Preparation and performance of a coal gasification slag-based composite for simultaneous immobilization of Cd and As

Abstract

Coal gasification slag (CGS) and Fe-modified CGS (FGS) were employed to remediate cadmium (Cd) and arsenic (As) in co-contaminated agricultural soils. Adsorption experiments in aqueous systems and stabilization experiments in soil were conducted to evaluate the passivation potential of the CGS and FGS. The maximum adsorption capacities of FGS for Cd and As were 5.82 and 9.69 mg/g, while those of CGS were only 0.99 and 0.92, respectively. X-ray diffraction patterns showed that iron oxide was successfully loaded onto FGS. And the complexation of Cd and As with Fe₂O₃ and FeOOH significantly improved the adsorption capacity of FGS. The concentration of soil extractable Cd (DTPA) was reduced from 0.70 to 0.58 mg/kg with FGS application, which was likely facilitated by the pH increased from 6.46 to 7.03 and the complexation of Cd with oxygen-containing functional groups or FeOOH. The concentration of dissolved As in soil decreased from 15.33 to 13.72 mg/kg owing to the complexation of As with FeOOH. By demonstrating the application potential of FGS as soil remediation agents and revealing the stabilization mechanism of Cd and As, this study is expected to facilitate the recycling of CGS as an adsorbent for soil remediation.

Keywords

cadmium / arsenic / iron modified / coal gasification slag

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