Remediation of lead-contaminated shooting range soil: Biodegradable chelator-assisted washing and subsequent post-treatment using FeCl3 and CaO

Lead (Pb) contamination in shooting range soils is an increasing concern due to high Pb content, threatening the ecosystems and human health. Chelator-assisted washing and chemical immobilization are the most viable treatment options for Pb-contaminated soil remediation. Ethylenediaminetetraacetic acid (EDTA) has been the most widely used chelators in washing remediation. However, the prolonged environmental persistence and subsequent toxicity of EDTA have governed eco-concerns. Alternatively, biodegradable chelators have received substantial focus as a promising substitute for EDTA. Herein, the performance and efficiency of [S,S]-ethylenediaminedisuccinic acid (EDDS), N,N-dicarboxymethyl glutamic acid (GLDA), and 3-hydroxy-2,2′ -iminodisuccinic acid (HIDS) were evaluated as eco-compliant alternatives to EDTA for the remediation of Pb-contaminated shooting range soil. Additionally, a post-treatment preference for immobilizing residual Pb in treated soils using FeCl3 and CaO was highlighted. Among the tested biodegradable chelators, EDDS exhibited the highest Pb extraction and displayed comparable efficiency to EDTA. The Pb removal efficiency of chelators was positively correlated with soil washing parameters. In contrast, the post-treatment using FeCl3 and CaO significantly reduced the leachable Pb-content in chelator-washed soils. The proposed remediation strategy coupled with washing and fixation could be a practical treatment option for extracting bulk Pb from soil and suppressing the leaching potential of residual Pb.