Simultaneous degradation of organoarsenic and immobilization of arsenate by an electroactive CuFe2O4-CNT/peroxymonosulfate platform: Insights into the distinct roles of the Cu and Fe sites

Abstract

Phenylarsonic acid (PAA) compounds, widely used in animal husbandry, pose a considerable environmental threat owing to their potential transformation into toxic inorganic arsenic species. To efficiently decontaminate PAA and adsorb secondary As(V), a hybrid CuFe₂O₄-modified carbon nanotube (CuFe₂O₄-CNT) filter was developed in this study. The hybrid CuFe₂O₄-CNT filter functioned as an effective catalyst, convective filtration medium, electrode, and adsorbent. Moreover, it removed 97% PAA within 80 min in circulation mode under optimal conditions (25 °C, pH₀ = 7, peroxymonosulfate [PMS] = 1.5 mM, and voltage = 1.0 V), with a total As removal efficiency of 94%. Experimental and theoretical studies showed that the (100) and (211) planes of CuFe₂O₄-CNT contributed to PMS activation and As(V) adsorption, respectively. Quantum chemical calculations and high-performance liquid chromatography-mass spectrometry analysis determined the energy barriers for reactions between the transient state and SO₄^•− and HO^•, based on which potential PAA degradation pathways were proposed. Additionally, the negligible loss of efficiency in practical water samples and acceptable leached metal ion concentrations (Cu < 0.1 mg/L and Fe < 0.15 mg/L) confirmed the reusability and stability of the filter. This study provides a promising strategy for organoarsenic decontamination by combining electrocatalytic PMS oxidation and filtration techniques.