Carbon nanotubes redirect electrooxidation pathways from mineralization to polymerization for efficient phenolics removal

Boron-doped diamond (BDD) anode-assisted electrochemical advanced oxidation processes (EAOPs) hold significant promise for industrial wastewater treatment due to their environmental friendliness, adaptability, strong oxidation capability, and the growing commercialization of BDD electrodes. However, achieving complete mineralization of organic contaminants with BDD anode-assisted EAOPs typically necessitates high applied potentials and prolonged reaction durations, resulting in substantial energy consumption. Here, we report a strategy by integrating carbon nanotubes (CNTs) (0.75 g/L) into the BDD anode-assisted EAOPs. This integration enhanced the phenol (1.0 mM) removal rate constant by 115 % and concurrently increased the removal of total organic carbon (TOC) by 180 % in a 100 mM Cl⁻ matrix at 2.3 V vs. SCE, reducing energy consumption by 49 % compared to the system without CNTs. Mechanistic investigations revealed CNTs suppressed the generation of HO^• and Cl^• while enhancing the oxidative contributions of free chlorine species. More importantly, CNTs promoted the formation of phenoxyl radicals and triggered their non-degradative oxidative coupling/transfer onto the surface of CNTs. Continuous flow experiments further confirmed the scalability, demonstrating >50% lower energy consumption and 23.37% reduced effluent toxicity when CNTs were integrated into the EAOPs for treating authentic phenolics-rich wastewater. Taken together, this work establishes a paradigm-shifting approach merging radical oxidation with energy-saving polymerization pathways for environmentally friendly treatment.