Sustainable K+/Na+ monovalent-selective membranes with hot-pressed PSS-PVA saloplastics

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Abstract

Monovalent selective cation exchange membranes could play an important role in balancing the K+/Na+ ratio in agricultural feed streams to prevent the toxic effects of excess Na+ in the plant and soil systems, especially in greenhouses and dry areas. A polyelectrolyte complex of polystyrenesulfonate and polyvinylamine in the monomer ratio 1:2.5 is hot-pressed to form a dense saloplastic. The plastic takes up 42% w/w water when equilibrated, while ion-exchange capacity measurements show that it is negatively charged with a net ion-exchange capacity of 1.1 ± 0.4. Resistance measurements show a very promising preferred conductivity for K+ over Na+. This was confirmed by measuring K+ and Na+ transport through the membrane under diffusive conditions from an aqueous mixture of KCl and NaCl. Commercial membranes show resistance-based selectivities of 1.32 ± 0.1 to 1.19 ± 0.1, and diffusion based selectivities of 0.99 ± 0.1 to 0.78 ± 0.1. In contrast, the selectivities for the newly developed saloplastic membrane were 1.80 ± 0.33 for the resistance-based selectivity while the diffusion-based selectivity was 1.91 ± 0.1. The procedure is green as toxic solvents and/or halogenating agents, typically used to make cation exchange membranes, are not needed. This work thus highlights how monovalent selective membranes with a relevant K+/Na+ selectivity can be prepared by a simple and sustainable hot-pressing approach.

Original languageEnglish
Article number120463
JournalJournal of membrane science
Volume652
DOIs
Publication statusPublished - 15 Jun 2022

Keywords

  • Hot-press
  • Ion-exchange membrane
  • Monovalent-selective
  • Polyelectrolyte complex
  • Saloplastic
  • UT-Hybrid-D

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