in activated carbons. These carbon materials have different pore size distributions, leading to a variety of uptake characteristics. Utilizing these distributions, we accurately predict experimental uptakes and heats of adsorption without empirical potentials or lengthy simulations. We demonstrate that materials with smaller pores have higher heats of adsorption, leading to a higher gas density in these pores. This pore-size dependence must be accounted for, in order to predict and understand the adsorption behavior. The theoretical approach combines: (1) ab initio calculations with a van der Waals density functional to determine adsorbent-adsorbate interactions, and (2) a thermodynamic method that predicts equilibrium adsorption densities by directly incorporating the calculated potential energy surface in a slit pore model. The predicted uptake at P=20 bar and T=298 K is in excellent agreement for all five activated carbon materials used. This approach uses only the pore-size distribution as an input, with no fitting parameters or empirical adsorbent-adsorbate interactions, and thus can be easily applied to other adsorbent-adsorbate combinations.

  9. Adsorption of pharmaceuticals to microporous activated carbon treated with potassium hydroxide, carbon dioxide, and steam.

    PubMed

    Fu, Heyun; Yang, Liuyan; Wan, Yuqiu; Xu, Zhaoyi; Zhu, Dongqiang

    2011-01-01

    Adsorption of sulfapyridine, tetracycline, and tylosin to a commercial microporous activated carbon (AC) and its potassium hydroxide (KOH)-, CO-, and steam-treated counterparts (prepared by heating at 850°C) was studied to explore efficient adsorbents for the removal of selected pharmaceuticals from water. Phenol and nitrobenzene were included as additional adsorbates, and nonporous graphite was included as a model adsorbent. The activation treatments markedly increased the specific surface area and enlarged the pore sizes of the mesopores of AC (with the strongest effects shown on the KOH-treated AC). Adsorption of large-size tetracycline and tylosin was greatly enhanced, especially for the KOH-treated AC (more than one order of magnitude), probably due to the alleviated size-exclusion effect. However, the treatments had little effect on adsorption of low-size phenol and nitrobenzene due to the predominance of micropore-filling effect in adsorption and the nearly unaffected content of small micropores causative to such effect. These hypothesized mechanisms on pore-size dependent adsorption were further tested by comparing surface area-normalized adsorption data and adsorbent pore size distributions with and without the presence of adsorbed antibiotics. The findings indicate that efficient adsorption of bulky pharmaceuticals to AC can be achieved by enlarging the adsorbent pore size through suitable activation treatments.

  10. Understanding the kinetics of adsorption in narrow channel metal organic frameworks

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Simmons, Jason; Yildirim, Taner

    2010-03-01

    Advancements in the controlled synthesis of metal organic frameworks (MOFs) have lead to impressive increases in hydrogen storage capacities and enhanced binding energies that may offer higher temperature operation. Given that the optimum pore size for hydrogen adsorption is on the order of 7 Angstroms, diffusion of hydrogen into these materials can play an important role in their ultimate implementation. In this presentation we use a combination of experimental and computational techniques, including gas sorption and neutron scattering measurements and detailed first-principles calculations, to better understand the kinetic limitations to adsorption in narrow channel MOF. In particular we show that the adsorption is diffusion limited with a significant activation barrier of ˜70 meV, and that this barrier is phonon-mediated. This work demonstrates the importance of considering kinetic effects in addition to pore volume and heats of adsorption when optimizing MOF materials for hydrogen storage.

  11. Adsorption features of flavonoids on macroporous adsorption resins functionalized with ionic liquids.

    PubMed

    Lou, Song; Di, Duolong

    2012-10-08

    A series of macroporous adsorption resins (MARs) with novel structures is synthesized via Friedel-Crafts catalyzed reaction. The adsorption kinetics of the synthetic resins with respect to the purification effect is systematically investigated by means of the response surface methodology (RSM). The kinetic data cannot be fitted to the classical model because it does not take multicompartments and desorption rates into consideration. A new multicompartment louver-tide theory is thus developed considering that adsorption is an indefinite dynamic equilibrium process, which can be divided into innumerable ingredients with different desorption rates. This theory produces much better fits to the experimental data and provides a quantitative explanation with multicompartments and adsorption/desorption rates. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

    PubMed

    Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

    2014-07-15

    Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    PubMed

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent.

  14. Molecular simulation study of adsorption and diffusion on silicalite for a benzene/CO2 mixture.

    PubMed

    Yue, Xiaopeng; Yang, Xiaoning

    2006-03-28

    The adsorption and diffusion of a binary mixture of supercritical CO2 and benzene on silicalite (MFI-type) have been studied through the grand canonical Monte Carlo and molecular dynamics (MD) simulations. The adsorption behavior of pure CO2 on silicalite was discussed in detail from the adsorption isotherms, adsorption sites, interaction energies, and isosteric heats of adsorption. For the mixture, the influences of temperature, pressure and composition on the adsorption isotherms have been examined. The adsorption site behavior of the mixture has been analyzed, and benzene molecules get adsorbed preferentially in the more spacious channel intersection positions. These simulation results suggest that SC-CO2 fluid can be used as an efficient desorbent of larger aromatics in the zeolite material. The diffusion characteristic for the benzene/CO2 mixture was studied on the basis of MD simulation. It was found that the large coadsorbed benzene molecule has a pronounced effect on the CO2 diffusion in the mixture, while the mobility of benzene molecules is very small due to geometrical restrictions.

  15. Rigorous Mathematical Modeling of Adsorption System with Electrothermal Regeneration of the Used Adsorbent

    DTIC Science & Technology

    2006-12-01

    U0 (V) - Supply voltage u (cm/s) - Radial superficial gas velocity VPA, VPB, VP D - Wagner constants v (cm/s) - Axial superficial gas velocity W...heated activa er cloth element” US Patent No. 6,346,936 B1(2002) 10. Petko athematical Modeling of Adsorption System with Electr of the Used

  16. Adsorption of chloridazon from aqueous solution on modified kerolite-rich materials.

    PubMed

    Ureña-Amate, María D; Socías-Viciana, María M; González-Pradas, E; Cantos-Molina, A; Villafranca-Sánchez, M; López-Teruel, C

    2008-02-01

    The adsorption of chloridazon (5-amine-4-chloro-2-phenylpyridazin-3(2H)-one) on kerolite samples heated at 110 degrees C (K-110), 200 degrees C (K-200), 400 degrees C (K-400), 600 degrees C (K-600) and acid-treated with H(2)SO(4) solutions of two different concentrations (0.25 and 0.5 M) (K-0.25 and K-0.5, respectively) from pure water at 25 degrees C has been studied by using batch and column experiments. The adsorption experimental data points were fitted to the Freundlich equation in order to calculate the adsorption capacities (K(f)) of the samples; K(f) values ranged from 184.7 mg kg(-1) (K-0.5) up to 2253 mg kg(-1) (K-600). This indicated that the heat treatment given to the kerolite greatly increases its adsorption capacity for the herbicide whereas the acid treatment produces a clear decrease in the amount of chloridazon adsorbed. The removal efficiency (R) was also calculated; R values ranging from 52.8% (K-0.5) up to 88.3% (K-600). Thus, the results showed that the 600 degrees C heat-treated kerolite was more effective in relation to adsorption of chloridazon and it might be reasonably used in removing this herbicide from water.

  17. Adsorption of ammonia on multilayer iron phthalocyanine

    SciTech Connect

    Isvoranu, Cristina; Knudsen, Jan; Ataman, Evren; Andersen, Jesper N.; Schnadt, Joachim; Schulte, Karina; Wang Bin; Bocquet, Marie-Laure

    2011-03-21

    The adsorption of ammonia on multilayers of well-ordered, flat-lying iron phthalocyanine (FePc) molecules on a Au(111) support was investigated by x-ray photoelectron spectroscopy. We find that the electron-donating ammonia molecules coordinate to the metal centers of iron phthlalocyanine. The coordination of ammonia induces changes of the electronic structure of the iron phthalocyanine layer, which, in particular, lead to a modification of the FePc valence electron spin.

  18. Molecular basis for the high CO2 adsorption capacity of chabazite zeolites.

    PubMed

    Pham, Trong D; Hudson, Matthew R; Brown, Craig M; Lobo, Raul F

    2014-11-01

    CO2 adsorption in Li-, Na-, K-CHA (Si/Al=6,=12), and silica chabazite zeolites was investigated by powder diffraction. Two CO2 adsorption sites were found in all chabazites with CO2 locating in the 8-membered ring (8MR) pore opening being the dominant site. Electric quadrupole-electric field gradient and dispersion interactions drive CO2 adsorption at the middle of the 8 MRs, while CO2 polarization due to interaction with cation sites controls the secondary CO2 site. In Si-CHA, adsorption is dominated by dispersion interactions with CO2 observed on the pore walls and in 8 MRs. CO2 adsorption complexes on dual cation sites were observed on K-CHA, important for K-CHA-6 samples due to a higher probability of two K(+) cations bridging CO2. Trends in isosteric heats of CO2 adsorption based on cation type and concentration can be correlated with adsorption sites and CO2 quantity. A decrease in the hardness of metal cations results in a decrease in the direct interaction of these cations with CO2. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Adsorption of Atmospheric Gases on Pu Surfaces

    SciTech Connect

    Nelson, A J; Holliday, K S; Stanford, J A; Grant, W K; Erler, R G; Allen, P G; McLean, W; Roussel, P

    2012-03-29

    Surface adsorption represents a competition between collision and scattering processes that depend on surface energy, surface structure and temperature. The surface reactivity of the actinides can add additional complexity due to radiological dissociation of the gas and electronic structure. Here we elucidate the chemical bonding of gas molecules adsorbed on Pu metal and oxide surfaces. Atmospheric gas reactions were studied at 190 and 300 K using x-ray photoelectron spectroscopy. Evolution of the Pu 4f and O 1s core-level states were studied as a function of gas dose rates to generate a set of Langmuir isotherms. Results show that the initial gas dose forms Pu{sub 2}O{sub 3} on the Pu metal surface followed by the formation of PuO{sub 2} resulting in a layered oxide structure. This work represents the first steps in determining the activation energy for adsorption of various atmospheric gases on Pu.

  20. [Characteristic of ammonia nitrogen adsorption on karst underground river sediments].

    PubMed

    Guo, Fang; Chen, Kun-Kun; Jiang, Guang-Hui

    2011-02-01

    Karst aquifers are one of the most important aquifers in Southwestern China. One of the characteristics of karst aquifers is the enhanced permeability permits high flow velocities are capable of transporting suspended and bedload sediments. Mobile sediment in karst may act as a vector for the transport of contaminates. 14 sediment samples were collected from two underground rivers in two typical karst areas in Liuzhou city, Guangxi Autonomous Region, China. According to simulated experiment methods, characteristic of adsorption of ammonia nitrogen on sediment was studied. The results of ammonia nitrogen adsorption dynamics on sediments showed that the maximum adsorption velocity was less than 2 h. The adsorption balance quantity in 5 h accounted for 71% - 98% of the maximum adsorption quantity. The maximum adsorption quantity of ammonia nitrogen was 385.5 mg/kg, which was sediment from a cave in the middle areas of Guancun underground river system. The study of isotherm adsorption indicated adsorption quantity of NH4+ increase followed by incremental balance concentration of NH4+ in the aquatic phase. Adsorption quantity of ammonia nitrogen in sediments has a relative linear relationship with adsorption balance concentrations. Adsorption-desorption balance concentrations were all low, indicating sediments from underground rivers have great adsorption potential. Under the condition of low and high concentrations of ammonia nitrogen in overlying water, Langmuir and Tempkin couldn't simulate or simulate results couldn't reach remarkable level, whilst Linear and Freundlich models could simulate well. Research on different type sediments, sampling times and depths from two underground rivers shows characteristic of ammonia nitrogen adsorption on karst underground river sediments doesn't have good correspondence with the type of sediments. One of the reasons is there is no big difference between sediments in the development of climate, geology, hydrological conditions

  1. Study of Solar Driven Silica gel-Water based Adsorption Chiller

    NASA Astrophysics Data System (ADS)

    Habib, K.; Assadi, M. K.; Zainudin, M. H. B.

    2015-09-01

    In this study, a dynamic behaviour of a solar powered single stage four bed adsorption chiller has been analysed designed for Malaysian climate. Silica gel and water have been used as adsorbent-refrigerant pair. A simulation program has been developed for modeling and performance evaluation of the chiller using the meteorological data of Kuala Lumpur. The optimum cooling capacity and coefficient of performance (COP) are calculated in terms of adsorption/desorption cycle time and regeneration temperature. Results indicate that the chiller is feasible even when low temperature heat source is available. Results also show that the adsorption cycle can achieve a cooling capacity of 14 kW when the heat source temperature is about 85°C.

  2. Adsorption of crude oil on anhydrous and hydrophobized vermiculite.

    PubMed

    da Silva, Umberto G; de F Melo, Marcus A; da Silva, Adaílton F; de Farias, Robson F

    2003-04-15

    This publication reports the adsorption of crude oil on vermiculite samples, expanded and hydrophobized with carnauba (Copernícia Cerífera) wax. The adsorption studies were performed by using columns filled with the vermiculite matrices and by dispersion of the vermiculite samples in an oil-water (50 ppm of oil) emulsion. The hydrate vermiculite exhibits a very low adsorption capacity against crude oil. On the other hand, anhydrous (expanded) and hydrophobized matrices show a high adsorption capacity. The 10% hydrophobized matrix show a 50% increased adsorption capacity, in comparison with the expanded one. For adsorption performed in the water-oil emulsion, saturation of the solid hydrophobized matrix is achieved after 60 min. The hydrophobized samples exhibit adsorption factors in the 0.7-1.0 range.

  3. Adsorption of EDTA on activated carbon from aqueous solutions.

    PubMed

    Zhu, Hai-song; Yang, Xiao-juan; Mao, Yan-peng; Chen, Yu; Long, Xiang-li; Yuan, Wei-kang

    2011-01-30

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R(2) = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (E(a), ΔG(0), ΔH(0), ΔS(0)) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  4. Adsorption of dextrin on hydrophobic minerals.

    PubMed

    Beaussart, Audrey; Mierczynska-Vasilev, Agnieszka; Beattie, David A

    2009-09-01

    The adsorption of dextrin on talc, molybdenite, and graphite (three naturally hydrophobic minerals) has been compared. Adsorption isotherms and in situ tapping mode atomic force microscope (TMAFM) imaging have enabled polymer adsorbed amount and morphology of the adsorbed layer (area coverage and polymer domain size) to be determined and also the amount of hydration water in the structure of the adsorbed layer. The effect of the polymer on the mineral contact angles, measured by the captive bubble method on cleaved mineral surfaces, indicates clear correlations between the hydrophobicity reduction of the minerals, the adsorbed amount, and the surface coverage of the adsorbed polymer. Predictions of the flotation recovery of the treated mineral phases have been confirmed by performing batch flotation experiments. The influence of the polymer surface coverage on flotation recovery has highlighted the importance of this key parameter in the predictions of depressant efficiency. The roles of the initial hydrophobicity and the surface structure of the mineral basal plane in determining adsorption parameters and flotation response of the polymer-treated minerals are also discussed.

  5. Removal of mercury by adsorption: a review.

    PubMed

    Yu, Jin-Gang; Yue, Bao-Yu; Wu, Xiong-Wei; Liu, Qi; Jiao, Fei-Peng; Jiang, Xin-Yu; Chen, Xiao-Qing

    2016-03-01

    Due to natural and production activities, mercury contamination has become one of the major environmental problems over the world. Mercury contamination is a serious threat to human health. Among the existing technologies available for mercury pollution control, the adsorption process can get excellent separation effects and has been further studied. This review is attempted to cover a wide range of adsorbents that were developed for the removal of mercury from the year 2011. Various adsorbents, including the latest adsorbents, are presented along with highlighting and discussing the key advancements on their preparation, modification technologies, and strategies. By comparing their adsorption capacities, it is evident from the literature survey that some adsorbents have shown excellent potential for the removal of mercury. However, there is still a need to develop novel, efficient adsorbents with low cost, high stability, and easy production and manufacture for practical utility.

  6. Activated carbon adsorption of humic substances

    SciTech Connect

    Lee, M.C.

    1981-08-01

    Activated carbon pore-size distribution is an important parameter relative to the carbon's capacity for adsorbing humic substances. The effect of coagulation on adsorption should also be examined wherever granular activated carbon is to be used following coagulation. Experimental investigations using a commercial humic acid and a fulvic acid extracted from peat, and a number of commercial activated carbons, several of which were coal-based, are reported.

  7. Interlamellar adsorption of carbon dioxide by smectites

    USGS Publications Warehouse

    Fripiat, J.J.; Cruz, M.I.; Bohor, B.F.; Thomas, J.

    1974-01-01

    The adsorption of CO2 at low temperature (~ -70 ??C) on thin films of homoionic smectites was studied by X-ray diffraction and by i.r. absorption. An increase in the d001 spacings of these clay films upon adsorption of CO2 was observed. In addition, a dichroic effect was readily discernible by comparing the i.r. spectra at two different orientations of the smectite films; i.e. with the film normal and tilted 35 with respect to the i.r. beam. The CO2 stretching vibration at 2350 cm-1 was used for the i.r. study. These observations conclusively show that CO2 intercalates the smectite structure rather than being adsorbed only in pores between clay tactoids- the limiting process proposed by other investigators. Adsorption isotherm data from earlier surface area studies are re-examined here through application of the Dubinin equation. Again, intercalation is demonstrated by convergence of the plotted experimental data for smectites containing large monovalent interlayer cations toward a pore volume that is near the calculated theoretical value for a monolayer of intercalated CO2. Scanning electron photomicrographs of Li-and Cs- smectites provide additional evidence that aggregation differences are not responsible for the large observed difference in BET surface areas obtained for these smectites with CO2 as the adsorbate. At low magnification, visual differences in macro-aggregates are apparent, but at high magnification no significant differences are observed in the micro-structure of individual aggregates where the major amount of gas adsorption really occurs. ?? 1974.

  8. IMPORTANCE OF ACTIVATED CARBON'S OXYGEN SURFACE FUNCTIONAL GROUPS ON ELEMENTAL MERCURY ADSORPTION

    EPA Science Inventory

    The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury [Hg(0)] was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N2), air oxidat...

  9. IMPORTANCE OF ACTIVATED CARBON'S OXYGEN SURFACE FUNCTIONAL GROUPS ON ELEMENTAL MERCURY ADSORPTION

    EPA Science Inventory

    The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury [Hg(0)] was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N2), air oxidat...

  10. Siderophore Adsorption to and Dissolution of Kaolinite

    NASA Astrophysics Data System (ADS)

    Rosenberg, D. R.; Maurice, P. A.

    2001-12-01

    This study examined the effect of the synthetic trihydroxamate siderophore, desferrioxamine mesylate (DFAM), on the dissolution of and Fe removal from an Fe-containing ( ~0.1 weight %) kaolinite. Batch adsorption and dissolution experiments were conducted at pH 3, 5.5, and 7, at 25° C, in the dark, to 96 hours. Adsorption was considerably stronger than previously reported on goethite (Kraemer et al., 1999, GCA), most probably because of differences in the surface charge properties of these two minerals. Adsorption of DFAM was weakest at pH < 5, which is the pH point of zero charge for KGa-2, and increased by several fold as pH increased to 8. In contrast to dissolution in the simple organic ligand, oxalate, DFAM-promoted dissolution was mostly pH-independent from pH 3 to 7. Si concentrations released in the presence of DFAM remained at the levels of HNO3 controls over this pH range. Al concentrations were greatly enhanced versus controls, most likely due at least in part to DFAM-Al complexation and enhanced solubility. Aqueous Fe concentrations were negligible at pH 3, and in controls at all 3 pH values, but were in the 10 ppb range at pH 5.5 and 7, in the presence of DFAM. These results show that micromolar amounts of Fe, sufficient for the metabolic needs of aerobic microorganisms, can be extracted from natural kaolinite by DFAM.

  11. Adsorption of soft particles at fluid interfaces

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Isa, Lucio; Dufresne, Eric R.

    Soft particles can be better emulsifiers than hard particles because they stretch at fluid interfaces. This deformation can increase adsorption energies by orders of magnitude relative to rigid particles. The deformation of a particle at an interface is governed by a competition of bulk elasticity and surface tension. When particles are partially wet by the two liquids, deformation is localized within a material-dependent distance $L$ from the contact line. At the contact line, the particle morphology is given by a balance of surface tensions. When the particle radius $R \\ll L$, the particle adopts a lenticular shape identical to that of an adsorbed fluid droplet. Particle deformations can be elastic or plastic, depending on the relative values of the Young modulus, $E$, and yield stress, $\\sigma_p$. When surface tensions favour complete spreading of the particles at the interface, plastic deformation can lead to unusual fried-egg morphologies. When deformable particles have surface properties that are very similar to one liquid phase, adsorption can be extremely sensitive to small changes of their affinity for the other liquid phase. These findings have implications for the adsorption of microgel particles at fluid interfaces and the performance of stimuli-responsive Pickering emulsions.

