Arsenic Removal from Effluents of Copper Plants: Fid-Bau Portal

Arsenic Removal from Effluents of Copper Plants

Nenov, V. / Dimitrova, N. / Dobrevsky, I.

Abstract It is known that at certain stages of treatment of ores, containing heavy and rare elements, liquid streams with high acidity and arsenic are obtained. Specifically, waste water with high arsenic content originates from copper and sulphuric acid production plants where sulphide ore with increased content of arsenic is used. Existing methods of arsenic removal, based on the process of coagulation-precipitation with lime, alum or ferric sulphate, are costly, produce a wet bulky sludge and often require final filters for polishing. Some possible techniques for removing arsenic include ion exchange, reverse osmosis, electrodialysis, distillation and adsorbing colloid flotation, among others. When dealing with dilute wastes, processes which concentrate arsenic from the water into another phase may offer uneconomic advantage over others. In this regard foam flotation, ion exchange and adsorption appear to have certain advantages namely, low energy requirements, easy of operation, better resistance to fouling and low residual concentrations. During recent years studies of the effect of Fe(III)/As molar ratio on arsenic precipitation has stimulated a re-evaluation of the effect of ferric salts on arsenic removal. By the data presented, it is confirmed that a molar ratio higher than one gives better effluent quality and stable precipitates. It was proved also that arsenic contaminated natural water (i.e. the case of lake ‘Topolniza’, Bulgaria) could be treated effectively by Fe2(SO4)3 without pH correction of the lake water, at high mole ratio, which ensured a residual concentration of arsenic below the required level even for drinking water. A stable fixation of arsenic in the calcium-arsenate sediments of the lake occured at mole ratio Fe/As=10. The data presented revealed that the arsenic/acid separation from copper-sulphuric acid industrial waste can be done by strong acid cation exchangers in Na-form.