How to Improve Selectivity of a Material for Adsorptive Separation Applications

Abstract

This chapter analyzes how adsorption selectivity of natural and synthetic materials was improved with different approaches, particularly for their adsorptive water treatment applications. To explain this approach, it includes some of the frequent modification in natural materials like activated carbon, natural zeolite, natural clay, biopolymer (like chitosan, cellulosic waste), sand, and some of the post-synthetic modification in materials like metal oxides, mesoporous silica, and metal-organic frameworks (MOFs). Herein, different types of modification approaches applied to an individual category of material were reviewed, systematically. The effects of these modifications on surface area, porosity, adsorption capacity, and surface chemistry were discussed in terms of change in their adsorption selectivity. For instance, it comprises impacts of oxidation, sulfurization, nitrogenation, and coordinate ligands on the surface properties of activated carbon. Similarly, the role of metal ion, surfactant cations, metal oxides, and polymers on the change in ion exchange properties of zeolites was explained. The change in physicochemical properties of clay on thermal treatment and treatment with ionic and organic species was compared. Likewise, the adsorption selectivity of the clay-based composite with different polymers and effects of modification of chitosan, agricultural by-products, sand, silica, metal oxides, and MOFs were deliberated. In the end, some of the future challenges in the field of adsorption selectivity are discussed.