  12. Interfacial adsorption and aggregation of amphiphilic proteins

    NASA Astrophysics Data System (ADS)

    Cheung, David

    2012-02-01

    The adsorption and aggregation on liquid interfaces of proteins is important in many biological contexts, such as the formation of aerial structures, immune response, and catalysis. Likewise the adsorption of proteins onto interfaces has applications in food technology, drug delivery, and in personal care products. As such there has been much interest in the study of a wide range of biomolecules at liquid interfaces. One class of proteins that has attracted particular attention are hydrophobins, small, fungal proteins with a distinct, amphiphilic surface structure. This makes these proteins highly surface active and they recently attracted much interest. In order to understand their potential applications a microscopic description of their interfacial and self-assembly is necessary and molecular simulation provides a powerful tool for providing this. In this presentation I will describe some recent work using coarse-grained molecular dynamics simulations to study the interfacial and aggregation behaviour of hydrophobins. Specifically this will present the calculation of their adsorption strength at oil-water and air-water interfaces, investigate the stability of hydrophobin aggregates in solution and their interaction with surfactants.

  13. Adsorption of Nanoplastics on Algal Photosynthesis

    NASA Astrophysics Data System (ADS)

    Turner, James; Bhattacharya, Priyanka; Lin, Sijie; Ke, Pu Chun

    2010-03-01

    The rapid accumulation of disposed plastics in the environment, especially in the Pacific Ocean, has become a global concern in recent years. Photo, chemical and physical degradations constantly fragment these plastics into a wide array of macroscopic to microscopic particles. As a result, marine organisms such as algae may be exposed to plastic particles through ingestion, adsorption and other forms of uptake. Such interactions, currently little understood, could potentially impact on the health state of the entire food chain. Here we report on polystyrene-algae interaction and its impact on algal photosynthesis. We first investigated the adsorption of polystyrene beads (20 nm) on a cellulose film coated on a 96-well plate. We derived a supralinear increase of the adsorption with the beads concentration for both positively and negatively charged polystyrene beads, with a saturation observed for the negatively charged polystyrene beads of concentration above 1.6 mg/mL. Using a bicarbonate indicator we discovered decreased carbon dioxide depletion due to polystyrene-algae binding. Since polystyrene beads also mediated algae aggregation, nanoplastics may alternatively be harnessed for waste water treatment.

  14. Multisite adsorption of cadmium on goethite

    SciTech Connect

    Venema, P.; Hiemstra, T.; Riemsdijk, W.H. van

    1996-11-10

    Recently a new general ion adsorption model has been developed for ion binding to mineral surfaces (Hiemstra and van Riemsdijk, 1996). The model uses the Pauling concept of charge distribution (CD) and is an extension of the multi-site complexation (MUSIC) approach. In the CD-MUSIC model the charge of an adsorbing ion that forms an inner sphere complex is distributed over its ligands, which are present in two different electrostatic planes. In this paper the authors have applied the CD-MUSIC model to the adsorption of metal cations, using an extended data set for cadmium adsorbing on goethite. The adsorption of cadmium and the cadmium-proton exchange ratio were measured as function of metal ion concentration, pH, and ionic strength. The data could be described well, taking into account the surface heterogeneity resulting from the presence of two different crystal planes (the dominant 110 face and the minor 021 face). The surface species used in the model are consistent with recent EXAFS data. In accordance with the EXAFS results, high-affinity complexes at the 021 face were used in the model.

  15. Adsorptive separation of propylene-propane mixtures

    SciTech Connect

    Jaervelin, H.; Fair, J.R. )

    1993-10-01

    The separation of propylene-propane mixtures is of great commercial importance and is carried out by fractional distillation. It is claimed to be the most energy-intensive distillation practiced in the United States. The purpose of this paper is to describe experimental work that suggests a practical alternative to distillation for separating the C[sub 3] hydrocarbons: adsorption. As studied, the process involves three adsorptive steps: initial separation with molecular sieves with heavy dilution with an inert gas; separation of propylene and propane separately from the inert gas, using activated carbon; and drying of the product streams with any of several available desiccants. The research information presented here deals with the initial step and includes both equilibrium and kinetic data. Isotherms are provided for propylene and propane adsorbed on three zeolites, activated alumina, silica gel, and coconut-based activated carbon. Breakthrough data are provided for both adsorption and regeneration steps for the zeolites, which were found to be superior to the other adsorbents for breakthrough separations. A flow diagram for the complete proposed process is included.

  16. Calorimetric measurement of adsorption and adhesion energies of Cu on Pt(111)

    NASA Astrophysics Data System (ADS)

    James, Trevor E.; Hemmingson, Stephanie L.; Sellers, Jason R. V.; Campbell, Charles T.

    2017-03-01

    The adsorption energies of submonolayer amounts of one metal on the surface of another metal have been measured for decades by temperature programmed desorption. However, that method fails for metals that alloy. We report here the first measurement of the adsorption energy for any such metal-on-metal combination that forms a bulk alloy. The adsorption and interfacial energetics of vapor deposited Cu onto Pt(111) at 300 K has been studied using single crystal adsorption calorimetry (SCAC) and X-ray photoelectron spectroscopy (XPS). The Cu grows as 2D pseudomorphic islands in the first layer and its heat of adsorption decreased linearly from 358 to 339 kJ/mol. This is attributed to increasing lattice strain with island size, associated with the small lattice mismatch (8%). It adsorbs 2 kJ/mol more weakly in the 2nd layer than above 3 ML, where it reaches the bulk heat of sublimation of Cu(solid), 337 kJ/mol. The adhesion energy of multilayer Cu onto Pt(111) is 3.76 J/m2. The extra stability of the first Cu monolayer compared to bulk Cu measured here is 12 kJ/mol, compared to a difference of 83 kJ/mol for underpotential deposition of Cu on a Pt(111) electrode, with the difference attributed to stronger bonding of Cu to the solvent and double layer compared to Pt.

  17. Adsorption of Single and Binary Gases on Polystyrene and Carbon Adsorbents

    NASA Astrophysics Data System (ADS)

    Rothstein, Daniel P.

    Time-dependent transmissions of light organic gases at low concentrations through crosslinked polystyrene and activated carbon adsorbents were measured and analyzed to extract kinetic and equilibrium parameters and to evaluate these parameters in terms of several models of adsorption. Mass -balance in the adsorber bed allows calculation of the equilibrium adsorbed-phase concentration and the model-independent adsorption capacity. Adsorption isotherms are calculated from transmission curves for eight light organic gases adsorbed on polystyrene at several temperatures. The power-law forms of the Freundlich and Chakravarti-Dhar isotherms and the concentration-dependent adsorption capacities indicate heterogeneous adsorption well below monolayer coverage. The effects of heterogeneity increase as non-linearity of the isotherm increases. A mesopore structure is indicated for polystyrene. Characteristic curves are independent of temperature, but the use of an affinity coefficient is not able to demonstrate their independence of adsorbate. Isosteric hearts of adsorption are larger than the heats of vaporization and decrease with increasing surface coverage for three alkanes adsorbed on polystyrene. The transmission curves of several binary mixtures of gases with non-linear isotherms reveal adsorption interference, with adsorption capacities smaller than those from single -component experiments. The pairs with unequal adsorption capacities exhibit displacement, in qualitative agreement with adsorption interference models. The equilibrium adsorption of the binary mixtures cannot be reproduced by single-component isotherm parameters alone, but are described by modified Freundlich isotherms requiring binary experiments. Adsorption in a porous medium is described by a model including four dynamic processes: gas- and solid -phase diffusion, interfacial mass-transfer resistance, and a first-order chemical reaction. A new time-dependent solution to the differential equations of

  18. Enthalpies of proton adsorption onto Bacillus licheniformis at 25, 37, 50, and 75 °C

    NASA Astrophysics Data System (ADS)

    Gorman-Lewis, Drew

    2011-03-01

    Understanding bacterial surface reactivity requires many different lines of investigation. Toward this end, we used isothermal titration calorimetry to measure heats of proton adsorption onto a Gram positive thermophile Bacillus licheniformis at 25, 37, 50, and 75 °C. Proton adsorption under all conditions exhibited exothermic heat production. Below pH 4.5, exothermic heats decreased as temperature increased above 37 °C; above pH 4.5, there was no significant difference in heats evolved at the temperatures investigated. Total proton uptake did not vary significantly with temperature. Site-specific enthalpies and entropies were calculated by applying a 4-site, non-electrostatic surface complexation model to the calorimetric data. Interpretation of site-specific enthalpies and entropies of proton adsorption for site L1, L2, and L4 are consistent with previous interpretations of phosphoryl, carboxyl, and hydroxyl/amine site-identities, respectively, and with previous calorimetric measurements of proton adsorption onto mesophilic species. Enthalpies and entropies for surface site L3 are not consistent with the commonly inferred phosphoryl site-identity and are more consistent with sulfhydryl functional groups. These results reveal intricacies of surface reactivity that are not detectable by other methods.

  19. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    NASA Astrophysics Data System (ADS)

    Cimino, R.; Rasmussen, C. J.; Neimark, A. V.

    2013-11-01

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of "infinite" chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy.

  20. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    SciTech Connect

    Cimino, R.; Neimark, A. V.; Rasmussen, C. J.

    2013-11-28

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of “infinite” chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy.

  1. Adsorption mechanism-based screening of cyclodextrin polymers for adsorption and separation of pesticides from water.

    PubMed

    Liu, Huihui; Cai, Xiyun; Wang, Yu; Chen, Jingwen

    2011-05-01

    A rational screening of cyclodextrin-based polymer (CDP), in terms of the relationship between adsorption potential and adsorbent-adsorbate, was investigated to adsorb and separate pesticides from water. Seven spherical porous CDPs were prepared with onefold or composite cyclodextrin(s) as complex and epichlorohydrin as cross-linking reagent. The adsorption kinetics and isotherms of the polymers toward a mixture of ten distinct pesticides clearly demonstrate that the adsorbents with a homogeneous open network structure can absorb pesticides via multiple adsorption interactions such as CD inclusion, loading into swelling water and physical adsorption on network. The multivariate regression analysis distinguishes the quantitative contributions of polymer properties to its adsorption potential, among which CD content, swelling capacity and pore size appear to be major influencing factors. Consequently, a facile mixture of three CDPs (i.e., β-CDP, RM-CDP and HP-CDP) was screened to obtain above prerequisite properties. The multiplex polymer could superiorly separate the pesticides at environmentally relevant levels from water. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Adsorption dynamics of methyl violet onto granulated mesoporous carbon: Facile synthesis and adsorption kinetics.

    PubMed

    Kim, Yohan; Bae, Jiyeol; Park, Hosik; Suh, Jeong-Kwon; You, Young-Woo; Choi, Heechul

    2016-09-15

    A new and facile one-step synthesis method for preparing granulated mesoporous carbon (GMC) with three-dimensional spherical mesoporous symmetry is prepared to remove large molecular weight organic compounds in aqueous phase. GMC is synthesized in a single step using as-synthesized mesoporous carbon particles and organic binders through a simple and economical synthesis approach involving a simultaneous calcination and carbonization process. Characterization results obtained from SEM, XRD, as well as surface and porosity analysis indicate that the synthesized GMC has similar physical properties to those of the powdered mesoporous carbon and maintains the Brunauer-Emmett-Teller (BET) surface area and pore volume because the new synthesis method prevents the collapse of the pores during the granulation process. Batch adsorption experiments revealed GMC showed a substantial adsorption capacity (202.8 mg/g) for the removal of methyl violet as a target large molecular contaminant in aqueous phase. The mechanisms and dynamics modeling of GMC adsorption were also fully examined, which revealed that surface diffusion was rate limiting step on adsorption process of GMC. Adsorption kinetics of GMC enables 3 times faster than that of granular activated carbon in terms of surface diffusion coefficient. This is the first study, to the best of our knowledge, to synthesize GMC as an adsorbent for water purification by using facile granulation method and to investigate the adsorption kinetics and characteristics of GMC. This study introduces a new and simple method for the synthesis of GMC and reveals its adsorption characteristics for large molecular compounds in a water treatment.

  3. Characterization of the adsorption of water vapor and chlorine on microcrystalline silica

    NASA Technical Reports Server (NTRS)

    Skiles, J. A.; Wightman, J. P.

    1979-01-01

    The characterization of water adsorption on silica is necessary to an understanding of how hydrogen chloride interacts with silica. The adsorption as a function of outgas temperatures of silica and as a function of the isotherm temperature was studied. Characterization of the silica structure by infrared analysis, X-ray diffraction and differential scanning calorimetry, surface area determinations, characterization of the sample surface by electron spectroscopy for chemical analysis (ESCA), and determinations of the heat of immersion in water of silica were investigated. The silica with a scanning electron microscope was examined.

  4. Adsorption of tetramethylsilane molecules on the basal face of graphite

    NASA Astrophysics Data System (ADS)

    Yashkin, S. N.

    2008-06-01

    The thermodynamic adsorption characteristics of tetramethylsilane (TMS) molecules on graphitized carbon black (GCB) were for the first time determined experimentally and by molecular statistics methods. The potential function parameters of pair molecular interactions (φ( r)) between Si and C atoms on the basal face of graphite were calculated in the atom-atom approximation of the semiempirical molecular-statistical theory of adsorption. The contributions of Si and C atoms to thermodynamic adsorption characteristics are compared for the example of nonspecific adsorption of TMS and isostructural neopentane molecules on the flat surface of GCB.

  5. Adsorption mechanism of chloroacetanilide herbicides to modified montmorillonite.

    PubMed

    El-Nahhal, Yasser

    2003-09-01

    This study was undertaken to characterize the adsorption mechanism of alachlor and metolachlor on montmorillonite modified with cationic surfactants. Adsorbed amounts of cationic surfactant on montmorillonite surfaces were determined by CNHSO analyzer. Equilibrium concentrations of alachlor and metolachlor were determined by GC and adsorption results were fit to a linear regression equation. The slope of the isotherms (Kd) was normalized to the fraction of organic carbon on montmorillonite complexes to produce corresponding Koc. Adsorption of surfactants fit very well to Langmuir equation. Increased basal spacing indicates that surfactant molecules could penetrate through the interlayer spacing and arrange themselves in different ways. Equilibrium data of alachlor and metolachlor suggest that adsorption may occur via physical or chemical bonds. Koc values of alachlor or metolachlor decreased as the fraction of the organic carbon increased in montmorillonite complexes indicating independent adsorption process. Changes of the molar free energy of the adsorption reactions were in the range of physical adsorption, indicating that adsorption reactions are spontaneous and the molecules either adsorb on the surface or penetrate into the inter-layers of montmorillonite-surfactant complex. Careful investigation of the adsorption data suggests that interaction may occur via the active groups such as carbonyl group (-C=O), anilidic (C-N) group and/or phenyl rings. This information may provide better understanding on adsorption mechanism and be useful in designing ecologically acceptable herbicide formulations.

  6. Effect of pore blockage on adsorption isotherms and dynamics: Anomalous adsorption of iodine on activated carbon

    SciTech Connect

    Bhatia, S.K.; Liu, F.; Arvind, G.

    2000-04-18

    Isotherm hysteresis and pore-clocking effects of trapped molecules on adsorption dynamics is studied here, using the iodine-carbon system in the 300--343 K temperature range. It is found that a portion of the iodine is strongly adsorbed, and does not desorb, even over very long time scales, while the remainder adsorbs reversibly as a homogeneous monolayer with a Langmuirian isotherm in mesopores. The strongly adsorbed iodine appears to adsorb in micropores and at the mesopore mouths, hindering uptake of the reversible iodine. The uptake data for the adsorption and desorption dynamics of the reversible part is found to be best explained by means of a pore mouth resistance control mechanism. it is concluded that the dynamics of the adsorption and desorption at the pore mouth is important at early stages of the process.

  7. Enhancement of heat transfer

    NASA Astrophysics Data System (ADS)

    Nakayama, W.

    Recent publications on enhancement of heat transfer are reviewed, emphasizing the effects of roughness elements, fins, and porous surfaces. Enhancement of forced convective heat transfer on roughened surfaces, performance evaluation of enhanced surfaces, viscous flows in cooled tubes and tubes with swirlers, and active methods of enhancement are addressed. Aspects of pool boiling heat transfer are considered, including nucleate boiling heat transfer on rough surfaces and porous surfaces, and maximum and minimum heat fluxes. Evaporative heat transfer is discussed for thin-film evaporation on structured surfaces and liquid spray cooling of a heated surface. Condensation heat transfer on external surfaces is covered, including filmwise condensation on vertical finned and fluted surfaces and on horizontal tubes. In-tube boiling and condensation are treated, discussing their enhancement by fins and inserts, as well as critical heat flux in coiled, rifled, and corrugated tubes.

  8. Microscopic theory of hysteretic hydrogen adsorption in nanoporous materials.

    PubMed

    Kang, Joongoo; Wei, Su-Huai; Kim, Yong-Hyun

    2010-02-10

    Understanding gas adsorption confined in nanoscale pores is a fundamental issue with broad applications in catalysis and gas storage. Recently, hysteretic H(2) adsorption was observed in several nanoporous metal-organic frameworks (MOFs). Here, using first-principles calculations and simulated adsorption/desorption isotherms, we present a microscopic theory of the enhanced adsorption hysteresis of H(2) molecules using the MOF Co(1,4-benzenedipyrazolate) [Co(BDP)] as a model system. Using activated H(2) diffusion along the small-pore channels as a dominant equilibration process, we demonstrate that the system shows hysteretic H(2) adsorption under changes of external pressure. For a small increase of temperature, the pressure width of the hysteresis, as well as the adsorption/desorption pressure, dramatically increases. The sensitivity of gas adsorption to temperature changes is explained by the simple thermodynamics of the gas reservoir. Detailed analysis of transient adsorption dynamics reveals that the hysteretic H(2) adsorption is an intrinsic adsorption characteristic in the diffusion-controlled small-pore systems.

  9. Adsorption of ammonium on biochar prepared from giant reed.

    PubMed

    Hou, Jie; Huang, Lei; Yang, Zhimin; Zhao, Yaqi; Deng, Chaoren; Chen, Yucheng; Li, Xin

    2016-10-01

    Giant reed was used as precursor for making biochar in order for the adsorption of NH4 (+)-N from aqueous solution. And the adsorption of the product to NH4 (+)-N was examined. The surface features of biochar were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD). XRD patterns showed several peaks and correspond to the high amount of crystalline material. The crystals contain KCl, K2O, CaO, MgO, and SiO and possess high surface area which enhances adsorption. The influence of different parameters such as initial concentration, adsorption time, pH, and ionic strength has been carried out. The adsorption could reach equilibrium through 24 h reaction and had the best adsorption amount at the solution pH values from 7 to 9. The cation has great influence on the adsorption of NH4 (+)-N, whereas the anion exerted a weaker effect. The adsorption followed pseudo-first-order and pseudo-second-order models. And the intraparticle diffusion and desorption studies further elucidated that the mechanism of adsorption on the product was ion exchange. The product equilibrium data was well described by the Langmuir and Freundlich model. The maximum adsorption capacities were 1.490 mg/g. Biochar derived from giant reed at 500 °C was suggested as a promising adsorbent for the removal of NH4 (+)-N from slightly polluted wastewater.

  10. Effect of cropping systems on adsorption of metals by soils: I. Single-metal adsorption

    SciTech Connect

    Basta, N.T.; Tabatabai, M.A. )

    1992-02-01

    The effect of long-term cropping systems on adsorption of metals was studied for soils obtained from two sites, Clarion-Webster Research Center (CWRC site) at Kanawha and Galva-Primghar Research Center (GPRC site) at Sutherland, under long-term rotation experiments in Iowa. Each experiment consisted of three cropping systems: continuous corn (CCCC), corn-soybean-corn-soybean (CSCS), and corn-oats-meadow-meadow (COMM), and treated with (+N) and without (0 N) ammoniacal fertilizer. In general, CSCS and COMM cropping systems did not significantly affect the metal adsorption maxima of soils obtained from both sites. Cadmium, Cu, and Pb adsorption were significantly correlated with pH and percentage base saturation for soils from both sites.

  11. Adsorption Behavior of Pb(II) Onto Potassium Polytitanate Nanofibres.

    PubMed

    Shahid, Mohammad; Tiling, Leonard D; El Saliby, Ibrahim; McDonagh, Andrew; Kim, Jong-Beom; Kim, Jong-Ho; Shon, Ho Kyong

    2016-02-01

    Potassium polytitanate nanofibres prepared by a hydrothermal method were investigated for their possible application in removing toxic metals from aqueous solution. Particular attention was paid to employing the titanate as a novel effective adsorbent for the removal of Pb(II). Batch adsorption experiments demonstrated that the adsorption was influenced by various conditions such as solution pH, adsorbent dosage and initial Pb(II) concentration. The results showed that the adsorption rate was faster in the first 5 min and equilibrium was achieved after 180 min. The maximum amount of adsorption was detected at pH 5. Potassium titanate showed much higher adsorption capacity compared to P25. The kinetic studies indicated that the adsorption of Pb(II) onto titanate best fit the pseudo-second-order kinetic model. FTIR spectra revealed that the hydroxyl groups in titanate were responsible for Pb(II) adsorption. The principal mechanism of the adsorption of Pb(II) in the present study is attributed to both ion exchange and oxygen bonding. The adsorption-desorption results demonstrated that the titanate could be readily regenerated after adsorption. Therefore, the present titanate exhibits great potential for the removal of Pb(II) from wastewater.

