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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - E-motion (Electro-motion for the sustainable recovery of high-value nutrients from waste water)

Teaser

Summary

Current water treatment technologies are mainly aimed to improve the quality of water. High-value nutrients, like nitrate and phosphate ions, often remain present in waste streams. Electro-driven separation processes offer a sustainable way to recover these nutrients. Ion-selective polymer membranes are a strong candidate to achieve selectivity in such processes.

The aim of E-motion is to chemically modify porous electrodes with membranes to introduce selectivity in electro-driven separation processes. New, ultrathin ion-selective films will be designed, synthesized and characterized. The films will be made by successively adsorbing polycations and polyanions onto the electrodes. Selectivity will be introduced by the incorporation of ion-selective receptors. The adsorbed multilayer films will be studied in detail regarding their stability, selectivity and transport properties under varying experimental conditions of salinity, pH and applied electrical field, both under adsorption and desorption conditions.

The first main challenge is to optimize and to understand the film architecture in terms of 1) stability towards an electrical field, 2) ability to facilitate ion transport. Also the influence of ion charge and ion size on the transport dynamics will be addressed. The focus of E-motion is set on phosphate ions, which is rather complex due to their large size, pH-dependent speciation and the development of phosphate-selective materials. Theoretical modelling of the solubility equilibria and electrical double layers will be pursued to frame the details of the electrosorption of phosphate.

E-motion represents a major step forward in the selective recovery of nutrients from water in a cost-effective, chemical-free way at high removal efficiency. The proposed surface modification strategies and the increased understanding of ion transport and ionic interactions in membrane media offer also applications in the areas of batteries, fuel cells and solar fuel devices.

Work performed

Project team has been built: 3 PhD students, 1 postdoctoral researcher and technical assistance. Equipment has been purchased (Quartz Crystal Microbalance) and installed and a H-cell + several Capacitive Deionization (CDI) set-ups have been built and installed in our labs. First papers got accepted Phys. Rev. Applied and Desalination and currently we have 1 manuscript submitted and 3 manuscripts in preparation.

Polymers have been used to modify electrodes/membranes, resulting in a switch from magnesium/sodium selectivity to sodium/magnesium selectivity. Furthermore, intercalation electrodes made from nickel-based Prussian-blue Analogues (PBA) showed a monovalent/bivalent selectivity of 20+.

Final results

Polymer-coated electrodes/membranes will be further investigated in detail, not only in terms of the layer-by-layer build-up, but also in terms of the further application in ion selectivity and recovery. Also, alternative intercalation materials will be explored to achieve ion selectivity. The results on polymer-coated electrodes/membranes and intercalation materials will be extended to phosphate.