IRON AND ARSENIC REMOVAL FROM BACTERIAL LEACHING EFFLUENTS BY PRECIPITATION WITH LIMESTONE

By bacterial leaching of bulk concentrates of complex sulphide ores, a cid leachates are produced which besides valuable metals as zinc and c opper also contain high concentrations of impurities such as iron and arsenic, In order to evaluate the proper conditions for removal of iro n and arsenic by precipitation as ferric arsenate with limestone, a se ries of batch precipitation experiments was conducted at various pH va lues in the range 2-6. The results from these tests showed that pentav alent arsenic and ferric iron can be effectively precipitated to low c oncentrations when the precipitation is carried out at pH 3 without ca using losses of zinc; however, the ferrous iron, approximately 1 g/l, remains in solution. When the precipitation is carried out at pH above 3 in order to oxidize ferrous iron, unacceptable high zinc losses wer e obtained.