  12. Mechanisms of soil humic acid adsorption onto montmorillonite and kaolinite.

    PubMed

    Chen, Hongfeng; Koopal, Luuk K; Xiong, Juan; Avena, Marcelo; Tan, Wenfeng

    2017-10-15

    To explore the adsorption mechanisms of a soil humic acid (HA) on purified kaolinite and montmorillonite, a combination of adsorption measurements, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and isothermal titration calorimetry (ITC) was employed at pH 4.0, 6.0 and 8.0. The adsorption affinities and plateaus of HA on the two clays increased with decreasing pH, indicating the importance of electrostatic interaction. The effects were more significant for kaolinite than for montmorillonite. The substantial adsorption at pH 8.0 indicated hydrophobic interaction and/or H-bonding also played a role. The ATR-FTIR results at pH 8.0 showed that the Si-O groups located at basal faces of the two clays were involved in the adsorption process. For kaolinite, at pH 4.0 and 6.0, HA adsorption occurred via OH groups on the edge faces and basal octahedral faces (both positively charged), plus some adsorption at Si-O group. The exothermic molar adsorption enthalpy decreased relatively dramatically with adsorption up to adsorption values of 0.7μmol/g on montmorillonite and 1.0μmol/g on kaolinite, but the decrease was attenuated at higher adsorption. The high exothermic molar enthalpy of HA binding to the clays was ascribed to ligand exchange and electrostatic binding, which are enthalpy-driven. At high adsorption values, JGHA adsorption by hydrophobic attraction and H-bonding also occurs. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Adsorption of Candida rugosa lipase at water-polymer interface: The case of poly( DL)lactide

    NASA Astrophysics Data System (ADS)

    Kamel, Gihan; Bordi, Federico; Chronopoulou, Laura; Lupi, Stefano; Palocci, Cleofe; Sennato, Simona; Verdes, Pedro V.

    2011-12-01

    Insights into the interactions between biological macromolecules and polymeric surfaces are of great interest because of potential uses in developing biotechnologies. In this study we focused on the adsorption of a model lipolytic enzyme, Candida rugosa lipase (CRL), on poly-(D,L)-lactic acid (PDLLA) polymer with the aim to gain deeper insights into the interactions between the enzyme and the carrier. Such studies are of particular relevance in order to establish the optimal conditions for enzyme immobilization and its applications. We employed two different approaches; by analyzing the influence of adsorbed CRL molecules on the thermodynamic behavior of Langmuir films of PDLLA deposited at air-water interface, we gained interesting information on the molecular interactions between the protein and the polymer. Successively, by a systematic analysis of the adsorption of CRL on PDLLA nanoparticles, we showed that the adsorption of a model lipase, CRL, on PDLLA is described in terms of a Langmuir-type adsorption behavior. In this model, only monomolecular adsorption takes place (i.e. only a single layer of the protein adsorbs on the support) and the interactions between adsorbed molecules and surface are short ranged. Moreover, both the adsorption and desorption are activated processes, and the heat of adsorption (the difference between the activation energy for adsorption and desorption) is independent from the surface coverage of the adsorbing species. Finally, we obtained an estimate of the number of molecules of the protein adsorbed per surface unit on the particles, a parameter of a practical relevance for applications in biocatalysis, and a semi-quantitative estimate of the energies (heat of adsorption) involved in the adsorption process.

  14. Fundamentals of heat measurement. [heat flux transducers

    NASA Technical Reports Server (NTRS)

    Gerashchenko, O. A.

    1979-01-01

    Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

  15. Efficiently mapping structure-property relationships of gas adsorption in porous materials: application to Xe adsorption.

    PubMed

    Kaija, A R; Wilmer, C E

    2017-09-08

    Designing better porous materials for gas storage or separations applications frequently leverages known structure-property relationships. Reliable structure-property relationships, however, only reveal themselves when adsorption data on many porous materials are aggregated and compared. Gathering enough data experimentally is prohibitively time consuming, and even approaches based on large-scale computer simulations face challenges. Brute force computational screening approaches that do not efficiently sample the space of porous materials may be ineffective when the number of possible materials is too large. Here we describe a general and efficient computational method for mapping structure-property spaces of porous materials that can be useful for adsorption related applications. We describe an algorithm that generates random porous "pseudomaterials", for which we calculate structural characteristics (e.g., surface area, pore size and void fraction) and also gas adsorption properties via molecular simulations. Here we chose to focus on void fraction and Xe adsorption at 1 bar, 5 bar, and 10 bar. The algorithm then identifies pseudomaterials with rare combinations of void fraction and Xe adsorption and mutates them to generate new pseudomaterials, thereby selectively adding data only to those parts of the structure-property map that are the least explored. Use of this method can help guide the design of new porous materials for gas storage and separations applications in the future.

  16. Storage of low grade solar thermal energy by adsorption of organics

    NASA Astrophysics Data System (ADS)

    Kohler, Tobias; Müller, Karsten

    2017-06-01

    In this work the efficiency of new systems for adsorptive energy storage for low grade solar thermal energy is evaluated. They are based on different adsorption systems with alcohols as adsorbates on activated carbon as adsorbent. They showed superior storage characteristics compared to the reference working pair water / zeolite 13X. The maximum efficiencies of the systems methanol and ethanol on activated carbon lie in the same range as the efficiency of the reference pair, but are reached at lower regeneration temperatures. Therefore, these systems are perfectly suited for the storage of low grad heat from collector types like the flat-plate collector or vacuum-collectors.

  17. Gravimetric analysis of CO2 adsorption on activated carbon at various pressures and temperatures using piezoelectric microcantilevers.

    PubMed

    Jin, Yusung; Lee, Dongkyu; Lee, Sangkyu; Moon, Wonkyu; Jeon, Sangmin

    2011-09-15

    We investigated the adsorption and desorption of CO(2) on activated carbon using piezoelectric microcantilevers. After coating the free end of a cantilever with activated carbon, variations in the resonance frequency of the cantilever were measured as a function of CO(2) pressure, which is related to mass changes due to the adsorption or desorption of CO(2). The pressure-dependent viscous damping effects were compensated in the calculation of the CO(2) adsorption capacity of the activated carbon by comparing the frequency differences between the coated and uncoated cantilevers. The mass sensitivity of the piezoelectric cantilever was found to be better than 1 pg. The fractional coverage of CO(2) agreed with a Langmuir adsorption isotherm, indicating that a submonolayer of adsorbed CO(2) occurred on the surface of the activated carbon under the experimental conditions. The heat of adsorption was determined using the Clausius-Clapeyron relation and the fractional coverage of CO(2) at various temperatures and pressures.

  18. Adsorption of carbon black using carboxymethyl chitosan in deinking process

    NASA Astrophysics Data System (ADS)

    Muryeti, Budimulyani, Estuti; Sinurat, Ellya

    2017-03-01

    The study about synthesis, characterization, and application carboxymethyl chitosan as adsorbent in deinking process was conducted. Adsorption of carbon black onto carboxymethyl chitosan has been investigated in a batch system. This research was conducted to obtain the adsorption capacity of carboxymethyl chitosan. The experiments were carried out to study the effect of carbon black concentration, contact time and dosage of carboxymethyl chitosan to the adsorption capacity of carboxymethyl chitosan. The optimum condition of carbon black adsorption was achieved at contact time of 60 min and weight doses of 1.0 g. The adsorption capacity of carboxymethyl chitosan was 14.34 mg/g and the adsorption effectivity was 70.54%. The result indicates that carboxymethyl chitosan could be used as adsorbent of carbon black in deinking process.

  19. Single-crystal adsorption calorimetry and density functional theory of CO chemisorption on fcc Co{110}.

    PubMed

    Liao, Kristine; Fiorin, Vittorio; Gunn, David S D; Jenkins, Stephen J; King, David A

    2013-03-21

    Using single-crystal adsorption calorimetry (SCAC) and density functional theory (DFT), the interaction of carbon monoxide on fcc Co{110} is reported for the first time. The results indicate that adsorption is consistent with molecular chemisorption at all coverages. The initial heat of adsorption of 140 kJ mol(-1) is found in the range of heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. DFT adsorption energies are in good agreement with the experimental results, and comparison between SCAC and DFT for CO on other ferromagnetic surfaces is made. The calculated dissociation barrier of 2.03 eV implies that dissociation at 300 K is unlikely even at the lowest coverage. At high coverages during the adsorption-desorption steady state regime, a pre-exponential factor for CO desorption of 1.2 × 10(17) s(-1) is found, implying a localised molecular adsorbed state prior to desorption in contrast to what we found with Ni surfaces. This result highlights the importance of the choice of the pre-exponential factor in evaluating the activation energy for desorption.

  20. The adsorption of pharmaceutically active compounds from aqueous solutions onto activated carbons.

    PubMed

    Rakić, Vesna; Rac, Vladislav; Krmar, Marija; Otman, Otman; Auroux, Aline

    2015-01-23

    In this study, the adsorption of pharmaceutically active compounds - salicylic acid, acetylsalicylic acid, atenolol and diclofenac-Na onto activated carbons has been studied. Three different commercial activated carbons, possessing ∼650, 900 or 1500m(2)g(-1) surface areas were used as solid adsorbents. These materials were fully characterized - their textural, surface features and points of zero charge have been determined. The adsorption was studied from aqueous solutions at 303K using batch adsorption experiments and titration microcalorimetry, which was employed in order to obtain the heats evolved as a result of adsorption. The maximal adsorption capacities of investigated solids for all target pharmaceuticals are in the range of 10(-4)molg(-1). The obtained maximal retention capacities are correlated with the textural properties of applied activated carbon. The roles of acid/base features of activated carbons and of molecular structures of adsorbate molecules have been discussed. The obtained results enabled to estimate the possibility to use the activated carbons in the removal of pharmaceuticals by adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Adsorption of acetaldehyde on ice as seen from computer simulation and infrared spectroscopy measurements.

    PubMed

    Darvas, Mária; Lasne, Jérôme; Laffon, Carine; Parent, Philippe; Picaud, Sylvain; Jedlovszky, Pál

    2012-03-06

    Detailed investigation of the adsorption of acetaldehyde on I(h) ice is performed under tropospheric conditions by means of grand canonical Monte Carlo computer simulations and compared to infrared spectroscopy measurements. The experimental and simulation results are in a clear accordance with each other. The simulations indicate that the adsorption process follows Langmuir behavior in the entire pressure range of the vapor phase of acetaldehyde. Further, it was found that the adsorption layer is strictly monomolecular, and the adsorbed acetaldehyde molecules are bound to the ice surface by only one hydrogen bond, typically formed with the dangling H atoms at the ice surface, in agreement with the experimental results. Besides this hydrogen bonding, at high surface coverages dipolar attraction between neighboring acetaldehyde molecules also contributes considerably to the energy gain of the adsorption. The acetaldehyde molecules adopt strongly tilted orientations relative to the ice surface, the tilt angle being scattered between 50° and 90° (i.e., perpendicular orientation). The range of the preferred tilt angles narrows, and the preference for perpendicular orientation becomes stronger upon saturation of the adsorption layer. The CH(3) group of the acetaldehyde molecules points as straight away from the ice surface within the constraint imposed by the tilt angle adopted by the molecule as possible. The heat of adsorption at infinitely low coverage is found to be -36 ± 2 kJ/mol from the infrared spectroscopy measurement, which is in excellent agreement with the computer simulation value of -34.1 kJ/mol.

  2. Adsorption studies of methylene blue dye on tunisian activated lignin

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Hamdi, N.; Srasra, E.

    2011-02-01

    Activated carbon prepared from natural lignin, providing from a geological deposit, was used as the adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch adsorption studies were conducted to evaluate various experimental parameters like pH and contact time for the removal of this dye. Effective pH for MB removal was 11. Kinetic study showed that the adsorption of dye was gradual process. Quasi equilibrium reached in 4 h. Pseudo-first-order, pseudo-second-order were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. The experimental isotherms data were also modelled by the Langmuir and Freundlich equation of adsorption. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 147 mg/g. Activated lignin was shown to be a promising material for adsorption of MB from aqueous solutions.

  3. Computational Investigation of Conformational Changes in Proteins upon Adsorption

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Anand, Gaurav; Belfort, Georges; Kumar, Sanat K.

    2009-03-01

    Amyloidogenic diseases, such as, Alzheimer's, are caused by adsorption and aggregation of partially unfolded proteins. Protein adsorption is often accompanied by conformational rearrangements, which are thought to affect many properties such as their adhesion strength to the surface, biological activity, and aggregation tendency. Experiments have shown that many proteins, upon adsorption to hydrophobic surfaces, undergo a helix to sheet or random coil secondary structural rearrangement. To better understand the equilibrium structural complexities of this phenomenon, we have performed Monte Carlo (MC) simulations and Single Chain Mean Field calculations of adsorption of different proteins, modeled as lattice chains, to study the adsorption behavior and equilibrium protein conformations at different temperatures, protein concentration and surface hydrophobicity. Free energy and entropic effects on adsorption have been studied by determining density of states using Weighted Histogram Analysis Method. Conformational transitions of proteins on surfaces will be discussed as a function of surface hydrophobicity.

  4. Selective adsorption for removal of nitrogen compounds from hydrocarbon streams over carbon-based adsorbents

    NASA Astrophysics Data System (ADS)

    Almarri, Masoud S.

    desulfurization of model diesel fuel, which contains equimolar concentrations of nitrogen (i.e., quinoline and indole), sulfur (i.e., dibenzothiophene and 4,6-dimethyldibenzothiophene), and aromatic compounds (naphthalene, 1-methylnaphthalene, and fluorene), was examined. The results revealed that when both nitrogen and sulfur compounds coexist in the fuel, the type and density of oxygen functional groups on the surface of the activated carbon are crucial for selective adsorption of nitrogen compounds but have negligible positive effects for sulfur removal. The adsorption of quinoline and indole is largely governed by specific interactions. There is enough evidence to support the importance of dipole--dipole and acid-base-specific interactions for the adsorption of both quinoline and indole. Modified carbon is a promising material for the efficient removal of the nitrogen compounds from light cycle oil (LCO). Adsorptive denitrogenation of LCO significantly improved the hydrodesulfurization (HDS) performance, especially for the removal of the refractory sulfur compounds such as 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. An essential factor in applying activated carbon for adsorptive denitrogenation and desulfurization of liquid hydrocarbon streams is regeneration after saturation. The regeneration method of the saturated adsorbents consisted of toluene washing followed by heating to remove the remaining toluene. The results show that the spent activated carbon can be regenerated to completely recover the adsorption capacity. The high capacity and selectivity of activated carbon for nitrogen compounds, along with their ability to be regenerated, indicate that activated carbon is a promising adsorbent for the deep denitrogenation of liquid hydrocarbon streams.

  5. Studies on adsorption of formaldehyde in zirconium phosphate-glyphosates

    NASA Astrophysics Data System (ADS)

    Zhang, Yuejuan; Yi, Jianjun; Xu, Qinghong

    2011-01-01

    In our previous work [22], a kind of layered compound of zirconium phosphate-glyphosate (ZrGP) was synthesized. Its large surface area (445 m 2/g) indicates this compound has possible application in adsorptions. In this paper, adsorption to formaldehyde in ZrGP and mechanisms of the adsorption were studied carefully. Balance time of adsorption (about 6 h) and largest adsorbed amount (7.8%) were found when adsorption temperature was at 40 °C and pH value of adsorption environment was about 3.0. H-bonds were found existing between molecules of formaldehyde and ZrGP, and formaldehyde molecules could exist in ZrGP stably.

  6. Factors affecting the adsorption of chromium (VI) on activated carbon

    SciTech Connect

    Yavuz, R.; Orbak, I.; Karatepe, N.

    2006-09-15

    The aim of this investigation was to determine the adsorption behavior of chromium (VI) on two different activated carbon samples produced from Tuncbilek lignite. The effects of the initial chromium (VI) concentration (250-1000 mg/L), temperature (297-323 K) and pH (2.0-9.5) on adsorption were investigated systematically. The effectiveness of the parameters on chromium adsorption was found to be in the order of pH, the initial Cr(VI) concentration and the temperature. Increasing the pH from 2.0 to 9.5 caused a decrease in adsorption. However, the adsorption was increased by increasing the initial Cr(VI) concentration and temperature. The multilinear mathematical model was also developed to predict the Cr(VI) adsorption on activated carbon samples within the experimental conditions.

  7. Synergistic adsorption of phenol from aqueous solution onto polymeric adsorbents.

    PubMed

    Ming, Zhang W; Long, Chen J; Cai, Pan B; Xing, Zhang Q; Zhang, B

    2006-02-06

    Adsorption of phenol from aqueous solution onto a nonpolar adsorbent, aminated adsorbent and weak base adsorbent (Amberlite XAD4, NDA103 and Amberlite IRA96C, respectively) at temperatures from 293 to 313K was studied for the weak interactions between the phenol molecules and the polymeric adsorbents. Isotherms of Langmuir and Freundlich equation with characteristic parameters for different adsorbents were well fitted to the batch equilibrium adsorption data. The adsorption capacity on NDA103 driven by hydrogen bonding and van der Waals interaction together is higher than that on IRA96C driven by hydrogen bonding interaction only and on XAD4 driven by van der Waals interaction only. For evaluating synergistic adsorption for phenol-water systems onto polymeric adsorbents, the adsorption capacity is normalized to the amounts of specific surface area and amino groups of adsorbents. The synergistic effect with other weak interactions would contribute more to the adsorption as acting simultaneously than that of acting individually.

  8. Study of carbon dioxide adsorption on a Cu-nitroprusside polymorph

    DOE PAGES

    Roque-Malherbe, R.; Lozano, C.; Polanco, R.; ...

    2011-03-26

    A careful structural characterization was carried out to unequivocally determine the structure of the synthesized material. The TGA, DRIFTS and a Pawley fitting of the XRD powder profiles indicate that the hydrated and in situ dehydrated polymorph crystallizes in the orthorhombic space group Pnma. Meanwhile, the CO2 isosteric heat of adsorption appears to be independent of loading with an average value of 30 kJ/mol. This translates to a physisorption type interaction, where the adsorption energy corresponding to wall and lateral interactions are mutually compensated to produce, an apparently, homogeneous adsorption energy. The somewhat high adsorption energy is probably due tomore » the confinement of the CO2 molecules in the nitroprusside pores. Statistical Physics and the Dubinin theory for pore volume filling allowed model the CO2 equilibrium adsorption process in Cu-nitroprusside. A DRIFTS test for the adsorbed CO2 displayed a peak at about 2338 cm-1 that was assigned to a contribution due to physical adsorption of the molecule. Another peak found at 2362 cm-1 evidenced that this molecule interacts with the Cu2+, which appears to act as an electron accepting Lewis acid site. In conclusion, the aim of the present paper is to report a Pnma stable Cu-nitroprusside polymorph obtained by the precipitation method that can adsorb carbon dioxide.« less

  9. Study of carbon dioxide adsorption on a Cu-nitroprusside polymorph

    SciTech Connect

    Roque-Malherbe, R.; Lozano, C.; Polanco, R.; Marquez, F.; Lugo, F.; Hernandez-Maldonado, A.; Primera-Pedrozo, J. N.

    2011-03-26

    A careful structural characterization was carried out to unequivocally determine the structure of the synthesized material. The TGA, DRIFTS and a Pawley fitting of the XRD powder profiles indicate that the hydrated and in situ dehydrated polymorph crystallizes in the orthorhombic space group Pnma. Meanwhile, the CO2 isosteric heat of adsorption appears to be independent of loading with an average value of 30 kJ/mol. This translates to a physisorption type interaction, where the adsorption energy corresponding to wall and lateral interactions are mutually compensated to produce, an apparently, homogeneous adsorption energy. The somewhat high adsorption energy is probably due to the confinement of the CO2 molecules in the nitroprusside pores. Statistical Physics and the Dubinin theory for pore volume filling allowed model the CO2 equilibrium adsorption process in Cu-nitroprusside. A DRIFTS test for the adsorbed CO2 displayed a peak at about 2338 cm-1 that was assigned to a contribution due to physical adsorption of the molecule. Another peak found at 2362 cm-1 evidenced that this molecule interacts with the Cu2+, which appears to act as an electron accepting Lewis acid site. In conclusion, the aim of the present paper is to report a Pnma stable Cu-nitroprusside polymorph obtained by the precipitation method that can adsorb carbon dioxide.

  10. Adsorption and excess fission Xe - Adsorption of Xe on vacuum crushed minerals

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Kramer, F. E.; Podosek, F. A.; Honda, M.

    1982-01-01

    It is hypothesized that adsorption is not likely to provide a sufficiently precise mechanism for the concentration of excess fission Xe in the entire lunar regolith, in view of laboratory analogs of the lunar soil and calculations of the residence times of noble gases in the present day regolith. Lunar cold trap and episodic degassing models are difficult to reconcile, however, with the generality of excess fission Xe in all gas-rich highland breccias. It is concluded that the high Xe concentration in such highland breccias is not the result of Xe adsorption prior to the trapping of this component.

  11. Adsorption to fish sperm of vertically transmitted fish viruses

    USGS Publications Warehouse

    Mulcahy, D.; Pascho, R.J.

