Mercury immobilization

Keywords mercury immobilization biotechnology bacteria enzyme purification mercury reductase volatilization heavy metals... 

Graphite and carbon can be washed, the mercury immobilized, and the decontaminated material sent to landfill. Other methods are washing with chlorinated brine and distillation in a mercury furnace (not an option with iodine-impregnated carbon). 

Liver is 1 of the tissues most frequently analyzed for contaminant residne in wildlife, but maybe 1 of the least useful because of the poor correlation between fiver mercniy concentration and effects, and because of the tendency of the liver to accumulate mercury over time (Stewart et al. 1999 Scheuhammer et al. 2001). Liver is a major site of demethylation therefore, the proportion of fiver mercury present as MeHg is not representative of exposure to MeHg. Moreover, most mercury in fiver is botmd to metallothionein or other suUydryl-bearing proteins, which immobilize it (Med-insky and Klaassen 1996 Yasutake etal. 1997 Aschner 1999). Therefore, fiver mercury residue values must be used with caution, and only when more suitable tissues are unavailable. 

Precipitation is the most promising method for immobilizing dissolvable metals such as lead, cadmium, zinc, and iron.15 Some forms of arsenic, chromium, mercury, and some fatty acids can also be treated by precipitation.47 The common precipitating chemicals for metal cations are sulfide, phosphate, hydroxide, or carbonate. Among them, sulfide is the most promising, because sulfides have low solubility over a broad pH range. Precipitation is most applicable to sites with sand or coarse silt strata. 

Heavy metal ions detection with porphyrin in sol-gel is possible, too56. The porphyrin, used for detection of heavy metal ions (Hg2+, Pb2+, Cd2+), was 5,10,15,20-tetra(4-N-methylpyridil)porphyrin (TMPyP) preferred to other porphyrins because it was not leaked out of the matrix. The study of metallation of the porphyrin immobilized in sol-gel emphasized the formation of 1 1 complex for each ion with a constant of complexation depending on the nature of the ions. The strongest effects were observed for mercury due to the specific interaction of this metal with the porphyrin. 

Zeroual Y, Moutaouakkil A, Blaghen M (2001) Volatilization of mercury by immobilized bacteria (Klebsiella pneumoniae) in different support by using fluidized bed bioreactor. Curr Microbiol 43 322-327... 

With respect to Cr a distinction should be made between Cr(III), which is the common oxidation state in the soils, being rather immobile and so toxic, and Cr(VI), which is very mobile and very toxic. With respect to Hg, the situation is even more complex, due to the occurrence of mercuric mercury (Hg2+), mercurous mercury (Hg2+), elemental mercury (Hg°) and organic mercury species, such as methyl mercury, (CH3)2Hg (see Section 18.5). Furthermore, volatilization of elemental mercury and organic mercury species is common. A description of these... 

Much of the Hgt pool was found in the upper part of the soil, which is rich in organic matter. This pattern is likely due to an elevated atmospheric deposition of Hgt over the extended period and immobilization of mercury by organic functional groups and accumulation of organic matter as part of the soil-forming process. The retention of mercury in the mor humus layer was almost complete due to the very strong association between Hgt and humic substances. 

Mercury occurs in soils predominantly in the +2 oxidation state. Elemental Hg in the atmosphere is oxidized to Hg + and deposited in rainfall. It is a strong chalcophile and under anaerobic conditions forms the extremely insoluble sulfide cinnabar (HgS, pK = 52.7). Nonetheless it is not entirely immobilized under anaerobic conditions because it is reduced to volatile Hg° or methylated to volatile methyl mercury compounds by microbial action, and so returned to the atmosphere. The methylation is mediated by various bacteria, especially methanogens, through the reactions ... 

The immobilized lactose (37 a) was employed in sulfatation reactions using SOs-NEts complex. After mercury(II) trifluoroacetate cleavage, a 2.7 1 mixture of 3 -sulfated lactose and lactose was isolated and separated using anionic exchange resin. 

Electrochemical impedance measurements of the physical adsorption of ssDNA and dsDNA yields useful information about the kinetics and mobihty of the adsorption process. Physical adsorption of DNA is a simple and inexpensive method of immobilization. The ability to detect differences between ssDNA and dsDNA by impedance could be applicable to DNA biosensor technology. EIS measurements were made of the electrical double layer of a hanging drop mercury electrode for both ssDNA and dsDNA [34]. The impedance profiles were modeled by the Debye equivalent circuit for the adsorption and desorption of both ssDNA and dsDNA. Desorption of denatured ssDNA demonstrated greater dielectric loss than desorption of dsDNA. The greater flexibility of the ssDNA compared to dsDNA was proposed to account for this difference. 

