Chelating Agents in Assisting Phytoremediation of Uranium-Contaminated Soils: A Review

Abstract

Massive stockpiles of uranium (U) mine tailings have resulted in soil contamination with U. Plants for soil remediation have low extraction efficiency of U. Chelating agents can mobilize U in soils and, hence, enhance phytoextraction of U from the soil. However, the rapid mobilization rate of soil U by chelating agents in a short period than plant uptake rate could increase the risk of groundwater contamination with soluble U leaching down the soil profile. This review summarizes recent progresses in synthesis and application of chelating agents for assisting phytoremediation of U-contaminated soils. In detail, the interactions between chelating agents and U ions are initially elucidated. Subsequently, the mechanisms of phytoextraction and effectiveness of different chelating agents for phytoremediation of U-contaminated soils are given. Moreover, the potential risks associated with chelating agents are discussed. Finally, the synthesis and application of slow-release chelating agents for slowing down metal mobilization in soils are presented. The application of slow-release chelating agents for enhancing phytoextraction of soil U is still scarce. Hence, we propose the preparation of slow-release biodegradable chelating agents, which can control the release speed of chelating agent into the soil in order to match the mobilization rate of soil U with plant uptake rate, while diminishing the risk of residual chelating agent leaching to groundwater.

Roles and significance of chelating agents for potentially toxic elements (PTEs) phytoremediation in soil: A review

“…Cow and poultry manure, risk husk ash and fly ash are some examples of valuable wastes that previously studied as biological chelators in the phytoremediation of PTEs (Fergusson, 2015;Shen et al, 2017). The results exhibited that the biological wastes are potentially added as a chelator to enhance the uptake of PTEs and create an alternative for the disposal of these wastes (Hai et al, 2022;You et al, 2022).…”

Phytoremediation of potentially toxic elements and rare earth elements by perennial plants in floating wetlands

“…In this context, different chelators, for example, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), ethylene diamine disuccinic acid (EDDS) and low-molecular-weight organic acids (LMWOA) have been widely exploited in phytoremediation research to enhance the bioavailability of PTE in the soil, as well as to foster PTE accumulation in plants (Guo et al 2018;Duo et al 2022). In general, chelators refer to a ligand that can form a cyclic structure complex with metal ions, and can, for example, chelate with PTE in the soil to configure water-soluble and exchangeable metal-chelating agent complexes, which subsequently increase metal mobility and bioavailability, and eventually enhance metal uptake by the plants (You et al 2022).…”

Enhancing Phytoextraction Potential of Brassica napus for Contaminated Dredged Sediment Using Nitrogen Fertilizers and Organic Acids

“…Although they are suggested to be efficient in enhancing metal uptake [ 3 , 18 , 19 , 20 ], there is the risk of heavy metal leaching due to the increased mobility of metal–chelator complexes [ 21 ], which are very stable [ 22 ]. Moreover, the half-life of EDTA in soil is reported to be more than 60 days [ 23 ].…”