    1984-01-01

    More than 99 percent of a vertically transmitted fish rhabdovirus, infectious hematopoietic necrosis virus, was removed from suspension in less than 1 minute by adsorption to the surface membrane of sperm from two genera of salmonid fishes. The vertically transmitted, infectious pancreatic necrosis virus adsorbed to a lesser degree, but no adsorption occurred with a second fish rhabdovirus that is not vertically transmitted. Such adsorption may be involved in vertical transmission of these viruses.

  12. Kinetic studies of the sucrose adsorption onto an alumina interface

    NASA Astrophysics Data System (ADS)

    Singh, Kaman; Mohan, Sudhanshu

    2004-01-01

    An account is given of an experimental kinetic study of adsorption of analar reagent sucrose (ARS) onto an alumina interface spectrometrically ( λmax=570 nm) at pH 8.0 and at room temperature. The adsorption isotherm is a typical Langmuirian isotherm (S-type) and adsorption parameters have been deduced according to the Langmuir's model. The adsorption coefficient evaluated from the Langmuir's equation was found to be 2.52×10 2 l mol -1. Adsorption mechanism has been interpreted on the basis of metal-saccharide interaction as found in organometallic compounds and interaction due to negatively charged ends on the disaccharide molecules and positively charge groups on the surface on alumina which depends on the pH value. The effects of variation in experimental conditions of the adsorption system have also been investigated. The adsorption exhibited a typical response to the pH effect and on going towards the PZC the net charge decreases and any reaction making dependence on charge and maximum adsorption (amount) was found near the isoelectric point of alumina (pH 9.0). The presence of ions like Cl -, SO 42- and PO 43- affect the adsorbed amount quantitatively and it seems that these anions compete with sucrose for the positively charged surface sites. The addition of similar concentration of cations was found to reduce the adsorbed amount. The temperature was found to have an inverse effect on adsorption. The additions of catonic and anionic detergents influence both the adsorbed amount and the adsorption rate. The thermodynamics of the titled adsorption model indicates the spontaneous and exothermic nature. The negative value of entropy is an indication of probability of favorable and complex nature of the adsorption.

  13. CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS

    SciTech Connect

    Xiao, S.; Heung, L.

    2010-10-07

    Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D{sub 2} adsorption than that of H{sub 2}, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content has significant impact to its hydrogen uptake. A material without adequate drying could result in complete loss of its adsorption capacity. Even though some materials present higher H{sub 2} adsorption capacity at full pressure, their adsorption at low vapor pressure may not be as good as others. Adsorption capacity in a dynamic system is much less than in a static system. A sharp desorption is also expected in case of temperature upset.

  14. Synthesis and adsorption of functionalized polystyrenes

    SciTech Connect

    Iyengar, D.R.

    1992-12-31

    The effect of specifically interacting functional groups located at the chain ends of polystyrene on the absorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid-end-groups in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC) is developed as an analytical technique to predict trends in the adsorption of the polymers in a range of solvents. In particular the information about the localization of the end-group and therefore different chain architectures at the interface are inferred from this simple technique. Adsorption isotherms are obtained for each of the functionalized polymers of four different molecular weights, the selection of which was based on the TLC results. Kinetics of adsorption and the adsorbance data are determined by liquid counting of tritium labelled polymers. Graft density and surface excess data are calculated from the adsorbance data and other known parameters. It is shown, from these data, that polystyrenes with a carboxylic acid end-group form weakly stretched brushes at the glass-cyclohexane interface and mushrooms at the glass-toluene interface a result consistent with the higher osmotic repulsions towards packing in good solvents. Polystyrenes with function groups at both the chain ends are hypothesized to form a range of structures from those dominated by tails at higher concentrations to those dominated by loops and trains at lower solution concentrations. At higher molecular weights it is shown that functionalized a result consistent with the TLC predictions. Hydroxyl end-group is shown to be an ineffective sticky foot from its adsorbance vis-a-vis polystyrene.

  15. Molecular simulation of fluid adsorption in buckytubes and MCM-41

    SciTech Connect

    Maddox, M.W.; Gubbins, K.E.

    1994-11-01

    We report canonical Monte Carlo (GCMC) molecular-simulation studies of argon and nitrogen in models of two novels adsorbents, buckytubes and MCM-41. Buckytubes are monodisperse carbon tubes with internal diameters of 1-5 nm and a regular pore structure. MCM-41 is one member of a new family of highly uniform mesoporous aluminosilicates produced by Mobil. The pore size of MM-41 can be accurately controlled within the range 1.5-1.0 nm. The adsorption of argon in a buckytube and the adsorption of nitrogen in two different MCM-41 pores are studied at 77 K. Both fluids are modeled as Lennard-Jones spheres, and an averaged fluid-wall potential, dependent only on the distance of the adsorbed molecule from the center of the tube or pore is used. Isotherms and isosteric heats are calculated. Layering transitions and a hysteresis loop are observed for the buckytube and good agreement is found between simulated and experimental isotherms for the MCM-41 systems.

  16. Mechanisms of chromate adsorption on boehmite.

    PubMed

    Johnston, Chad P; Chrysochoou, Maria

    2015-01-08

    Adsorption reactions play an important role in the transport behavior of groundwater contaminants. Molecular-scale information is needed to elucidate the mechanisms by which ions coordinate to soil mineral surfaces. In this study, we characterized the mechanisms of chromate adsorption on boehmite (γ-AlOOH) using a combination of extended X-ray absorption fine structure (EXAFS) measurements, in situ attenuated total reflectance Fourier transform infrared spectroscopy, and quantum chemical calculations. The effects of pH, ionic strength, and aqueous chromate concentration were investigated. Our overall findings were that chromate primarily forms outer-sphere complexes on boehmite over a broad range of pH and aqueous concentrations. Additionally, a small fraction of monodentate and bidentate inner-sphere complexes are present under acidic conditions, as evidenced by two sets of chromate stretching vibrations at approximately 915, 870, and 780cm(-1), and 940, 890, 850, and 780cm(-1), respectively. The bidentate complex is supported by a best-fit CrAl distance in the EXAFS of 3.2Å. Results from DFT also support the formation of monodentate and bidentate complexes, which are predicted to results in Gibbs energy changes of -140.4 and -62.5kJmol(-1), respectively. These findings are consistent with the intermediate binding strength of chromate with respect to similar oxyanions such as sulfate and selenite. Overall, the surface species identified in this work can be used to develop a more accurate stoichiometric framework in mechanistic adsorption models. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Fractional statistical theory of finite multilayer adsorption

    NASA Astrophysics Data System (ADS)

    Takara, E. A.; Quiroga, E.; Matoz-Fernandez, D. A.; Ochoa, N. A.; Ramirez-Pastor, A. J.

    2016-01-01

    In the present paper, finite multilayer adsorption is described as a fractional statistics problem, based on Haldane's statistics. In this scheme, the Helmholtz free energy and its derivatives are written in terms of a parameter g, which relates to the configuration of the molecules in the adsorbed state. For values of g ranging between 0 and 1 the formalism is used to model experimental data of bovine serum albumin (BSA) adsorbed onto an ion exchange resin for different values of pH and temperature. Excellent agreement between theory and experiments was found.

  18. Cryogenic Adsorption of Nitrogen and Carbon Dioxide in Activated Carbon

    NASA Astrophysics Data System (ADS)

    Shen, Fuzhi; Liu, Huiming; Xu, Dong; Zhang, Hengcheng; Lu, Junfeng; Li, Laifeng

    2017-09-01

    Activated carbon have been used for a long time at low temperature for cryogenic applications. The knowledge of adsorption characteristics of activated carbon at cryogenic temperature is essential for some specific applications. However, such experimental data are very scare in the literature. In order to measure the adsorption characteristics of activated carbon under variable cryogenic temperatures, an adsorption measurement device was presented. The experiment system is based on the commercially available PCT-pro adsorption analyzer coupled to a two-stage Gifford McMahon refrigerator, which allows the sample to be cooled to 4.2K. Cryogenic environment can be maintained steadily without the cryogenic liquid through the cryocooler and temperature can be controlled precisely between 5K and 300K by the temperature controller. Adsorption measurements were performed in activated carbon for carbon dioxide and nitrogen and the adsorption isotherm were obtained.

  19. DFT study of methanol adsorption on PtCo(111)

    NASA Astrophysics Data System (ADS)

    Orazi, V.; Bechthold, P.; Jasen, P. V.; Faccio, R.; Pronsato, M. E.; González, E. A.

    2017-10-01

    Methanol adsorption on PtCo(111) surface at low coverage is studied using Density Functional Theory (DFT) calculations without and with van der Waals corrections. We investigated the PtCo FCT alloy surface with a uniform distribution. The most favorable site for CH3OH adsorption is on top of a Co atom, with an adsorption energy of -0.92 eV. Methanol attachs to the surface by the O atom, with a distance of 2.24 Å. The molecule presents a small distortion after adsorption. The Csbnd Osbnd Co bond angle is 142°. The Csbnd H bonds are strengthened whereas the Csbnd O and Osbnd H bonds are weakened. A charge transfer from C atom to O atom occurs upon adsorption, and then further transfer occurs to the Co atom on the surface. The calculated vibrational frequencies for adsorbed methanol present a red-shift displacement compared to gas-phase, confirming the adsorption process.

  20. Adsorption of argon on sintered tin dioxide analyzed by several methods

    NASA Technical Reports Server (NTRS)

    Hinman, D. C.; Halsey, G. D.

    1977-01-01

    Argon adsorption measurements are presented over a wide range of temperature and coverage on a series of three progressively sintered SnO2 surfaces. These data are analyzed by mercury porosimetry, the BET method, the CAEDMON distribution analysis, and the Singleton-Halsey equation. Isosteric heats are computed, and the high-temperature virial expansion of the data presented. The advantages and disadvantages of each method are discussed with particular attention to the ability of physical adsorption to discriminate among surfaces beyond the measurement of surface area.

  1. Adsorption of argon on sintered tin dioxide analyzed by several methods

    NASA Technical Reports Server (NTRS)

    Hinman, D. C.; Halsey, G. D.

    1977-01-01

    Argon adsorption measurements are presented over a wide range of temperature and coverage on a series of three progressively sintered SnO2 surfaces. These data are analyzed by mercury porosimetry, the BET method, the CAEDMON distribution analysis, and the Singleton-Halsey equation. Isosteric heats are computed, and the high-temperature virial expansion of the data presented. The advantages and disadvantages of each method are discussed with particular attention to the ability of physical adsorption to discriminate among surfaces beyond the measurement of surface area.

  2. Adsorption of cellulase from Trichoderma viride on cellulose

    SciTech Connect

    Ooshima, H.; Sakata, M.; Harano, Y.

    1983-12-01

    The adsorption of cellulase from Trichoderma viride (Meicelase CEP) on the surface of pure cellulose was studied. The adsorption was found to obey apparently the Langmuir isotherm. From the data concerning the effects of temperature and the crystallinity of cellulose on the Langmuir adsorption parameters, the characteristics of the adsorption of the individual cellulase components, namely CMCase (endoglucanase) and Avicelase (exoglucanase), were discussed. While beta-glucosidase also adsorbed on the surface of cellulose at 5 degrees C, it did not at 50 degrees C. (Refs. 27).

  3. Adsorption characteristics of brilliant green dye on kaolin.

    PubMed

    Nandi, B K; Goswami, A; Purkait, M K

    2009-01-15

    Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (DeltaG0), enthalpy (DeltaH0) and entropy (DeltaS0) changes are calculated to know the nature of adsorption. The calculated values of DeltaG0 at 299K and 323K indicate that the adsorption process is spontaneous. The estimated values of DeltaH0 and DeltaS0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm.

  4. Aerodynamic adsorption of permeable chemical protective suit.

    PubMed

    Li, L; Liu, J; Cheng, D

    2001-01-01

    A new laboratory apparatus and method were developed to test the protective ability of a permeable chemical protective suit (PCPS). The key features of this method are using a wind tunnel system and an aerodynamic model that could incorporate the complicated flow pattern around the protective clothing. This method illustrates the process of the PCPS system performance and can provide a system assessment through bench-scale experiments. A new aerodynamic adsorption equation for PCPS breakthrough curve calculation based on an aerodynamic model has been suggested, and the calculated breakthrough curves of benzene vapor on PCPS conform to the experiment curves.

  5. Topotactic growth, selective adsorption, and adsorption-driven photocatalysis of protonated layered titanate nanosheets.

    PubMed

    Wu, Qili; Yang, Xianfeng; Liu, Jia; Nie, Xin; Huang, Yongliang; Wen, Yuping; Khan, Javid; Khan, Wasim U; Wu, Mingmei; An, Taicheng

    2014-10-22

    Layered titanates with selective adsorption ability and adsorption-driven photocatalytic property can be quite attractive due to their potential applications in water purification. In this work, lepidocrocite-like layered protonated titanate (H2Ti2O5·H2O, denoted as HTO) nanosheets were successfully synthesized by an ion-exchange process. It turns out that this layered structure displays an abundant and selective adsorption toward the fluoroquinolone pharmaceutical compared with some large dye molecules due to a size selectivity of the interlayer spacing of HTO and the molecular horizontal size, as well as their electrostatic interaction. The uptake ability of HTO could be readily controlled through adjusting the pH values of adsorbate solution, and the maximum uptake capacity was achieved at the pH value of about 5.5 for ciprofloxacin (CIP) and 6.5 for moxifloxacin (MOX). The adsorption amount of smaller nalidixic acid (NAL) showed an increasing tendency as the pH value decreased. Moreover, the two-dimensional layered crystal structure also permits such HTO nanosheets to have a large percentage of (010) faces exposed, which is considerably provided by the interlayer surfaces of these nanosheets. The (010) surface has a similar Ti and O atomic arrangement as to the highly reactive anatase TiO2(001) one. Due to these specific characteristics, these HTO nanosheets show excellent photocatalytic activity in degrading CIP under UV light irradiation as well as possess a superior adsorption ability to remove CIP from aqueous solution selectively and efficiently. The photocatalytic reaction is believed to be mainly conducted on the active anatase (001)-like interlayer (010) surfaces of the layered structures since the as-prepared HTO performs an adsorption-driven molecular recognitive photocatalytic reaction.

  6. Adsorption of glucose, cellobiose, and cellotetraose onto cellulose model surfaces.

    PubMed

    Hoja, Johannes; Maurer, Reinhard J; Sax, Alexander F

    2014-07-31

    Reliable simulation of molecular adsorption onto cellulose surfaces is essential for the design of new cellulose nanocomposite materials. However, the applicability of classical force field methods to such systems remains relatively unexplored. In this study, we present the adsorption of glucose, cellobiose, and cellotetraose on model surfaces of crystalline cellulose Iα and Iβ. The adsorption of the two large carbohydrates was simulated with the GLYCAM06 force field. To validate this approach, quantum theoretical calculations for the adsorption of glucose were performed: Equilibrium geometries were studied with density functional theory (DFT) and dispersion-corrected DFT, whereas the adsorption energies were calculated with two standard density functional approximations and five dispersion-containing DFT approaches. We find that GLYCAM06 gives a good account of geometries and, in most cases, accurate adsorption energies when compared to dispersion-corrected DFT energies. Adsorption onto the (100) surface of cellulose Iα is, in general, stronger than onto the (100) surface of cellulose Iβ. Contrary to intuition, the adsorption energy is not directly correlated with the number of hydrogen bonds; rather, it is dominated by dispersion interactions. Especially for bigger adsorbates, a neglect of these interactions leads to a dramatic underestimation of adsorption energies.

  7. A continuum hard-sphere model of protein adsorption

    NASA Astrophysics Data System (ADS)

    Finch, Craig; Clarke, Thomas; Hickman, James J.

    2013-07-01

    Protein adsorption plays a significant role in biological phenomena such as cell-surface interactions and the coagulation of blood. Two-dimensional random sequential adsorption (RSA) models are widely used to model the adsorption of proteins on solid surfaces. Continuum equations have been developed so that the results of RSA simulations can be used to predict the kinetics of adsorption. Recently, Brownian dynamics simulations have become popular for modeling protein adsorption. In this work a continuum model was developed to allow the results from a Brownian dynamics simulation to be used as the boundary condition in a computational fluid dynamics (CFD) simulation. Brownian dynamics simulations were used to model the diffusive transport of hard-sphere particles in a liquid and the adsorption of the particles onto a solid surface. The configuration of the adsorbed particles was analyzed to quantify the chemical potential near the surface, which was found to be a function of the distance from the surface and the fractional surface coverage. The near-surface chemical potential was used to derive a continuum model of adsorption that incorporates the results from the Brownian dynamics simulations. The equations of the continuum model were discretized and coupled to a CFD simulation of diffusive transport to the surface. The kinetics of adsorption predicted by the continuum model closely matched the results from the Brownian dynamics simulation. This new model allows the results from mesoscale simulations to be incorporated into micro- or macro-scale CFD transport simulations of protein adsorption in practical devices.

  8. EFFECT OF GAC CHARACTERISTICS ON ADSORPTION OF ORGANIC POLLUTANTS

    EPA Science Inventory

    The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected...

  9. EFFECT OF GAC CHARACTERISTICS ON ADSORPTION OF ORGANIC POLLUTANTS

    EPA Science Inventory

    The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected...

  10. Adsorption properties and gaseous mercury transformation rate of natural biofilm.

    PubMed

    Cheng, Jinping; Zhao, Wenchang; Liu, Yuanyuan; Wu, Cheng; Liu, Caie; Wang, Wenhua

    2008-11-01

    Biofilms were developed on glass microscope slides in a natural aquatic environment and their mercury adsorption properties were evaluated. Results demonstrated that the biofilms contained a large number of bacterial cells and associated extracellular polymers. Mercury forms detected in the biofilms were mainly bound to residual matter and organic acids. The adsorption processes could be described by a Langmuir isotherm. The optimum conditions for adsorption of mercury to natural biofilm were an ionic strength of 0.1 mol/L, pH 6 and an optimum adsorption time of 40 min. The transformation rate was 0.79 microg gaseous mercury per gram of biofilm.

  11. [Effects of dissolved organic matter on phenanthrene adsorption by soil].

    PubMed

    Xiong, Wei; Ling, Wan-ting; Gao, Yan-zheng; Li, Qiu-ling; Dai, Jing-yu

    2007-02-01

    This paper studied the effects of exotic and native dissolved organic matter (DOM) on the phenanthrene adsorption by three soils differed in soil organic carbon content (foc). The exotic DOM came from decayed rice straw, while the native DOM was extracted from the test soils. In all cases, the adsorption of phenanthrene by treated soils could be well described with linear-type model, and there was a positive correlation between adsorption coefficient (Kd) and foc Compared with the control, the Kd value of test soils after native DOM removed was increased by 7. 08% -21. 4% , and the increment (deltaKd) was positively correlated with fo,, indicating that the presence of soil native DOM impeded the phenanthrene adsorption by soil. The effects of exotic DOM on phenanthrene adsorption had a close relation with its added concentration in soil-water system. Within the range of 0-106 mg DOC x L(-1) , the K, value increased first, and then decreased with the increase of added exotic DOM concentration. Lower concentrations of added exotic DOM promoted the phenanthrene adsorption by soil, while higher concentrations ( I> or =52 mg DOC x L(-1)) of it obviously impeded this adsorption. These effects of exotic and native DOM on soil phenanthrene adsorption were considered to be related to the association of phenanthrene with DOM in solution, and the ' cumulative adsorption effect' between soil solid and aqueous phases.

  12. Effective surface areas of coals measured by dye adsorption

    SciTech Connect

    Spitzer, D.P.

    1988-01-01

    The primary interest has been to examine adsorption behavior especially at short contact times, ten minutes to an hour, to determine whether such measurements might give useful data on effective surface areas - i.e., the surface that would be accessible to reagents within times comparable to those typical of most coal processing. Accordingly, most of the emphasis is on the effect of time on adsorption, rather than on traditional adsorption isotherms. Although most literature on cationic dye adsorption (mostly on carbons) uses methylene blue, it happened that the authors originally used safranin O instead because this dye was reported to be useful in distinguishing oxidized coals from fresh coals. Many of their experiments were repeated using methylene blue (in water), with very similar results. It was noted early that swelling of coals in water was common, especially for more oxidized or lower rank coals, and adsorption experiments were also done in another solvent, namely methanol. This produced quite striking differences for some coals. Coal surfaces that are readily accessible to adsorption by safranin are found to correlate well with N/sub 2/ surface areas, with adsorption of 1.0 mg safranin per gram of coal corresponding to essentially a surface area of 1.0 m/sup 2//g. Highly oxidized coals were found to swell considerably in water, with correspondingly increased adsorption. Areas of such coals can be estimated by adsorption of safranin from methanol solutions.

