Remediation of vanadium contaminated soils in a waste smelter by eco-friendly chitosan@mineral composites

Abstract

The immobilization of vanadium(V) on the soil via green materials like chitosan (CS) and minerals is an eco-friendly remediation technique. In this study, chitosan cross-linked attapulgite (ATP), bentonite (BT) and hydroxyapatite (HAP) composites (CS@ATP, CS@BT and CS@HAP) were prepared and applied to the V contaminated soils in a waste smelter. To reveal the influence of various factors on the stabilization effect, batch and European Community Bureau of Reference (BCR) extraction tests were carried out. The results indicated that the stabilization efficiency of 6% CS@ATP, CS@BT and CS@HAP on V reached 75.47%, 68.93% and 67.94%, respectively. Soil moisture content and dry–wet alternating environment have influence on stabilization to some extent. Langmuir and pseudo-second-order kinetic models were more suitable for the immobility process of V by the composites. After stabilization, the porosity, pH, cation exchange capacity (CEC) and soil organic matter (SOM) of soil increased, which improved soil fertility. The BCR extraction test indicated the acid soluble (AC), reducible (RE) and oxidizable (OX) fractions of V decreased, while the residual fraction (RES) increased obviously. In general, the stabilizers had excellent remediation effects on V polluted soil. The main stabilization mechanism is that amino groups and other oxygen-containing groups such as hydroxyl form complexes with V. Overall, the work provided some valuable ideas for the remediation of V contaminated soil by environmentally friendly materials.