Organoclays in Water Cause Expansion That Facilitates Caffeine Adsorption

Abstract

This study investigates the adsorption of caffeine in water on organically modified clays (a natural montmorillonite and synthetic saponite, which are smectite group of layered clay minerals). The organoclays were prepared by cation-exchange reactions of benzylammonium and neostigmine with interlayer exchangeable cations in the clay minerals. Although less caffeine was uptaken on neostigmine-modified clays than on raw clay minerals, uptake was increased by adding benzylammonium to the clays. The adsorption equilibrium constant was considerably higher on benzylammonium-modified saponite (containing small quantities of intercalated benzylammonium) than on its montmorillonite counterpart. These observations suggest that decreasing the size and number of intercalated cations enlarges the siloxane surface area available for caffeine adsorption. When the benzylammonium-smectite powders were immersed in water, the intercalated water molecules expanded the interlayer space. Addition of caffeine to the aqueous dispersion further expanded the benzylammonium-montmorillonite system but showed no effect on benzylammonium-saponite. We assume that intercalated water molecules were exchanged with caffeine molecules. By intercalating benzylammonium into smectites, we have potentially created an adaptable two-dimensional nanospace that sequesters caffeine from aqueous media.

Effect of surfactant molecular structure on perchlorate removal by various organo-montmorillonites

“…Theoretically, Mt has a large specific surface area (700-800 m 2 /g) which depends on the amount of internal surface exposed by expansion in aqueous solution (Zadaka et al, 2010). The ideal surface area of the expanded Mt was assumed to be 750 m 2 /g (Okada et al, 2015). Taking into account the cross-sectional area of benzyldimethylammonium (-BM, 70.5 Å 2 ) and trimethylammonium (-TM, 44 Å 2 ) (Kwolek et al, 2003), the maximum amounts of packed monomolecular adsorption on the Mt surface are 1.77 mmol/g·Mt for C14-, C16-and C18-BM, and 2.83 mmol/g·Mt for C18-TM.…”

“…where q e (mmol/g) is the amount of adsorbed perchlorate per unit mass of organo-Mt for an equilibrium concentration C e (mmol/L) in bulk solution, q 0 (mmol/g) is the maximum monolayer adsorption capacity, and b (L/mmol) is the Langmuir constant, which reflects the binding energy between adsorbent and adsorbate (Okada et al, 2015). The data show perfect fits to the model with R 2 N 0.99, which indicates that perchlorate is adsorbed on the surface of the composites by the monolayer model.…”

“…The -BM head group was stronger than the -TM head group, and slightly better than the -PY head group in terms of the adsorption capacity of the modified Mt adsorbent. The π-π interactions of pyridine or benzene rings might enhance the loading of counter ion-accompanying surfactant and resulted in greater q 0 (Praus et al, 2006;Okada et al, 2015). Compared with C18-TM/Mt, 2C18-DM/Mt showed greater q 0 (Table S1).…”

Changes the Structure and Caffeine Adsorption Property of Calcined Montmorillonite

“…For this reason, the material is often used as a cation exchanger in a water system. On the one hand, nonionic organic compounds are thought to be adsorbed at different sites depending on factors such as the polarity of the chemical compound [6], [7]. A chemical compound that can get into the layers is believed to be adsorbed by its intercalation between the layers [8], [9].…”

Crystal architectures of a layered silicate on monodisperse spherical silica particles cause the topochemical expansion of the core-shell particles

“…[16,23] The cation exchange capacity (CEC), which directly correlates with the negative-layer charge density, is an important determiner of the distance between adjacent interlayer cations (the spatial density). Achieving an appropriate distance can allow the material to act as a molecular sieve for nonionic organic compounds [24][25][26][27][28][29] or to improve the photofunctions of photoactive molecules. [30][31][32][33][34] It has therefore been recognised that one of the advantages smectites offer (in addition to the many other important properties of smectites and their intercalation compounds) is that the CEC can be varied in order to control the spatial distribution of organic moieties.…”