Abstract
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.
Highlights
Organic micropollutants (OMP) comprise a broad spectrum of chemicals of anthropogenic origin, e.g., pharmaceuticals, pesticides, personal care products, or plasticizers
The protons were transported from the anode compartment through the outer cationexchange membranes (CEM) into the ion-exchange membrane (IEM) stack
Low system pH accelerates the adsorption of OMPs in IEMs, which efficiently prevents their transport toward seawater
Summary
Organic micropollutants (OMP) comprise a broad spectrum of chemicals of anthropogenic origin, e.g., pharmaceuticals, pesticides, personal care products, or plasticizers. The direct production of drinking water from wastewater is currently beyond reach due to the presence of OMPs, legal regulations, and social acceptance. Developments in ion-exchange membrane (IEM) technology have allowed electrodialysis (ED) to reach better performance and competitiveness towards other seawater desalination techniques [14]. Hybrid seawater desalination systems have gained increasing attention as cost-effective processes to produce drinking water from seawater. For this reason, the reuse of treated wastewater as a low-salinity stream in electrodialysis (ED)-based processes constitutes a promising approach for the pre-desalination of seawater and subsequent production of drinking water [14,15]. The potential transport of OMPs from wastewater to seawater channels through ion exchange membranes (IEM) is not yet fully understood and requires additional research efforts
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