Organic pollutants degradation by glyoxylic acid boosted Fenton-like system: An overlooked Fe(III)/Fe(II) cycles with low-molecular-weight organic acid

Abstract

Herein, glyoxylic acid (GA) was incorporated into the Fenton-like (Fe(III)/H2O2) system to rigorously examine its impact on the degradation of organic pollutants. It was found that the degradation efficiencies of atrazine (ATR), ofloxacin (OFL), rhodamine B (RhB), and carbamazepine (CBZ) in the Fe(III)/GA/H2O2 system were ∼95%, and the apparent ATR degradation rate constant (1.60 × 10−2 min−1) was 4-fold as high as that (0.40 × 10−2 min−1) in the Fe(III)/H2O2 system at pH 3.6. The UV–vis spectral and cyclic voltammetry (CV) analyses demonstrated that GA could be used as a ligand and reductant to coordinate and reduce Fe(III), thereby promoting the Fe(III)/Fe(II) cycles in the Fenton-like process. Testing results for reactive oxygen species (ROS) confirmed that superoxide ions (•O2–) and hydroxyl radicals (•OH) respectively undertake the Fe(III)/Fe(II) cycles and ATR degradation in the Fe(III)/GA/H2O2 system. The reaction stoichiometric efficiencies (RSE) in the Fe(III)/GA/H2O2 system (37.5%–76.9%) were significantly higher than those (2.8%–4.9%) in the Fe(III)/H2O2 system within 180 min, and the maximum concentration of •OH in the Fe(III)/GA/H2O2 system was 4.6 times that in the Fe(III)/H2O2 system. A series of the important variables were optimized in detail, including solution pH, GA dosage, amount of Fe(III) and H2O2. These findings provide compelling evidence for the non-negligible role of GA in the processes of organic pollutants degradation based on the Fe(III)/Fe(II) cycles and radicals generation in the Fenton-like system.