Sustainable and scalable K+/Na+ selective cation exchange membranes from hot-pressed PVA-PVS saloplastics and modification methods
- Persons involved: Hanxiao Zhou (PhD Candidate), Wiebe de Vos (Promotor), Saskia Lindhoud (Co-promotor)
- Duration: 2024-2028
- Funding: China Scholarship Council (CSC) Scholarship
Introduction
Within electrochemical cells, ion exchange membranes (IEMs) act as separators between the anode and cathode compartments and are used to regulate the transport of ions based on charge exclusion. Some IEMs are also ion selective, not just for anions over cations or vice versa, but for ions of the same charge sign. This includes membranes that allow passage to monovalent ions, but reject multi-valent ions, but even membranes where there is a different selectivity for different monovalent ions. The most researched of these monovalent selectivities is K+/Na+ selective membranes, as they could play an important role in the efficient re-use of water in agriculture. As plant selectively take up K+ ions, Na+ ions will accumulate in the water intended for re-use and ultimately this has a negative impact on the plant growth. Selectively removing the Na+ ions, while keeping the K+ ions in water would be a way to circumvent this.
Key words
Ion exchange membranes, hot-pressing, saloplastics, strong-weak polyelectrolyte, polyelectrolyte complex
Technological/Scientific challenges
It has recently been demonstrated that sustainable and highly stable ion exchange membranes can be produced through the hot-pressing of non-stoichiometric polyelectrolyte complexes, resulting in so-called saloplastic membranes. This simple approach facilitates the fabrication of IEMs using saltwater, thereby eliminating the reliance on toxic solvents typically associated with conventional membrane production methods. Furthermore, saloplastic materials are recyclable which further highlights the sustainability of this approach. Finally, one specific type of saloplastic, PSS/PVAm, has shown an interesting ionic selectivity for K+/Na+.
Objectives
The objective of this project is to enhance the K+/Na+ selectivity of PSS/PVAm based saloplastic cation exchange membranes through changing the external pH and adding the chemical crosslinking.
