Sample records for thiocyanides
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DOE Office of Scientific and Technical Information (OSTI.GOV)
G.I. Alekseev
Wastewater generation, water consumption, and water management at coke plants are considered. Measures to create runoff-free water-supply and sewer systems are discussed. Filters for water purification, corrosion inhibitors, and biocides are described. An integrated single-phase technology for the removal of phenols, thiocyanides, and ammoniacal nitrogen is outlined.
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Shan, Mingjun; Zhang, Yan; Kou, Lihong
2014-01-01
This paper describes the total nitrogen balance, and the direction and degree of nitrogen transformation during the nitrification process of coking wastewater. According to the actual nitrification process, the conventional nitrification kinetic equation was amended. After 48 h of nitrification, the total nitrogen content remained almost the same with error less than 0.6%. The total removal efficiency of NH4(+)-N was 91.1%, in which blow-off, producing cells and transforming to nitrate nitrogen accounted for 1.1, 17.8 and 72.2% respectively. Considering the influences of NH4(+)-N blow-off and conversion from cyanide, thiocyanide and organic nitrogen, the nitrification kinetic equation was amended as μ'=0.82·S/(0.48+S).
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The use of oxidation ditches for treatment of sewage for small communities*
Baars, J. K.
1962-01-01
The system of prolonged aeration in an oxidation ditch permits the full treatment of sewage from small communities at the same proportionate cost as that of the conventional activated-sludge system for large communities. It must be considered an important means of abating surface-water pollution. The treatment may be continuous or discontinuous, depending on the local situation and the quantity of sewage to be purified. Several plants are at present in operation, ranging in capacity from 200 to 4000 population-equivalent. The system may be used not only for the purification of domestic sewage, but also for the treatment of wastes from dairies and other industrial activities, even when these contain phenols, thiocyanides or peak loads of cyanides. ImagesFIG. 1FIG. 2FIG. 5FIG. 6FIG. 7FIG. 9FIG. 10 PMID:13863606
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Imparting in situ stability to displacing fluids
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jones, S.C.
1970-07-14
An aqueous preslug containing electrolyte an/or isopropanol was injected before a micellar-polymer flood to inhibit the tendency of the formation to degrade the flood. Berea cores were saturated with water from Henry lease in Illinois (18,000 ppm TDS), flooded with Henry crude (7 cp viscosity at 72/sup 0/F, specific gravity 0.843), and waterflooded with Henry water. A recovery of 86.3 percent OIP was obtained with the following preslug, micellar slug, and polymer flood. The preslug contained water from the water reservoir in Palestine, Illinois (400 ppm TDS) and sodium hydroxide. Ammonium petroleum sulfonate, Henry crude, isopropanol, nonyl phenol, sodium hydroxide,more » and Palestine water were combined to form the water-external micellar slug. The polymer flood was composed of Pusher 530, Palestine water, isopropanol, and ammonium thiocyanide.« less
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Poliovirus antibody titres, relative affinity, and neutralising capacity in maternal milk.
Zaman, S; Carlsson, B; Morikawa, A; Jeansson, S; Narayanan, I; Thiringer, K; Jalil, F; Hanson, L A
1993-02-01
Varying titres of secretory IgA antibodies to poliovirus type 1 were found previously in the milk of unvaccinated, lactating Pakistani mothers during two different years, reflecting the antigenic exposure on mucosal membranes. To study further the changes in the extent and the form of antigenic exposure reflected in the human milk, human milk samples from Pakistani, Indian, Japanese, and Swedish mothers were collected. The quality and the neutralising capacity of the antibodies was also studied. Secretory IgA, IgG, and IgM antibodies to poliovirus type 1 were determined using enzyme linked immunosorbent assay (ELISA) and relative affinity was measured in ELISA by elution with potassium thiocyanide. Microneutralisation tests were also performed. The higher secretory IgA antibody titres to poliovirus type 1 in the unvaccinated, naturally exposed Pakistani and Indian mothers' milk, compared with the Swedish and Japanese mothers, presumably reflect the epidemiological situation in these countries. Neutralising capacity and the relative antibody affinity seemed to be higher both in the Pakistani mothers and the group without natural exposure but only given inactivated poliovirus vaccine, that is the Swedish mothers, than the group meeting only live vaccine strains, that is the Japanese mothers.
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Coal hydrogenation and environmental health.
