Sustainable remediation of Cr(VI)-contaminated soil using mechanochemically activated phosphogypsum-slag composites

Abstract

With rapid industrialization, the environmental challenges of industrial solid waste demand urgent solutions. This study develops a novel composite environmental material (PSEM) via mechanochemical activation of phosphogypsum (PG) and slag. The influence of PSEM mix ratios on the solidification of hexavalent chromium [Cr(VI)]-contaminated soil was investigated through particle size analysis, unconfined compression tests, volume shrinkage, and toxicity leaching assessments, supported by Brunauer–Emmet–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and x-ray photoelectron spectroscopy (XPS) characterizations. Mechanochemical activation significantly reduced PSEM particle size and enhanced reactivity. At a slag-to-PG ratio of 1:1.2, compressive strength reached 3.927 MPa, volume shrinkage stabilized at 0.388%–2.530%, and Cr(VI) leaching declined to 0.137 mg/L. The solidified matrix exhibited mesoporous structures with increased surface area, while Cr(VI) was immobilized through chemical substitution and physical encapsulation. These findings demonstrate the potential of PSEM for Cr(VI) stabilization and promote the sustainable utilization of PG.