A comparative study on the efficacy of conventional and green chelating agents for soil heavy metal remediation

Abstract

Soil heavy metal contamination poses significant risks to ecological balance, vegetation, agricultural productivity, and human health due to the toxicity, persistence, and resistance to degradation of heavy metal ions. Chelation presents a widely employed method for heavy metal ion removal. While conventional chelating agents exhibit high removal efficiencies, they are associated with ecological hazards. In contrast, green chelating agents have gained prominence for their environmentally friendly attributes. This paper meticulously examines the heavy metal removal efficiencies, mechanisms, application advantages and limitations, as well as optimal pH ranges of both the traditional chelating agent Ethylenediaminetetraacetic acid (EDTA) and the green chelating agents Tetrasodium glutamate diacetate (GLDA), Methylglycine diacetic acid (MGDA), and [S, S]-ethylenediaminedisuccinic acid (EDDS). A comprehensive comparison reveals that EDDS exhibits superior performance followed by MGDA, GLDA, and EDTA, with MGDA displaying the broadest pH range spanning from 2 to 13.5. EDDS emerges as the most biodegradable option. Moreover, in terms of elimination rates, both MGDA and EDDS demonstrate comparable efficacy to EDTA. In conclusion, the green chelating agents scrutinized herein hold promise to potentially supplant conventional EDTA in large-scale practical applications.