CNT/Nafion functionalized Ti/SnO2-Sb/β-PbO2-CNT/Nafion composite electrode toward highly active and robust degradation of octadecylamine and 4-dodecylmorpholine in real high-salinity system

Abstract

The efficient removal of recalcitrant organics in high-salinity systems, specifically brine, poses a significant challenge for electrochemically advanced oxidation processes in terms of both activity and stability. Herein, a composite electrode comprising of CNT/Nafion functionalized Ti/SnO2-Sb/β-PbO2-CNT/Nafion was developed for efficient and stable removal of octadecylamine (ODA) and 4-dodecylmorpholine (DMP) in a real high-salinity environment. The degradation efficiencies of ODA and DMP on the composite electrode can reach 100 % within 60 min, respectively. The total organic carbon (TOC) removal efficiency of ODA and DMP was significantly improved to 78 % and 66 % with remarkably low energy consumption (0.414 and 1.402 kWh/g TOC), respectively. The electrochemical characterizations demonstrate that the composite electrode exhibits improved electrochemical activity (oxygen evolution potentials = 1.791 V) and electrode surface area (ECSA = 20 cm2), while maintaining reduced charge transfer resistance (Rct = 18.21 Ω/cm2) and enhanced corrosion-resistant capacity (corrosion potential = 1.115 V). Based on recycling and accelerated lifespan testing, the composite electrode demonstrates exceptional stability and recyclability. Additionally revealed was the linked stability mechanism. The electrocatalytic degradation of ODA and DMP begins with the removal of amino and morpholine rings, and then the decomposition of the carbon chains. Gas chromatography-mass spectrometry (GC–MS) and theoretical calculations were used to identify intermediate products generated during the degradation of ODA and DMP, and possible degradation pathways were provided in high-salinity systems, respectively. This work offered a fresh perspective on electrocatalytic oxidation for a real high-salinity system that is more efficient and stable.