Immobilization of antimony in soil and groundwater using ferro-magnesium bimetallic organic frameworks

Sb(III) is often detected in contaminated soil and groundwater. Hence, high-efficiency technology is needed. In this study, bimetallic organic frameworks were used for the first time to immobilize Sb(III) from contaminated soil and groundwater. The materials were synthesized by the hydrothermal method. Both ends of the prepared material were hexagonal tip rods, and the length became shorter as the ratio of Fe/Mg decreased. The bimetallic organic framework with a Fe/Mg feeding ratio of 0.5 was the optimum material for Sb(III) removal, which could effectively immobilize Sb(III). The adsorption isotherm was fitted well with the Freundlich model, and the optimal adsorption capacity can reach 106.97 mg/g. The adsorption capacity of 84% can be completed in 10 min, which conformed to the pseudo-second-order kinetics. The Fe3+ could enhance the stability of the material, and the Mg2+ was conducive to freeing up adsorption sites for binding Sb(III) and forming stable chemical adsorption. Ion exchange is the predominant mechanism to remove Sb(III). After 14 days of remediation of Sb(III) contaminated soil, the Toxicity Characteristic Leaching Procedure (TCLP)-leached concentrations of Sb(III) were reduced by 86%, 91% and 94% when the material dosages were 1%, 2% and 3%, respectively. Immobilization of Sb(III) in soil resulted in a conversion of antimony speciation from more easily bioavailable species to less bioavailable species, further contributing to reduce the environmental risk of antimony. The results indicate that ferromagnesium bimetallic organic frameworks may serve as a kind of promising materials for the immobilization of Sb(III) in contaminated soil and groundwater. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study utilized bimetallic organic frameworks to immobilize Sb(III) in contaminated soil and groundwater for the first time. The materials exhibited high adsorption capacity and fast kinetics. The optimal material had a Fe/Mg feeding ratio of 0.5 and could effectively immobilize Sb(III). The immobilization of Sb(III) led to a conversion of antimony speciation and reduced the environmental risk.