Fabrication and characterization of hierarchically porous titanium membrane for dye wastewater treatment

Hierarchically porous titanium (hp-Ti) membranes with three different atomic ratios of Mg and Cu (Mg: Cu = 55:45, 65:35 and 75:25) were prepared by the methods of sintering and melt-dealloying. The membranes loaded nano-MnOx (MnOx/hp-Ti) were employed as an anode to constitute electrocatalytic membrane reactor (ECMR) for congo red wastewater treatment. The average pore size, porosity, water flux, hardness and electrochemical measurements were explored to evaluate the properties of the hp-Ti membranes. Results showed that the hp-Ti membrane with an atomic ration of Mg:Cu = 75:25 exhibited the best performance. The average pore size, porosity, water flux and hardness obtained from hp-Ti membrane with an atomic ratio of Mg:Cu = 75:25 were 4.72 m, 64%, 5810 L/(h m2 bar) and 20 HV, respectively. The peak current, effective surface area, charge transfer resistance (RCT) and the diffusion coefficient obtained from MnOx/hp-Ti membrane with an atomic ratio of Mg:Cu = 75:25 were 3.59 mA cm−2, 0.965 cm2, 2.6 and 2.8 × 10−5 cm2 s−1, respectively. Further, the decolorization rate and the TOC removal rate obtained from MnOx/hp-Ti membrane with an atomic ration of Mg:Cu = 75:25 for 150 mg l−1 congo red wastewater under the optimum operating conditions (residence time of 12 min, pH of 7 and current density of 0.3 mA cm−2) were up to 99.8% and 63.8%, respectively. The high efficiency obtained are related to the higher specific surface areas, greater electron transfer ability and lower mass transfer resistance of hp-Ti membrane.