Efficient Electroadsorptive Capture of Perfluorooctanoic Acid Using a Regenerable Ti3C2Tx MXene Electrode Modified with Flower-Like CuO Nanorod Assemblies.

Abstract

Perfluorooctanoic acid (PFOA) is a persistent anionic contaminant that remains difficult to remove through conventional water-treatment processes. In this study, Ti3C2Tx MXene/copper (II) oxide composite electrodes with different MXene loadings were fabricated through electrostatic self-assembly and evaluated for PFOA electroadsorption. Structural, morphological, textural, and electrochemical analyses identified MCO-20 as the optimal electrode because of its accessible mesoporous architecture, improved charge-storage capability, and low interfacial resistance. Under the selected operating conditions of 5 mM Na2SO4 and an applied voltage of 0.8 V, MCO-20 achieved 96.12% PFOA removal. The electrode maintained high performance under acidic conditions and moderate electrolyte concentrations, whereas excessive ionic strength and increasing humic acid levels reduced removal because of competitive adsorption and interfacial screening. Kinetic analysis showed that the pseudo-second-order model provided the best fit, while intraparticle-diffusion analysis indicated sequential contributions from external mass transfer, surface adsorption, and internal diffusion. The Langmuir model yielded a maximum adsorption capacity of 57.51 mg g-1. Post-adsorption XPS supported the proposed surface interactions between PFOA and MCO-20. Regeneration and reuse tests further demonstrated satisfactory operational stability, with the electrode retaining 89.40% of its initial PFOA electroadsorption capacity after six cycles. These results demonstrate that MCO-20 is a promising, efficient, and reusable electrode for PFOA removal from water.