On the pillaring and delamination of smectite clay catalysts by polyoxo cations of aluminum

Pinnavaia, Thomas J.; Tzou, Ming-Shin; Landau, Steven D.; Raythatha, Rasik

doi:10.1016/0304-5102(84)85080-4

Cited by 342 publications

(130 citation statements)

References 22 publications

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“…The exceptional uptake at high salt concentration can be explained by the natural tendency of the MB to form dimmers, trimmers and superior macroagregates (27) and a special morphology of the pillared clay (28). Pinnavaia et al (28) had proposed a pillared clay model with large volumes of mesoporosity ( Figure 16) created after the drying of the flocculated polyoxoaluminium-clay system. Our pillared clay mesoporosity (41% - Table 1) seems to match the size of the aggregates of the MB molecules in the region of high salt concentration, resulting in the record amount of adsorbed MB.…”

Section: Methylene Bluementioning

confidence: 99%

Improvement in the Adsorption of Anionic and Cationic Dyes from Aqueous Solutions: A Comparative Study using Aluminium Pillared Clays and Activated Carbon

Aguiar

Bezerra

Siqueira

et al. 2014

Separation Science and Technology

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The aim of this work was evaluate the adsorption properties of anionic dye Reactive Black 5 (RB5) and cationic dye Methylene Blue (MB) from salted aqueous solution using natural clay, aluminum pillared clay (Al-PILC) and activated carbon. The textural properties of the materials were obtained by N 2 adsorption at 77 K and structural properties of natural and pillared clays were determined by Xray diffraction. The effect of pH, contact time, initial concentration of dye and influence of the addition of NaCl were evaluated by batch adsorption. Adsorption isotherms of Al-PILC, in different salt concentration, were compared with natural clay and activated carbon. The adsorption isotherms were well fitted by Langmuir and Langmuir-Freundlich models. The process of pillaring only improved the adsorption of the anionic dye RB5. Depending on the system adsorbent/adsorbate analyzed, the salt concentration can either help or hinder dye adsorption. We found that a special morphology formed during the process of pillaring greatly increased adsorption of the MB cationic dye in the range of high salt concentrations. This unexpected result may help in developing new pillarization strategies to treat effluents with high salt content.

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Section: Methylene Bluementioning

confidence: 99%

Improvement in the Adsorption of Anionic and Cationic Dyes from Aqueous Solutions: A Comparative Study using Aluminium Pillared Clays and Activated Carbon

Aguiar

Bezerra

Siqueira

et al. 2014

Separation Science and Technology

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“…In order to satisfy this requirement, care needs to be taken in choosing an appropriate method of drying the sample. PILCs which have been freeze-dried may be delaminated (Pinnavaia et al, 1984) or may even be completely X-ray amorphous and, in contrast to smectites and other clays, the delamination may be irreversible. This delaminated state is preferred by many workers because it confers favourable catalytic properties, but it is less suitable for structural studies and investigations of possible magnetic ordering.…”

