The potential use of manganese oxidation in treating metal effluents

A technique of using microbially formed manganese oxides to takeup and immobilise metal effluents is described. An algal facilitated bacterial oxidation of manganese (Mn2+, which overcomes slow rates of bacteria-only manganese oxidation, was used to produced high yields of oxides using 1.6 g/L Mn2+ at neutral pH. Metals such as Cu, Zn, Co and Ni can be immobilised in stable co-precipitated manganese oxides. This effect was achieved either by the direct addition of metals during oxidation or by pretreating algal cells with metals prior to oxidation. Acid leaching (pH 2 H2SO4) showed that the immobilised metals were tightly bound by the manganese oxides. Transmission electron microscopy and X-ray analysis (TEM/EDAX) confirmed that bioformed manganese oxides had physically encapsulated the added metal ions, thereby preventing their release.