Efficient degradation of benzalkonium chloride by FeMn-CA300 catalyst activated persulfate process: Surface hydroxyl potentiation mechanism and degradation pathway

Efficient degradation of benzalkonium chloride (BAC) by zero-valent iron activated persulfate: Kinetics, reaction mechanisms, theoretical calculations and toxicity evolution

The present study systematically investigated the elimination of benzalkonium chloride (BAC) in the zero valent iron activated persulfate (Fe0/PS) system. The influence of operational parameters, including PS concentration, Fe0 dosage and pH, were investigated through a series of kinetic experiments. When the Fe0 dosage was 5.0 mM, the initial ratio of [PS]:[BAC] was 10:1, the degradation efficiency could achieve 91.7% at pH 7.0 within 60 min. Common inorganic anions and humic acid did not significantly affect BAC degradation, implying that Fe0/PS system had a potential application prospect in the actual wastewater remediation. Based on the electron paramagnetic resonance test and quenching experiments, the BAC degradation was found to be contributed by •OH, SO4•- and Fe(IV). A total of 23 intermediates were identified by the liquid chromatography-mass spectrometry, and the degradation pathways were proposed accordingly, including dealkylation and demethylation, hydroxylation, sulfate substitution and benzyl C-N cleavage reactions. Density functional theory based calculations were conducted to realize the rationality of the proposed reaction mechanisms. The toxicity of transformation products was predicted by ECOSAR program. This work demonstrated the possibility of BAC removal in hospital and municipal wastewater by Fe0/PS treatment, and also provides a safe choice for deep treatment of quaternary ammonium salt wastewater.

Bimetallic iron-nickel phosphide as efficient peroxymonosulfate activator for tetracycline hydrochloride degradation: Performance and mechanism

Sulfate radical-based advanced oxidation processes with (SR-AOPs) are widely employed to degrade organic pollutants due to their high efficiency, cost-effectiveness and safety. In this study, a highly active and stable FeNiP was successfully prepared by reduction and heat treatment. FeNiP exhibited high performance of peroxymonosulfate (PMS) activation for tetracycline hydrochloride (TC) removal. Over a wide pH range, an impressive TC degaradation efficiency 97.86% was achieved within 60 min employing 0.1 g/L FeNiP and 0.2 g/L PMS at room temperature. Both free radicals of SO4·-, ·OH, ·O2- and non-free radicals of 1O2 participated the TC degradation in the FeNiP/PMS system. The PMS activation ability was greatly enhanced by the cycling between Ni and Fe bimetal, and the active site regeneration was achieved due to the existence of the negatively charged Pn-. Moreover, the FeNiP/PMS system exhibited substantial TC degradation levels in both simulated real-world disturbance scenarios and practical water tests. Cycling experiments further affirmed the robust stability of FeNiP catalyst, demonstrating sustained degradation efficiency of approximately 80% even after four cycles. These findings illuminate its promising potential across natural water bodies, presenting an innovative catalyst construction approach for PMS activation in the degradation of antibiotic pollutants.