  13. Nanoscale Imaging of Molecular Adsorption

    DTIC Science & Technology

    1994-06-20

    LiAI2(OH)6 ÷X-.nH20,21 and for synthetic HT-like phases.22 This ordered arrangement is most likely a consequence of coulombic interactions within the...hydroxy-2-methoxy-benzenesulfonic acid (MBSA) on the surface of HT. This compound is of technological interest because of its utility in cosmetics ...J. Amer. Chem. Soc., 115, 11521-11535 (1993). 9 Figure Captions Figure 1: (a) Hexagonal HT crystals adhered to a freshly cleaved mica substrate by

  14. Assessment of multi-mycotoxin adsorption efficacy of grape pomace.

    PubMed

    Avantaggiato, Giuseppina; Greco, Donato; Damascelli, Anna; Solfrizzo, Michele; Visconti, Angelo

    2014-01-15

    Grape pomace (pulp and skins) was investigated as a new biosorbent for removing mycotoxins from liquid media. In vitro adsorption experiments showed that the pomace obtained from Primitivo grapes is able to sequester rapidly and simultaneously different mycotoxins. Aflatoxin B1 (AFB1) was the most adsorbed mycotoxin followed by zearalenone (ZEA), ochratoxin A (OTA), and fumonisin B1 (FB1), whereas the adsorption of deoxynivalenol (DON) was negligible. AFB1 and ZEA adsorptions were not affected by changing pH values in the pH 3-8 range, whereas OTA and FB1 adsorptions were significantly affected by pH. Equilibrium adsorption isotherms obtained at different temperatures (5-70 °C) and pH values (3 and 7) were modeled and evaluated using the Freundlich, Langmuir, Sips, and Hill models. The goodness of the fits and the parameters involved in the adsorption mechanism were calculated by the nonlinear regression analysis method. The best-fitting models to describe AFB1, ZEA, and OTA adsorption by grape pomace were the Sips, Langmuir, and Freundlich models, respectively. The Langmuir and Sips models were the best models for FB1 adsorption at pH 7 and 3, respectively. The theoretical maximum adsorption capacities (mmol/kg dried pomace) calculated at pH 7 and 3 decreased in the following order: AFB1 (15.0 and 15.1) > ZEA (8.6 and 8.3) > OTA (6.3-6.9) > FB1 (2.2 and 0.4). Single- and multi-mycotoxin adsorption isotherms showed that toxin adsorption is not affected by the simultaneous presence of different mycotoxins in the liquid medium. The profiles of adsorption isotherms obtained at different temperatures and pH and the thermodynamic parameters (ΔG°, ΔH°, ΔS°) suggest that mycotoxin adsorption is an exothermic and spontaneous process, which involves physisorption weak associations. Hydrophobic interactions may be associated with AFB1 and ZEA adsorption, whereas polar noncovalent interactions may be associated with OTA and FB1 adsorption. In conclusion, this study

  15. [Adsorption of carbon dioxide gas].

    PubMed

    Juniot, A; Seltzer, S; Louvier, N; Milesi-Defrance, N; Cros-Terraux, N

    1999-03-01

    To analyse the various methods for carbon dioxide absorption in anaesthesia, the available absorbents and their modes of use. We searched the Medline and Internet databases for papers using the key words: carbon dioxide absorption, soda-lime, zeolite. We also had correspondence and contacts with soda lime manufacturers. All types of articles containing data on CO2 absorption. The articles were analysed for the benefits and adverse effects of the various absorbents. Carbon dioxide absorption enables the use of low flow anaesthesia, and a decreased consumption of medical gases and halogenated anaesthetics, as well as reduced pollution. Chemical absorbents (soda-lime and barium hydroxide lime (Baralyme) may produce toxic compounds: carbon monoxide with all halogenated anaesthetics and compound A with sevoflurane. Simple measures against desiccation of the lime prevent carbon monoxide production. The toxicity of compound A, shown in the rat, has not been proven in clinical anaesthesia. Recent improvements in manufacture processes have decreased the powdering of lime. Moreover, filters inserted between the anaesthesia circuit and the patient abolish the risk for powder inhalation.

  16. Adsorption of malathion on thermally treated egg shell material.

    PubMed

    Elwakeel, Khalid Z; Yousif, Ahmed M

    2010-01-01

    Thermally treated egg shell materials were prepared at different temperatures. The samples were investigated by means of FT-IR and thermogravimetric analysis (TGA). The adsorption behaviour of malathion on egg shell and its thermally treated samples was studied using batch method and gave uptake capacities up to 0.964 mmol/g. Adsorption kinetics as well as the adsorption isotherms were discussed. Regeneration of the loaded adsorbent beads towards the successive cycles was also clarified. The adsorption of malathion is maintained until the third cycle without a significant activity loss.

  17. Adsorption of Ar on individual carbon nanotubes, graphene, and graphite

    NASA Astrophysics Data System (ADS)

    Dzyubenko, Boris; Kahn, Joshua; Vilches, Oscar; Cobden, David

    2015-03-01

    We compare and contrast results of adsorption measurements of Ar on single-walled carbon nanotubes, graphene, and graphite. Adsorption isotherms on individual suspended nanotubes were obtained using both the mechanical resonance frequency shift (sensitive to mass adsorption) and the electrical conductance. Isotherms on graphene mounted on hexagonal boron nitride were obtained using only the conductance. New volumetric adsorption isotherms on bulk exfoliated graphite were also obtained, paying special attention to the very low coverage region (less than 2% of a monolayer). This allowed us to compare the degree of heterogeneity on the three substrate types, the binding energies, and the van der Waals 2D parameters. Research supported by NSF DMR 1206208.

  18. An adsorption of carbon dioxide on activated carbon controlled by temperature swing adsorption

    NASA Astrophysics Data System (ADS)

    Tomas, Korinek; Karel, Frana

    2017-09-01

    This work deals with a method of capturing carbon dioxide (CO2) in indoor air. Temperature Swing Adsorption (TSA) on solid adsorbent was chosen for CO2 capture. Commercial activated carbon (AC) in form of extruded pellets was used as a solid adsorbent. There was constructed a simple device to testing effectiveness of CO2 capture in a fixed bed with AC. The TSA cycle was also simulated using the open-source software OpenFOAM. There was a good agreement between results obtained from numerical simulations and experimental data for adsorption process.

  19. Adsorption Isotherm Studies of CH4 on Tubular WS2

    NASA Astrophysics Data System (ADS)

    Mackie, Erica; Alkhafaji, Mazin; Migone, Aldo; Galvan, Donald

    1998-03-01

    We have measured adsorption-desorption isotherm cycles of CH4 on both tubular and non-tubular WS2. The tubular WS2 was produced (by Galvan et al.)(D.H.Galvan, R.Rangel and G.A.Nunez, submitted to Appl. Phys. Lett.) by electron irradiation of WS2 powder. The irradiation process results in WS2 tubes and paricles nanometric in diameter. The WS2 powder was manufactured by Alfa Aesar. We measured the surface area of both types of WS2 samples. We found an increase in surface area from 0.46 m^2/g for the non-irradiated, to 2.6 m^2/g for the irradiated WS2. We will present adsorption-desorption cycles for tubular and non-tubular WS2 subjected to different activation treatments: soaking in nitric acid, and, heating under vacuum to 700 C. Sufrace area comparisons between non-tubular and tubular, and between activated and non-activated WS2, will identify increases due to the potential opening of the tubes, the irradiation process itself, and/or the activation treatment.

  20. Effect of purity on adsorption capacities of a Mars-like clay mineral at different pressures

    NASA Technical Reports Server (NTRS)

    Jenkins, Traci; Mcdoniel, Bridgett; Bustin, Roberta; Allton, Judith H.

    1992-01-01

    There has been considerable interest in adsorption of carbon dioxide on Marslike clay minerals. Some estimates of the carbon dioxide reservoir capacity of the martian regolith were calculated from the amount of carbon dioxide adsorbed on the ironrich smectite nontronite under martian conditions. The adsorption capacity of pure nontronite could place upper limits on the regolith carbon dioxide reservoir, both at present martian atmospheric pressure and at the postulated higher pressures required to permit liquid water on the surface. Adsorption of carbon dioxide on a Clay Mineral Society standard containing nontronite was studied over a wide range of pressures in the absence of water. Similar experiments were conducted on the pure nontronite extracted from the natural sample. Heating curves were obtained to help characterize and determine the purity of the clay sample.

  1. Effect of purity on adsorption capacities of a Mars-like clay mineral at different pressures

    NASA Technical Reports Server (NTRS)

    Jenkins, Traci; Mcdoniel, Bridgett; Bustin, Roberta; Allton, Judith H.

    1992-01-01

    There has been considerable interest in adsorption of carbon dioxide on Marslike clay minerals. Some estimates of the carbon dioxide reservoir capacity of the martian regolith were calculated from the amount of carbon dioxide adsorbed on the ironrich smectite nontronite under martian conditions. The adsorption capacity of pure nontronite could place upper limits on the regolith carbon dioxide reservoir, both at present martian atmospheric pressure and at the postulated higher pressures required to permit liquid water on the surface. Adsorption of carbon dioxide on a Clay Mineral Society standard containing nontronite was studied over a wide range of pressures in the absence of water. Similar experiments were conducted on the pure nontronite extracted from the natural sample. Heating curves were obtained to help characterize and determine the purity of the clay sample.

  2. Adsorption properties of biomass-based activated carbon prepared with spent coffee grounds and pomelo skin by phosphoric acid activation

    NASA Astrophysics Data System (ADS)

    Ma, Xiaodong; Ouyang, Feng

    2013-03-01

    Activated carbon prepared from spent coffee grounds and pomelo skin by phosphoric acid activation had been employed as the adsorbent for ethylene and n-butane at room temperature. Prepared activated carbon was characterized by means of nitrogen adsorption-desorption, X-ray powder diffraction, scanning electron microscope and Fourier transform infrared spectroscope. It was confirmed that pore structure played an important role during the adsorption testes. Adsorption isotherms of ethylene and n-butane fitted well with Langmuir equation. The prepared samples owned better adsorption capacity for n-butane than commercial activated carbon. Isosteric heats of adsorptions at different coverage were calculated through Clausius-Clapeyron equation. Micropore filling effect was explained in a thermodynamic way.

  3. Water dissociative adsorption on NiO(111): Energetics and structure of the hydroxylated surface

    SciTech Connect

    Zhao, Wei; Bajdich, Michal; Carey, Spencer; Vojvodic, Aleksandra; Nørskov, Jens K.; Campbell, Charles T.

    2016-09-19

    The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 × 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of ~92 kJ/mol. Density functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 × 2) structure is the most stable NiO(111)-2 × 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 × 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 ± 5 kJ/mol in the low-coverage limit (very close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to ~30 kJ/mol experimentally). As a result, sensitivity of this reaction’s energy to choice of DFT method is tested using a variety of different exchange correlation functionals, including HSE06, and found to be quite weak.

  4. Water dissociative adsorption on NiO(111): Energetics and structure of the hydroxylated surface

    DOE PAGES

    Zhao, Wei; Bajdich, Michal; Carey, Spencer; ...

    2016-09-19

    The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 × 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of ~92 kJ/mol. Densitymore » functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 × 2) structure is the most stable NiO(111)-2 × 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 × 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 ± 5 kJ/mol in the low-coverage limit (very close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to ~30 kJ/mol experimentally). As a result, sensitivity of this reaction’s energy to choice of DFT method is tested using a variety of different exchange correlation functionals, including HSE06, and found to be quite weak.« less

  5. Water dissociative adsorption on NiO(111): Energetics and structure of the hydroxylated surface

    SciTech Connect

    Zhao, Wei; Bajdich, Michal; Carey, Spencer; Vojvodic, Aleksandra; Nørskov, Jens K.; Campbell, Charles T.

    2016-09-19

    The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 × 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of ~92 kJ/mol. Density functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 × 2) structure is the most stable NiO(111)-2 × 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 × 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 ± 5 kJ/mol in the low-coverage limit (very close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to ~30 kJ/mol experimentally). As a result, sensitivity of this reaction’s energy to choice of DFT method is tested using a variety of different exchange correlation functionals, including HSE06, and found to be quite weak.

  6. [Adsorption of Cd2+ on biochar from aqueous solution].

    PubMed

    Guo, Wen-juan; Liang, Xue-feng; Lin, Da-song; Xu, Ying-ming; Wang, Lin; Sun, Yue-bing; Qin, Xu

    2013-09-01

    Biomass-based materials such as biochar have a good performance in heavy metal adsorption. The adsorption of Cd2+ on biochar converted from cotton straw was studied. Adsorption isotherm, kinetics and effect factors such as temperature, pH and ionic strength were investigated. The adsorption of Cd2+ on biochar can be fitted by the Freundlich isotherm better than the Langmuir isotherm. The maximum adsorption amounts of Cd2+ at different temperatures were 9.738 mg x g(-1) (288.15 K), 10.14 mg x g(-1) (298.15 K), 10.40 mg x g(-1) (308.15 K) and 10.71 mg x g(-1) (318.15 K), respectively. The free energies AG(theta) were from -8.346 kJ x mol(-1) to -10.276 kJ x mol(-1) at different temperatures, indicating that the adsorption of Cd2+ onto biochar is spontaneous and is an endothermic process. The adsorption process can reach equilibrium within 40 minutes and can be fitted by the pseudo second order kinetic model. pH showed a significant effect on the adsorption of Cd2+ on biochar in the range of 2-8. The adsorption amount of Cd2+ on biochar shows a reducing trend with the increasing ionic strength.

  7. Effect of adsorption on solute dispersion: a microscopic stochastic approach.

    PubMed

    Hlushkou, Dzmitry; Gritti, Fabrice; Guiochon, Georges; Seidel-Morgenstern, Andreas; Tallarek, Ulrich

    2014-05-06

    We report on results obtained with a microscopic modeling approach to Taylor-Aris dispersion in a tube coupled with adsorption-desorption processes at its inner surface. The retention factor of an adsorbed solute is constructed by independent adjustment of the adsorption probability and mean adsorption sojourn time. The presented three-dimensional modeling approach can realize any microscopic model of the adsorption kinetics based on a distribution of adsorption sojourn times expressed in analytical or numerical form. We address the impact of retention factor, adsorption probability, and distribution function for adsorption sojourn times on solute dispersion depending on the average flow velocity. The approach is general and validated at all stages (no sorption; sorption with fast interfacial mass transfer; sorption with slow interfacial mass transfer) using available analytical results for transport in Poiseuille flow through simple geometries. Our results demonstrate that the distribution function for adsorption sojourn times is a key parameter affecting dispersion and show that models of advection-diffusion-sorption cannot describe mass transport without specifying microscopic details of the sorption process. In contrast to previous one-dimensional stochastic models, the presented simulation approach can be applied as well to study systems where diffusion is a rate-controlling process for adsorption.

  8. Effect of complexing ligands on the adsorption of Cu(II) onto the silica gel surface. 1: Adsorption of ligands

    SciTech Connect

    Park, Y.J.; Jung, K.H.; Park, K.K.; Park, K.K.

    1995-04-01

    The adsorption of several ligands on silica gel was investigated in aqueous solutions. The ligands used were 2,2{prime},6{prime},2{double_prime}-terpyridine, pyridine, 3,4-lutidine, 2-aminomethyl pyridine, 2-pyridine methanol, picolinic acid, salicylic acid, and 5-sulfosalicylic acid. The adsorption behaviors of these ligands were interpreted by means of three adsorption modes: ion exchange, hydrogen bonding, and hydrophobic interaction. For 2,2{prime},6{prime},2{double_prime}-terpyridine, pyridine, and 3,4-lutidine, the adsorption maxima appeared near their respective pK{sub a} values and were found to be due mainly to ion exchange, whereas the adsorption of these ligands at low pH was strongly attributed to hydrophobic interaction. The adsorption of 2-aminomethyl pyridine increased with increasing pH over the entire pH range investigated and was due mainly to ion exchange. Picolinic acid was adsorbed mainly by hydrogen bonding either via pyridine N atoms at low pH or via carboxylic O atoms at high pH. 2-Pyridine methanol was adsorbed by hydrophobic interaction at low pH and by hydrogen bonding at high pH. The adsorptions of salicylic and 5-sulfosalicylic acid were very small over the entire pH ranges investigated. For the adsorption mechanism, the Stern model was used to fit adsorption data.

  9. Adsorption dynamics of CO2 on Zn-ZnO(0001): A molecular beam study

    NASA Astrophysics Data System (ADS)

    Wang, J.; Burghaus, U.

    2005-01-01

    Presented are initial S0 and coverage Θ dependent, S(Θ), adsorption probability measurements, respectively, of CO2 adsorption on the polar Zn-terminated surface of ZnO, parametric in the impact energy Ei, the surface temperature Ts, the impact angle αi, varied along the [001] azimuth, the CO2 flux, and the density of defects, χ(Ar+), as varied by rare gas ion sputtering. S0 decreases linearly from 0.72 to 0.25 within Ei=0.12-1.33 eV and is independent of Ts. Above Ei=0.56 eV, S0 decreases by ˜0.2 with increasing αi. The shape of S(Θ) curves is consistent with precursor-mediated adsorption (Kisliuk shape, i.e., S˜const) for low Ei; above Ei=0.56 eV, however, a turnover to adsorbate-assisted adsorption (S increases with Θ) has been observed. The initial slope of S(Θ) curves decreases thereby with increasing αi, χ(Ar+), and Ts, i.e., the adsorbate-assisted adsorption is most distinct for normal impact on the pristine surface at low Ts and is independent of the CO2 flux. The S(Θ) curves have been parametrized by analytic precursor models and Monte Carlo simulations have been conducted as well. The temperature dependence of the saturation coverage shows two structures which could be assigned to adsorption on pristine and intrinsic defect sites, respectively, in agreement with a prior thermal desorption spectroscopy study. The heat of adsorption Ed for the pristine sites amounts to 34.0-5.4Θ, whereas for adsorption on the intrinsic defect sites Ed of ˜43.6 kJ/mol could be estimated. Thus, a kinetic structure-activity relationship was present.

  10. Volumetric Interpretation of Protein Adsorption: Kinetics of Protein-Adsorption Competition from Binary Solution

    PubMed Central

    Barnthip, Naris; Parhi, Purnendu; Golas, Avantika; Vogler, Erwin A.

    2009-01-01

    The standard solution-depletion method is implemented with SDS-gel electrophoresis as a multiplexing, separation-and-quantification tool to measure competition between two proteins (i and j) for adsorption to the same hydrophobic adsorbent particles (either octyl sepharose or silanized glass) immersed in binary-protein solutions. Adsorption kinetics reveal an unanticipated slow protein-size-dependent competition that controls steady-state adsorption selectivity. Two sequential pseudo-steady-state adsorption regimes (State 1 and State 2) are frequently observed depending on i, j solution concentrations. State 1 and State 2 are connected by a smooth transition, giving rise to sigmoidally-shaped adsorption-kinetic profiles with a downward inflection near 60 minutes of solution/adsorbent contact. Mass ratio of adsorbed i, j proteins (mi mj) remains nearly constant between States 1 and 2, even though both mi and mj decrease in the transition between states. State 2 is shown to be stable for 24 hours of continuous-adsorbent contact with stagnant solution whereas State 2 is eliminated by continuous mixing of adsorbent with solution. In sharp contrast to binary-competition results, adsorption to hydrophobic adsorbent particles from single-protein solutions (pure i or j) exhibits no detectable kinetics within the timeframe of experiment from either stagnant or continuously-mixed solution, quickly achieving a single steady-state value in proportion to solution concentration. Comparison of binary competition between dissimilarly-sized protein pairs chosen to span a broad molecular-weight (MW) range demonstrates that selectivity between i and j scales with MW ratio that is proportional to protein-volume ratio (ubiquitin, Ub, MW = 10.7 kDa; human serum albumin, HSA, MW = 66.3 kDa; prothrombin, FII, 72 kDa; immunoglobulin G, IgG, MW = 160 kDa; fibrinogen, Fib, MW = 341 kDa). Results are interpreted in terms of a kinetic model of adsorption that has protein molecules rapidly

  11. New way to analyze the adsorption behavior of flavonoids on macroporous adsorption resins functionalized with chloromethyl and amino groups.

    PubMed

    Lou, Song; Chen, Zhenbin; Liu, Yongfeng; Ye, Helin; Di, Duolong

    2011-08-02

    A series of macroporous adsorption resins (MARs) with novel structure were synthesized on the basis of the Friedel-Crafts catalyzed and amination reaction. Adsorption feature of the synthetic resins with respect to the purification effect were investigated systemically by employing rutin as the adsorbate. Different from traditional adsorption patterns, the results showed interesting conclusions: (1) With the increase in the temperature of the experiment, the adsorption capacity increased gradually; with the increase in the concentration of the initial solution, the adsorption capacity increased to the maximum and then decreased gradually. (2) The classical models that the inductive effect transmitted to the first layer and the adsorption process contained in one compartment could not explain our experimental results reasonably. Thus, a new adsorption isotherm model that the inductive effect passed on to a higher layer and a new adsorption kinetics model in which the adsorption process contained more compartments were created according to the multiparameter theory and Karickhoff's theory by investigating the regression of the experimental results. The conclusion that the inductive effect passed to the fourth layer and the adsorption process contained four compartments was drawn.

