Adsorption of n-Aliphatic Alcohols from Dilute Aqueous Solutions on RNH₃-Montmorillonites. III. Interlamellar Aggregation of the Adsorbate

Abstract

Abstract--The large amount of water in the interlamellar space of alkylammonium montmorillonites in aqueous solutions is not fixed by intercalated hexanol or octanol. The hydration of the NH3+-group and the filling of the empty spaces between the carbon chains are responsible for this phenomenon. Hydrogen bonds between the alcohols and the ammonium groups reduce the enthalpy of solution of hexanol and octanol in the interlamellar region at infinite dilution to + 17.6 and + 12.7 kJ/mole, respectively. Selfassociation of the alcohols further diminishes the enthalpy of solution at higher alcohol concentration. The interlamellar fixation of the RNH3 cations prevents a micellization as has been obtained in bulk solutions. At a given alcohol concentration smectic type aggregates, i.e., double layers of alcohol molecules, appear as shown by an increase of the basal spacing of the organo-clay complexes. The aggregate formation is favored by a longer chain length of both the cation and the alcohol. Key Words--Adsorption, Alcohol, Alkylammonium cations, Intercalation, Micellization, Montmorillonire. Samenvatting--Het hoge watergehalte van de interlamellaire faze van alkylammonium-montmorillonieten in waterige oplossing is niet gefixeerd door de binnenkomende hexanol of oktanol. De hydratatie van de NH3+-groep en het opvullen van de ruimtes tussen de koolwaterstofketens zijn er verantwoordelijk voor. Bij oneindige verdunning reduceren waterstotbruggen tussen alkoholen en ammoniumgroepen de oplossings-enthalpie van respektievelijk hexanol en oktanol in de interlamellaire raze tot + 17,6 en 12,7 kJ/mol. Bij hogere alkoholkoncentratie vermindert deze oplossings-enthalpie verder door associatie van de alkoholen. De interlamellaire fixatie van RNH3 kationen verhindert her miceUisatiefenomeen zoals het zich in bulk oplossingen voordoet. Bij een bepaalde alkoholkoncentratie duidt een verhoging van de basisafstand van de organo-kleikompleksen het optreden aan van aggregaten van het smektiet type, d.i. een dubbellaag van alkohol molekulen. Deze aggregaat vorming wordt bevorderd door een langere keten van zowel het kation als van de alkohol.

Organic Pillared Clays

“…The interlayers distance also is influenced by the presence of organic solvents, e.g., higher alcohols. An endothermal Van der Waals expansion energy of organic modified smectites was derived from these results to be around 5 kJ per mol of CH 2 units (28)(29)(30).…”

Adsorption of crude oil on anhydrous and hydrophobized vermiculite

“…Taking into account their adsorption ability, clay minerals can be successfully hydrophobized with cationic surfactants [5]. Such hydrophobized matrices can be employed to promote the interlayer adsorption of many organic species, such as 1-pentanol [6].…”

TiO2-Based Photocatalytic Degradation of 2-Chlorophenol Adsorbed on Hydrophobic Clay

“…Selective adsorption of various organic compounds from aqueous solutions has been extensively studied; on the basis of these results, the adsorption of organic compounds on clay minerals may be determined (26)(27)(28)(29). A wide range of organic components are very efficiently adsorbed on clay minerals hydrophobized with cationic surfactants: the organophilic bentonites (30)(31)(32)(33).…”