Effective degradation of ibuprofen through an electro-Fenton process, in the presence of zero-valent iron (ZVI-EF)

Abstract

The Fenton-like reaction based on zero-valent iron (ZVI-Fenton) is a promising and relatively cheap method for the removal of contaminants in water treatment. However, effective contaminant degradation often requires splitting the H2O2 dose among multiple additions, to avoid •OH scavenging by a single, large dose of H2O2. Moreover, H2O2 storage and handling may hinder practical applications of the method. Modified ZVI-Fenton with gradual and in-situ electrochemical generation of H2O2 would help circumvent both problems, thereby enabling easier application to water treatment. Here we show that ZVI-electro-Fenton can achieve complete degradation of a contaminant of emerging concern (the non-steroidal, anti-inflammatory drug ibuprofen) under a variety of conditions, including pH 6 (more compatible with water treatment, than the more acidic pH values often needed by Fenton processes). A correct ratio between ZVI loading and H2O2 production rate is fundamental for ibuprofen degradation to be effective, avoiding an excess of either reactant that would entail •OH consumption, and thus decrease the degradation efficiency. Low ZVI loading, coupled with the application of square-wave potential, achieved good performance in the degradation of ibuprofen, with considerable resource economy in terms of materials and energy supply.