Max M. Mortland

Clay-organic complexes as adsorbents for phenol and chlorophenols

Several clay-organic complexes were synthesized by placing quaternary ammonium cations on smectite by cation exchange. They were then examined for their ability to adsorb phenol and several of its chlorinated congeners. The organic cations used were: hexadecylpyridinium (HDPY+), hexadecyltri-methyl ammonium (HDTMA+), trimethylphenyl ammonium (TMPA), and tetramethylammonium (TMA+). The complexes containing long-chain alkyl (hexadecyl) groups were the most hydrophobic and adsorbed the phenols from water in proportion to their hydrophobicities, which increase with chlorine addition (phenol < chlorophenol < dichloropohenol < trichlorophenol). With n-hexane as the solvent, different adsorption was found which depended on the type and degree of solvent interactions with the compound and the clay-organic complex. Thus, the amount of adsorption of these phenols on clay-organic complexes was dependent on the relative energies of adsorbent-adsorbate and adsorbate-solvent interactions.

Adsorption of benzene, toluene, and xylene by two tetramethylammonium-smectites having different charge densities

A high-charge smectite from Arizona [cation-exchange capacity (CEC) = 120 meq/100 g] and a low-charge smectite from Wyoming (CEC = 90 meq/100 g) were used to prepare homoionic tetra-methylammonium (TMA)-clay complexes. The adsorption of benzene, toluene, and o-xylene as vapors by the dry TMA-clays and as solutes from water by the wet TMA-clays was studied. The adsorption of the organic vapors by the dry TMA-smectite samples was strong and apparently consisted of interactions with both the aluminosilicate mineral surfaces and the TMA exchange ions in the interlayers. In the adsorption of organic vapors, the closer packing of TMA ions in the dry high-charge TMA-smectite, compared with the dry low-charge TMA-smectite, resulted in a somewhat higher degree of shape-selective adsorption of benzene, toluene, and xylene. In the presence of water, the adsorption capacities of both samples for the aromatic compounds were significantly reduced, although the uptake of benzene from water by the low-charge TMA-smectite was still substantial. This lower sorption capacity was accompanied by increased shape-selectivity for the aromatic compounds. The reduction in uptake and increased selectivity was much more pronounced for the water-saturated, high-charge TMA-smectite than for the low-charge TMA-smectite. Hydration of the TMA exchange ions and/or the mineral surfaces apparently reduced the accessibility of the aromatic molecules to interlamellar regions. The resulting water-induced sieving effect was greater for the high-charge TMA-smectite due to the higher density of exchanged TMA-ions. The low-charge Wyoming TMA-smectite was a highly effective adsorbent for removing benzene from water and may be useful for purifying benzene-contaminated water.

Shape-selective adsorption of aromatic molecules from water by tetramethylammonium–smectite

The adsorption of aromatic compounds by smectite exchanged with tetramethylammonium (TMA) has been studied. Aromatic compounds adsorbed by TMA–smectite are assumed to adopt a tilted orientation in a face-to-face arrangment with the TMA tetrahedra. The sorptive characteristics of TMA–smectite were influenced strongly by the presence of water. The dry TMA–smectite showed little selectivity in the uptake of benzen, toluene and xylene. In the presence of water, TMA–smectite showed a high degree of selectivity based on molecular size/shape, resulting in high uptake of benzene and progressively lower uptake of larger aromatic molecules. This selectivity appeared to result from the shrinkage of interlamellar cavities by water.

