Acta Petrologica et Mineralogica

In order to study the passivation remediation effect of attapulgite-double-crosslinked hydrogel microspheres (SA/PVA/ATP) on cadmium contaminated soil, SA/PVA/ATP was added to cadmium contaminated soil with concentration of 3.72 mg/kg for flooding cultivation, using simulated acid rain, mixed extractant of diethylenetriamine pentaacetic acid (DTPA) and triethanolamine (TEA) (DTPA extractant) to extract available cadmium, and using sequential extraction method of the European Community Bureau of Standards (BCR) to extract different forms of cadmium in soil. The correlation between SA/PVA/ATP addition, available cadmium and various forms of cadmium in soil was discussed. The passivation capacity, remediation efficiency and heavy metal risk assessment index were calculated, and the passivation mechanism of SA/PVA/ATP on soil cadmium was explored. The results show that with the increase of the amount of SA/PVA/ATP, the available cadmium content of DTPA extractant and acid rain extraction decrease significantly from 1.72 mg/kg and 0.024 mg/kg to 0.66 mg/kg and 0.004 4 mg/kg respectively, the content of weak acid extractable and reducible cadmium in soil decrease significantly from 1.40 mg/kg and 0.81 mg/kg to 1.01 mg/kg and 0.41 mg/kg, respectively, while the content of oxidizable and residual cadmium increase significantly from 0.86 mg/kg and 0.63 mg/kg to 0.95 mg/kg and 1.27 mg/kg, respectively. The addition of material has a significant negative correlation with available cadmium, weakly acid extractable cadmium and reducible cadmium, while a significant positive correlation with oxidizable cadmium and residual cadmium. When the addition of SA/PVA/ATP is 2.0%, the maximum passivation capacity is 19.15 mg/kg, the maximum remediation efficiency is 34.89%, and the soil environment fall from high risk to medium risk. SA/PVA/ATP can reduce the bioavailability of cadmium and realize the passivation remediation of cadmium contaminated soil through transforming the weak acid extracted and reducible forms into oxidizable and residual forms in soil.

cadmium; soil; passivation remediation; attapulgite-double-crosslinked hydrogel microspheres; form transformation