Electrochemical abatement of aquatic metoprolol by porous foam-titanium based metal oxide anodic membranes

Electrochemical membrane filtration (EMF) is a promising advanced oxidation technology for eliminating aquatic refractory pharmaceuticals. In this work, three porous foam-titanium based metal oxide (MOx) anodic membranes were prepared for comparison of their effectiveness against the model pharmaceutical pollutant metoprolol. The electrooxidation efficiencies of metoprolol by all flow-by operated anodic membranes were found to be elevated with increasing charging voltage and decreasing electrolyte solution pH, in which the PbO2 membrane exhibited more efficient metoprolol degradation efficiency over SnO2 and RuO2 membranes. At the chosen charging voltage of 2 V and electrolyte solution pH 7, compared to the flow-by mode, the higher total organic carbon (TOC) removal and less electrical energy consumption was achieved by the flow-through operated PbO2 membrane, ascribed to the enhanced mass-transfer of metoprolol and its intermediate by-products toward the anode surface. The physisorbed and free HO• produced by PbO2 membrane were found to be the key oxidants accounting for metoprolol degradation, which induced the transformation of metoprolol by attacking its benzene ring and side chains. Apart from the capacity for detoxifying metoprolol-containing influent, PbO2 membrane also exhibited favorable stability in flow-through mode. The study provides an effective strategy for the electrochemical remediation of pharmaceutical-polluted water and wastewater.