Efficient electrochemical oxidation of sulfamethoxazole by a novel reduced TiO2 nanotube arrays-based flow-through electrocatalytic membrane

The reduced TiO2 nanotube arrays (RTNA) electrode is a cost-effective anode, but its limited electrocatalytic activity is an obstacle for the application. To solve this problem, a reduced TiO2 nanotube arrays-based titanium membrane (RTNA/TM) was fabricated by a facile electrochemical method to promote the electrocatalytic performance. The one-dimensional nanostructure and reduction treatment increased the electrocatalytic capacity and reduced the energy consumption, resulting in the sulfamethoxazole (SMX) removal rate of 86.1% and electrical efficiency per order of 0.55 kWh/m3 for RTNA/TM. Compared with the batch mode, the SMX removal efficiency of the flow-through mode was significantly increased by 71%, verifying the superiority of a porous flow-through anode. The SMX degradation performances of RTNA/TM were strongly affected by the fluid velocity, current density and initial SMX concentration, except for pH. Both hydroxyl radicals and direct electron transfer were responsible for the SMX removal, while the contribution of sulfate radicals could be ignored. Furthermore, RTNA/TM displayed stable performances for five experimental cycles and showed remarkable degradation efficiencies of SMX spiked into the natural water (76.5%) and wastewater effluent (75.4%). Therefore, RTNA/TM has been proven to be a promising flow-through anode for electrochemical oxidation.