Insights into the mechanism of non-radical activation of persulfate via activated carbon for the degradation of p-chloroaniline

Abstract

Persistent organic pollutants (POPs) are widely distributed and have significant negative environmental impacts. Advanced oxidation processes (AOPs) based on sulfate radicals produced from persulfate (PS) have attracted considerable attention for the degradation of POPs, however, there are several disadvantages with these radical activation systems. This study examined the degradation of p-chloroaniline (PCA) by persulfate (PS) activated with activated carbon (AC). The effects of initial pH and dosage of AC were also investigated. Results showed that AC exhibits good catalytic activity toward PS. Increasing AC dosage significantly improved the PCA degradation rate but PCA removal was not obviously influenced by initial pH ranging from 3 to 9. PS activation in the PS/AC system was a non-radical process as demonstrated by (i) ethanol and tert-butyl alcohol having little effect on PCA removal and (ii) Electron Paramagnetic Resonance results showing no radicals signals in the PS/AC system. Results also demonstrated that TOC could be removed in PS oxidation and PCA dechlorination was rapid (in the initial 30 min). The three major intermediates identified during the PCA degradation in the non-radical oxidation process were N-(4-chloro-phenyl)-benzene-1,4-diamine, 4-chloro-phenyl-diazene and hydroquinone and two pathways of PCA degradation was proposed. This study proposes a new insights into the mechanism of PS activation by AC and an efficient method for POPs removal.