Removal zinc ions from contaminated soil using biodegradable polyaspartate via soil washing process

Abstract

This work reports the potential use of polyaspartate (PASP) synthesized from L-aspartic acid via a newly modified thermal procedure as a soil washing chelating agent for Zn ions removal from contaminated-soil. Response surface methodology (RSM) via faced central composite design was employed for evaluating and optimizing the influence of operational parameters. RSM response models developed describe well the Zn removal efficiency with high R2 (> 0.994-0.998; p-values < 0.001) and in-significant lack of fit. Zn washing efficiency was found to increase with increase in Zn initial concentration and decrease in PASP/soil ratio. The relative contribution of the operating conditions on Zn removal follows the order; PASP/soil ratio, initial heavy metal concentration, PASP concentration, initial pH and extraction time. Optimal conditions occurred at 500 mg/kg Zn concentration, 36 mM PASP concentration, 10 polymer-soil ratio, pH 4 and 6 hours retention time when Zn ions removal was 39% with most efficient PASP utilization. Although, 100% removal of Zn was achieved at low Zn concentration (100 mg/kg), yet, more amount of the PASP was needed. These results demonstrated the feasibility of effective utilization of PASP for decontamination of Zn ions polluted soils.