INTERCALATION OF SILICA IN SMECTITE 1

Silica has been intercalated in swelling clays by hydrolysis and/or oxidation of tris(acetylacetonato)siIicon(IV) cations, Si(acac)3+, and polychlorosiloxanes, (-SiOCl2-)n, in the interla-mellar regions of the minerals. The Si(acac)3+ ions have been placed on the interlamellar surfaces by ion exchange and by in situ reaction of the acetylacetone-solvated clays with SiCl4. The (-SiOCl2-)n polymers were formed in the interlayers by reaction of adsorbed benzaldehyde with SiCl4. The optimum (001) spacing observed after firing the clays in air at 500°C (12.6 Å) corresponds to the presence of a monolayer of siloxane chains. Nitrogen BET surface areas range from 40 to 240 m2/g, depending on the amount of internal surface covered by the intercalated silica. In some cases, highly ordered products were formed which exhibit four orders of (00ℓ) reflection. Interstratifled products with d(001) values between 9.6 and 12.6 Å exhibit surface areas consistent with the presence of a random mixture of totally collapsed interlayers and interlayers containing siloxane monolayers. Attempts to achieve silica intercalation by hydrolysis of SiCl4 in the clay interlayers were not productive.РезюмеКремнезем был включен в разбухающие глины с помощью гидролиза и/или окисления катионов три (ацетилацетоната) силикона(IV), Si(асас)3+, полихлоросилоксанов (-SiOCl2)n в межслойных областях минералов. Ионы Si(асас)3+ были помещены на межслойные поверхности ионным обменом и реакцией in situ глин, растворенных в ацетилацетоне, с SiСl4. Полимеры (-SiOCl2)n, образовывались в межслоях реакцией адсорбированного бензалдегида с SiСl4. Оптимальные (001) промежутки, наблюдаемые после прокаливания глин в ваздухе при 500°С (12,6Å) соответствуют присутствию монослоя силоксановых цепей. Азотные ВЕТ поверхностные площади изменяются от 40 до 240 m2/г, в зависимости от размера внутренней поверхности, покрытой внедренным кремнеземом. В некоторых случаях образуются высоко-порядковые продукты, которые проявляют четыре порядка отражения 001. Переслаивающиеся продукты с величинами d(001) в пределах 9,6 и 12,6А прявляют поверхностные площади, согласующиеся с присутствием беспорядочной смеси полностью разрушенных межслоев и межслоев, содержащих силоксановые монослои. Попытки достичь интеркалации кремнезема гидролизом SiCl4 в межслоях глины не дали результатов. [N.R.]ResümeeSiO2 wurde in quellfähige Tone durch die Hydrolyse und/oder Oxidation von Tris(acetylacetonato)silicon(IV)-Kationen, Si(acac)3+, und Polychlorosilioxane (-SiOCl2-)n in die Zwischenschichtbereiche der Minerale eingelagert. Die Si(acac)3+-Ionen wurden auf die Zwischenschichtoberflächen durch Ionenaustausch und durch die in situ Reaktionen von in Acetylaceton gelösten Tonen mit SiCl4 aufgebracht. Die (-SiOCl2-)n-Polymere wurden in den Zwischenschichten durch die Reaktion von adsorbiertem Benzaldehyd mit SiCL, gebildet. Der optimale (001) Schichtabstand, der nach dem Erhitzen der Tone auf 500°C in Luft (12,6 Å) beobachtet wurde, stimmt mit dem Vorhandensein einer Monoschicht von Siloxanketten überein. Stickstoff BET Oberflächenbereiche reichen von 40–240 m2/g, abhängig von der Größe der inneren Oberfläche, die durch das eingelagerte SiO2 bedeckt ist. In einigen Fällen entstehen gut geordnete Produkte, die vier Ordnungen der 00ℓ-Reflexion zeigen. Wechsellagerungsprodukte mit d(001)-Werten zwischen 9,6 und 12,6 Å zeigen Oberflächenbereiche, die mit dem Vorhandensein einer unregelmäßigen Mischung aus volständig zusammengebrochenen Zwischenschichten und Zwischenschichten, die Siloxan-Monoschichten enthalten, übereinstimmen. Versuche, eine SiO2-Einlagerung durch die Hydrolyse von SiCL, in den Tonzwischenschichten zu erreichen, waren nicht erfolgreich. [U.W.]RésuméLa silice a été intercalatée dans des argiles gonflants par hydrolyse et/ou par oxidation des cations tris(acétylatonato)silicés(IV), Si(acac)3+, et polychlorosilioxanes, (-SiOCl2-)n, dans les régions interfo-laires des minéraux. Les ions Si(acac)3+ ont été placés sur les surfaces interfolaires par échange d’ions, et par la réaction in situ des argiles dissolus à l’acétylatone avec SiCl4. Les polymères (-SiOCl2-)n ont été formées dans les intercouches par la réaction de benzaldehyde adsorbée avec SiCl4. L’espacement (001) optimal observé après la cuisson des argiles à l’air à 500°C (12,6 Å) correspond à la présence d’une mono-couche de chaînes siloxanes. Les régions de surface de nitrogène BET s’étagent de 40 à 240 m2/g, dépendant de l’étendue de surface interne couverte par la silice intercalatée. Dans quelques cas, des produits qui exhibent 4 ordres de reflection (00ℓ sont formés. Des produits interstratifiés avec des valeurs d(001) entre 9,6 et 12,6 Å exhibent des surfaces fidèles à la présence d’un mélange fait au hasard d’intercouches totalement effondrées et d’intercouches contenant des monocouches siloxanes. Des efforts faits pour obtenir l’intercalation de la silice par l’hydrolyse de SiCl4, dans les intercouches d’argile ne se sont pas montrés productifs. [D.J.]

