Mechanism and influence factors of 2,4‐D dechlorination by sodium citrate‐activated bimetallic palladium‐zero valent iron nanoparticles

Abstract

Nanoscale zero‐valent iron (nZVI) has high removal efficiency and strong reductive ability to organic contaminants, but this reactivity soon ceases and is attributed to rapid passivation of the nZVI surface due to the formation of iron oxides. In the present study, bimetallic palladium‐zero valent iron nanoparticles were activated with sodium citrate (SC‐nPd/Fe) to enhance 2,4‐D dechlorination from aqueous solutions. FTIR and XRD analyses showed that there was no passivation layer on the surface of nZVI after the addition of SC, and XPS analysis confirmed the nZVI after the reaction still maintained high reactivity and surface Pd ratio. The existence of SC facilitated the transfer of electrons from Fe0 to contaminants, thus accelerating the reductive dechlorination of 2,4‐D. The dechlorination efficiency of 2,4‐D on nPd/Fe was only 56.4% in 210 min, while complete dechlorination could be achieved on SC‐nPd/Fe under the same conditions, and simultaneously 97.1% of phenoxyacetic acid (PA) was generated. Moreover, the effect of reaction conditions on the dechlorination such as Pd ratio, SC dosage, initial pH and temperature was also investigated, and it was well described by pseudo‐first‐order kinetic model. In particular, The chelating abilities of SC is similar to EDTA, but it is an environmentally‐friendly chelating agent. Findings from the present study suggested that the SC could be a promising substitute for application in the remediation of 2,4‐D contained water.