Preparation of Fe2O3-coated vermiculite composite by hydrophobic agglomeration and its application in As/Cd co-contaminated soil.

Exploring an economic and efficient method for simultaneous passivation of As and Cd in soils is of great current significance. In this study, a low-cost composite material, Fe2O3-vermiculite (Fe-V), for effectively passivating As/Cd was synthesized successfully based on hydrophobic aggregation method. The reaction products were characterized by XRD, SEM, EDS and FTIR, results showed that Fe2O3 was successfully loaded onto the surface of vermiculite by the connection with sodium stearate and employed this composite material to passivate the co-contaminated soil with As/Cd. All the percentage of toxicity reduction (Pd value) was higher than the control group, which indicated the passivation was effective. In soil A (As 45 mg/kg and Cd 6 mg/kg), the Pd of As were higher than 90%, the Pd of Cd were 80-100%. And in soil B (As 80 mg/kg and Cd 10 mg/kg), the Pd of As were more than 84.68%, the Pds of Cd were about 99%. In the meantime, the application of Fe-V could apparently increase the residual fraction of As and Cd in soil A and soil B. Moreover, the passivation of As and Cd in soils by Fe-V composite materials was a combined physical and chemical action system. This research shows that Fe-V could play a good role in the passivation of As/Cd in different pollution levels of soils.