Enhancing Fe(II) generation via graphene oxide to activate peroxydisulfate for phenol degradation: Mechanism, molecular descriptors, and environmental application

Phenol-polluted water poses significant risks, inflicting serious harm on both aquatic and terrestrial organisms. While Fenton and Fenton-like processes have been widely employed in wastewater treatment, their effectiveness is hindered by a major limitation: the sluggish cycle of Fe(III)/Fe(II). This slow cycle has become the Achilles' Heel of these methods, preventing their broader application. In this study, graphene oxide (GO) was introduced to facilitate the generation of Fe(II) from Fe(III), enhancing peroxydisulfate (PDS) activation for pollutant degradation. The Fe(III)/GO/PDS system demonstrated effective pollutant degradation capability with 100 % treatment efficiency (phenol = 10 mg L −1 , GO = 50 mg L −1 , Fe(III) = 0.2 mM, PDS = 1 mM, and initial pH of 3). The radical-mediated oxidation mechanism was proposed based on radical scavenger effects, oxidation products, and electron paramagnetic resonance spectra. The conversion of methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO 2 ) indicated the formation of Fe(IV) in Fe(III)/GO/PDS system. To reveal degradation rules for multiple substrates, eighteen molecular descriptors were calculated using density functional theory (DFT) and correlated them with degradation rate constants ( k ). BO n , E B3LYP , and F (−) x emerged as significant parameters in this relationship. The Fe(III)/GO/PDS system demonstrated excellent reusability during the first five runs, effectively treating contaminants. However, its performance was hindered by kinetic retardation when certain anions, such as phosphate and bicarbonate, were present. These findings contribute to both scientific understanding and technical development of persulfate activation via the Fe(III)/Fe(II) cycle using carbonaceous materials, particularly for environmental remediation applications.