Ion exchange: An essential piece in the fabrication of zeolite adsorbents

Abstract

Adsorptive separation, which relies on the size, polarity, and affinity of guest molecules, is an efficient, eco-friendly, and cost-effective method. Zeolite-based adsorbents, known for their uniform pore size and regenerability, have exhibited exceptional performance in many challenging adsorption processes, such as the separation of n-paraffin/i-paraffin and xylene isomers. Ion exchange, as an essential piece in the fabrication of zeolite-based adsorbents, significantly affects overall performance. In this review, we survey the recent key developments and issues within ion exchange research of zeolite-based adsorbents, including the solution pH, solution concentration, ion-exchange cycles, ion-exchange temperature, ion-exchange time, calcination temperature, and discuss the mechanisms of their influence on zeolite adsorption. This review also elaborates on the negative effects of improper ion exchange on incomplete cation exchange, cation migration, collapse of the zeolite structure, and blockage of zeolite pores. Other parameters that lack of research but have been proven to affect ion exchange are also mentioned. We hope to generate interest in the wider community and encourage others to make use of ion exchange in tackling challenges of adsorption separation science and engineering.