[Simultaneous Immobilization of Cadmium and Arsenic in Paddy Soils with Novel Fe-Mn Combined Graphene Oxide]

Novel Fe-Mn combined graphene oxide （GO-FM） material was produced and tested for its efficacy in remediating agricultural soil co-contaminated by Cd and As. In a 60-day soil incubation experiment， the remediation mechanism and immobilization effects of GO and GO-FM at different addition ratios （0.1%， 0.2%， and 0.3%） were investigated in Shangyu and Foshan soils， which had varying physicochemical properties and contamination degrees. The dynamic changes in pH， DOC concentration， bioavailable Cd and As content， and morphology of Cd and As were explored to determine the remediation efficacy of the materials. The results demonstrated that compared with that in the blank control， GO-FM increased the pH in Shangyu soil but decreased the pH in Foshan soil. After culture， both GO and GO-FM increased the soil DOC content. GO-FM decreased the soluble Cd concentration by 5.08%-19.19% and the bioavailability of Cd by 36.57%-42.8% in Foshan soil， and the main immobilization mechanism was electrostatic adsorption， complexation， and hydroxylated metal ion formation. The immobilization ability of GO-FM on Cd was lower than that of Foshan soil due to the influence of electrostatic repulsion in Shangyu acidic soil. However， with the increase in the amount of GO-FM， the trend of increasing the bioavailability of Cd by graphene oxide was inhibited. The addition of 0.2% and 0.3% GO-FM decreased the bioavailability of Cd by 6.45%-13.56% in Shangyu soil. Additionally， GO-FM decreased the bioavailability of As in Shangyu soil and Foshan soil by 4.34%-9.15% and 0.87%-5.71%， respectively. This was due to the immobilization mechanism of oxidation of As by manganese oxides and inner surface chelate between As and the surface hydroxyl group of iron oxides. In summary， the immobilization effect of GO-FM on Cd in Foshan soil was better than that in Shangyu soil， and the immobilization effect of GO-FM on As in Shangyu soil was better than that in Foshan soil， which can provide a theoretical basis and reference for the prevention and control of Cd and As co-contamination in different types of soil.