Enhanced dechlorination of 2,4-dichlorophenoxyacetic acid by Pd/Fe nanoparticles in the presence of environment-friendly iminodisuccinic acid

Environment-friendly iminodisuccinic acid (IDS) has been recognized to enhance the reactivity of Pd/Fe nanoparticles (nPd/Fe) for the effective dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D). In this study, the improving effects of IDS and other experimental parameters, such as IDS concentration, initial pH, Pd ratio and reaction temperature, on the reduction of 2,4-D were investigated. Characterization analyses of nPd/Fe with and without IDS were performed, and the mechanism of the improvement by IDS of nPd/Fe reactivity was also elucidated. Results revealed that IDS not only removed the passivation layer on nanoscale zero-valent iron (nZVI) surface, but also inhibited the iron ions from forming nZVI surface passivation layer through complexation. As a result, nPd/Fe maintained their reactivity throughout the reaction. In the presence of IDS, the removal efficiency of 2,4-D by nPd/Fe was significantly increased from 32.5 to 99.2%, and nearly 96.2% phenoxyacetic acid (PA) was simultaneously generated. The findings from the present study demonstrate that IDS could be a promising alternative complexing agent for inhibiting surface passivation and enhancing the effective utilization of nPd/Fe for dechlorination.