Section: Characteristics Of Metal Oxide Pillared Claysmentioning

confidence: 99%

Preparation and characterization of iron oxide pillared montmorillonite

et al. 1988

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A B S T RA C T : Pillared smectites in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties. Several possible routes by which such materials might be made have been investigated, namely intercalation of hydroxy-Fe(III) polycations, mixed hydroxy-Fe(III)/Al polycations, phenanthroline-Fe(II) cations, and trinuclear Fe(III) acetato cations into Na-montmorillonite. Only the last of these yielded a pillared clay (PILC) on calcination. The products have been characterized using X-ray powder diffraction and 57Fe M6ssbauer spectroscopy. The precursor Fe-PILC has a d-spacing of 21 A and expands to 23 A on solvation with glycol. The calcined Fe-PILC has a d-spacing of 19 A (gallery height 9.4 A) and does not expand with glycol, confirming cross-linking of the layers. From M6ssbauer spectra at 4.2 K it is estimated that there are of the order of some hundred Fe atoms per pillar.Pillared or cross-linked smectites, in which the interlayer is converted into a two dimensional zeolite-like structure, have recently attracted much interest because of their catalytic and molecular sieving properties (Pinnavaia, 1983;Barrer, 1986). The best understood pillared clays (PILCs) are those in which Al oxide pillars act as molecular-sized props permanently separating the silicate layers of the clay, and the structure of these materials has been investigated using 27A1 and 29Si solid state MAS NMR (Tennakoon et al., 1986;Plee et al., 1985Plee et al., , 1987. If, however, the pillars are formed of Fe oxide instead of A1 oxide, interesting and novel magnetic properties may be expected (Gangas et al., 1985) and M6ssbauer spectroscopy can be utilized to obtain structural information.Metal oxide pillared clays are normally the product of a two step process. The first step is one of cation exchange in which the simple interlayer cation of a smectite (usually Na +) is replaced by a large complex cation. The second step consists of a heat treatment which crosslinks the silicate layers. In this paper, the terms precursor-PILC and calcined-PILC are used in order to make a clear distinction between the products obtained after each step.The complex cation which is used in the preparation of A1-PILCs is the Keggin-like ion [AllaO4(OH)24(H20)12] 7+ (Baes & Mesmer, 1976). In this study we have investigated the PILC-forming potential of a number of large Fe cations which can occupy the exchange sites in smectite interlayers. These are hydroxy-Fe(III) polycations, mixed hydroxy-Fe(III)/Al cations, phenanthroline-Fe(II) complexes and trinuclear Fe(III) carboxylate complexes. CHARACTERISTICS OF METAL OXIDE PILLARED CLAYSIntercalation of complex cations into a smectite followed by heat treatment may, or may not, result in the formation of a PILC. The following three criteria have been used to identify 9 1988 The Mineralogical Society

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“…This partially disordered structure of Mt could be described as a 'card-house' caused by edge-toface and/or edge-to-edge associations of clay particles (Benna et al, 1999). The 'card-house' structure was previously reported for Al-pillared interlayered clay by Pinnavaia et al (1984b) and characterized by a broad PSD and an absent or broadened (001) XRD reflection (Occelli et al, 1987). Recently, a broad XRD peak at a very low 2y angle has also been cited as evidence for the 'card-house' arrangement in mesoporous structures (Clinard et al, 2003;Bergaya et al, 2005;Yuan et al, 2006aYuan et al, , 2006b).…”

Section: Discussionmentioning

confidence: 62%

A Critical Textural Evolution Study of Zerovalent Iron/Montmorillonite Nanosized Heterostructures Under Various Iron Loadings

Fan

Yuan

Bergaya

et al. 2011

Clays and clay miner.

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Abstract-Heterostructures formed by nanoparticles hybridized with porous hosts are of great potential in many practical applications such as catalysis, adsorption, and environmental remediation, based on their intrinsic properties. The objectives of this study were to synthesize zerovalent iron nanoparticles/ montmorillonite heterostructures and to investigate their textural evolution under different Fe loadings. Iron nanoparticles were hybridized with montmorillonite by impregnation of montmorillonite by ferric ions followed by chemical reduction with sodium borohydride in solution. These hybridized Fe nanoparticles were well dispersed on the montmorillonite surface, size adjustable, and resistant to oxidation under the protection of native Fe-oxide shells. The textural evolution of these heterostructures under various Fe loadings was investigated using nitrogen physisorption, X-ray diffraction, electron microscopy, and elemental analyses. As the Fe loadings increased, the total pore and mesopore volumes were almost unchanged; the total, micropore, and external surface areas as well as the micropore volume decreased; and the average pore diameter increased. These textural changes could be attributed to the filling of the interparticle pores of montmorillonite by a variable amount of Fe nanoparticles. In addition, with increasing Fe loadings, the mesoporous character was enhanced for these heterostructures. These fundamental results are important in understanding the structure of these heterostructures as well as in developing some novel applications in related fields.

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On the pillaring and delamination of smectite clay catalysts by polyoxo cations of aluminum

Cited by 342 publications

References 22 publications

Improvement in the Adsorption of Anionic and Cationic Dyes from Aqueous Solutions: A Comparative Study using Aluminium Pillared Clays and Activated Carbon

Improvement in the Adsorption of Anionic and Cationic Dyes from Aqueous Solutions: A Comparative Study using Aluminium Pillared Clays and Activated Carbon

Preparation and characterization of iron oxide pillared montmorillonite

A Critical Textural Evolution Study of Zerovalent Iron/Montmorillonite Nanosized Heterostructures Under Various Iron Loadings

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