Heterogeneous fenton-like catalytic degradation of 2,4-dichlorophenoxyacetic acid in water with FeS

The degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution has been studied by heterogeneous Fenton-like process using synthetic FeS as a catalyst, and the properties of FeS were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Several operation parameters including pH, FeS dosage, H2O2 concentration and temperature were investigated and the results showed that 2,4-D was efficiently removed from aqueous solution using FeS as a catalyst over a wide range of pH values from 2.0 to 6.5. At the initial pH of 4.5 (without pH adjustment), 10 mM of H2O2, 10 mg/L of 2,4-D and a FeS dose of 0.5 g/L, 2,4-D was almost completely removed within 300 min and the total organic carbon (TOC) removal could reach 70.4%. The degradation intermediates such as 2,4-dichlorophenol, 2-chlorohydroquinone, 4,6-dichlororesorcinol, 2-chlorobenzoquinone, several short-chain acids and chloride ion have been identified by a gas chromatography mass spectrometry (GC-MS) and an ion chromatography (IC). Based on the findings, a possible reaction pathway was proposed. The results of five consecutive experiments indicated the good stability and reusability of FeS and the scavenging experiments revealed that 2,4-D was mainly decomposed by the attack of HO radicals, especially the surface-bounded HO.