Toxic heavy metals

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Reduction of cnviromncntal pollution requires lower energy use and new technology to decrease emission of gases such as sulfur dioxide and carbon dioxide, and to prevent toxic fluoride, heavy metal, and radioactive wastes from discharging into the environment. 

Heavy metals the total of chromium, lead, copper and other toxic metals expressed in mg/l. 

In fact, one of the major applications of chitosan and some of its many derivatives is based on its ability to bind precious, heavy and toxic metal ions. Another article reviews the various classes of chitosan derivatives and compares their ion-binding abihties under varying conditions, as well as the analytical methods to analyze them, the sorption mechanism, and structural analysis of the metal complexes. Data are also presented exhaustively in tabular form with reference to each individual metal ion and the types of compounds that complex with it under various conditions, to help reach conclusions regarding the comparative efficacy of various classes of compounds [112]. 

Mancy, K.H. Allen, H.E. A Controlled Bioassay System for Measuring Toxicity of Heavy Metals. U.S. Environmental Protection Agency Washington D.C., 1977. 

Metals that are soft Lewis acids, for example cadmium, mercury, and lead, are extremely hazardous to living organisms. Tin, in contrast, is not. One reason is that tin oxide is highly insoluble, so tin seldom is found at measurable levels in aqueous solution. Perhaps more important, the toxic metals generally act by binding to sulfur in essential enz Tnes. Tin is a harder Lewis acid than the other heavy metals, so it has a lower affinity for sulfur, a relatively soft Lewis base. 

Canli M, Furness RW. 1993. Toxicity of heavy metals dissolved in sea water and influences of sex and size on metal accumulation and tissue distribution in the Norway lobster (Nephrops norvegicus). Mar Environ Res 36 217-236. 

Heavy metals with no known biological function, such as aluminum, arsenic, lead, and mercury, are nonessential metals.4-5 These metals are toxic because they can irreversibly bind to enzymes that require metal cofactors. Toxic metals readily bind to sulfhydryl groups of proteins.6-7 In fact,... 

Some microbes are able to decrease the permeability of their membranes to prevent toxic metals from entering. If the toxic metals are not able to physically enter the cell, they will not be able to affect vital metal-sensitive structures, such as proteins. One way to prevent heavy metals from entering is by decreasing the production of membrane channel proteins.18 It is also possible for the metal-binding sites in the membrane and periplasm to be saturated with nontoxic metals.37 A third possibility is the formation of an extracellular polysaccharide coat, which binds and prevents metals from reaching the surface of the cell.24,38... 

Microbes that lack a specific active transport system for removing toxic metals may be able to sequester heavy metals either inside or outside of the cell. Intracellular sequestration occurs when cytoplasmic metal-binding molecules are produced in response to metal stress, preventing the metals from interacting with vital cell structures. The two most common molecules used for intracellular... 

Metals are divided into light (also called alkali-earth metals) and heavy. All toxic metals are heavy metals except for beryllium and barium. Additionally, other categories of elements that are or may be significant chemically as dissolved species in deep-well-injection zones include the following ... 

Collins Y.E., Stotzky G. Factors affecting the toxicity of heavy metals to microbes. In Metal Ions and Bacteria, Beveridge T.J, Doyle R.J., eds. New York, NY Wiley, 1989. 

Giller, K.E., Witter, E. and McGrath S.P(1998). Toxicity of heavy metals in microorganisms and microbial processes in agricultural soils a review , Soil Biology and Biochemistry, 30, 1389-1421. 

Some heavy metal-tolerant bacterial strains and their sorption capacities for Cu and Cd are listed in Table 1. These bacteria show great potential for remediating soils that are contaminated with toxic metals. Our pot culture experiments showed that the growth of tobacco plants in a Cd-polluted Yellow Brown Soil (Alfisol) was significantly promoted by inoculating the soil with P. Putida in comparison with the non-inoculated soil (Fig. 2). 

Bhat, U.G. and K. Vamsee. 1993. Toxicity of heavy metals Cu, Cd and Hg to the gammarid amphipod Parhalella natalensis. Sci. Total Environ., Suppl. 1993, Part 2 887-897. 

Mukhopadhyay, M.P., B.B. Ghosh, and M.M. Bagchi. 1994. Toxicity of heavy metals to fish, prawn and fish food organisms of Hooghly estuarine system. Geobios 21 13-17. 

Overmann, S.R. and J.J. Krajicek. 1995. Snapping turtles (Chelydra serpentina) as biomonitors of lead contamination of the Big River in Missouri s old lead belt. Environ. Toxicol. Chem. 14 689-695. Osweiler, G.D. and G.A. Van Gelder. 1978. Epidemiology of lead poisoning in animals. Pages 143-177 in F.W. Oehme (ed.). Toxicity of Heavy Metals in the Environment. Part 1. Marcel Dekker, NY. 

Denizeau, F., M. Marion, M. Chtaib, and J.P. Schmit. 1990. Toxicity of heavy metals in cultured hepatocytes. Environ. Toxicol. Chem. 9 737-743. 

Buck, W.B. 1978. Copper/molybdenum toxicity in animals. Pages 491-515 in F.W. Oehme (ed.). Toxicity of Heavy Metals in the Environment. Part I. Marcel Dekker, New York. 

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