  12. Studies on adsorption characteristics and mechanism of adsorption of chlorhexidine mainly by carbon black.

    PubMed

    Akaho, E; Fukumori, Y

    2001-09-01

    The extent of adsorption of chlorhexidine to carbon black and sanitary cotton was determined by measuring the amounts of chlorhexidine adsorbed to carbon black or sanitary cotton from the chlorhexidine solution containing specific amount of carbon black or sanitary cotton. As another comparative antiseptic example of adsorption phenomena, adsorption of acrinol to sanitary cotton was also studied. The specific surface area of carbon black was measured by the BET method of adsorption isotherm. The pattern of adsorption of chlorhexidine to carbon black was temperature-dependent Langmuir isotherms, and the amounts adsorbed increased as the temperature was raised. Since chlorhexidine, whose pKa's are 2.2 and 10.3, is considered to exist in aqueous solution as the di-cation, an ion-ion interaction should be formed between protonated biguanide and anionic portions of carbon black or sanitary cotton. The chlorophenyl and hexane moieties interact with hydrophobic portions of carbon black or sanitary cotton. The perturbation experiment conducted on this interaction system showed that the nature of interaction was irreversible. The enthalpy change calculated from Langmuir constants was small, indicating the existence of ion-ion interaction. The entropy values, 27.4 to 28.2 e.u. obtained in this system, suggested that the hydration shells of the ions were rather tightly bound. The area occupied by a chlorhexidine molecule, 548 (A)(2), was twice greater than the projection area, 276 (A)(2), suggesting that chlorhexidine was adsorbed in such a way that each molecule is sufficiently well spaced.

  13. Heat pump augmentation of nuclear process heat

    SciTech Connect

    Koutz, S.L.

    1986-03-18

    A system is described for increasing the temperature of a working fluid heated by a nuclear reactor. The system consists of: a high temperature gas cooled nuclear reactor having a core and a primary cooling loop through which a coolant is circulated so as to undergo an increase in temperature, a closed secondary loop having a working fluid therein, the cooling and secondary loops having cooperative association with an intermediate heat exchanger adapted to effect transfer of heat from the coolant to the working fluid as the working fluid passes through the intermediate heat exchanger, a heat pump connected in the secondary loop and including a turbine and a compressor through which the working fluid passes so that the working fluid undergoes an increase in temperature as it passes through the compressor, a process loop including a process chamber adapted to receive a process fluid therein, the process chamber being connected in circuit with the secondary loop so as to receive the working fluid from the compressor and transfer heat from the working fluid to the process fluid, a heat exchanger for heating the working fluid connected to the process loop for receiving heat therefrom and for transferring heat to the secondary loop prior to the working fluid passing through the compressor, the secondary loop being operative to pass the working fluid from the process chamber to the turbine so as to effect driving relation thereof, a steam generator operatively associated with the secondary loop so as to receive the working fluid from the turbine, and a steam loop having a feedwater supply and connected in circuit with the steam generator so that feedwater passing through the steam loop is heated by the steam generator, the steam loop being connected in circuit with the process chamber and adapted to pass steam to the process chamber with the process fluid.

  14. Adsorption of dimeric surfactants in lamellar silicates

    NASA Astrophysics Data System (ADS)

    Balcerzak, Mateusz; Pietralik, Zuzanna; Domka, Ludwik; Skrzypczak, Andrzej; Kozak, Maciej

    2015-12-01

    The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay - hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1‧-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  15. Equilibrium and kinetic adsorption study of the adsorptive removal of Cr(VI) using modified wheat residue.

    PubMed

    Chen, Suhong; Yue, Qinyan; Gao, Baoyu; Xu, Xing

    2010-09-01

    A new adsorbent modified from wheat residue was synthesized after reaction with epichlorohydrin and triethylamine by using the modifying agents of diethylenetriamine in the presence of organic medium of N,N-dimethylformamide. The performance of the modified wheat straw (MWS) was characterized by Fourier transform infrared spectroscopy and point of zero charge analysis. The adsorption was investigated in a batch adsorption system, including both equilibrium adsorption isotherms and kinetics. Results showed that MWR had great anion-adsorbing capacity, due to the existence of a large number of introduced amino groups, and the value of pH(PZC) was around 5.0. Equilibrium data were analyzed using the Langmuir, Freundlich, and Temkin isotherm models and were found to be best represented by the Freundlich isotherm model. Evaluation of the adsorption process identified its endothermic nature. The maximum adsorption capacity of MWS for the removal of Cr(VI) was 322.58mg/g at 328K, indicating that MWS has high chromium removal efficiency, compared to other adsorbents reported. The kinetics of adsorption followed the pseudo-second-order kinetic equation. The mechanism of adsorption was investigated using the intraparticle diffusion model. Thermodynamic parameters (free energy change, enthalpy change, and entropy change) revealed that the adsorption of Cr(VI) onto MWS was endothermic and spontaneous; additionally, the adsorption can be characterized as an ion-exchange process. The results suggest that MWS is an inexpensive and efficient adsorbent for removing Cr(VI) ions from aqueous solution.

  16. Reuse of Solid Waste in Adsorption of the Textile Dye

    NASA Astrophysics Data System (ADS)

    Meziti, Chafika; Boukerroui, Abdelhamid

    This work presents the study of the reuse of a regenerated spent bleaching earth (RSBE). The RSBE material was tested in the removal of a basic textile dye presents in aqueous solution. The effect of physicochemical parameters such as stirring speed, initial concentration, contact time and temperature have been invested and thermodynamic nature of the adsorption process was determined by calculating the ΔH°, ΔS° and ΔG° values The results obtained show that the adsorption mechanism was described by the Langmuir model and the adsorption capacity, qmax (72.41 to 82.37 mg.g-1), increases with temperature (20-50 °C). The thermodynamic parameters show a presence of a strong affinity between two phases (liquid-solid) and an endothermic equilibrium adsorption process. However, the phenomenon of the adsorption kinetic follows the pseudo second order kinetic model.

  17. Thermal effects in dynamic storage of hydrogen by adsorption

    SciTech Connect

    Lamari, M.; Aoufi, A.; Malbrunot, P.

    2000-03-01

    Thermal effects in dynamic hydrogen storage by adsorption at room temperature and high pressure are studied theoretically and experimentally. The system of adsorbate-adsorbent used was hydrogen in granular activated carbon. The theoretical analysis was based on heat- and mass-transfer modeling in a packed-bed adsorber, with particular emphasis on the thermal effects occurring during charge and discharge steps. The influence of gas flow rate and storage pressure (up to 15 MPa) on the total amount stored or delivered was investigated. Operating conditions were compatible with practical application for onboard vehicle storage. The experimental study was carried out in cylindrical 2-L reservoirs filled with granular activated carbon in which the bed temperature was measured at various positions. The temperature changes during both charge and discharge agreed well with the model predictions.

  18. Highly porous activated carbon based adsorption cooling system employing difluoromethane and a mixture of pentafluoroethane and difluoromethane

    NASA Astrophysics Data System (ADS)

    Askalany, Ahmed A.; Saha, Bidyut B.

    2017-01-01

    This paper presents a simulation for a low-grade thermally powered two-beds adsorption cooling system employing HFC-32 and a mixture of HFC-32 and HFC-125 (HFC-410a) with activated carbon of type Maxsorb III. The present simulation model adopts experimentally measured adsorption isotherms, adsorption kinetics and isosteric heat of adsorption data. Effect of operating conditions (mass flow rate of hot water, driving heat source temperature and evaporator temperature) on the system performance has been studied in detail. The simulation results showed that the system could be powered by low-grade heat source temperature (below 85 °C). AC/HFC-32 and AC/HFC-410a adsorption cooling cycles achieved close specific cooling power and coefficient of performance values of 0.15 kW/kg and 0.3, respectively at a regeneration temperature of 90 °C along with evaporator temperature of 10 °C. The investigated semi continuous adsorption cooling system could produce a cooling power of 9 kW.

  19. Thermodynamic study of seven micropollutants adsorption onto an activated carbon cloth: Van't Hoff method, calorimetry, and COSMO-RS simulations.

    PubMed

    Masson, Sylvain; Vaulot, Cyril; Reinert, Laurence; Guittonneau, Sylvie; Gadiou, Roger; Duclaux, Laurent

    2017-04-01

    The thermodynamic of the adsorption of seven organic pollutants, namely benzotriazol, bisphenol A, caffeine, carbamazepine, diclofenac, ofloxacin, and pentachlorophenol, was studied on a microporous-activated carbon fabric. The isosteric adsorption quantities (Gibbs energy, enthalpy, and entropy variations) at high coverage ratio (around 1 mmol/g) have been determined from the adsorption isotherms at three temperatures (13, 25, and 40 °C). The adsorption heats at very low coverage (about 10(-5) mmol/g) have been measured by flow micro calorimetry. The experimental adsorption energies were correlated to the adsorbate-adsorbent and the adsorbate-solvent interaction energies calculated by simulations using the COSMO-RS model. The main role of the van der Waals forces in the adsorption of the studied molecules was established. The bulkier the adsorbate is, the lower the adsorption Gibbs energy variation at high coverage deduced from the isotherms. The heterogeneity of the adsorption sites was brought out by calorimetric measurements. At high coverage, a physisorption phenomenon was observed. At very low coverage, high values of the adsorption heats were found (ranging from -58 to -110 kJ/mol), except for pentachlorophenol characterized by an athermal adsorption controlled by Pi-anions interactions.

  20. Model carcinogen adsorption dynamics of DNA gel.

    PubMed

    Tomita, Naoko; Naito, Daisuke; Rokugawa, Isamu; Yamamoto, Takao; Dobashi, Toshiaki

    2014-09-01

    We have derived theoretical equations describing the adsorption of carcinogen to gels in an immersion medium containing carcinogens. The theory was developed for a cylindrical boundary condition under the assumption of a carcinogen diffusion-limited process combined with the "moving boundary picture (Furusawa et al., 2007)". The time course of the adsorbed carcinogen layer thickness and that of the carcinogen concentration in an immersion medium were expressed by a set of scaled variables, and the asymptotic behavior in the initial stage was derived. Experiments based on the theory were performed using a DNA gel sandwiched between a set of coverglasses in a medium containing acridine orange (AO). The boundary between the AO-adsorbed gel layer and AO-nonadsorbed gel layer was traced during the immersion. The time courses of the AO-adsorbed gel layer thickness and the AO concentration in the immersion medium were well explained by the theory, and the number ratio of the total AO molecules to the adsorption sites in the DNA gel was determined. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Molecular simulation of preferential adsorption of CO2 over CH4 in Na-montmorillonite clay material

    NASA Astrophysics Data System (ADS)

    Yang, Nannan; Liu, Shuyan; Yang, Xiaoning

    2015-11-01

    Grand canonical Monte Carlo simulations have been conducted to study the adsorption of carbon dioxide and methane, as well as their binary mixtures on Na-montmorillonite clay material. It was found that the adsorption behavior near the clay structure for the two species is distinctively different. The Na-montmorillonite clay shows obviously high adsorption capacity for CO2, as compared with CH4. The adsorption behavior and mechanism have been characterized by the interlayer interfacial structures and isosteric heats of adsorption. Meanwhile, the mixture adsorption demonstrates that CO2 molecules with enhanced adsorption strength are able to competitively replace CH4 molecules within the clay structure. The high separation selectivity of CO2 over CH4 implies the possibility of separating CO2 from natural gas mixtures using the clay minerals. The interlayer sodium cations and negatively charged clay surface can provide enhanced interaction with CO2 molecules that have high quadrupole moment, which is responsible for the higher adsorption loading of CO2.

  2. Method and apparatus for thermal swing adsorption and thermally-enhanced pressure swing adsorption

    DOEpatents

    Wegeng, Robert S.; Rassat, Scot D.; TeGrotenhuis, Ward E.; Drost, Kevin; Vishwanathan, Vilayanur V.

    2004-06-08

    The present invention provides compact adsorption systems that are capable of rapid temperature swings and rapid cycling. Novel methods of thermal swing adsorption and thermally-enhanced pressure swing adsorption are also described. In some aspects of the invention, a gas is passed through the adsorbent thus allowing heat exchangers to be very close to all portions of the adsorbent and utilize less space. In another aspect, the adsorption media is selectively heated, thus reducing energy costs. Methods and systems for gas adsorption/desorption having improved energy efficiency with capability of short cycle times are also described. In another aspect, the apparatus or methods utilize heat exchange channels of varying lengths that have volumes controlled to provide equal heat fluxes. Methods of fuel cell startup are also described. Advantages of the invention include the ability to use (typically) 30-100 times less adsorbent compared to conventional systems.

  3. Cadmium-109 Radioisotope Adsorption onto Polypyrrole Coated Sawdust of Dryobalanops aromatic: Kinetics and Adsorption Isotherms Modelling

    PubMed Central

    Olatunji, Michael Adekunle; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Mahmud, Habibun Nabi Muhammad Ekramul

    2016-01-01

    A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor’s materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents. PMID:27706232

  4. Cadmium-109 Radioisotope Adsorption onto Polypyrrole Coated Sawdust of Dryobalanops aromatic: Kinetics and Adsorption Isotherms Modelling.

    PubMed

    Olatunji, Michael Adekunle; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Mahmud, Habibun Nabi Muhammad Ekramul

    2016-01-01

    A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor's materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents.

  5. Adsorption and co-adsorption of diclofenac and Cu(II) on calcareous soils.

    PubMed

    Graouer-Bacart, Mareen; Sayen, Stéphanie; Guillon, Emmanuel

    2016-02-01

    Pharmaceuticals are emerging contaminants and their presence in different compartments of the environment has been detected in many countries. In this study, laboratory batch experiments were conducted to characterize the adsorption of diclofenac, a widely used non-steroidal anti-inflammatory drug, on six calcareous soils. The adsorption of diclofenac was relatively low, which may lead to a risk of groundwater contamination and plant uptake. A correlation between the soil-water distribution coefficient Kd and soil characteristics has been highlighted. Indeed, diclofenac adsorption as a function of soil organic matter content (% OM) and Rt=% CaCO3/% OM was successfully described through a simple empirical model, indicating the importance of considering the inhibiting effect of CaCO3 on OM retention properties for a better assessment of diclofenac fate in the specific case of calcareous soils. The simultaneous co-adsorption of diclofenac and copper - a ubiquitous pollutant in the environment - at the water/soil interface, was also investigated. It appeared quite unexpectedly that copper did not have a significant influence on diclofenac retention. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose.

    PubMed

    Gebald, Christoph; Wurzbacher, Jan A; Borgschulte, Andreas; Zimmermann, Tanja; Steinfeld, Aldo

    2014-02-18

    A fundamental analysis of single-component and binary CO2 and H2O adsorption of amine-functionalized nanofibrillated cellulose is carried out in the temperature range of 283-353 K and at CO2 partial pressures in the range of 0.02-105 kPa, where the ultralow partial pressure range is relevant for the direct capture of CO2 from atmospheric air. Single-component CO2 and H2O adsorption experimental data are fitted to the Toth and Guggenheim-Anderson-de Boer models, respectively. Corresponding heats of adsorption, derived from explicit solutions of the van't Hoff equation, are -50 kJ/mol CO2 and -48.8 kJ/mol H2O. Binary CO2/H2O adsorption measurements for humid air reveal that the presence of H2O at 2.55 kPa enhances CO2 adsorption, while the presence of CO2 at 0.045 kPa does not influence H2O adsorption. The energy demand of the temperature-vacuum-swing adsorption/desorption cycle for delivering pure CO2 from air increases significantly with H2O adsorption and indicates the need to reduce the hygroscopicity of the adsorbent.

  7. Experimental comparison of adsorption characteristics of silica gel and zeolite in moist air

    NASA Astrophysics Data System (ADS)

    Xin, F.; Yuan, Z. X.; Wang, W. C.; Du, C. X.

    2017-02-01

    In this work, the macro adsorption characteristic of water vapor by the allochroic silica gel and the zeolite 5A and ZSM-5 were investigated experimentally. BET analysis method presented the difference of the porosity, the micro pore volume, and the specific surface area of the material. The dynamic and the equilibrium characteristics of the sample were measured thermo-gravimetrically in the moist air. In general, the ZSM-5 zeolite showed an inferior feature of the adsorption speed and the equilibrium concentration to the others. By comparison to the result of SAPO-34 zeolite in the open literature, the 5A zeolite showed some superiorities of the adsorption. The equilibrium concentration of the ZSM-5 zeolite was higher than that of the SAPO-34 calcined in the nitrogen, whereas it was lower than that calcined in the air. The adsorption isotherm was correlated and the relation of the isotherm to the microstructure of the material was discussed. With more mesopore volume involved, the zeolite presented an S-shaped isotherm in contrast to the exponential isotherm of the silica gel. In addition, the significance of the S-shaped isotherm for the application in adsorption heat pump has also been addressed.

  8. Adsorption of mercury on laterite from Guizhou Province, China.

    PubMed

    Yu, Xiaohong; Zhu, Lijun; Guo, Baiwei; He, Shouyang

    2008-01-01

    The adsorption behaviors of Hg(II) on laterite from Guizhou Province, China, were studied and the adsorption mechanism was discussed. The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(II). Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(II). The pH of the solution is an important factor affecting the adsorption of Hg(II) on laterite. The alkalescent environment (pH 7-9) is favorable to the adsorption of Hg(II). The amount of adsorbed Hg(II) increases with increasing pH. When the pH reaches a certain value, the amount of the adsorbed Hg(II) will reach the maximum level. The amount of adsorbed Hg(II) decreases with increasing pH. The optimal pHs of laterite and kaolinite are 9 and 8, respectively. The optimal initial concentrations of Hg(II) on laterite and kaolinite are 250 and 200 microg/ml, respectively. The adsorption isotherms were described by the Langmuir model. The adsorption of Hg(II) on laterite is a quick process while that of Hg(II) on kaolinite is a slow reaction. Laterite from Guizhou Province is a promising environmental material which can be used in the removal of Hg(II) from wastewater.

  9. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Feng, Qinzhong; Zhang, Zhiyong; Ma, Yuhui; He, Xiao; Zhao, Yuliang; Chai, Zhifang

    2012-01-01

    The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (Δ H 0 , Δ S 0 , and Δ G 0 ) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment.

  10. Mechanism of Cr(VI) adsorption by coir pith studied by ESR and adsorption kinetic.

    PubMed

    Suksabye, Parinda; Nakajima, Akira; Thiravetyan, Paitip; Baba, Yoshinari; Nakbanpote, Woranan

    2009-01-30

    The oxidation state of chromium in coir pith after Cr(VI) adsorption from aqueous solution was investigated using electron spin resonance (ESR). To elucidate the mechanism of chromium adsorption on coir pith, the adsorption studies of Cr(VI) onto lignin, alpha-cellulose and holocellulose extracted from coir pith were also studied. ESR signals of Cr(V) and Cr(III) were observed in coir pith adsorbed Cr(VI) at solution pH 2, while ESR spectra of lignin extracted from coir pith revealed only the Cr(III) signal. In addition, ESR signal of Cr(V) was observed in alpha-cellulose and holocellulose extracted from coir pith adsorbed Cr(VI). These results confirmed that lignin in coir pith reduced Cr(VI) to Cr(III) while alpha-cellulose and holocellulose extracted from coir pith reduced Cr(VI) to Cr(V). The Cr(V) signal exhibited in ESR of alpha-cellulose and holocellulose might be bound with glucose in cellulose part of coir pith. In addition, xylose which is main in pentosan part of coir pith, indicated that it is involved in form complex with Cr(V) on coir pith. The adsorption kinetic of Cr(VI) from aqueous solution on coir pith was also investigated and described well with pseudo second order model. ESR and desorption experiments confirmed that Cr(VI), Cr(V) and Cr(III), exist in coir pith after Cr(VI) adsorption. The desorption data indicated that the percentage of Cr(VI), Cr(V) and Cr(III) in coir pith were 15.63%, 12.89% and 71.48%, respectively.

  11. [Adsorption of perfluorooctanesulfonate (PFOS) onto modified activated carbons].

    PubMed

    Tong, Xi-Zhen; Shi, Bao-You; Xie, Yue; Wang, Dong-Sheng

    2012-09-01

    Modified coal and coconut shell based powdered activated carbons (PACs) were prepared by FeCl3 and medium power microwave treatment, respectively. Batch experiments were carried out to evaluate the characteristics of adsorption equilibrium and kinetics of perfluorooctanesulfonate (PFOS) onto original and modified PACs. Based on pore structure and surface functional groups characterization, the adsorption behaviors of modified and original PACs were compared. The competitive adsorption of humic acid (HA) and PFOS on original and modified coconut shell PACs were also investigated. Results showed that both Fe3+ and medium power microwave treatments changed the pore structure and surface functional groups of coal and coconut shell PACs, but the changing effects were different. The adsorption of PFOS on two modified coconut shell-based PACs was significantly improved. While the adsorption of modified coal-based activated carbons declined. The adsorption kinetics of PFOS onto original and modified coconut shell-based activated carbons were the same, and the time of reaching adsorption equilibrium was about 6 hours. In the presence of HA, the adsorption of PFOS by modified PAC was reduced but still higher than that of the original.

