Simultaneous removal of cadmium and arsenic co-contamination by iron/sulfur-modified zeolites combined with sulfate-reducing bacteria

Abstract

As common water environmental pollutants, the problem of co-contamination of cadmium (Cd) and arsenic (As) has aroused widespread concern. To solve the problem, microbial remediation technology, represented by its high efficiency, cheapness, and stability, has gained increased attention. In this study, we conducted an investigation on the efficacy of Fe/S modified zeolites (Z-FeOS) and sulfate-reducing bacteria (SRB) in removing Cd(II) and As(III) contained wastewater. The Cd(II) and As(III) removal efficacy of Z-FeOS+SRB were investigated by differing the addition time of heavy metals, SRB dosage, Z-FeOS dosage, pH, and reaction time. The produced precipitates were characterized to elucidate the removal mechanism. The results showed that the removal efficiency of Z-FeOS+SRB was much better than that of separate Z-FeOS and SRB treatments. At the Cd(II) and As(III) concentrations of 10 and 5 mg/L, respectively, the ideal removal conditions of Z-FeOS+SRB were post-heavy metal addition time of 48 h, SRB dosage of 20 % v/v, Z-FeOS dosage of 0.7 % m/v, pH 8.0, and reaction time of 168 h. Under these conditions, Cd(II) and As(III) removal efficiencies were 93.4 % and 39.9 %, respectively. The characterization results illustrated the existence of CdS and As2S3 in the precipitation products, suggesting that Cd and As were removed through sorption/co-precipitation in these forms. This study demonstrated the application potential of Z-FeOS+SRB in the bioremediation of Cd and As from environments.