Synthesis of carboxymethyl cellulose stabilized sulfidated nanoscale zero-valent iron (CMC-S-nZVI) for enhanced reduction of nitrobenzene

Abstract

Sulfidated nanoscale zero-valent iron (S-nZVI) had been widely applied for in situ groundwater remediation, but it still suffered from aggregation, surface passivation, and low reactivity in the reaction system. Herein, sodium carboxymethyl cellulose (CMC) was used as a stabilizer, and the effects of the CMC on the physicochemical properties, reactivity, and reusability of S-nZVI on nitrobenzene (NB) degradation were investigated. The characterizations revealed that the CMC improved the degree of sulfidation and accumulated more FexSy phase on the particle surface. The NB degradation rate by Fe/CMC mass ratio of 0.25 was the highest, and its pseudo-first order degradation rate constant (0.203 min−1) was nearly 15 times higher than that of S-nZVI (0.014 min−1), mainly because CMC significantly inhibited the surface oxidation of S-nZVI, improved the hydrophobicity, and reduced the electron transfer resistance compared to S-nZVI. Meanwhile, CMC-S-nZVI exhibited superior reusability than S-nZVI on NB degradation. The product distribution indicated that almost all NB was reduced to aniline (AN) without accumulation of intermediate after reaction. Besides, the effects of initial NB concentration, initial pH, S/Fe molar ratio, and particles dosage on NB degradation by CMC-S-nZVI were also investigated systematically. These results suggested that CMC-S-nZVI provided better reactivity and reusability than S-nZVI, which can guide the optimal design of robust CMC-S-nZVI and display great potential for in situ remediation application.