Kinetics of Acid-Dissolution of Palygorskite (Attapulgite) and Sepiolite

Abdul-Latif, Numan

doi:10.1346/ccmn.1969.0170305

Cited by 54 publications

(13 citation statements)

References 5 publications

(14 reference statements)

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“…The silica obtained after acid treatment maintalned the fibrous morphology of natural silicates, which proves that the attack was produced throughout the structural microchannels and not by "out to in" dissolution of the particles, in accord with the continuous reaction model proposed by Abdul-Latif and Weaver (1969). Proton diffusion to the pores of sepiolite and palygorskite is possible.…”

Section: Electron Microscopysupporting

confidence: 72%

“…However, the literature contains few references to acid treatment of palygorskite as compared with other clays (Singer 1976;Gonz~lez et al 1989;Corma et al 1990;Su~ez et al 1995). One paper has reported the treatment of sepiolite and palygorskite under the same experimental conditions, but only a chemical study was performed (Abdul-Latif and Weaver 1969). These authors indicate that sepiolite is less stable under chemical weathering than palygorskite.…”

Section: Introductionmentioning

confidence: 99%

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Structural and Textural Modifications of Palygorskite and Sepiolite Under Acid Treatment

Myriam

1998

Clays and clay miner.

131

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Abstraet--Sepiolite from Mara (Zaragoza, Spain) and palygorskite from Attapulgus (Georgia, USA) were activated by treatment at different concentrations with solutions of boiling HC1 under reflux conditions. The natural and treated solids were characterized by mineralogical, chemical and textural analyses.Acid attack resulted in a progressive dissolution of the octahedral layer of these silicates. Silica contents increased and octahedral cations (A1, Mg and Fe) decreased with the intensity of the acid attack. In both cases, fibrous free silica was obtained.The sepiolite was destroyed more rapidly than palygorskite under the conditions used because of its magnesic composition and the larger size of its structural microchannels. The maximum increase in specific surface area was obtained for sepiolite at 3 N and for palygorskite at 9 N. Cleaning and disaggregation of the particles and the increase in the number of micropores were responsible for this increase in specific surface area.

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Section: Electron Microscopysupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Structural and Textural Modifications of Palygorskite and Sepiolite Under Acid Treatment

Myriam

1998

Clays and clay miner.

131

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“…Acid dissolution studies by Abdul-Latif and Weaver (1969) indicated that the reaction rate constant for magnesium in sepiolite was about 240 times that for magnesium in palygorskite.…”

Section: Chemistrymentioning

confidence: 99%

Discussion of the Occurrence and Origin of Sedimentary Palygorskite-Sepiolite Deposits

Isphording

1973

Clays and clay miner.

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Abstract--Marine and non-marine palygorskite-sepiolite deposits are found throughout the world and occur interbedded with chert, dolomite, limestone, phosphates and other non-detrital sedimentary rocks. The origin of these high-magnesium clays has long been attributed to either alteration of volcanic ash or the structural transformation of smectite clays. More recently, others have argued origin by direct crystallization (neo-formation). Recent laboratory studies support this latter concept, particularly in environments where the concentration of alumina is low, the silica concentration high, and the pH alkaline. Such an origin is proposed for the Georgia-Florida deposits in southeastern United States, since major obstacles exist against formation by alteration of volcanic ash or by transformarion of smectites. Lateritic weathering during the Miocene would have favored direct precipitation of these clays in the shallow, marginal seas. The basinward increase in the MgO: AI~O3 ratio is further support.Deep weathering of crystalline rocks in northern British Honduras and Guatemala would have produced similar high silica, low alumina conditions on the adjacent submerged Yucatan Platform during the late Tertiary. The seaward increase in the MgO:Al203 ratio, the lack of associated detrital constituents, and the absence of associated smectites strongly indicate a similar origin by direct crystallization of these Yucatan palygorsldte-sepiolite clays.Some occurrences of palygorskite and sepiolite may well be related to the alteration of smectite clays or volcanic ash. However, many of the large sedimentary deposits are more probably the result of direct crystallization adjacent to areas undergoing tropical or subtropical weathering.

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“…Several works have shown that the acid treatment modifies the number of acid sites by disaggregation of particles, elimination of mineral impurities, removal of metal exchange cations and proton exchange [9,12]. There are three different acid species which have been described to activate natural sepiolite: HCl [13], HNO 3 [14] and H 2 SO 4 [15]. Although the variation of sepiolite surface area under various HNO 3 concentrations (1 − 5N) and heat treatment conditions (110 − 900°C, for 100 hours) had been performed by Jimenez-Lopez et al [16], the effect of these modified sepiolite samples on ammonium removal efficiency has not been studied.…”

Section: Introductionmentioning

confidence: 99%

Effect of Pretreatment on Ammonium Adsorption Properties of Sepiolite: Equilibrium, Kinetics and Thermodynamic Studies

Duc

Koga

Wei

et al. 2016

J. of Wat. & Envir. Tech.

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Sepiolite is considered as a selective adsorbent to remove ammonium from wastewater. However, ammonium adsorption capacity under different pretreatment conditions has not been well documented. In this study, batch experiments were performed to investigate the ammonium adsorption capacity of low-strength wastewater by modified sepiolite. Sepiolite was conditioned with an acid, HCl, HNO 3 or H 2 SO 4 , then thermally treated. Results showed that the modification process enhanced ammonium adsorption and sepiolite treated with 1N HNO 3 followed by calcination at 400°C exhibited superior adsorption property. Adsorption capacity increased with contact time and initial concentration but decreased with increasing temperature and sepiolite dosage. A maximum adsorption capacity of 143 mg/g was achieved at pH 8 and a dosage of 1/70 g sepiolite/mL solution. In contrast, an increase of dosage from 1/70 to 1/10 improved the ammonium adsorption efficiency from 45 to 75%. Overall, the ammonium adsorption followed the pseudo-second-order kinetics. The equilibrium data were best fitted with Redlich Peterson isotherm. Through thermodynamic analysis, the ammonium adsorption was not spontaneous with sepiolite dosage of 1/70. However, the spontaneity of adsorption was feasible with ΔG° of −2.5 kJ/mol at 25°C and a dosage of 1/10. This study provided a potential pathway for ammonium removal during wastewater treatment.

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Kinetics of Acid-Dissolution of Palygorskite (Attapulgite) and Sepiolite

Cited by 54 publications

References 5 publications

Structural and Textural Modifications of Palygorskite and Sepiolite Under Acid Treatment

Structural and Textural Modifications of Palygorskite and Sepiolite Under Acid Treatment

Discussion of the Occurrence and Origin of Sedimentary Palygorskite-Sepiolite Deposits

Effect of Pretreatment on Ammonium Adsorption Properties of Sepiolite: Equilibrium, Kinetics and Thermodynamic Studies

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