Synthesis of Highly Microporous and Hydrophilic Alumina-Pillared Montmorillonite: Water-Sorption Properties (original) (raw)
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Materials Research Bulletin, 2013
Aluminum pillared montmorillonites (Alpill-MMTs) were prepared by two different methods, i.e. conventional intercalation and ultrasonic assisted intercalation, in order to study the effects of preparation methods on their structures and adsorption abilities. In the conventional intercalation, a base-hydrolyzed solution of [AlO 4 Al 12 (OH) 24 (OH 2) 12 ] 7+ , Al 13 7+ , was firstly prepared and then mixed with a suspension of sodium montmorillonite (Na +-MMT) for 24 h with vigorous stirring, resulting in the cation exchange between Al 13 7+ and Na + balancing ions in the MMT interlayers. On the other hand, the high power ultrasonic was used in the second method for creating the Al 13 7+ ions and then in situ intercalating into the MMT suspension, in which the reaction was performed for 20 min. Both Al 13 7+ intercalated MMTs were calcined at 500 8C for 2 h in order to obtain the Alpill-MMTs. The ultrasonic could not only shortening the intercalation process, but also increasing the amount of intercalated Al 13 7+ in the MMT. The ultrasonic synthesized Alpill-MMT (Alpill-MMT-ultra) consisted of mesoporous structure with multiple pore sizes ranging from 3 to 30 nm; therefore, it possessed higher specific surface area and pore volume than the conventionally synthesized Alpill-MMT (Alpill-MMT-str). Adsorption capacities of Alpill-MMTs were investigated using cationic adsorbate, i.e. Basic Yellow 1 (BY1). The highest adsorption capacities were respectively about 95 and 81 mg/g for the Alpill-MMTultra and Alpill-MMT-str, when using initial BY1 concentration of 2000 mg/L. The Alpill-MMT-ultra showed higher efficiency for BY1 removal than the Alpill-MMT-str even after thermal regeneration. The adsorption kinetics of both Alpill-MMTs for BY1 removals were found to follow a pseudo-second-order model, while their adsorption data corresponded to Langmuir isotherm. These results indicated the competency of Alpill-MMTs as the adsorbents for treatment of wastewater containing cationic dye.
Factors affecting the preparation of alumina pillared montmorillonite employing ultrasonics
Microporous and Mesoporous Materials, 2000
In the preparation of alumina pillared clays, the intercalation step is shown to be completed within a few minutes using ultrasonics, and such materials show enhanced textural properties and improved thermal stability. The role of ultrasonics and various preparative parameters that govern the preparation of alumina pillared montmorillonite are presented. This includes the effect of exchangeable cations (Na, Ca, La), three different pillaring precursors, the concentration of pillaring species, and the concentration of the clay in suspension. It is shown that the exchangeable cations and their mode of binding influence the diffusional rates of the pillaring species. When different pillaring precursors are employed, not much variation in the textural properties of pillared clays is noticed. However, their optimum concentration is essential. It is also observed that this method can handle a concentrated clay suspension for pillaring with alumina. From the kinetics of calcium exchange experiments during pillaring, it was observed that the exchange under conventional conditions is completed instantaneously, while under ultrasonic treatment only 26% of Ca2+ exchange took place instantaneously and further exchange occurred only after ultrasonic treatment. From these observations, it is proposed that the role of ultrasonics in the present synthesis is the acceleration of diffusion of the intercalating aluminium pillaring species followed by an ion exchange process.
Synthesis and characterization of Al-pillared montmorillonite in presence of Mn(II)
Applied Clay Science, 2011
The possibility of substituting aluminum in the Keggin tridecamer [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7+ by Mn(II) has been investigated and then the obtained polycation has been used as pillars for smectite. Pillaring solutions are prepared by a slow and partial hydrolysis of Al(III)-Mn(II) aqueous solutions with different Mn/(Al + Mn) molar ratio (r = Mn/(Al + Mn) = 0, 1/13, 2/13 and 3/13) and examined by 27 Al NMR spectroscopy. Powder Xray diffraction (XRD), physisorption of N 2 , chemical analysis and scanning electron microscope analyses (SEM) are used to study the precipitated sulfate salts and/or pillared clay minerals. This study reveals the absence of MnAl 12 species in the pillaring solution. The crystal system of the obtained Al 13 -SO 4 salt is cubic (tetrahedral particles) in absence of Mn(II) and monoclinic (plate particles) in presence of Mn(II). When r is equal to 3/13, in addition to the monoclinic phase, an amorphous phase takes place. The intercalation process of montmorillonite is only disturbed, when r is equal to 3/13, because of the presence of a high polymeric aluminum phase.