REMOVAL OF THE INORGANIC MERCURY FROM WATER BY BITUMINOUS COAL

Abstract

Along with the industrial development, mercury and mercury based industries such as chloro-alkali plant, chemical plant, papers & pulp industry paint, fungicide etc. are alo developed, simultaneously in the world. Water pollution due to the discharge of heavy metals particularly due to mercury is serious global problem. In India there are 37 mercury based chloro-alkali plants discharging about 200 tonnes of mercury every year in the environment, specially in the aquatic environment. Mercury being the most toxic of all the heavy metals, it creates a serious problem when it eiliers into human food chain apart from the direct injection. The maximum allowable limit of mercury in the effluent is .01 mg/1 (IS : 7968: 1976) and that for drinking water is .005 mg/l. Therefore it is essential to remove mercury from waste--water :before it is released to the environment. The toxicological effect of mercury are neurolosjical damqe, including irritability, paralysis, blindness „Jr chromosome breakage etc. The health hazard due to toxic effect of mercury at Minamata, Japan (1953), Niigata. Japan (1965) and Iraq (1972) are well known. Therefore, a systematic study of the removal of mercury from waste-water is important from an environmental point of view. Synthetic ion-exchange resins, activated carbon filtration, preceeded by treatment with lime and ferric chloride or alum are known methods for the removal of heavy metals. These methods are not only expensive, but also have a problem associated with regeneration of activated carbon and hence are beyond the capacity of the developing countries. Bituminous coal treated with various chemicals like hydrogen peroxide (H202) , manganese chloride (MnC12), carbon disulphide (CS2),eto, have been successfully demonstrated in the, removal of mercury by adsorption system. In this study details of the adsorption process for the removal of mercury in nitric acid (HNO3) treated coal, and sulphuric acid (H2SO4) treated Coal are presented. The results of the batch sorption test carried out to evaluate the effect of pre-treatment of coal on removal of mercury and column t,Ist to assess the practical usefulness of the treated coal on the removal of mercury have been discussed. The results o)J both the systems are found to be encouraging in the remodl of mercury from waste-water.