Reductive carbon tetrachloride degradation by surfactant derived radicals in persulfate activation system

Abstract

Despite the wide range of applications for persulfate-based advanced oxidation processes (PS-based AOPs) in groundwater remediation, the elimination of perchlorinated hydrocarbon contaminants such as carbon tetrachloride (CT) remains a challenge. In this research, we discovered that CT degradation in PS/Fe(II) system was greatly promoted with the presence of surfactant Tween-80 (TW-80), whereas it was hardly removed without TW-80 presence. The introduction of citric acid (CA) or nano zero-valent iron (nZVI) could both enhance the efficacy of PS/Fe(II) system. Through scavenging experiments and electron paramagnetic resonance analysis, the generated secondary surfactant radicals (R•CHOH) from TW-80 and superoxide radicals (O2−•) were identified as the driving factors behind CT degradation. CT dechlorination reached 70.6% and 71.8% in PS/Fe(II)/CA and PS/Fe(II)/nZVI systems, respectively, and the potential degradation routes of CT were offered. Additionally, the effect of TW-80 concentration and solution matrixes (solution pH and inorganic ions) on CT degradation was assessed. Furthermore, the removal of mixed chlorinated hydrocarbon contaminants and actual groundwater tests were also performed. Given that surfactants are commonly used in soil and groundwater remediation, this research provides a new prospect and theoretical support for the treatment of perchlorinated contaminants in groundwater with the presence of surfactants.