Chloroalkali industry

The mining of mercury has declined in recent decades, as major international concern over the health threat of mercury s extensive pollution of the environment has mounted. Much American freshwater fish is contaminated. The U.S. Environmental Protection Agency estimates 3,000 uses of mercury. Mercury usage is down in the chloroalkali industry, in which mercury is the cathode material used in the electrolysis of sodium chloride solutions, which produce sodium hydroxide and chlorine. An abundance of... 

Besides the industrial production of PCNs there is also a release of PCNs to the environment via polychlorinated biphenyl (PCB) commercial products, in which PCNs are present as minor contaminants [3], PCNs are also formed in various incineration processes [4, 5] and industrial processes such as the production of magnesium [6], copper [7] and in chloroalkali production [8,9]. PCNs are currently widespread in the environment and are to be regarded as an environmental problem [4]. In general, PCNs are present in biota at ng g 1 levels (on lipid weight basis). High levels (2.4 pgg J) have been reported in e. g., whitetailed sea eagle from Poland [5]. 

One example (out of many) to illustrate the complexity of adsorption from solution (as compared with gas-phase adsorptions), is the removal of mercury, an unacceptable toxic pollutant in aqueous systems. It is found in wastewaters (before treatment) from such manufacturing industries as chloroalkali, paper and pulp, oil refining, plastic and batteries, and can exist as free metal, as Hg(I) and Hg(II). Mercury adsorption capacity, on AC, increases as the pH of the aqueous systems decreases. Carbons with different activation methods have widely different capacities. Sulfurization of the carbon, loading the carbon with zirconium, as well as the dispersion of FeOOH species over the carbon, enhanced Hg(II) uptake. Mercury vapor can be taken up using AC which have been pre-treated with sulfur, the effect of chemisorbed oxygen being to retard (not prevent) the uptake of mercury, Lopez-Gonzalez et al. (1982). 

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