T0789 Texilla Environmental, Inc., Synthetic Mineral Immobilization Technology (SMITE) T0791 The Chlorine Institute, Inc., Thermal Desorption (Mercury Contamination)... 

Colloids The Thickness of the Double Layer and the Bulk Dimensions Are of the Same Order. The sizes of the phases forming the electrified interface have not quantitatively entered the picture so far. There has been a certain extravagance with dimensions. If, for instance, the metal in contact with the electrolyte was a sphere (e.g., a mercury drop), its radius was assumed to be infinitely large compared with any dimensions characteristic of the double layer, e.g., the thickness K-1 of the Gouy region. Such large metal spheres, dropped into a solution, sink to the bottom of the vessel and lie there stable and immobile. 

Polystyrene-bound alkenes react with alcohols or amines in the presence of mercury(II) trifluoroacetate to yield 2-alkoxy- or 2-aminoethylmercury compounds [30]. The C-Hg bond can be reduced to a C-H bond by treatment with LiBH4, or converted into a C-I bond by treatment with iodine [30]. Organomercury compounds have been immobilized with polystyrene-bound carboxylates [31]. The resulting product was used as starting material for the preparation of radiolabelled 6-iodo DOPA (Figure 4.4). 

Once the fungicides penetrate to the cell membrane or into the cytoplasm they may operate by devious means to disrupt vital functions. There is substantial evidence that the quinones immobilize the sultliydryl and imino prosthetic group of enzymes. The 8-hydroxyquinoline and dithiocarbamate compounds are active against copper and other metallic members of an enzyme system, presumably hy their ability to chelate metals. Heavy metals such as mercury alTect certain enzymes such as amylases and may serve as general protein precipitants. 

Using the negatively charged nafion film, Rodriguez et al. have improved the sensitivity of urease immobilized reaching a limit of 64 and 55 pgl 1 of mercury and copper, respectively, instead of 2.9 and 29.8 mgl 1 using the alginate gel alone [14],... 

The feasibility of amperometric sucrose and mercury biosensors based on the immobilization of invertase, glucose oxidase, and muta-rotase entrapped in a clay matrix (laponite) was investigated by Mohammadi et al. [31]. In this work, the effect of pH of a tri-enzymatic biosensor in which the optimum pH of the three enzymes is different (Invertase, pH 4.5 Glucose oxidase, pH 5.5 and Mutarotase, pH 7.4) [41] was studied. The pH effect on the biosensor response was analyzed between pH 4 and 8 and the highest activity was found at pH 6.0. In order to improve the selectivity of the invertase toward mercury and to avoid silver interference, a medium exchange technique was carried out. The biosensor was exposed to mercury in an acetate buffer solution at pH 4 while the residual activity was evaluated with phosphate buffer solution at pH 6 [41]. 

Recently, a renewable potentiometric urease inhibition biosensor based on self-assembled gold nanoparticles has been developed by Yunhui et al. for the determination of mercury ions [43]. The advantages of self-assembled immobilization are low detection limit (0.05 iM), fast response, and relatively easy regeneration of the biosensors. The assembled gold nanoparticles and inactivated enzyme layers denatured by Hg2+ can be rinsed out via a saline solution with acid and alkali successively. 

Literally hundreds of complex equilibria like this can be combined to model what happens to metals in aqueous systems. Numerous speciation models exist for this application that include all of the necessary equilibrium constants. Several of these models include surface complexation reactions that take place at the particle-water interface. Unlike the partitioning of hydrophobic organic contaminants into organic carbon, metals actually form ionic and covalent bonds with surface ligands such as sulfhydryl groups on metal sulfides and oxide groups on the hydrous oxides of manganese and iron. Metals also can be biotransformed to more toxic species (e.g., conversion of elemental mercury to methyl-mercury by anaerobic bacteria), less toxic species (oxidation of tributyl tin to elemental tin), or temporarily immobilized (e.g., via microbial reduction of sulfate to sulfide, which then precipitates as an insoluble metal sulfide mineral). 

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