Removal Of Cu²⁺ And Zn²⁺ In Water Solution With Sulfate Reducing Bacteria And Fe²⁺/Fe³⁺

The treatment method of acid wastewater containing heavy metal with sulfatereducing bacteria (SRB) has good prospects. In order to intensify the metabolismactivities of SRB, to allevivate the toxic effects of heavy metal and to improve thetreatment efficiency, the following studies have been done in this research. Effects ofdifferent factors on the biosorption of heavy metals by SRB were investigated. Therole of Fe2+/Fe3+in improving the activity of SRB was also studied. Then, the treatingeffect of acid wastewater containing heavy metal with Fe2+and SRB was examined.Firstly, the effects of biosorbent concentration, initial pH value, temperature andthe presence of the other ion on biosorption of Cu2+and Zn2+by SRB wereinvestigated. The experimental results showed that increasing SRB biosorbentconcentration resulted in an increase in removal percentage but a decrease in specificmetal biosorption for both Cu2+and Zn2+; the maximum specific metal biosorption93.25mg·g-1and81.57mg·g-1occurred at initial pH4.5and3.5for Cu2+and Zn2+,respectively; the temperature did not have a significant effect on biosorption; specificbiosorption capacity of Cu2+decreased with the presence of Zn2+and the heavier ofthe Zn2+concentration, the less of the specific biosorption capacity of Cu2+. The FTIRanalysis results of the SRB biosorbent with and without metal ions verified thatfunctional groups of SRB biosorbent involved in the biosorption process werehydroxyl, carboxyl, amine groups and carbonyl.The intensifying effects of Fe2+/Fe3+on SRB were studied by batch experiments.The concentration range of both Fe2+and Fe3+is0mg·L-1-50mg·L-1. The lag phasewas shortened and the reduction rate of sulfate also increased with the addition ofFe2+/Fe3+. The optimum concentration of Fe2+and Fe3+was30mg·L-1and40mg·L-1,respectively. The change of sulfate and substrate COD in the Fe3+system were similarwith those in the Fe2+system. In the Fe3+system, the intesitying function of Fe3+wasdue to Fe2+, which was the reaction product of Fe3+and S2-.Lastly, treatment of acid wastewater containing Cu2+and Zn2+was studied withthe collaboration of Fe2+and SRB. The sulfate concentration and the Cu2+/Zn2+concentration in the SRB system and the SRB+Fe2+system were compared. Theexperimental results showed that the toxicity of Cu2+and Zn2+to the activity of SRB were weakened with the addition of Fe2+, which was more obvious when the Cu2+andZn2+concentration was higher.