Remediation of iron oxide bound Pb and Pb-contaminated soils using a combination of acid washing agents and l-ascorbic acid

摘要

Soil washing is an efficient, rapid, and cost-effective remediation technique to dissolve target pollutants from contaminated soil. Here we studied the effects of leaching agents: hydrochloric acid (HCl), ethylenediamine tetraacetic acid disodium salt (Na _(2) EDTA) and citric acid (CA), and reductants: hydroxylamine hydrochloride (NH _(2) OH·HCl) and L -ascorbic acid (VC) on the leaching of Pb from synthetic iron oxide; the changes in mineralogy, morphology, and occurrence of Pb were shown by XRD, SEM, and sequential extraction analyses. Although the washing efficiency of Pb follows the trend HCl (44.24%) > Na _(2) EDTA (39.04%) > CA (28.85%), the cooperation of the leaching agent with reductant further improves the efficiency. VC is more suitable as a reductant considering the higher washing efficiency by HCl-VC (98.6%) than HCl–NH _(2) OH·HCl (88.8%). Moreover, increasing the temperature can promote the decomposition and dehydrogenation reaction of VC with more H ~(+) . Among the mixture agents, Na _(2) EDTA + VC is the most effective agent to remediate the two kinds of contaminated soils owing to the formation of Fe( II )–EDTA, a powerful reducing agent so that the efficiencies can reach up to 98.03% and 92.81%, respectively. As a result, these mixture agents have a great prospect to remediate Pb-contaminated soils.