Abstract
Functionalization of the kaolinite (K) interlayer space is challenging. In this work, a new kaolinite-based nanohybridmaterial (K-NI) was successfully synthesized by grafting on the interlayer aluminol surfaces the ionic liquid, 1-(1-methylnaphthyl)-3-(2-hydroxyethyl) imidazolium chloride (NI), using a guest displacement strategy. A substantial increase of the basal spacing (10.8 Å) was obtained. This is a grafted derivative of kaolinite possessing one of the largest d-values. Washing in water for several days and other vigorous treatments such as sonication showed a minor effect on the integrity of the material. FTIR and 13C NMR confirmed the conservation of the structure of the ionic liquid after the grafting. Thermal analysis confirmed the presence of grafted material and was used to estimate the abundance of the grafted ionic liquid (0.44 mole per mole of kaolinite structural formula, (Al2Si2O5(OH)4)). By using cyclic voltammetry, the permeability of a film of K-NI for the bulky ferricyanide ions was demonstrated. The accumulation of nitrophenolate anions was effective (maximum capacity of 190 μmol/g), but was less important than what was expected due to the steric hindrance of the bulky grafted NI. Although the presence of chloride anions reduced the adsorption capacity, the affinity of the modified kaolinite interlayer space for the nitrophenolate anions was demonstrated.
Highlights
Combining the thermal and mechanical stabilities of inorganic materials with the selectivity and specificity of organic groups in organo-inorganic nanohybrid materials results in robust and efficient chemical structures
The band related to the bending vibrational mode of physisorbed water molecules was observed at 1630 cm−1. This band appeared on the spectrum of kaolinite, but with a low intensity, indicating that the chemical modification increased the hydrophilicity of kaolinite as can be seen by the thermal gravimetric analyse (TGA)
The mobility of the counter-anion was previously used for the electroanalysis of anions, with the limitation that large anions could not fit into the confined interlayer space when the grafted organic cation was not large enough [21]
Summary
Combining the thermal and mechanical stabilities of inorganic materials with the selectivity and specificity of organic groups in organo-inorganic nanohybrid materials results in robust and efficient chemical structures. Thesetwo twoeffects effectsstrongly stronglymaintain maintainthe the stacking layers stacking of of thethe layers in in c direction This basis the book-like structure kaolinite[8]. Some some salts salts of of small organic organic anions and a few few dipolar dipolar molecules molecules such as as dimethylsulfoxide dimethylsulfoxide (DMSO) or urea can be directly intercalated between the layers of of kaolinite kaolinite with with substantial substantial expansion expansion of the the interlayer interlayer space, space, and and delamination delamination [9,10] These pre-intercalates pre-intercalates have have been been widely widely used used as as starting starting material for the intercalation of other compounds (alcohols, amino alcohol, polymers, ionic liquids ...) [11,12,13,14,15,16].
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