Visible light induced acceleration of Fe(III)/Fe(II) cycles for enhancing phthalate degradation in C60 fullerenol modified Fe(III)/peroxymonosulfate process

Abstract

Hydroxylated fullerene (fullerenol) has gained increasing attention in the field of water environment remediation based on its intrinsic properties of photosensitivity and high water solubility. In this work, C60 fullerenol was added to the Fe(III)/PMS process to enhance diethyl phthalate (DEP) degradation both with and without visible light. The DEP removal ratio was increased from 2.2% to 58.8% with the addition of fullerenol at 60 min in dark condition, and the removal of DEP was completely achieved within 50 min under visible light irradiation. Mechanism investigation shows that carboxyl and carbonyl were formed via keto-enol isomerization at acid condition, resulting in the formation of open-cage fullerenol. The open-cage fullerenol can act as complex agent and electron donor to enhance oxidizing capability of the Fe(III)/PMS process by promoting Fe(III)/Fe(II) cycles. Competitive radical capture tests by electron spin resonance (ESR) and radical quenching analysis demonstrate that hydroxyl radical and sulfate radical were primarily responsible for DEP removal, but not superoxide radical and singlet oxygen. The DEP removal in the F/Fe(III)/PMS process is more efficiency at initial pH ranging from 2.1 to 4.9. Moreover, the DEP degradation route was proposed involving the generation of various intermediary products. This study provides a novel method for the application of fullerene derivatives on environment remediation by combining with metal catalyzed advanced oxidation processes.