Stabilization of arsenic, antimony, and lead in contaminated soil with montmorillonite modified by ferrihydrite: Efficiency and mechanism

Abstract

Co-contamination of As, Sb, and Pb in soil has aroused public concern due to their wide application in industries. However, the efficient stabilization materials with simultaneous cations and anions stabilization capacities are still lacking and remain a challenge. Herein, a new type of montmorillonite modified by amorphous ferrihydrite (amFe@Mont) was synthesized and the immobilization performance of amFe@Mont for As, Sb, and Pb in soil was investigated comprehensively, mainly by TCLP, SBET, and DTPA extraction. The stabilization efficiency assessed by TCLP reached 86.28 % for Sb and 94.60 % for Pb after 56 days, and the As could not be detected in the leachate after 10 days. For As, Sb and Pb, the SBET method achieved a reduction of 87.34 %, 54.59 % and 17.59 % respectively. The DTPA extractable content of the metal(loid)s also declined significantly, especially for As. By applying amFe@Mont, the soil properties as well as the bacterial richness and diversity in the soil were obviously improved. The amFe@Mont adsorption data are well fitted to the Langmuir model and the pseudo-second-order model. The principal stabilization mechanisms were ascribed to inner-sphere complexation, surface precipitation and co-precipitation, and structural incorporation into amFe@Mont. This is the first study to exhibit the feasibility of amFe@Mont as an effective and environmentally friendly stabilizer for remediation of As/Sb/Pb co-contaminated soils.