Sulfidation of nano-Fe/Pd bimetal for highly efficient remediation of Cr (VI) from water: Enhanced reactivity and applicability

Sulfidation of zero-valent iron nanoparticles (S-nZVI) has been considered as a common means to improve its reactivity. In this paper, Pd and Na2S were chosen as the catalyst and sulfidation regent via a modified post sulfidation approach to fabricate a kind of sulfidated bimetallic Fe/Pd nanoparticles (S-nZVIPd). The structure and composition have been clearly confirmed by a combination of various techniques. Morphology analysis showed that S-nZVIPd had a core–shell framework and hierarchical structure. The reactivity performance of S-nZVIPd, nZVIPd and S-nZVI toward Cr (VI) remediation from aqueous solution was compared, and the underlying mechanisms for the improvement effect of Cr (VI) removal were also investigated. S-nZVIPd exhibited a superior remediation reaction to remove Cr (VI) with higher removal capacity of 234.9 mg/g, with the comparison of nZVIPd (192.3 mg/g) and S-nZVI (137.5 mg/g). Additionally, the effects of common anions and cations, pH, and temperature on Cr (VI) removal were also investigated in batch experiments. Also, kinetic fitting of results revealed that remediation obeyed a pseudo-second-order model, where the apparent activation energy was 37.7 KJ/mol, illustrating that the removal of Cr (VI) was mainly dominated by chemical reduction. The enhanced removal rate of Cr (VI) by S-nZVIPd suggested that Pd and FeSx played a dual role in accelerating the corrosion of nZVI, and were facilitated to electron transfer between nZVI and Cr (VI). The results indicated that the research of the novel S-nZVIPd composite delivered new ideas theoretically for specific inquiries in the future.