  12. Derivation of the Freundlich Adsorption Isotherm from Kinetics

    ERIC Educational Resources Information Center

    Skopp, Joseph

    2009-01-01

    The Freundlich adsorption isotherm is a useful description of adsorption phenomena. It is frequently presented as an empirical equation with little theoretical basis. In fact, a variety of derivations exist. Here a new derivation is presented using the concepts of fractal reaction kinetics. This derivation provides an alternative basis for…

  13. Derivation of the Freundlich Adsorption Isotherm from Kinetics

    ERIC Educational Resources Information Center

    Skopp, Joseph

    2009-01-01

    The Freundlich adsorption isotherm is a useful description of adsorption phenomena. It is frequently presented as an empirical equation with little theoretical basis. In fact, a variety of derivations exist. Here a new derivation is presented using the concepts of fractal reaction kinetics. This derivation provides an alternative basis for…

  14. Modeling studies: Adsorption of aniline blue by using Prosopis Juliflora carbon/Ca/alginate polymer composite beads.

    PubMed

    Kumar, M; Tamilarasan, R

    2013-02-15

    The research article describes the experimental and modeling study for the adsorptive removal of aniline blue dye (AB dye) from aqueous matrices using a Prosopis Juliflora modified carbon/Ca/alginate polymer bead as a low cost and eco-friendly adsorbent. The rate of adsorption was investigated under various experimental parameters such as contact time, adsorbent dose, dye concentration, pH and temperature. The kinetics, equilibrium and thermodynamic studies were assessed to find out the efficiency of the adsorption process. The equilibrium uptake capacity of the adsorption process was found with Freundlich and Langmuir adsorption isotherm equations and it was evaluated by dimensionless separation factor (R(L)). The dynamics of adsorption was predicted by pseudo-first order, pseudo-second order Lagergren's equation and intra particle diffusion model. Adsorption feasibility was assessed with thermodynamic parameters such as isosteric heat of adsorption (ΔH°), standard entropy (ΔS°) and Gibbs free energy (ΔG°) using VantHoff plot. The alginate bead was characterized with FTIR spectroscopy and Scanning Electron Microscopy (SEM). Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  15. Adsorption of dimethylamine from aqueous solution by manganese dioxide.

    PubMed

    Yang, L; Chen, Z; Zhang, D; Liu, Y; Han, Y; Shen, J

    2011-01-01

    Removal of precursors of N-nitrosodimethylamine (NDMA), such as the most direct precursor dimethylamine (DMA), might be an effective method to control NDMA formation during practical water treatment process. Adsorption of DMA onto manganese dioxide (MnO₂) from aqueous solution has been investigated using batch experiments in this study. Results indicate that DMA adsorption is initially rapid (in the first 5 h) and the adsorption process reaches a steady state after 15 h. The adsorption isotherms are well described by the Freundlich models. The desorption shows an irreversibility of DMA adsorption onto MnO₂. The effects of temperature, pH, ionic strength, humic acid, and the presence of other secondary aliphatic amines on adsorption processes are also examined. According to the experimental results, the amount of DMA adsorbed increases with an increase of temperature from 288 to 308 K, and with a decrease of ionic strength from 1 to 10 mM. The maximum adsorption appeared at pH 7.0. However, the amount of DMA adsorbed onto MnO₂ does not show obvious difference in the presence of humic acid. According to the results, it suggests that the adsorption is primarily brought about by electrostatic interaction between DMA and MnO₂ surface.

  16. Investigation into adsorption mechanisms of sulfonamides onto porous adsorbents.

    PubMed

    Yang, Weiben; Zheng, Fangfang; Xue, Xiaoxu; Lu, Yiping

    2011-10-15

    The presence of sulfonamide antibiotics in aquatic environments poses potential ecological risks and dangers to human health. In this study, porous resins as adsorbents for the removal of two sulfonamides, sulfadiazine and sulfadimidine, from aqueous solutions were evaluated. Activated carbon F-400 was included as a comparative adsorbent. Despite the different surface properties and pore structures of the three resins, similar patterns of pH-dependent adsorption were observed, implying the importance of sulfonamide molecular forms to the adsorption process on the resins. Sulfonamide adsorption to the three resins exhibited different ionic strengths and temperature dependence consistent with sulfonamide speciation and the corresponding adsorption mechanism. Adsorption of sulfadiazine to F-400 was relatively insensitive to pH and ionic strength as micropore-filling mainly contributed to adsorption. The adsorption mechanism of sulfadiazine to the hypercrosslinked resin MN-200 was similar to that of the macroporous resin XAD-4 at lower pH values, whereas it was almost identical to the aminated resin MN-150 at higher pH. This work provided an understanding of adsorption behavior and mechanism of sulfonamide antibiotics on different adsorbents and should result in more effective applications of porous resin for antibiotics removal from industrial wastewater. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. Competitive adsorption of plasma proteins at solid-liquid interfaces.

    PubMed

    Lensen, H G; Breemhaar, W; Smolders, C A; Feijen, J

    1986-04-11

    The competitive adsorption of human serum albumin (HSA), human immuno-gamma-globulin (HIgG) and human fibrinogen (HFb) onto polystyrene (PS) at 20 degrees C and a pH of 7.35 (phosphate-buffered saline) was studied. Protein adsorption was studied using enzyme immunoassay. The results obtained with the immunoassay were compared with those obtained using radiolabelled proteins. Recent studies revealed that the adsorption behaviour of radiolabelled proteins onto surfaces differs from that of the non-labelled proteins, which may lead to misinterpretation of adsorption data. Differences in the adsorption behaviour of the labelled proteins as compared to non-labelled proteins can possibly be explained by the formation of modified proteins during the labelling procedure as shown by ion-exchange high-performance liquid chromatography (HPLC). The competitive adsorption of HSA, HIgG and HFb onto a PS latex was studied by measuring the depletion of proteins in solution. The decrease in protein concentration in solution was determined by HPLC techniques. A strong preferential adsorption of HFb was observed with maximum adsorption values of 0.6 micrograms/cm2.

  18. Low-temperature adsorption/storage of hydrogen on FAU, MFI, and MOR zeolites with various Si/Al ratios: effect of electrostatic fields and pore structures.

    PubMed

    Jhung, Sung Hwa; Yoon, Ji Woong; Lee, Ji Sun; Chang, Jong-San

    2007-01-01

    Several zeolites, such as faujasite, mordenite, and ZSM-5, with various aluminum contents have been used to analyze the effect of aluminum or cation concentration (strength of electrostatic field) on hydrogen adsorption at low temperature. Irrespective of the zeolite structure, the adsorption capacity, isosteric heat of adsorption (-DeltaHads), surface coverage, and micropore occupancy increase with increasing aluminum content of a zeolite. Zeolites with a higher amount of aluminum favorably adsorb hydrogen at relatively low pressures. For zeolites with similar aluminum contents, the adsorption capacity, isosteric heat of adsorption, surface coverage, and micropore occupancy are in the order of mordenite>ZSM-5>faujasite, probably due to differing pore sizes and the presence or absence of pore intersections. This work demonstrates that zeolites with strong electrostatic fields and narrow pores without intersections are beneficial for high hydrogen uptake.

  19. DFT study of gases adsorption on sharp tip nano-catalysts surface for green fertilizer synthesis

    NASA Astrophysics Data System (ADS)

    Yahya, Noorhana; Irfan, Muhammad; Shafie, Afza; Soleimani, Hassan; Alqasem, Bilal; Rehman, Zia Ur; Qureshi, Saima

    2016-11-01

    The energy minimization and spin modifications of sorbates with sorbents in magnetic induction method (MIM) play a vital role in yield of fertilizer. Hence, in this article the focus of study is the interaction of sorbates/reactants (H2, N2 and CO2) in term of average total adsorption energies, average isosteric heats of adsorption energies, magnetic moments, band gaps energies and spin modifications over identical cone tips nanocatalyst (sorbents) of Fe2O3, Fe3O4 (magnetic), CuO and Al2O3 (non-magnetic) for green nano-fertilizer synthesis. Study of adsorption energy, band structures and density of states of reactants with sorbents are purely classical and quantum mechanical based concepts that are vividly illustrated and supported by ADSORPTION LOCATOR and Cambridge Seriel Total Energy Package (CASTEP) modules following classical and first principle DFT simulation study respectively. Maximum values of total average energies, total average adsorption energies and average adsorption energies of H2, N2 and CO2 molecules are reported as -14.688 kcal/mol, -13.444 kcal/mol, -3.130 kcal/mol, - kcal/mol and -6.348 kcal/mol over Al2O3 cone tips respectively and minimum over magnetic cone tips. Whereas, the maximum and average minimum values of average isosteric heats of adsorption energies of H2, N2 and CO2 molecules are figured out to be 3.081 kcal/mol, 4.842 kcal/mol and 6.848 kcal/mol, 0.988 kcal/mol, 1.554 kcal/mol and 2.236 kcal/mol over aluminum oxide and Fe3O4 cone tips respectively. In addition to the adsorption of reactants over identical cone sorbents the maximum and minimum values of net spin, electrons and number of bands for magnetite and aluminum oxide cone structures are attributed to 82 and zero, 260 and 196, 206 and 118 for Fe3O4 and Al2O3 cones respectively. Maximum and least observed values of band gap energies are figured out to be 0.188 eV and 0.018 eV with Al2O3 and Fe3O4 cone structures respectively. Ultimately, with the adsorption of reactants an

  20. Basicity, Catalytic and Adsorptive Properties of Hydrotalcites

    NASA Astrophysics Data System (ADS)

    Figueras, Francois

    Solid bases have numerous potential applications, not only as catalyst for the manufacture of fine chemicals, in refining and petrochemistry, but also for adsorption and anion exchange. The present processes use liquid bases, typically alcoholic potash, and require neutralisation of the reaction medium at the end of the reaction, with production of salts. The substitution of these liquid bases by solids would provide cleaner and safer processes, due to the reduction of salts, and facilitate separation of the products and recycling of the catalyst. This chapter reviews the recent ideas on the modification of the basic properties of hydrotalcites by anion exchange and on the catalytic properties of solid bases as catalysts. Many examples of successful applications are given, with emphasis to industrial processes recently presented such as isomerisation of olefins. The basic properties of hydrotalcites can also be used to carry the exchange of toxic anions, humic acids or dyes, and have driven recent developments proposing HDT as drug carriers.

  1. Adsorption of low-molecular-weight sodium polyacrylate on hydroxyapatite.

    PubMed

    Misra, D N

    1993-10-01

    Adsorption of low-molecular-weight sodium polyacrylate from aqueous solution onto synthetic hydroxyapatite was studied at room temperature so that the mechanism of adhesion of polyacrylate cements to tooth mineral could be elucidated. The adsorption isotherm of sodium polyacrylate was Langmuirian in shape and was thus qualitatively different from that of polyacrylic acid (Misra, 1991), which exhibited an adsorption maximum. The self-association of the molecules that probably causes the maximum to occur with polyacrylic acid was effectively absent for the relatively well-ionized, electrostatically repelling polyacrylate ions of the salt. With the adsorption of acrylate ions, the concentration of phosphate ions increased monotonically, while the concentration of calcium ions showed a minimum. The adsorption of sodium polyacrylate was irreversible, as it was for polyacrylic acid.

  2. Research and Development of a Small-Scale Adsorption Cooling System

    NASA Astrophysics Data System (ADS)

    Gupta, Yeshpal

    The world is grappling with two serious issues related to energy and climate change. The use of solar energy is receiving much attention due to its potential as one of the solutions. Air conditioning is particularly attractive as a solar energy application because of the near coincidence of peak cooling loads with the available solar power. Recently, researchers have started serious discussions of using adsorptive processes for refrigeration and heat pumps. There is some success for the >100 ton adsorption systems but none exists in the <10 ton size range required for residential air conditioning. There are myriad reasons for the lack of small-scale systems such as low Coefficient of Performance (COP), high capital cost, scalability, and limited performance data. A numerical model to simulate an adsorption system was developed and its performance was compared with similar thermal-powered systems. Results showed that both the adsorption and absorption systems provide equal cooling capacity for a driving temperature range of 70--120 ºC, but the adsorption system is the only system to deliver cooling at temperatures below 65 ºC. Additionally, the absorption and desiccant systems provide better COP at low temperatures, but the COP's of the three systems converge at higher regeneration temperatures. To further investigate the viability of solar-powered heat pump systems, an hourly building load simulation was developed for a single-family house in the Phoenix metropolitan area. Thermal as well as economic performance comparison was conducted for adsorption, absorption, and solar photovoltaic (PV) powered vapor compression systems for a range of solar collector area and storage capacity. The results showed that for a small collector area, solar PV is more cost-effective whereas adsorption is better than absorption for larger collector area. The optimum solar collector area and the storage size were determined for each type of solar system. As part of this dissertation

  3. Adsorptive removal of PPCPs by biomorphic HAP templated from cotton.

    PubMed

    Huang, Bin; Xiong, Dan; Zhao, Tingting; He, Huan; Pan, Xuejun

    2016-01-01

    Biomorphic nano-hydroxyapatite (HAP) was fabricated by a co-precipitation method using cotton as bio-templates and employed in adsorptive removal of ofloxacin (OFL) and triclosan (TCS) that are two representative pharmaceuticals and personal care products (PPCPs). The surface area and porosity, crystal phase, functional group, morphology and micro-structure of the synthesized HAP were characterized by Brunauer-Emmett-Teller isotherm, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron macroscopic and transmission electron microscopy. The effects of initial pH, ionic strength, initial concentration, contact time and temperature on the removal of PPCPs were studied in a batch experiment. The adsorption of OFL and TCS was rapid and almost accomplished within 50 min. Kinetic studies indicated that the adsorption process of OFL and TCS followed the pseudo-first-order and pseudo-second-order models, respectively. The Freundlich isotherm described the OFL adsorption process well but the adsorption of TCS fitted the Langmuir isotherm better. Thermodynamics and isotherm parameters suggested that both OFL and TCS adsorption were feasible and spontaneous. Hydrogen bond and Lewis acid-base reaction may be the dominating adsorption mechanism of OFL and TCS, respectively. Compared to other adsorbents, biomorphic HAP is environmentally friendly and has the advantages of high adsorption capacity, exhibiting potential application for PPCPs removal.

  4. Two-dimensional modeling of volatile organic compounds adsorption onto beaded activated carbon.

    PubMed

    Tefera, Dereje Tamiru; Jahandar Lashaki, Masoud; Fayaz, Mohammadreza; Hashisho, Zaher; Philips, John H; Anderson, James E; Nichols, Mark

    2013-10-15

    A two-dimensional heterogeneous computational fluid dynamics model was developed and validated to study the mass, heat, and momentum transport in a fixed-bed cylindrical adsorber during the adsorption of volatile organic compounds (VOCs) from a gas stream onto a fixed bed of beaded activated carbon (BAC). Experimental validation tests revealed that the model predicted the breakthrough curves for the studied VOCs (acetone, benzene, toluene, and 1,2,4-trimethylbenzene) as well as the pressure drop and temperature during benzene adsorption with a mean relative absolute error of 2.6, 11.8, and 0.8%, respectively. Effects of varying adsorption process variables such as carrier gas temperature, superficial velocity, VOC loading, particle size, and channelling were investigated. The results obtained from this study are encouraging because they show that the model was able to accurately simulate the transport processes in an adsorber and can potentially be used for enhancing absorber design and operation.

  5. A Study of Hydrogen Adsorption in Pretreated Nanocarbon

    DTIC Science & Technology

    2003-01-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP014294 TITLE: A Study of Hydrogen Adsorption in Pretreated Nanocarbon ...Materials Research Society 112•3 A Study of Hydrogen Adsorption in Pretreated Nanocarbon Sang Moon Lee, Satoshi Ohshima, Kunio Uchida and Motoo Yumura

  6. Adsorption behavior of some radionuclides on the Chinese weathered coal.

    PubMed

    Wu, Jianfeng; Xu, Qichu; Bai, Tao

    2007-08-01

    The equilibrium and kinetic properties of Am(III), Eu(III) and Cs(I) ions adsorption by three weathered coals (WCs) from China, have been investigated in batch stirred-tank experiments. The effects of contact time, solution acidity and initial sorbate concentration on the adsorption of Am(III), Eu(III) and Cs(I) by Yuxian(YX) Tongchuan (TC) and Pingxiang (PX) WC were evaluated. The radionuclide ions are able to form complex compounds with carboxylic and phenolic groups of WCs and they are also bounded with phenolic groups even at high acidity reaction solution (>0.1 mol/L). Mechanisms including ion exchange, complexation and adsorption to the coal surface are possible in the sorption process. The acidity of the solution played an important role in the adsorption. Even acidity as high as 0.1 mol/L, 60% of Am(III) or Eu(III), 40% of Cs(I) were found to be sorbed on the YX WC, which had the best adsorption capacity for Am(III) and Eu(III). Our batch adsorption studies showed the equilibrium adsorption data fit the linear Langmuir and Freundlich adsorption isotherm. The maximum equilibrium uptake of Eu(III) were 0.412, 3.701, 5.446 mmol/g for JXWC, TCWC and YXWC, respectively.

  7. Adsorption dynamics of molecular nitrogen at an Fe(111) surface.

    PubMed

    Nosir, M A; Martin-Gondre, L; Bocan, G A; Díez Muiño, R

    2017-03-08

    We present an extensive theoretical study of N2 adsorption mechanisms on an Fe(111) surface. We combine the static analysis of a six-dimensional potential energy surface (6D-PES), based on ab initio density functional theory (DFT) calculations for the system, with quasi-classical trajectory (QCT) calculations to simulate the adsorption dynamics. There are four molecular adsorption states, usually called γ, δ, α, and ε, arising from our DFT calculations. We find that N2 adsorption in the γ-state is non-activated, while the threshold energy is associated with the entrance channel for the other three adsorption states. Our QCT calculations confirm that there are activated and nonactivated paths for the adsorption of N2 on the Fe(111) surface, which is in agreement with previous experimental investigations. Molecular dynamics at a surface temperature Ts = 300 K and impact energies Ei in the 0-5 eV range show the relative occupancy of the γ, δ, α, and ε states. The δ-state, however, is only marginally populated despite its adsorption energy being very similar to that of the γ-state. Our QCT calculations trace the dependence of molecular trapping on the surface temperature Ts and initial impact energy Ei and quantify the rates of the different competitive channels that eventually lead to molecular adsorption.

  8. Adsorption of soluble oil from water to graphene.

    PubMed

    Wang, Na; Zhang, Yuchang; Zhu, Fuzhen; Li, Jingyi; Liu, Shuaishuai; Na, Ping

    2014-05-01

    The toxicity of soluble oil to the aquatic environment has started to attract wide attention in recent years. In the present work, we prepare graphene according to oxidation and thermal reduction methods for the removal of soluble oil from the solution. Characterization of the as-prepared graphene are performed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and contact angle analysis. The adsorption behavior of soluble oil on graphene is examined, and the obtained adsorption data are modeled using conventional theoretical models. Adsorption experiments reveal that the adsorption rate of soluble oil on graphene is notably fast, especially for the soluble diesel oil, which could reach equilibrium within 30 min, and the kinetics of adsorption is perfectly consistent with a pseudo-second-order model. Furthermore, it is determined that the adsorption isotherm of soluble diesel oil with graphene fit the Freundlich model best, and graphene has a very strong adsorption capacity for soluble diesel oil in the solution. These results demonstrate that graphene is the material that provided both good adsorptive capacity and good kinetics, implying that it could be used as a promising sorbent for soluble oil removal from wastewater.

  9. Adsorption of fulvic acid on goethite

    SciTech Connect

    Filius, J.D.; Lumsdon, D.G.; Meeussen, J.C.L.; Hiemstra, T.; Riemsduk, W.H. van

    2000-01-01

    The adsorption of fulvic acid by goethite was determined experimentally as a function of concentration, pH, and ionic strength. The data were described with the CD-MUSIC model of Hiemstra and Van Riemsdijk (1996), which allows the distribution of charge of the bound fulvate molecule over a surface region. Simultaneously, the concentration, pH, and salt dependency of the binding of fulvic acid can be described. Using the same parameters, the basic charging behavior of the goethite in the absence of fulvic acid could be described well. The surface species used in the model indicate that inner sphere coordination of carboxylic groups of the fulvate molecule is important at low pH, whereas at high pH the outer sphere coordination with reactive groups of the fulvate molecule with high proton affinity is important.

  10. Adsorption of multi-heavy metals Zn and Cu onto surficial sediments: modeling and adsorption capacity analysis.

    PubMed

    Li, Shanshan; Zhang, Chen; Wang, Meng; Li, Yu

    2014-01-01

    Improved multiple regression adsorption models (IMRAMs) was developed to estimate the adsorption capacity of the components [Fe oxides (Fe), Mn oxides (Mn), organic materials (OMs), residuals] in surficial sediments for multi-heavy metal Zn and Cu. IMRAM is an improved version over MRAM, which introduces a computer program in the model developing process. As MRAM, Zn(Cu) IMRAM, and Cu(Zn) IMRAM again confirmed that there is significant interaction effects that control the adsorption of compounded Zn and Cu, which was neglected by additional adsorption model. The verification experiment shows that the relative deviation of the IMRAMs is less than 13%. It is revealed by the IMRAMs that Mn, which has the greatest adsorption capability for compounded Zn and Cu (54.889 and 161.180 mg/l, respectively), follows by interference adsorption capacity of Fe/Mn (-1.072 and -24.591 mg/l respectively). Zn and Cu influence each other through different mechanisms. When Zn is the adsorbate, compounded Cu mainly affects the adsorption capacities of Fe/Mn and Fe/Mn/OMs; while when Cu is the adsorbate, compounded Zn mainly exerts its effect on Mn, Fe/Mn, and Mn/OMs. It also shows that the compounded Zn or Cu weakened the interference adsorption of Fe/Mn, and meanwhile, strengthened the interference adsorption of Mn/OMs.

