Clay Minerals—Ionic Liquids, Nanoarchitectures, and Applications

Abstract

Clay minerals, whose world resources are extremely large, have the potential to be more exploited as the basis for functional materials. Of interest are their interactions with ionic liquids (ILs). These compounds have found a large number of applications in the last few decades due to unique properties, such as low vapor pressure, high thermal stability, and remarkable solvation abilities. In the case of the swelling smectites, the organic cation of ILs can replace interlayer cations and find applications in the preparation of nanocomposites. This feature article is mainly focused on kaolinite, a nonswelling 1:1 phyllosilicate, whose layers are essentially neutral. Consequently, the intercalation of ILs involves both cation and anion. The organic cations can be designed to bear hydroxyl groups that will react with the aluminol internal surface of kaolinite, resulting in ionic liquids not only intercalated but also grafted. The resulting nanohybrid materials are characterized by a fixed, rigid, constrained 2D structure, whose dimension can be tuned by the size of the organic cation, whereas the anion is exchangeable. These materials are used for sensing applications such as the specific detection of anions as well as their quantitative analysis. They are also used as catalyst support for nanoparticles.

Kaolinite Clay Mineral Reactivity Improvement through Ionic Liquid Functionalization

“…If these processes occur with some delay, the expanded layers will collapse and the parent kaolinite regenerated. Using this approach, several compounds were successfully intercalated and used for several environmental, energy and medical applications As other clay minerals, kaolinite displays functional groups (silanol (Si‐OH) and mainly aluminol (Al‐OH) functions) on particles basal surfaces and borders that can be functionalized.…”

“…If these processes occur with some delay, the expanded layers will collapse and the parent kaolinite regenerated. Using this approach, several compounds were successfully intercalated and used for several environmental, energy and medical applications …”

“…Using this approach, several compounds were successfully intercalated and used for several environmental, energy and medical applications. [29,36,37] -As other clay minerals, kaolinite displays functional groups (silanol (Si-OH) and mainly aluminol (Al-OH) functions) on particles basal surfaces and borders that can be functionalized. For several clay minerals, these reactive sites are scarce.…”

Sensitive Amperometric Determination of Thiocyanates at Ionic Liquid Nanohybrid Kaolinite Modified Glassy Carbon Electrode

“…The functional groups are precisely selected according to expected favourable interaction with targeted analytes to be detected, in order to improve the sensitivity and the selectivity of the sensors [25]. Among clay minerals, kaolinite has been scarcely used compared to smectites for the synthesis of organoinorganic hybrid materials because of its lower reactivity [26][27][28]. This is due to its very low cation exchange capacity and its non-swelling nature resulting from a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 permanent dipole and a dense hydrogen bonds network that strongly hold together adjacent kaolinite layers [26][27][28].…”

“…Among clay minerals, kaolinite has been scarcely used compared to smectites for the synthesis of organoinorganic hybrid materials because of its lower reactivity [26][27][28]. This is due to its very low cation exchange capacity and its non-swelling nature resulting from a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 permanent dipole and a dense hydrogen bonds network that strongly hold together adjacent kaolinite layers [26][27][28]. Recently, it was shown that, using a kaolinite preintercalate followed by a guest-displacement strategy, it was possible to functionalize the very abundant interlayer surface aluminols by alcohols of some specific organic compounds to yield robust and stable organo-kaolinite hybrids [25,27,[29][30][31][32][33].…”