Key physicochemical characteristics governing organic micropollutant adsorption and transport in ion-exchange membranes during reverse electrodialysis

M Roman,L.H Van Dijk,L Gutierrez,M Vanoppen,J.W Post,B.A Wols,E.R Cornelissen,A.R.D Verliefde

doi:10.1016/j.desal.2019.114084

Abstract

The co-generation of electricity and electrodialysis of seawater in a hybrid system is a promising approach to overcome water scarcity. Reverse electrodialysis harvests energy from the salinity gradient, where seawater is used as a high salinity stream while secondary treated wastewater can be used as a sustainable low salinity stream. Treated wastewater contains organic micropollutants, which can be transported to the seawater stream. The current research establishes a connection between adsorption and transport of organic micropollutants in ion exchange membranes, using a cross-flow stack in adsorption and zero-current experiments. To mimic the composition of treated wastewater, a mixture of nineteen organic micropollutants of varied physicochemical characteristics (e.g. size, charge, polarity, hydrogen donor/acceptor count, hydrophobicity) at environmentally relevant concentrations was used. Depending on the charge, micropollutants develop different types of mechanisms responsible for short-distance interactions with ion-exchange membranes, which has a direct influence in their transport behavior. This study provides a rational basis for the optimization/design of next-generation ion-exchange membranes, in which the permeability toward organic micropollutants should be also included. This investigation highly contributes to understanding the potential hazard posed by organic micropollutants in reverse electrodialysis in seawater desalination systems, where treated wastewater is used as a low salinity stream.

Highlights

The desalination of seawater can provide a steady supply of highquality drinking water [1,2,3]
In a hybrid desalination processes, where Reverse Electrodialysis (RED) is used as a pretreatment step for drinking water production, the reuse of treated wastewater is related with a hazard of organic micropollutants (OMPs) contamination of the seawater stream, which will be the source of drinking water [7]
Based on these observations and the analysis of concentration profiles (Fig. S2, SI), it was concluded that the mechanism of the OMPs adsorption in the ion-exchange membrane (IEM) is dependent on their charge

Summary

Introduction

The desalination of seawater can provide a steady supply of highquality drinking water [1,2,3]. Recent developments in ion-exchange membrane (IEM) technology have allowed electrodialysis (ED) to reach better performances and competitiveness toward other seawater desalination techniques [4]. The energy required for ED could be produced in Reverse Electrodialysis (RED), prior to ED [1]. Reverse electrodialysis is an IEM-based process which harvest energy from a salinity gradient. Seawater is used as a high salinity stream in RED while treated wastewater can be used as a sustainable low salinity stream. In a hybrid desalination processes, where RED is used as a pretreatment step for drinking water production, the reuse of treated wastewater is related with a hazard of OMPs contamination of the seawater stream, which will be the source of drinking water [7]

Objectives

Methods

Results

Conclusion