Stabilization of nFeS with carboxymethyl cellulose for enhancing persulfate activation for p-Nitrophenol degradation

Abstract

Ferric sulfide is an appealing activator in persulfate (PS) activation process for degrading pollutants from aqueous environment, but the drawback of easy-agglomeration lead to a low utilization efficiency. In this study, we modified nFeS with sodium carboxymethyl cellulose (CMC) to improve its stability, and the performance for PS activation and p-nitrophenol (PNP) degradation is tested. After modification, the size further decreased from 23.8 to 18.4 nm, but with higher stability and catalytic reactivity. The CMC and nFeS is bonded by bidentate bridging of Fe-O bond. The degradation performance increased ∼7 times. The PS activation with CMC-nFeS activator shows higher reaction rate constant (0.093 min-1) with ∼90% of PNP removed compared to the pure nFeS with ∼80% of PNP removal at a low rate (0.014 min-1) with the same condition of 0.6 g/L activator, 8 mM PS, room temperature and initial pH in 90 min. Acidic condition and high temperature were more favorable for releasing Fe(II) to activate PS and produce active radicals. SO4-·and HO·radicals played critical roles to attack on PNP. Detailed XPS analysis of the activator before and after reaction described the removal pathway as heterogeneous and homogeneous systems. Density Functional Theory (DFT) simulation results confirmed that CMC addition effectively decreased the interaction energy and improved adsorption ability of PS onto the activator surface.