Enhanced simultaneous removal of acetamiprid and cadmium from soil and water in paddy fields by Fe-Mn-BC ternary micro-electrolysis: Performance, mechanism and pathway

Acetamiprid (Ace) and cadmium (Cd) in paddy fields had caused serious impact on natural ecosystems and human health. In this study, Fe-Mn-BC ternary micro-electrolysis filler was successfully prepared and used to remove Ace and Cd in situ in paddy fields via constructing “Fe-Mn-BC micro-electrolysis-microorganism” system. The adsorption capacity of Fe-Mn-BC on Cd and Ace were 62.92 mg/g and 236.18 mg/kg, which were twice and six times than those of zeolites, respectively. In the laboratory simulated experiments, the removal efficiencies of Ace and Cd in CW with Fe-Mn-BC were around 85.0 %. The Ace was decomposed into macromolecular substances by electron transfer in the anodic oxidation process by Fe-Mn-BC and then degraded to water and carbon dioxide by microorganism, while Cd was mainly removed through adsorption of filler and microorganism and the coprecipitation with OH^– form cathode and Feⁿ⁺ from anode to form Cd_XFe_(1-X)(OH)₂. The introduce of Fe-Mn-BC promoted the production of microbial extracellular polymeric substances (mainly protein), favorable for Cd and Ace adsorption. Metagenomic sequencing results showed that the Fe-Mn-BC enriched the microorganism related to Ace degradation such as Streptomyces, Nonomuraea, Pseudonocardia, and Nocardia, and enhanced the relative abundances of Cd resistance genes (ABC.CD.P, ABC-2.A and ABC-2.P), and the Ace degradation genes (mcp, pht5, etbAa, TENA_E, and ylmB), promoting the removal of Ace and Cd. This study proposed a multi-functional and easy-operated way for the removal of Ace and Cd from soil and water in paddy fields.