Heterogeneous Fenton oxidation of 2,4-dichlorophenol using iron-based nanoparticles and persulfate system

• Nanoscale zero-valent iron (nZVI) was used as the heterogeneous catalyst.
• Fe2+, nZVI, and nano-Fe3O4 (nFe3O4) used as the catalysts were compared.
• nZVI generated sulfate radicals for oxidation of 2,4-dichlorophenol (DCP).
• nZVI has two functions – dechlorination and Fenton oxidation.

Nanoscale zero-valent iron (nZVI) has received attention for its potential applications in contaminated site remediation due to its reactivity. However, it is still unclear how nZVI acts as a catalyst to generate sulfate radicals in heterogeneous Fenton oxidation of 2,4-dichlorophenol (DCP). In this paper, various Fe materials such as Fe2+, nano-ZVI, and nano-Fe3O4 (nFe3O4) were used as heterogeneous catalysts, where the removals of DCP by Fe2+, nZVI, and nFe3O4 were 11.9%, 9.0%, and 5.5%, while the degradation of DCP in the presence of persulfate increased to 34.4%, 37.8%, and 5.8%, respectively. These data indicate nZVI can potentially generate sulfate radicals. UV, SEM, EDS and XRD demonstrated that changes on the surface of nZVI occurred owing to the Fe2+ leaching. It was further observed that DCP degradation increased when the dosage of nZVI and persulfate concentration also increased. However, it decreased when the initial pH and DCP concentration increased. More than 98% of DCP degradation was achieved within 180 min under optimum conditions, but less than 40% of chemical oxygen demand (COD) was removed. The degradation of DCP follows the pseudo-first-order kinetics and it is a chemical control reaction with an activation energy of 91.5 kJ mol−1. Finally, a possible mechanism of DCP degradation using the nZVI/PS system was proposed.