Electro-catalytic membrane reactors for the degradation of organic pollutants – a review
The occurrence and accumulation of persistent organic pollutants (POPs) in wastewater represent global challenges since they are bio-refractory pollutants, which cannot be remediated with classical wastewater treatment systems. Amongst emerging technologies, POPs may be treated by electrochemical advanced oxidation processes to remediate selective contaminants through specific degradation pathways. Although dense anodic electrodes have been extensively employed in such electrochemical processes, the surface and bulk properties of such electrodes limit the mass transfer and degradation rates of these pollutants, opening the route to the application of porous electrode materials, referred to as electro-catalytic membrane reactors (ECMRs). The application of ECMRs facilitates the degradation of these compounds, while also simultaneously allowing for fine filtration operation. This paper is focussed on discussing the recent development and preparative methods of anodic membranes, and the catalytic performance of these membranes for degradation of organics in wastewater. The effect of physicochemical characteristics such as the surface area, porosity, and morphology on the catalytic performance of the membranes is elaborated. A summary of the most relevant electro-catalytic membrane materials and parameters, which contribute to the electrocatalytic process optimisation, is presented, to investigate the impact of the material properties on the catalytic rate of the reaction for efficient output. Therefore, this aims at critically assessing the properties of electrocatalytic membranes used in ECMR, mechanisms involved in degradation of organic pollutants and optimal parameters to carry out electrocatalytic reactions, which helps in identifying and bridging the research gaps for the large scale employment of ECMRs in wastewater remediation.