MnOx/Ti Composite Membrane Anode in the Electrocatalytic Membrane Reactor for Phenolic Wastewater Treatment

MnOx/Ti composite membranes, MnOx coated on the original porous Ti support membrane, were synthesized by sol-gel method. The effect of heat-treatment temperature (220-380°C) on the crystal structure of nano-MnOx was investigated by XRD, FESEM and XPS. The XRD results showed that crystal gain size increased with the rise of heat-treatment temperature, and at the temperature of 220 to 300°C, the crystal structure was mainly Mn3O4, which transformed to Mn3O4 and α-Mn2O3 mixed crystal after 300°C. Electrocatalytic membrane reactor (ECMR) assembled with MnOx/Ti composite membrane as an anode and a stainless steel mesh as a cathode was employed for phenolic wastewater treatment. The phenol, COD and TOC removal rate of ECMR with MnOx/Ti heat-treated at 220°C reached the maximum value of 93.09%, 79.25% and 68.54%, whereas were 54.85%, 40.25% and 35.10% in case of the original Ti membrane as the anode, respectively. The sequence of catalytic activity was as follows: Mn3O4 > Mn2O3, which was also correlated with the grain size of the catalyst. The higher phenol removal obtained were related to the synergistic effect of the electrochemical oxidation and separation in ECMR, whose MnOx as catalysts also played a key role on the electrocatalytic oxidation of the phenolic wastewater.