Reduction-stabilization characteristics, long-term stability and biotoxicity evaluation of Fe(II)/Al layered double hydroxides on Cr(VI) in contaminated soil

Chromium(Cr) poses a significant challenge for soil remediation due to its varying oxidation states, which often result in insufficient long-term effectiveness. In this study, Fe/Al-LDH with an excellent reduction-stabilization effect was synthesized for the remediation of Cr(VI)-contaminated soil, and long-term incubation experiments were conducted over 360 days. The Cr(VI) concentration in both soil types decreased significantly, with stabilization efficiencies reaching 99.82 % and 87.93 %, respectively. Even after multiple freeze-thaw and dry-wet cycles, the leaching concentrations of BS and YS soils remained within the corresponding standard limits after remediation. Moreover, the application of Fe/Al-LDH significantly enhanced plant germination indices, particularly root length. Furthermore, results from in vitro bioaccessibility and soil film diffusion gradient extraction experiments indicated a notable reduction in Cr bioaccessibility within the treatment group. Following remediation, soil enzyme activity, microbial species richness, and diversity increased. The relative abundance of Bacillus, a key Cr(VI)-reducing microorganism, rose from 17.57 % to 19.46 %–30.24 %, further contributing to the synergistic remediation of Cr pollution. Hence, this study provides technical support for the economic, environmentally friendly, and efficient remediation of Cr(VI) pollution control projects.