Destabilization and exchange removal of arsenic in contaminated soils by washing: A new remediation strategy with high efficiency and low mineral loss

Abstract

Mineral loss is considered a reason of the adverse effect induced by soil washing. In this research, we established a destabilization and exchange removal strategy, whose removal efficiency is higher but whose Fe mineral loss extent is lower than that of traditional soil washing method in the same dosage. In our research, three destabilizers, including oxalic acid (OA), citric acid (CA), tartaric acid (TA), and one exchanger KH2PO4 (KP), were used as single and composite agents for soil washing of As-contaminated soil. The influence of dosage, pH, washing time, and As fractions change along with time were carefully investigated. Our results showed a higher As removal efficiency and lower iron loss extent by composite washing agents than single agents. The removal efficiency was in the order of OA&KP>OA>CA&KP>CA>TA>KP at the concentration of 0.4 mol/L. The Fe loss extent was OA>OA&KP>CA&KP>CA>TA>KP. The mechanism was supposed to be the synergistic effect between destabilizer and exchanger, in which Fe minerals were destabilized by the former and benefitted by the latter to absorb on the mineral surface instead of As. In addition to a low iron loss extent, this strategy is a potential fertilizer, which benefits the reuse of washed soils and soil function recovery. Thus, destabilization and exchange removal strategy will be a more suitable method compared with traditional soil washing methods for contaminated soils.Capsule: The synergistic effect between organic acids and phosphate gives us novel insights into remediation of arsenic-contaminated soils more environment-friendly.