![]() Also, adsorption process provides an attractive alternative treatment, especially if the adsorbent is inexpensive and readily available. Īdsorption techniques have gained favor recently due to their efficiency in the removal of pollutants. The former is well suited for a regenerable process, while the latter generally destroys the capacity of the adsorbent. Physical adsorption or physisorption involves van der Waals forces (as in vapor condensation), and retard chemical adsorption or chemisorption, which involves chemical bonding. Two classes of adsorption are identified, physical adsorption and chemical adsorption. ![]() The accumulation per unit surface area is small thus, highly porous solids with very large internal area per unit volume are preferred. The most adsorption processes are of gas–solid and liquid–solid interfaces, with solute distributed selectively between the fluid and solid phases. Īdsorption involves, in general, the accumulation (or depletion) of solute molecules at an interface (including gas–liquid interfaces, as in foam fractionation, and liquid–liquid interfaces, as in detergency). Anionic resins involve quaternary ammonium groups (strongly basic) or other amino groups (weakly basic). In ion exchanger, cation exchange resins generally contain bound sulfonic acid groups less commonly, these groups are carboxylic, phosphonic, phosphinic, and so on. The ion exchanger exhibits permanently bound functional groups of different charge. In ion exchange, ions of positive charge in some cases (cations) and negative charge in others (anions) from the fluid, replace dissimilar ions of the same charge initially in the solid. Ion exchange occurs throughout a polymeric solid, which dissolves some fluid-phase solvent. Those used on a large scale are activated carbon, molecular sieves, silica gel, and activated alumina. These processes involve the transfer and distribution of solutes between a fluid phase and particles.Īdsorbents are natural or synthetic materials of the amorphous or microcrystalline structure. International Union of Pure and Applied Chemistry (IUPAC) endorsed a general classification of zeolites structures, that is, FAU for faujasites, mordenite framework inverted (MFI) for ZSM-5, and mordenite zeolite (MOR) for mordenite.Īdsorption and ion exchange, take advantage of many common features in regard to application in batch and fixed-bed processes for a unified treatment. Nearly 600 known zeolites were discovered. Due to the excellent ion exchange ability and high surface area, natural zeolites, and synthetic zeolites. Several authors studied the use of modified natural zeolite on environmental applications, mainly anions uptake from effluents by adsorption processes. New functional groups may introduce to zeolites through several processes of modification that improve its activity and selectivity on the removal several substances. ![]() Zeolites have in its internal structure cavities and channels interconnected of molecular dimensions, where compensation cations allowing the ion exchange. Natural zeolites are hydrated aluminosilicates compounds with a characteristic three-dimensional structure of tetrahedrons as TO 4 (T = Si, Al, B, Ge, Fe, P, and Co) joined by oxygen atoms, with large pore apertures and pore system that allow the relatively easy exchange of cations between aqueous solutions and intracrystalline sites. Zeolites are classified into two classes, one is natural zeolites, and the other is synthetic zeolites. The specific adsorption and ion exchange properties of zeolites are used in industries, color removal, detergents, toothpaste, and desiccants, whereas their acidity makes them attractive catalysts. The zeolite framework is very open and contains channels and cages, where cations, water, and adsorbed molecules may reside and react. Zeolites form a unique class of oxides, consisting of microporous, crystalline aluminosilicates that can be found in nature, or synthesized artificially.
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