Wadden, R A
1976-01-01
Planning of coal hydrogenation processes, such as liquifaction and gasification, requires consideration of public health implications. Commercial plants will require coal quantities greater than or equal to 20,000 tons/day and the large size of these plants calls for careful consideration of the potential health hazards from the wastes and products of such processes. Analysis of pollution potential can roughly be divided into three categories: raw material structure and constituents, process design, and mode of plant operation. Identifiable pollutants include hydrogen cyanide, phenols, cresols, carbonyl and hydrogen sulfides, ammonia, mercaptans, thiocyanides, aniline, arsenic, trace metals and various polycyclic hydrocarbons. One study of workers in a hydrogenation process has revealed an incidence of skin cancer 16-37 times that expected in the chemical industry. In addition, a number of high boiling point liquid products were identified as being carcinogenic, and air concentrations of benzo[a]pyrene up to 18,000 mug/1000 m3 were reported. Health statistics on occupational groups in other coal conversion industries have shown significantly higher lung cancer rates, relative to groups without such occupational exposures. These data suggest that coal hydrogenation plants must be carefully planned and controlled to avoid harm to environmentally and occupationally exposed populations. PMID:789066
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Dye-Sensitized Approaches to Photovoltaics
NASA Astrophysics Data System (ADS)
Grätzel, Michael
2008-03-01
Sensitization of wide band-gap semiconductors to photons of energy less than the band-gap is a key step in two technically important processes - panchromatic photography and photoelectrochemical solar cells. In both cases the photosensitive species is not the semiconductor - silver halide or metal oxide - but rather an electrochemically active dye. The gap between the highest occupied molecular level (HOMO) and the lowest unoccupied molecular level (LUMO) is less than the band-gap of the semiconductor with which it is associated. It can therefore absorb light of a wavelength longer than that to which the semiconductor itself is sensitive. The electrochemical process is initiated when the dye molecule relaxes from its photoexcited level by electron injection into the semiconductor, which therefore acts as a photoanode. If the dye is in contact with a redox electrolyte, the negative charge represented by the lost electron can be recovered from the reduced state of the redox system, which in return is regenerated by charge transfer from a cathode. An external load completes the electrical circuit. The system therefore represents a conversion of the energy of absorbed photons into an electrical current by a regenerative device in every functional respect analogous to a solid-state photovoltaic cell. As in any engineering system, choice of materials, their optimization and their synergy are essential to efficient operation. While a semiconductor-electrolyte contact is analogous to a Schottky contact, in that a barrier is established between two materials of different conduction mechanism, with the possibility of optical absorption, charge carrier pair generation and separation, it should be remembered that the photogenerated valence band hole in the semiconductor represents a powerful oxidizing agent. Given that the band-gap is related to the strength and therefore the stability of chemical bonding within the semiconductor, for narrow-gap materials the most likely reaction of such a hole is the photocorrosion of the semiconductor itself. However, only relatively narrow band-gap materials have an effective optical absorption through the visible spectrum, towards and into the infra-red. Materials with an optimal band-gap match to the solar spectrum, of the order of 1.5eV, are therefore electrochemically unstable. A stable photoelectrochemical cell, without some process of optical sensitization, and necessarily using a wide-gap semiconductor is sensitive only to the ultra-violet limit of the visible spectrum. Over recent years a suitable combination of semiconductor and sensitizer has been identified and optimized, so that now a solar spectrum conversion efficiency of over 11% has been verified in a sensitized photoelectrochemical device. One key to such an efficient system is the suppression of recombination losses. When the excited dye relaxes by electron loss, the separated charge carriers find themselves on opposite sides of a phase barrier -- the electron within the solid-state semiconductor, the positive charge externally, in association with the dye molecule. There is no valence---band involvement in the process, so the system represents a majority-carrier device, avoiding one of the major loss mechanisms in conventional photovoltaics. In consequence also a highly-disordered, even porous, semiconductor structure is acceptable, enabling surface adsorption of a sufficient concentration of the dye to permit total optical absorption of incident light of photon energy greater than the HOMO-LUMO gap of the dye molecule. The accepted wide-band semiconductor for photoelectrochemical applications is titanium dioxide in the anatase crystal structure. The size of the nanocrystals making up the semiconductor photoanode can be determined by hydrothermal processing of a precursor sol, and the film can be deposited on a transparent conducting oxide (TCO) substrate by any convenient thin-film process such as screen printing or tape casting. The preferred dye system is inspired by the natural processes involving chlorophyll, the coloring material in plants on which all earthly life depends. Chlorophyll is an organometallic dye, with a metal ion, Mg, within a porphyrin cage of nitrogen atoms. The synthetic chemist of course can select any convenient metal within the periodic table, and experience shows that ruthenium has the optimal properties expected. A ruthenium-pyridyl complex provides the chromophore of the dye, with the HOMO-LUMO gap, and thence the absorption spectrum bring modified by substitution with thiocyanide groups. Chemisorptive attachment of the dye to the metal oxide surface is obtained by carboxyl groups attached to the pyridyl components. The energetics of the dye is such that the LUMO level is just above the conduction band edge of the semiconductor, enabling relaxation by electron injection as required. A satisfactory electroactive dye structure, with good attachment properties and a wide optical absorption spectrum is therefore a sophisticated molecular engineering product. The electrolyte is also an optimized electrochemical system. The basic redox behavior is provided by the iodine/iodide system, with the advantage that the ions, both oxidized and reduced are relatively small, and therefore mobile in the supporting electrolyte. Energy losses due to slow diffusion are minimized. Early experiments used aqueous electrolytes, though with limited cell lifetime due to hydrolysis of the chemisorptive dye---semiconductor bond. A wide range of organic systems were therefore investigated, with the present favored formulation being based on imidazole salts. These have the additional advantage of low vapor pressure, very necessary as the photoactive sites under mid---day sun illumination may reach 80 C or higher. Low losses at the cathode counterelectrode are also a requirement for cell efficiency. The cathode is not necessarily transparent, and prototype cells on thin metal foils have been produced. However a TCO on glass or polymer counterelectrode is widely used. In either case suitable electrocatalytic behavior is required and frequently a nanodispersed Pt precipitated from haxachloride solution is employed. It is by now evident that the achievement of an industrially-competitive sensitized photoelectrochemical solar cell is the result of the optimization of several components, associated obviously with their effective synergy. Each change of a single component has repercussions on the choice and performance of others. However as already mentioned an efficiency of over 11% has now been certified, and a stability of over 14,000 hours under accelerated testing with continuous simulated AM1.5 illumination was recently reported. In consequence there is increasing confidence on the part of industry. Several licensees of EPFL patents on dye---sensitized photovoltaic systems are now preparing for large-scale production. G24 Innovations PLC in Wales is commissioning a manufacturing plant, and Dyesol PLC in Australia is making available the required materials on an industrial scale. In conclusion, then, it can be stated that the DSC system is much more than a fascinating scientific artifact illustrating charge-transfer mechanisms at electrochemical interfaces; an efficiency and reliability with industrial credibility have been demonstrated and verified, and a significant role in competition with other photosystems can be foreseen.