Analysis of the microporosity in pillared clays

Gil, A.; Montes, Mario

doi:10.1021/la00013a043

Cited by 89 publications

(61 citation statements)

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“…While several studies [13,14] postulated that the Dubinin-Radushkevich equation applies only to solids with a uniform structure of micropores, others [15][16][17][18][19] proposed a modification of this equation when a microporous solid possesses micropores of the same shape but of different sizes. One of those modifications is the Dubinin-Astakhov equation, which can be applied to the description of the adsorption onto structurally heterogeneous solids [8,20].…”

Section: Influence Of Activation Conditionsmentioning

confidence: 99%

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Jiménez-Cordero

Heras

Alonso-Morales

et al. 2013

Chemical Engineering Journal

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h i g h l i g h t sNovel method of activation by cycles permits good control of porosity development. S BET values above 1000 m 2 /g can be obtained with burn-off values lower than 40%. The low burn-off helps to maintain granular morphology of the activated carbons.Carbons with unique hollow core structure and wall thickness of 250 lm are produced.The activated carbons showed a good mechanical strength during attrition test. a r t i c l e i n f o t r a c tActivation of grape seeds char upon cyclic oxygen chemisorption-desorption permits a controlled development of porosity versus burn-off using air as a cheap activation agent. In this work the influence of chemisorption and desorption temperature and the number of cycles is investigated. A fast increase of BET surface area (S BET ) is obtained in the two first cycles; that increase becomes then lower although the S BET continues increasing upon the successive cycles. Regarding the Dubinin-Astakhov surface area (S DA ) a slow increase was observed from cycle to cycle. The activation process led to the development of both micro and mesoporosity. Under the optimum conditions for surface area development, i.e. an oxidation temperature of 275°C and desorption temperatures between 850 and 950°C, values of 1129-1256 and 1339-1219 m 2 /g were obtained for S BET and S DA , respectively. Porosity was found to increase mainly during the desorption stage, although chemisorption also led to some surface area development. SEM characterization showed that the activated carbon maintained the granular morphology of the seeds even after 10 cycles showing the egg-shell structure of the precursor with longer and deeper cracks at the outer surface. The activated carbons showed a good mechanical strength during attrition tests.

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Section: Influence Of Activation Conditionsmentioning

confidence: 99%

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Jiménez-Cordero

Heras

Alonso-Morales

et al. 2013

Chemical Engineering Journal

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“…At OH/A1 ratios >2.5, Al13 tends to aggregate to larger polymers (Furrer et al, 1992). To accelarate the formation of All3 , the solution was aged for 3 h at 90~ (Tokarz and Shabtai, 1985;Gil and Montes, 1994;LahodnySarc and Khalaf, 1994), and then held overnight at room temperature. To quantify the amount of All3 in the pillaring solution, 27A1 NMR spectra were recorded with a Bruker DPX 250 spectrometer operating at 65.2 MHz (5.7 Tesla).…”

Section: Preparation Of Hal Ai Hzr and Zr-mx80mentioning

confidence: 99%

“…A1-MX80 was obtained by 5 h calcination at 400~ (Gil and Montes, 1994;Poncelet and Schutz, 1986) in a furnace ("RP Economy-Pico") coupled with a Therrot-Computer TC 405 (Neue Kiag, Switzerland). Initially, the heating rate of the calcination was adjusted to 10~ min ~ because immediate heat exposure of the hydroxy-interlayered montmorillonite may result in an irregular stacking of the 2:1 layers (Zhu et al, 1995).…”

Section: Preparation Of Hal Ai Hzr and Zr-mx80mentioning

confidence: 99%

“…In solutions of aluminum chloride, All3 is dominant at OH/Al-ratios between 1.5-2.5 (Schoenherr et al, 1983). The quantity of All3 in the clay can be optimized by aging of the pillaring solution at elevated temperatures (Tokarz and Shabtai, 1985;Kloprogge, 1992;Gil and Montes, 1994). A1-hydroxy-intercalated montmorillonites exhibit an interlayer spacing -9 A, which corresponds to the size of the intercalated Al~3.…”

Section: Introductionmentioning

confidence: 99%

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Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Matthes

Madsen

Kahr

1999

Clays and clay miner.

