Remediation of arsenic-contaminated soil by nano-zirconia modified biochar

Nowadays, the soil arsenic pollution is considered as a serious environmental issue, and the high toxicity of arsenic can seriously affect the quality and safety of agricultural products and human health. Biochar, as a solidifying/passivating agent, has been widely used in the treatment of soil heavy metal pollution. Pine biochar (BC) was used as a carrier in this study, and biochar-loaded nano-zirconia (N-ZrO₂-BC) was synthesized to investigate its adsorption and fixation characteristics on As (V) in soil and water. The adsorption experiment showed that the second-order kinetic equation had a good fitting effect on the adsorption curve of As (V) on the N-ZrO₂-BC surface, which indicated that chemical adsorption was the main factor controlling the reaction rate. FTIR and SEM results showed that ion exchange and surface complexation were the main mechanisms of As (V) adsorption by N-ZrO₂-BC. Soil culture experiments showed that the stabilization efficiency of arsenic in soil with 2% N-ZrO₂-BC reached 99.30% after 60 days, and the extractable arsenic content was reduced to 3.07 μg·L^-1, which reached the quality standard of class III groundwater (<0.01 mg·L^-1, GB/T 14848-2017). Comparing with the control, the content of acid extractable arsenic in soil decreased by 90.57%, and the residual arsenic increased by 51.46%, indicating that the addition of N-ZrO₂-BC could effectively promote the transformation of active arsenic to stable arsenic in soil.