Fe‐Mn oxide, microbe and biochar composite for remediation of Cd and As co‐contaminated water and soil

Abstract The novel Fe‐Mn oxide, microbe and biochar composite (FM‐DB) synthesized by mixing Fe‐Mn oxide, Cd(II)‐resistant microbe inoculated biochar, was to simultaneously remediate the co‐contamination of Cd and As. The adsorption behaviour and mechanism of Cd(II) and As(III) were studied by using adsorption experiments: the effects of the initial pH of solution, initial concentration of heavy metal, and addition order of Cd(II) and As(III) solutes on adsorption of FM‐DB. The adsorption capacity for Cd and As was 59.27 and 84.73 mg·kg −1 , respectively. The results showed both antagonism and synergistic interaction behaviour of Cd(II) and As(III) adsorption. Synergistic effects was primarily governed by electrostatic interaction, biochemistry/specific adsorption and Cd‐As co‐precipitation. To investigate the FM‐DB stabilization ability of heavy metal in two paddy soils, a 60‐days soil incubation experiment was carried out. The pH of SY was significantly increased by 0.39–1.21 units with FM‐DB addition, and the pH of FS remained relatively stable throughout the incubation periods. FM‐DB significantly increased the DOC of the two soils by 40.57% and 18.16%, respectively. The BCR extraction was employed in this study to assess the transformation of unstable Cd and As into residual fractions. FM‐DB significantly decreased the concentration of available Cd and As by 6.7%–20.4% and 8.7%–24.3%, respectively in SY, and by 4%–8% and 5.4%–25.2%, respectively in FS ( p < .05). Thus, it is feasible to apply FM‐DB to alleviate the Cd and As pollution in the environment.