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Abstract--The sorption of Cd, Cu, Pb, and Zn ions by Na-rich bentonite, AI and Zr-pillared Na-rich bentonite (A1-MX80, Zr-MX80), the uncalcined hydroxy-intercalated precursors (HA1, HZr-MX80), and commercial Al-pillared bentonite EXM 534 was investigated. Experiments were conducted in ultrapure water and artificial leachate with varying pH. The experiments were performed over periods to 30 wk. Sorption characteristics were described with one and two-site Langmuir isotherms. The non-exchangeable quantities of heavy metals were determined by fusion of the sorbents after ion exchange with ammonium acetate.The sorption of Cd, Cu, Pb, and Zn by bentonite was dominated by cation exchange. In artificial leachate, the sorption was reduced due to competition with alkali and alkaline-earth cations. The sorption of Cu, Zn, and Pb at pH 4.9 and Cd at pH 6.9 by A1 and Zr-hydroxy-intercalated and pillared MX80 was governed also by cation exchange. In contrast, the sorbed quantities of Zn at pH 6.9 exceeded the cation exchange capacity (CEC) of HA1, HZr, A1, Zr-MX80, and EXM 534 and were partially nonexchangeable. The increase of the sorption of Zn with pH and its independence of the ionic strength of the solution at neutral pH suggest a complexation of Zn ions to surface hydroxyl groups of the intercalated A1 and Zr-polyhydroxo cations and pillars. This complexation is the dominating sorption mechanism. Removal of dissolved Zn from solution with time is attributed to surface precipitation. Al-hydroxy and pillared bentonites are considered potential sorbents of Zn ions from neutral pH aqueous solutions, such as waste waters and leachates.

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“…El efecto de la razón cantidad de policatión/arcilla es muy similar al que se encuentra con la CIC de la arcilla. De hecho, un valor bajo de esta variable se traduce en una baja estabilidad térmica del sólido resultante, y una excesiva concentración de policatión reduce la accesibilidad a la estructura porosa (26). Desde el punto de vista de la disolución de intercalación, tanto el grado de polimerización como la carga del polihidroxicatión metálico están controlados por la concentración de la sal metálica en disolución, la razón de hidrólisis (o el pH), así como por la temperatura y el tiempo de envejecimiento.…”

Section: Introductionunclassified

Factores que controlan las propiedades texturales de arcillas intercaladas con disoluciones de circonio y aluminio

Gil¹,

Vicente²,

Gandı́a³

2000

Bol. Soc. Esp. Ceram. Vidr.

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En este trabajo se ha estudiado la evolución de las propiedades texturales de una saponita y una montmorillonita intercaladas con disoluciones de circonio y aluminio tras calcinación a 500 ºC. Los sólidos presentaron un diferente comportamiento en función de la naturaleza de la disolución de intercalación y de la arcilla empleada. Tras calcinación, la superficie específica y el volumen microporoso de las arcillas intercaladas con disoluciones de aluminio disminuyeron de manera importante, lo cual se ha relacionado con las distancias interlaminar e interpilar que presentaron los materiales intercalados. Por contra, las superficies específicas de las arcillas intercaladas con disoluciones de circonio aumentaron, probablemente gracias al efecto combinado de la descomposición térmica de los ligandos orgánicos unidos al circonio en los policationes y la posible presencia de partículas mesoporosas de ZrO 2 sobre la superficie de los sólidos. Palabras clave: arcillas intercaladas, distancia interlaminar, distancia interpilar, adsorción de nitrógeno. Factors controlling the textural properties of zirconia and alumina pillared claysThe texture development of a saponite and a montmorillonite, intercalated with zirconium and aluminium oligomers, after calcination at 500 ºC has been studied. Remarkable differences were observed among samples, depending on the source of the intercalating polycations and the parent material. On calcining, the alumina pillared clays suffered noticeable specific surface area and micropore volume losses, which have been related to the interlayer and interpillar distances of the samples. On the contrary, the zirconia pillared clays showed a slight surface area increase, which affected both micropores and mesopores and could be due to the combined effect of the thermal decomposition of the zirconium oligomers and the possible presence of mesoporous ZrO 2 particles.

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Analysis of the microporosity in pillared clays

Cited by 89 publications

References 2 publications

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Factores que controlan las propiedades texturales de arcillas intercaladas con disoluciones de circonio y aluminio

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