The filtration membrane with ultra-high ion selectivity is of vital importance for the high-precision separation of impurities in water. It can improve the water recovery rate in the seawater desalination system. Nanofiltration membranes have great uses in water purification, brine electrolysis, and high-quality water production and treatment. So far, researchers have carried out extensive research work on improving the performance of nanofiltration membranes. The common method is to reduce the thickness of the separation layer, thereby increasing the permeability of the membrane to improve the energy efficiency of the separation process. However, this type of method always retains specific ions and certain solutes at a high rejection rate. Therefore, designing high-performance nanofiltration membranes that exceed the permeability-selectivity upper limit of current polymer membranes is essential to achieve high selectivity and high permeability.
The Indian CSIR-Central Institute of Salt and Marine Chemistry Santanu Karan et al. reported that by maintaining the stoichiometric balance of the interface to precisely control the kinetics of the interfacial polymerization reaction, they developed a polyamide composite nanometer with super ion selectivity and high water permeability. Filter membrane. Maintaining kinetically favorable stoichiometric equilibrium conditions can avoid the formation of aggregate pores in the nanomembrane and the formation of tiny network pores with high negative surface charges. The degree of cross-linking of the nanomembrane is controllable, and the thickness is about 7 nanometers, which improves the water permeability. The super ion selective membrane shows a rejection rate of 99.99% for divalent salt (Na2SO4). The selectivity of the nanocomposite membrane exceeds the permeability-selectivity upper limit of the newly reported nanofiltration membrane, and is one or two orders of magnitude higher than that of the commercially available membrane with a pure water permeability as high as 23 L/m2/h/bar. The research was published in Advanced Functional Materials as a paper entitled "Ultraselective and Highly Permeable Polyamide Nanofilms for Ionic and Molecular Nanofiltration".