Synthesis and Investigation of Properties of Composite Ion-Exchange Membranes with Acidic Cerium Phosphate Particles

The electrodialysis process is the most well-known and industrially important electromembrane process. It is used in various applications, including water treatment, concentration, the production of acids and alkalis, and the desalting of foodstuffs. In a mixture of electrolytes, membranes mainly transfer ions with a larger sign of charge, leaving the singly charged ions in solution. One method to enhance selectivity for single-charged ions is to create a barrier on the membrane surface that impedes the permeation of multi-charged ions in the membrane. The principal drawback of this methodology is the necessity to enhance the ionic resistance of the system or to reduce the desalting current limit. Composite membranes comprising a variety of nanomaterials are remarkable and prospective in the search for barrier-free methods to enhance selectivity for single-charged ions. According to the available literature, these materials exhibit enhanced ionic conductivity, selectivity, mechanical strength, and stability. One of the most promising dopants for the fabrication of composite membranes with a given selectivity is metal phosphates. In this class of compounds, cerium phosphates are worthy of particular mention. They demonstrate a high ion exchange capacity, reaching 5 mg-eq/g, and high chemical stability in acidic and neutral medium. This study describes the impact of cerium phosphate nanoparticles on the transport properties of commercial anion-exchange membranes and examines their specific selectivity for the transport of single-charged ions. The incorporation of nanosized amorphous cerium phosphate into anion-exchange membranes resulted in enhanced selectivity towards chloride anions in the sulfate-chloride pair. This study represents the first demonstration of the potential for inorganic nanoparticles to enhance the stability of ion-exchange membranes against surface fouling.