Fabrication of Hierarchically Porous Titanium Membrane Electrode for Highly-Efficient Separation and Degradation of Congo Red Wastewater

Abstract

Commercially Ti membrane was chosen as the substrate of electrochemical technique because of its excellent conductivity and oxidation resistivity. However, a sole macroporous structure and low porosity limit reaction efficiency in application of electrochemical reaction. Nowadays, hierarchically porous structure have attracted interest in catalytic or electrochemical reactions owing to their large surface areas and rich pore channels. Herein, we report a hierarchically porous titanium (Ti) membrane (hp-Ti) with pore sizes mesopores (2–10 nm) and macropores (0.2–50 µm), which was fabricated by a combination of sintering and melt-dealloying processes. The macropores guaranteed an adequate flow rate through the membrane with low pressure, while the mesopores provided an ultrahigh surface area. The hierarchically porous Ti membrane with nano-MnOx loaded (MnOx/hp-Ti) by the sol–gel method exhibited better electrochemical properties than the commercially porous Ti membrane with nano-MnOx loaded (MnOx/cp-Ti), mainly due to the massive pathways of rapid diffusion, high surface areas, and abundant active sites. Further, MnOx/hp-Ti as the anode constituted an electrocatalytic membrane reactor (ECMR) for congo red wastewater treatment (50–200 mg·L−1). With the same energy consumption (0.654 kW·h·m−3) of ECMR, the removal rate of the total organic carbon (TOC) obtained by ECMR with MnOx/hp-Ti at an optimized condition was up to 80% which was higher than 73.8% of MnOx/cp-Ti. This work offers significant insights into developing new porous membrane electrodes for dye separation and degradation.