  11. Computational studies of adsorption in metal organic frameworks and interaction of nanoparticles in condensed phases

    SciTech Connect

    Annapureddy, HVR; Motkuri, RK; Nguyen, PTM; Truong, TB; Thallapally, PK; McGrail, BP; Dang, LX

    2014-02-05

    In this review, we describe recent efforts to systematically study nano-structured metal organic frameworks (MOFs), also known as metal organic heat carriers, with particular emphasis on their application in heating and cooling processes. We used both molecular dynamics and grand canonical Monte Carlo simulation techniques to gain a molecular-level understanding of the adsorption mechanism of gases in these porous materials. We investigated the uptake of various gases such as refrigerants R12 and R143a. We also evaluated the effects of temperature and pressure on the uptake mechanism. Our computed results compared reasonably well with available measurements from experiments, thus validating our potential models and approaches. In addition, we investigated the structural, diffusive and adsorption properties of different hydrocarbons in Ni-2(dhtp). Finally, to elucidate the mechanism of nanoparticle dispersion in condensed phases, we studied the interactions among nanoparticles in various liquids, such as n-hexane, water and methanol.

  12. Adsorption of trihalomethanes from water with carbon nanotubes.

    PubMed

    Lu, Chungsying; Chung, Yao-Lei; Chang, Kuan-Foo

    2005-03-01

    Commercial carbon nanotubes (CNTs) were purified by acid solution and were employed as adsorbents to study adsorption of trihalomethanes (THMs) from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after acid treatment which made CNTs become more hydrophilic and suitable for adsorption of low molecular weight and relatively polar THM molecules. The adsorption of THMs onto CNTs fluctuates very little in the pH range 3-7, but decreases with pH value as pH exceeds 7. A comparative study between CNTs and powdered activated carbon (PAC) for adsorption of THMs from water was also conducted. The short time needed to reach equilibrium as well as the high adsorption capacity of CHCl3, which accounts for a significant portion of THMs in the chlorinated drinking water, suggests that CNTs possess highly potential applications for THMs removal from water.

  13. Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).

    PubMed

    Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

    2014-07-30

    The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.

  14. Adsorption of Pyrene onto the Agricultural By-Product: Corncob.

    PubMed

    Li, Xiaojun; Tong, Dongli; Allinson, Graeme; Jia, Chunyun; Gong, Zongqing; Liu, Wan

    2016-01-01

    The adsorption behavior of pyrene on corncob was studied to provide a theoretical basis for the possible use of this material as an immobilized carrier for improving the bioremediation of PAH-contaminated soil. The results were as follows. Kinetic experiments showed that the adsorption processes obeyed a pseudo-second-order model. The intraparticle diffusion of Weber-Morris model fitting showed that the film and intraparticle diffusions were the key rate-limiting processes, and the adsorption process mainly consisted of three steps: boundary layer diffusion and two intra-particle diffusions. Experimental adsorption data for pyrene were successfully described by the adsorption-partition equilibrium model. The maximum adsorption capacity at 25°C was 214.8 μg g(-1). The adsorption contribution decreased significantly when the Ce/Sw (the equilibrium concentration/solubility in water) was higher than 1. Adsorption decreased with increased temperature. Based on the above results, the corncob particles could be helpful in the bioremediation of pyrene-contaminated soil.

  15. Zn adsorption by different fractions of Galician soils.

    PubMed

    Covelo, E F; Alvarez, N; Andrade Couce, M L; Vega, F A; Marcet, P

    2004-12-15

    To evaluate the contribution of organic matter, oxides, and clay fraction to Zn adsorption in six soils from Galicia (Spain), after soil characterization, adsorption isotherms were obtained by adding nine solutions containing between 20 and 500 mg L(-1) concentrations of Zn(NO(3))(2). Distribution coefficients were obtained from the data of adsorption isotherms. Zn adsorption isotherms corresponding to untreated soil and to the organic matter removed samples and organic matter and oxides removed samples were compared with curves pattern and adjusted to Langmuir and Freundlich empirical models. Untreated soils described L-curves whereas when soils were deprived of any component, the curves described were S-type. Distribution coefficients allowed knowing the Zn adsorption capacity of the untreated soil, and of the organic matter, oxides, and clay fraction. Soil organic matter is the main component that affects Zn adsorption as long as soil pH is near neutrality. At acid pH, the oxides are the main component that affects Zn adsorption, although to a much smaller extent than the organic matter near neutral conditions. So soil pH is the main soil factor that determines Zn adsorption, before any other soil property.

  16. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution.

  17. Insolubilization of Chestnut Shell Pigment for Cu(II) Adsorption from Water.

    PubMed

    Yao, Zeng-Yu; Qi, Jian-Hua; Hu, Yong; Wang, Ying

    2016-03-28

    Chestnut shell pigment (CSP) is melanin from an agricultural waste. It has potential as an adsorbent for wastewater treatment but cannot be used in its original state because of its solubility in water. We developed a new method to convert CSP to insolubilized chestnut shell pigment (ICSP) by heating, and the Cu(II) adsorption performance of ICSP was evaluated. The conversion was characterized, and the thermal treatment caused dehydration and loss of carboxyl groups and aliphatic structures in CSP. The kinetic adsorption behavior obeyed the pseudo-second-order rate law, and the equilibrium adsorption data were well described with both the Langmuir and the Freundlich isotherms. ICSP can be used as a renewable, readily-available, easily-producible, environmentally-friendly, inexpensive and effective adsorbent to remove heavy-metal from aquatic environments.

  18. Pulsed laser deposited metal oxide thin films mediated controlled adsorption of proteins

    NASA Astrophysics Data System (ADS)

    Kim, Se Jin

    Several metal oxide thin films were grown on Si substrate by pulsed laser deposition for controlling adsorption of proteins. No intentional heating of substrate and introduction of oxygen gas during growth were employed. Additionally, fibrinogen, bovine serum albumin (BSA), and lysozyme were used as model protein in this study. The film properties such as cyratllinity, surface roughness, surface electrical charge and chemistry were investigated by many techniques in order to obtain the relationship with protein adsorption. Firstly, as grown Ta2O5 and ZnO thin film were used to study the effects of surface charge on the behaviors of BSA and lysozyme adsorption. The protein thickness results by ellipsometry showed that negatively charged Ta2O5 had a stronger affinity to positively charged lysozyme, while positively charged ZnO had a stronger affinity to negatively charged BSA. The results confirmed electrostatic interaction due to surface charge is one of main factors for determining adsorption of proteins. Furthermore, annealing studies were performed by heat treatment of as grown Ta2O5 and ZnO at 800°C in air ambience. Annealed Ta2O5 thin film had almost wetting property (from 10.02° to less than 1˜2°) and the change of cystallinity (from amorphous to cyrsalline) while annealed ZnO thin film had a reduced contact angle (from 75.65° to 39.41°) and remained to crystalline structure. The fibrinogen thickness on annealed Ta2O5 film was increased compared with as grown sample, while heat treated ZnO film showed much reduction of fibrinogen adsorption. Binary Ta-Zn oxide thin films (TZ) were grown by preparing PLD target composed of 50 wt% Ta2O5 and 50 wt% ZnO. This binary film had IEP pH 7.1 indicating nearly neutral charge in pH 7.4 PBS solution, and hydrophilic property. Ellipsometrical results showed that TZ film had the lowest fibrinogen, BSA and lysozyme thickness after 120 min adsorption compared with Ta2O5 and ZnO. Other samples, bilayer oxide films in

  19. Adsorption of humic acids and trace metals in natural waters

    NASA Technical Reports Server (NTRS)

    Leung, W. H.

    1982-01-01

    Studies concerning the interactions between suspended hydrous iron oxide and dissolved humic acids and trace metals are reported. As a major component of dissolved organic matters and its readiness for adsorption at the solid/water interface, humic acids may play a very important role in the organometallic geochemistry of suspended sediments and in determining the fate and distribution of trace metals, pesticides and anions in natural water systems. Most of the solid phases in natural waters contain oxides and hydroxides. The most simple promising theory to describe the interactions of hydrous iron oxide interface is the surface complex formation model. In this model, the adsorptions of humic acids on hydrous iron oxide may be interpreted as complex formation of the organic bases (humic acid oxyanions) with surface Fe ions. Measurements on adsorptions were made in both fresh water and seawater. Attempts have been made to fit our data to Langmuir adsorption isotherm. Adsorption equilibrium constants were determined.

  20. Kinetic study of lead adsorption to composite biopolymer adsorbent

    SciTech Connect

    Seki, H.; Suzuki, A.

    1999-03-15

    A kinetic study of lead adsorption to composite biopolymer adsorbents was carried out. Spherical and membranous adsorbents containing two biopolymers, humic acid and alginic acid, were used for lead adsorption in dilute acidic solutions. The shrinking core model derived by M.G. Rao and A.K. Gupta was applied to describe the rate process of lead adsorption to spherical adsorbents (average radii of 0.12, 0.15, and 0.16 cm). Furthermore, the shrinking core model was modified and adapted for description of the rate process of lead adsorption to membranous adsorbent (average thickness of 0.0216 cm). The adsorption rate process for both the cases was well described and average apparent lead diffusion coefficients of about 6 {times} 10{sup {minus}6} and 7 {times} 10{sup {minus}6} cm{sup 2}/s were found for the spherical and membranous adsorbents, respectively.

  1. Optimization of Heat Exchangers

    SciTech Connect

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  2. Influence of alternating current on the adsorption of indigo carmine.

    PubMed

    Kesraoui, Aida; Selmi, Taher; Seffen, Monig; Brouers, François

    2017-04-01

    The main purpose of this work is to study the effect of a new process of accelerating which consist to couple the electrochemical process with the adsorption to remove an anionic dye, the indigo carmine. That is why, we investigated the effects of the new process of accelerating the adsorption process by using alternating current (AC) on the retention of an anionic dye, the indigo carmine. The adsorption capacity of dye (mg/g) was raised with the raise of current voltage in solution, temperature, and initial indigo carmine concentration and decreased with the increase of initial solution pH, current density, and mass of carbon. The results demonstrate that the removal efficiency of 97.0 % with the current voltage of 15 V is achieved at a current density of 0.014 A/cm(2), of pH 2 using zinc as electrodes and contact time of 210 min for adsorption in the presence of AC. Concerning the adsorption without AC, the results obtained showed that for an initial concentration equal to 20 mg/L, more than 95 % amount of adsorbed dye was retained after 405 min of contact in batch system. The comparison between adsorption in the presence and absence of an alternating current shows the importance of the alternating current in the acceleration of the adsorption method and improve the performances of FILTRASORB 200. For both cases, the adsorption mechanism follows the fractal kinetics BSf(n,α) model and the Brouers-Sotolongo isotherm model provides a good fit of the experimental data for both adsorption with and without alternating current.

  3. Adsorption of methylene blue from aqueous solution by graphene.

    PubMed

    Liu, Tonghao; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Jiao, Yuqin; Yang, Guangming; Wang, Zonghua; Xia, Yanzhi; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-02-01

    Graphene was prepared using a modified Hummers' method. The physico-chemical properties of graphene were characterized by TEM, BET specific surface area, FTIR, Raman and XRD measurements. The effect factors including pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto graphene were investigated. The experimental data of isotherm followed the Langmuir isotherm model better than the Freundlich model. The maximum adsorption capacity obtained from Langmuir isotherm equation at 293 K was 153.85 mg/g, indicating graphene is a good adsorbent for the adsorption of MB. The kinetic study illustrated that the adsorption of methylene blue onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of methylene blue onto graphene was an endothermic and spontaneous process. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Boronate affinity adsorption of RNA: possible role of conformational changes

    NASA Technical Reports Server (NTRS)

    Singh, N.; Willson, R. C.; Fox, G. E. (Principal Investigator)

    1999-01-01

    Batch equilibrium adsorption isotherm determination is used to characterize the adsorption of mixed yeast RNA on agarose-immobilized m-aminophenylboronic acid. It is shown that the affinity-enhancing influence of divalent cations depends strongly on the precise nature of the cation used, with barium being far more effective than the conventionally-used magnesium. This adsorption-promoting influence of barium is suggested to arise primarily from ionic influences on the structure and rigidity of the RNA molecule, as the adsorption of ribose-based small molecules is not similarly affected. The substitution of barium for the standard magnesium counterion does not greatly promote the adsorption of DNA, implying that the effect is specific to RNA and may be useful in boronate-based RNA separations. RNA adsorption isotherms exhibit sharp transitions as functions of temperature, and these transitions occur at different temperatures with Mg2+ and with Ba2+. Adsorption affinity and capacity were found to increase markedly at lower temperatures, suggestive of an enthalpically favored interaction process. The stoichiometric displacement parameter, Z, in Ba2+ buffer is three times the value in Mg2+ buffer, and is close to unity.

  5. Adsorption of organic phenols onto hexadecyltrimethylammonium-treated montmorillonite

    SciTech Connect

    Kim, Young S.; Song, Dong I.; Jeon, Young W.; Choi, Sang J.

    1996-12-01

    Montmorillonite used as an adsorbent was organically modified by using a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the removal capacity of organic phenol contaminants dissolved in an aqueous solution. This modification produces a change of the surface property of montmorillonite from hydrophilic to organophilic. The single- and multicomponent competitive adsorptions were performed in a batch reactor to investigate the removal of three toxic organic phenols, 2-chlorophenol, 3-cyanophenol, and 4-nitrophenol, on the modified HDTMA-montmorillonite. It was observed from the experimental results that the adsorption affinity for HDTMA-montmorillonite was 2-chlorophenol, 4-nitrophenol, 3-cyanophenol in decreasing order. Langmuir and the Redlich-Peterson models were used to analyze the single-component adsorption results, while the IAST and the LCM models predicted the multicomponent adsorption equilibria. These models yielded favorable representations of both individual and competitive adsorption behaviors.

  6. Hydrogen-graphite interaction: Experimental evidences of an adsorption barrier

    NASA Astrophysics Data System (ADS)

    Aréou, E.; Cartry, G.; Layet, J.-M.; Angot, T.

    2011-01-01

    The interaction of H atoms having relatively low average kinetic energy (˜0.025 eV) with both perfectly clean and D-covered HOPG surfaces is investigated using high resolution electron energy loss spectroscopy. From this study we confirm, in a controlled fashion, the presence of the theoretically predicted adsorption barrier since no adsorption is detected for such H atoms on HOPG. Moreover, we demonstrate that the exposure of a D saturated HOPG surface to these H atoms results in the complete removal of adatoms, with no further adsorption despite the prediction of the adsorption barrier to vanish for H dimers in para configuration. Therefore, the recombinative abstraction mechanism which competes with the adsorption process is more efficient.

  7. Adsorption of trichlorophenol on zeolite and adsorbent regeneration with ozone.

    PubMed

    Zhang, Yongjun; Mancke, Raoul Georg; Sabelfeld, Marina; Geißen, Sven-Uwe

    2014-04-30

    A FAU-type zeolite was studied as an adsorbent to remove 2,4,6-trichlorophenol (TCP), a frequently detected recalcitrant pollutant in water bodies. Both adsorption isotherm and kinetics were studied with TCP concentrations from 10 to 100mg/L. It was observed that TCP was effectively adsorbed onto the zeolite with a high adsorption capacity and a high kinetic rate. Freundlich model and pseudo-second-order kinetics were successfully applied to describe the experimental data. The influence of solution pH was also studied. Furthermore, ozone was applied to regenerate the loaded zeolite. It was found that an effective adsorption of TCP was kept for at least 8 cycles of adsorption and regeneration. The ozonation also increased the BET specific surface of zeolite by over 60% and consequently enhanced the adsorption capacity.

  8. Study of Methylene Blue adsorption on keratin nanofibrous membranes.

    PubMed

    Aluigi, A; Rombaldoni, F; Tonetti, C; Jannoke, L

    2014-03-15

    In this work, keratin nanofibrous membranes (mean diameter of about 220nm) were prepared by electrospinning and tested as adsorbents for Methylene Blue through batch adsorption tests. The adsorption capacity of the membranes was evaluated as a function of initial dye concentration, pH, adsorbent dosage, time and temperature. The adsorption capacity increased with increasing the initial dye concentration and pH, while it decreased with increasing the adsorbent dosage and temperature, indicating an exothermic process. The adsorption results indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich and Temkin isotherm models. A mean free energy evaluated through the Dubinin-Radushkevich model of about 16kJmol(-1), indicated a chemisorption process which occurred by ion exchange. The kinetic data were found to fit the pseudo-second-order model better than the pseudo-first-order model. The obtained results suggest that keratin nanofibrous membranes could be promising candidates as dye adsorption filters.

  9. Adsorption of Methylene Blue by ultrasonic surface modified chitin.

    PubMed

    Dotto, G L; Santos, J M N; Rodrigues, I L; Rosa, R; Pavan, F A; Lima, E C

    2015-05-15

    Chitin is a biopolymer which can be used as a low-cost and eco-friendly material for dyes adsorption. The use of chitin for dyes removal is little investigated, due its low surface area, porosity and high crystallinity. So, an ultrasonic surface modified chitin (USM-chitin) was prepared and used for Methylene Blue (MB) adsorption. Chitin was obtained from shrimp wastes and its surface was modified by an ultrasound-assisted treatment. USM-chitin was characterized by N2 adsorption/desorption isotherms (BET surface area, total pore volume), infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The adsorption of MB on USM-chitin was studied by kinetic, equilibrium, thermodynamic, interactions analysis, desorption and mass transfer aspects. USM-chitin presented surface area 25 times higher than raw chitin. The porosity was increased and the crystallinity was decreased. The general order model was suitable to represent the adsorption kinetics and the Langmuir model was adequate for the equilibrium. The maximum adsorption capacity was 26.69 mg g(-1). The adsorption was spontaneous, favorable and exothermic. USM-chitin can be used seven times maintaining the same adsorption capacity. Published by Elsevier Inc.

  10. Adsorption behavior of the catechins and caffeine onto polyvinylpolypyrrolidone.

    PubMed

    Dong, Zhan-Bo; Liang, Yue-Rong; Fan, Fang-Yuan; Ye, Jian-Hui; Zheng, Xin-Qiang; Lu, Jian-Liang

    2011-04-27

    Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperature was favorable for the adsorption of catechins. Elution tests showed that the desorption rates of catechins and caffeine were higher than 91% and 99% after two elution stages; in detail, almost all of the caffeine could be washed down at the water eluting stage, while catechins could be recovered at the dimethyl sulfoxide/ethanol solution eluting stage. Thus, the PVPP could be used as an excellent alternative adsorbent candidate for separating catechins from crude tea extracts, although some investigations, such as exploring the new

  11. Selective adsorption of flavor-active components on hydrophobic resins.

    PubMed

    Saffarionpour, Shima; Sevillano, David Mendez; Van der Wielen, Luuk A M; Noordman, T Reinoud; Brouwer, Eric; Ottens, Marcel

    2016-12-09

    This work aims to propose an optimum resin that can be used in industrial adsorption process for tuning flavor-active components or removal of ethanol for producing an alcohol-free beer. A procedure is reported for selective adsorption of volatile aroma components from water/ethanol mixtures on synthetic hydrophobic resins. High throughput 96-well microtiter-plates batch uptake experimentation is applied for screening resins for adsorption of esters (i.e. isoamyl acetate, and ethyl acetate), higher alcohols (i.e. isoamyl alcohol and isobutyl alcohol), a diketone (diacetyl) and ethanol. The miniaturized batch uptake method is adapted for adsorption of volatile components, and validated with column breakthrough analysis. The results of single-component adsorption tests on Sepabeads SP20-SS are expressed in single-component Langmuir, Freundlich, and Sips isotherm models and multi-component versions of Langmuir and Sips models are applied for expressing multi-component adsorption results obtained on several tested resins. The adsorption parameters are regressed and the selectivity over ethanol is calculated for each tested component and tested resin. Resin scores for four different scenarios of selective adsorption of esters, higher alcohols, diacetyl, and ethanol are obtained. The optimal resin for adsorption of esters is Sepabeads SP20-SS with resin score of 87% and for selective removal of higher alcohols, XAD16N, and XAD4 from Amberlite resin series are proposed with scores of 80 and 74% respectively. For adsorption of diacetyl, XAD16N and XAD4 resins with score of 86% are the optimum choice and Sepabeads SP2MGS and XAD761 resins showed the highest affinity towards ethanol.

  12. A review of protein adsorption on bioceramics.

    PubMed

    Wang, Kefeng; Zhou, Changchun; Hong, Youliang; Zhang, Xingdong

    2012-06-06

    Bioceramics, because of its excellent biocompatible and mechanical properties, has always been considered as the most promising materials for hard tissue repair. It is well know that an appropriate cellular response to bioceramics surfaces is essential for tissue regeneration and integration. As the in vivo implants, the implanted bioceramics are immediately coated with proteins from blood and body fluids, and it is through this coated layer that cells sense and respond to foreign implants. Hence, the adsorption of proteins is critical within the sequence of biological activities. However, the biological mechanisms of the interactions of bioceramics and proteins are still not well understood. In this review, we will recapitulate the recent studies on the bioceramic-protein interactions.

  13. A review of protein adsorption on bioceramics

    PubMed Central

    Wang, Kefeng; Zhou, Changchun; Hong, Youliang; Zhang, Xingdong

    2012-01-01