Separation of organic ions from aqueous solutions by membrane capacitive deionization

•Membrane capacitive deionization (MCDI) can be used to separate permanently charged organic cations or anions such as ionic liquids that can differ greatly in polarity and size.•The separation efficiency depends on the symmetry of mobility of the respective anion and cation.•Supports the suitability of MCDI for pollutant removal from (waste)water. Persistent and mobile organic chemicals are a growing concern for the management of water resources. Here, we propose membrane capacitive deionization (MCDI) for effective separation and selective recovery of these chemicals. Using a simple MCDI process, with activated-carbon-cloth electrodes, we experimentally demonstrate the feasibility of MCDI for adsorbing permanently charged ionic liquids (ILs) and ionogenic chemicals (IOCs) such as perfluorooctanoic acid (PFOA) and diclofenac. The total salt adsorption capacity (SAC) of ILs and IOCs is between 5.12 and 8.83 µmol/g and is strongly dependent on the symmetry of cation and anion mobilities, as represented by their diffusion coefficients. The system has a low energy consumption of 0.031 kWh/m3, with a productivity of 83.33 L/h/m2. As an example of pharmaceuticals in wastewater we examined diclofenac solution and show a total SAC of 3.03 µmol/g. These results demonstrate the potential of this deionization process for the cleanup of industrial or medical wastewater.