Immobilization of glucose oxidase on montmorillonite clay: hydrophobic and ionic modes of binding

Abstract Neutral, cationic and anionic forms of glucose oxidase (pH 3.0–8.0) bind to the external surfaces of hexadecyltrimethylammonium montmoril-lonite by a hydrophobic mechanism. At pH 4.0 the adsorption limit is 4.7 g/ 100 g clay. The pH for optimum activity is similar for the immobilized and free forms of the enzyme, but the immobilized conjugate is more sensitive to changes in pH. In contrast, Na+-montmorillonite binds active forms of glucose oxidase by an ionic intercalation mechanism at pH values below the isoelectric point. Denaturation of the intercalated enzyme occurs by two pathways. The faster pathway is inhibited by high enzyme loadings and by co-adsorption of tetrabutylammonium ions, suggesting that the enzyme uncoils on the interlayer surfaces of the mineral. Lower than expected values for the adsorption limit (

Dioxin radical formation and polymerization on Cu(II)-smectite

97 g/100 g clay) and for the 00l lattice expansion (

Hectorite Complexes with Cu(II) and Fe(II)-1,10-Phenanthroline Chelates*

35 A) also indicate uncoiling or flattening of the enzyme in the intercalated state. The slower denaturation pathway, which is less sensitive to surface coverage, may involve hydrolysis and loss of FAD cofactor.

TRIETHYLENE DIAMINE-CLAY COMPLEXES AS MATRICES FOR ADSORPTION AND CATALYTIC REACTIONS*

Decontamination of hazardous wastes containing dioxins (dibenzo-p-dioxin and its chlorinated analogues) remains a serious problem and new approaches for the degradation or alteration of dioxins are needed. We describe here dibenzo-p-dioxin radical cation formation and polymerization on a simple clay mineral (Cu(II)-smectite) in mild reaction conditions. Existence of the radical species was conclusively demonstrated using electron spin resonance (ESR), ultraviolet-visible, and infrared spectroscopy. The radical cation polymerized to form dimers and trimers as revealed by mass spectroscopy. Radical cations of 1- and 2-chlorodibenzo-p-dioxin were also formed on Cu(II)-smectite. The radical cations are formed by electron transfer from the dioxins to Cu(II). The formation of dioxin radicals may provide the basis for new detoxification methods in which the reactive radical species is coupled to other molecules or degraded by subsequent reactions.

THE CHEMISORPTION OF ANISOLE ON Cu(II) HECTORITE

Characteristics and properties of complexes of a smectite (hectorite) with 1,10-phenanthroline (phen) chelates with iron or copper were determined by a variety of physical and chemical measurements. The complex ions showed high selectivity for the hectorite surface. Basal spacings of 17.4 Å were produced by Fe(II) or Cu(II) analogues of M(phen)32+ hectorite. Adsorption of gases and vapors by the M(phen)32+ hectorite complex revealed large surface areas and reflected intrinsic characteristics of the complex ions. Lower surface areas were found for copper phen hectorite than iron phen hectorite probably because of the loss of a ligand from the Cu(II) ion. ESR spectra confirmed that appreciable Cu(II) existed as the bis-phen complex under certain conditions. An increase in the oxidation potential of the Fe(phen)32+-Fe(phen)33+ couple above that in pure solvent was noted when these complexes were supported by the mineral surface.

Perturbation of structural Fe (super 3+) in smectites by exchange ions

Complexes of 1,4-diazabicyclo [2.2.2] octane (triethylene diamine) with smectite and vermiculite were made for the purpose of exposing the internal surfaces of the clays for adsorption of gases and possible catalytic activity. When the diprotonated form of the amine saturated the exchange sites, internal surfaces of the clays were found to be available to nitrogen, ethane, and 2,4-dimethyl pentane. Proton lability in the smectites was studied with NH3, D2O, and C6D6 experiments. Catalytic function was demonstrated in the conversion of acetonitrile to acetamide in the smectite.