Efficient degradation of dodecyl dimethyl benzyl ammonium chloride by activated carbon-loaded nanoscale zero-valent iron activated persulfate

Abstract

Dodecyl dimethyl benzyl ammonium chloride (DDBAC) is a widely used antimicrobial disinfectant. Its extensive application results in wastewater containing disinfectants, which, if released directly into surface waters or wastewater treatment facilities, can pose significant threats to aquatic environments and ecosystems. To achieve efficient degradation of DDBAC, this study synthesized a novel catalyst, nZVI@AC, by loading nanoscale zero-valent iron (nZVI) onto activated carbon (AC). The catalyst effectively activates peroxydisulfate (PDS), establishing an advanced oxidation process (nZVI@AC/PDS) for the efficient degradation of DDBAC. Under optimal conditions, including an initial pH of 7, a catalyst dosage of 0.5 g L⁻¹, and a PDS concentration of 1.5 mM, the removal efficiency of DDBAC (initial concentration of 10 mg L⁻¹) achieved 90 % removal at 15 min. Moreover, the nZVI@AC/PDS system operates under mild reaction conditions, exhibits good adaptability to typical temperature ranges, and maintains stability across a wide pH spectrum. It also demonstrates strong resilience in the presence of coexisting interfering anions and consistently achieves high DDBAC removal efficiencies across a range of concentrations. These findings indicate that the nZVI@AC/PDS system has promising potential for the treatment of refractory quaternary ammonium wastewater. These findings indicate that the nZVI@AC/PDS system has promising potential for practical applications, particularly in medical wastewater treatment and advanced treatment processes in wastewater treatment plants. Electron paramagnetic resonance (EPR) analysis and radical quenching experiments confirmed that superoxide radicals (O₂^•-) and sulfate radicals (SO₄^•-) play a critical role in the degradation process. High-resolution mass spectrometry coupled with liquid chromatography (HPLC-MS) identified the reaction intermediates, and the degradation pathways were predicted, involving hydrogen abstraction, dealkylation, demethylation, hydroxylation, and benzyl CN bond cleavage reactions. Density functional theory (DFT) calculations further corroborated the plausibility of the proposed reaction mechanism. Furthermore, the toxicity of DDBAC and its degradation intermediates was assessed. These findings provide novel insights into the degradation of DDBAC and demonstrate the promising potential of the nZVI@AC/PDS system for real-world disinfection wastewater treatment applications. The results highlight the potential of the nZVI@AC/PDS system for real-world applications, offering an efficient and stable solution for treating refractory disinfectant wastewater.