The effect of Fe⁰/Fe²⁺/Fe³⁺ on nitrobenzene degradation in the anaerobic sludge

The influence of Fe⁰/Fe²⁺/Fe³⁺ on the nitrobenzene (NB) degradation in the anaerobic granular sludge was studied and the results demonstrated that: adding iron powder into the anaerobic sludge could exert an accelerative effect on the NB degradation and the degradation rate was faster than that by using iron or the anaerobic sludge alone. The external addition of Fe²⁺/Fe³⁺ exhibited different influences on the NB degradation depending on the concentrations of Fe²⁺/Fe³⁺ and the solution's pH. When Fe²⁺/Fe³⁺ are less than 100 mg/L at pH 6, Fe²⁺/Fe³⁺ inhibited the NB degradation slightly, and when Fe²⁺/Fe³⁺ was 100-200 mg/L, the NB degradation was enhanced. When pH was shifted to 9, Fe²⁺ of lower than 100 mg/L promoted the NB degradation, and 200 mg/L Fe²⁺ inhibit the NB degradation. The synergism of combined use of iron and the anaerobic sludge in treating NB wastewater was proposed, and adjusting the concentrations of Fe²⁺/Fe³⁺ in the anaerobic sludge according to the pH of the wastewater could be an effective method to obtain a high removal rate of NB.