Universal solution to the membrane selectivity challenge: Separation merit and efficiency

Membrane technology holds immense potential across multiple industries, offering sustainable solutions for challenging separations by reducing energy demand and transitioning from thermal to electrical energy. The inherent diversity of membrane technology results in various transport scenarios and phenomena, rendering robust process evaluation and optimization challenging. Addressing this problem, we formulate the cascading selectivity principle (CSP), a universal concept applicable across all membrane separation types, including gas, liquid, and particle filtration. Introducing a distinction between primary and secondary permselectivity, the CSP provides a theoretical basis for novel efficiency indices. We also present the first highly versatile selectivity merit descriptors for true membrane cross-comparison. We demonstrate the advantages of the novel descriptors through a series of real-life nanofiltration, ion separation, gas separation, membrane reactor, and ultrafiltration examples. Facilitated by an online calculator tool, this work offers a standardized framework for academic and industrial professionals to implement pioneering membrane separation systems efficiently across the multiple disciplines of membrane technology.