Removal of cadmium in contaminated soils by self-sustaining smoldering

Abstract

Soil contamination by Cd presents a significant challenge for global eco-environment, while pyrolysis is an effectively method to removal of Cd in the soil, the further application of the technology has obstacle by the high device cost, large energy consumption and soil degradation. This study explored the application of self-sustaining smoldering as an energy-efficient technique for remediating of Cd-contaminated soils. The results shown that Cd could be desirable evacuated from soil by manipulate the key experiment parameter, especially the Cd-contaminated soil-to-PNs ratio. In this process, the content of Poly(vinyl) chloride (PVC) significantly influences the efficiency of Cd removal. Only 18.53 % of Cd was removed without PVC compared to that of 74.30 % after 3 % PVC was added into the soils. Chlorination of Cd(II) is the main reason for the removal of Cd during smoldering with PVC, which contrast to the volatilization of Cd is governed by reduction without PVC. Importantly, smoldering could effectively decline Cd species in the acid-soluble fraction and lower the bioavailability of Cd in treated soils with the DPTA-Cd decreased by 4.90–17.23 times compared with the untreated soils. Furthermore, due to the formed solid products, smoldering operation significantly increased soil total phosphorus and available phosphorus in the remediated soils, which is benefit for the reclamation goals. Overall, this study shows a great potential for remediation of Cd-contaminated soils by self-sustaining smoldering in the remediation industry.