Effect of pH on the transport and adsorption of organic micropollutants in ion-exchange membranes in electrodialysis-based desalination

In energy-efficient electrodialysis desalination processes, salt ions are transported from seawater (high salinity) to wastewater (low salinity) through ion-exchange membranes. Besides salt ions, also organic micropollutants can be transported from wastewater (high in organics) to seawater (low in organics). The transport mechanisms of organic micropollutants through ion-exchange membranes are complex phenomena, and pH has a tremendous impact on them. Since pH variations in electrodialysis operation are common, it is of crucial importance to investigate its influence on these mechanisms. Therefore, a large pool of nineteen organic micropollutants of various physicochemical characteristics was selected and added to artificial wastewater, at environmentally relevant concentrations. Approximately twenty of these physicochemical properties were statistically analyzed to elucidate the dominant mechanisms affecting adsorption and transport of organic micropollutants as a function of pH. Additionally, the influence of different current densities on the transport of organic micropollutants at different pH conditions was studied. This pH effect has now been investigated for the very first time, leading to essential conclusions on the practical applicability of electrodialysis for seawater desalination. The presented findings advance our understanding of the type of interactions between organic micropollutants and ion-exchange membranes.