Acid resistant PVDF based copolymer alkaline anion exchange membrane for acid recovery and electrodialytic water desalination

Fabrication, characterization and electrochemical analysis of a polyvinylidene fluoride plus zeolite embedded manganese phosphate composite ion exchange membrane

Nanocomposite ion exchange membranes have significant potential in water purification, especially in desalination. In this study, a novel polyvinylidene fluoride and zeolite nanocomposite membrane, embedded with manganese phosphate (PVDF+Ze@MP), was prepared via the sol-gel method. This membrane demonstrated excellent ion exchange properties, and thermal, mechanical, and chemical stability. It showed resilience in both acidic and basic environments, with no visible degradation, and maintained a thickness of 0.085 cm and a water uptake of 0.070%. The structural configuration of PVDF+Ze@MP was ascertained by SEM, XRD, and FTIR, whereas the thermal properties were examined using TGA analysis. Electrochemical analysis, based on the Teorell-Meyer-Sievers (TMS) model, revealed that charge density significantly influenced ion transport and separation efficiency. The membrane exhibited high cation selectivity, with the membrane potential increasing as the electrolyte concentration decreased, indicating its ability to selectively transport specific ions. Additionally, performance metrics for mobility ratio, transport number, and membrane potential followed the trend KHCO3 < NaHCO3 < KCl < NaCl except for fixed charge density, which followed the reverse order highlighting the membrane's adaptability for efficient ion separation. The novelty of this work lies in the synergistic integration of PVDF, zeolites, and manganese phosphate to create a composite membrane with enhanced stability and selective ion exchange performance, making it a strong candidate for challenging water treatment applications. With superior electrochemical properties, low fouling behavior, and robust thermal and mechanical stability, this membrane holds strong potential for practical implementation in desalination and ion exchange processes.

Recent advancements in the synthesis of anion exchange membranes and their potential applications in wastewater treatment

Water treatment procedures are increasingly utilized for resource recovery and wastewater disinfection, addressing the current challenges of clean water depletion and wastewater management. Various pollutants, including dyes, acids, pharmaceuticals, and toxic heavy metals have been released into the environment through industrial, domestic, and agricultural activities, posing serious environmental and public health risks. Addressing these issues requires the development of more effective waste treatment processes. Membrane-based treatment technologies offer significant advantages, including high efficiency, versatility, and cost-effectiveness, making them a promising solution for mitigating the impact of these pollutants. In view of this, the potential of ion exchange membranes (IEMs) is continuously increasing due to their advanced characteristics compared to conventional techniques. Anion exchange membranes (AEMs), a special class of IEMs, selectively allow anions to pass through their pores due to the positive charge on their surface. This selective passage aids in resource recovery and removing specific types of pollutants. This review covers preparation methods, modification techniques, and classification of AEMs. It offers a practical classification based on the method of synthesis and structural properties of AEMs. The water-based applications of AEMs including, electrodialysis, diffusion dialysis, and electro-electrodialysis for various wastewater treatments such as heavy metal recovery, dye removal, pharmaceutical removal, and acid separation, have been discussed in detail. Additionally, the effect of various operational parameters on the performance and SWOT (strengths, weaknesses, opportunities, and threats) analysis of AEMs in effluent treatment are presented. The review provides detailed insights into the current status, challenges, and future directions of AEM-based technologies, offering suggestions for future advancements.

Valorization of Seawater Reverse Osmosis Brine by Monovalent Ion-Selective Membranes through Electrodialysis

This paper proposes the use of monovalent selective electrodialysis technology to concentrate the valuable sodium chloride (NaCl) component present in seawater reverse osmosis (SWRO) brine for direct utilization in the chlor-alkali industry. To enhance monovalent selectivity, a polyamide selective layer was fabricated on commercial ion exchange membranes (IEMs) through interfacial polymerization (IP) of piperazine (PIP) and 1,3,5-Benzenetricarbonyl chloride (TMC). The IP-modified IEMs were characterized using various techniques to investigate changes in chemical structure, morphology, and surface charge. Ion chromatography (IC) analysis showed that the divalent rejection rate was more than 90% for IP-modified IEMs, compared to less than 65% for commercial IEMs. Electrodialysis results demonstrated that the SWRO brine was successfully concentrated to 14.9 g/L NaCl at a power consumption rate of 3.041 kWh/kg, indicating the advantageous performance of the IP-modified IEMs. Overall, the proposed monovalent selective electrodialysis technology using IP-modified IEMs has the potential to provide a sustainable solution for the direct utilization of NaCl in the chlor-alkali industry.