Kinetic features of phase transformation of kaolinite into metakaolinite for kaolin clays from different deposits

Ламберов, А. А.; Sitnikova, Evgenia; Abdulganeeva, A. Sh.

doi:10.1134/s1070427212060109

Cited by 9 publications

(11 citation statements)

References 3 publications

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“…The disappearance of the kaolinite peaks is indicative of the appearance of an amorphous phase (metakaolinite) due to thermal transformation of the clay. A study of the phase transformations of kaolinite from different deposits in Russia and Ukraine showed similar results [33]. It is this amorphous metakaolinite (Al 2 O 3 •2SiO 2 ) that releases alumina (Al 2 O 3 ) for dissolution making the clay respond to acid leaching.…”

Section: Type and Composition Of Claymentioning

confidence: 77%

“…The temperatures at which these transformations (phase changes) begin and end depends on (i) degree of crystallinity of the kaolinite, (ii) its impurity oxides contents, (iii) particle sizes, rate of heating, and duration of heating at a given temperature. Therefore, clays from different localities vary considerably not just in mineralogy and chemical composition, but in degree of crystallinity and purity [28] [33]. There is need to investigate the peculiar characteristics of each clay deposit.…”

Section: Reversible Transformation Irreversible Transformationmentioning

confidence: 99%

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The Thermal Activation of Nsu Clay for Enhanced Alumina Leaching Response

Mark

Anyakwo

Onyemaobi

et al. 2019

IJET

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The thermal activation conditions for enhancing the leaching of alumina from Nsu clay from south-eastern Nigeria was investigated. The clay assayed 28.9% and 50.59% , comprising mainly kaolinite mineral (82.6%) and quartz (12.5%). Thermal activation rendered the alumina in the clay acid-soluble by transforming the clay from its crystalline nature to an amorphous phase or metakaolinite. The clay samples were heated at calcination temperatures of 500, 600, 700, 800, and 900 °C at holding times of 30, 60, and 90 minutes. Uncalcined clay samples and samples calcined at 1000 °C (holding for 60 minutes) were used in the control experiments. Leaching of alumina from the resulting clay calcines passing 300 μm sieve (-50 mesh) was done in 1M hydrochloric acid solution at room temperature using a solid/liquid ratio of 0.02g/ml and shaking speed of 100 rpm. The solubility data given by the fraction of Al ion taken into leach solution showed that the clay calcined at 700 °C (holding for 60 minutes) responded most to leaching. In general, it was observed that samples calcined for 60 minutes responded better than those held for 30 or 90 minutes. The activation energies for leaching the clay calcines were 29.50, 32.92, 26.71, 30.18, 29.18, and 33.24 kJ/mol for samples calcined for 60 minutes at 500, 600, 700, 800, 900, and 1000 °C, respectively. The activation energy of leaching for the uncalcined sample was 35.07 kJ/mol. Thus, calcines produced at 700 °C (holding for 60 minutes) had the highest leaching response for alumina and the lowest leaching activation energy of 26.71 kJ/mol. It is concluded therefore that Nsu kaolinite clay should be best calcined for alumina yield by heating up to 700 °C and holding for 60 minutes at that temperature. The clay deposit can be used as alternative resource for alumina production.

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Section: Type and Composition Of Claymentioning

confidence: 77%

Section: Reversible Transformation Irreversible Transformationmentioning

confidence: 99%

The Thermal Activation of Nsu Clay for Enhanced Alumina Leaching Response

Mark

Anyakwo

Onyemaobi

et al. 2019

IJET

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“…The disappearance of the kaolinite peaks is an indication of the appearance of an amorphous phase (i.e. metakaolinite) due to thermal transformation of the clay [28] [33]. It is this Al O 2SiO ⋅ ) that releases its alumina ( 2 3 Al O ) for dissolution making the clay respond to acid leaching.…”

Section: Type and Composition Of Claymentioning

confidence: 99%

Determination of the Calcination Procedure Required to Activate Edda Clay for Optimal Leaching of Alumina

Mark¹,

Anyakwo²,

Onyemaobi³

et al. 2019

JMMCE

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Nigeria is the highest consumer of aluminium in Africa but lacks bauxite deposits. The replacement of bauxite alumina with other alumina bearing resources (clays in particular) has been proposed. The present study investigated the thermal treatment required to activate Edda clay from southeastern Nigeria for optimal leaching of alumina. The clay is composed mainly of kaolinite and quartz, assaying 24.65% Al 2 O 3 and 52.81% SiO 2 . Thermal activation of the clay prior to leaching transformed the crystalline kaolinite mineral to an amorphous phase (metakaolinite) in which the alumina became soluble. Clay samples passing 300 µm sieve were calcined at temperatures of 500˚C, 600˚C, 700˚C, 800˚C, and 900˚C at holding times of 30, 60, and 90 minutes in each case. The uncalcined clay and sample heated at 1000˚C (for 60 minutes) were used in the control experiments. Leaching of alumina from the resulting clay calcines was done in 1 M hydrochloric acid solution at room temperature using a solid/liquid ratio of 0.02 g/ml and shaking speed of 100 rpm. The solubility data based on the percentage of Al ions taken into leach solution showed that the sample calcined at 700˚C (for 60 minutes) responded to leaching better than other samples. Samples calcined for 60 minutes at all temperatures studied were found to respond more than those held for 30 or 90 minutes. Studies on the activation energy of leaching revealed that calcines produced at 700˚C (for 60 minutes) had both the highest leaching response (49.96% after 1 hour at leaching temperature of 100˚C) and the lowest activation energy of 24.47 kJ/mol. It is concluded therefore that Edda kaolinite clay should be thermally activated for alumina yield by heating up to 700˚C and holding for 60 minutes. The clay deposit is therefore a potential alternative resource for alumina production.

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“…The disappearance of the kaolinite peaks is indicative of the appearance of an amorphous phase (metakaolinite) due to thermal transformation of the clay[28]. A study of the phase transformations of kaolinite from different deposits in Russia and Ukraine showed similar results[33]. It is this amorphous metakaolinite ( for dissolution making the clay respond to acid…”

mentioning

confidence: 92%

“…The temperatures at which these transformations (phase changes) begin and end depends on 1) degree of crystallinity of the kaolinite, 2) its impurity oxides contents, 3) particle sizes, rate of heating, and duration of heating at a given temperature. Therefore, clays from different localities vary considerably not just in mineralogy and chemical composition, but in degree of crystallinity and purity [28] [33]. There is need to investigate the characteristics of each clay deposit.…”

Section: Introductionmentioning

confidence: 99%

Conditions for Thermal Activation of Ngwo Clay as an Alternative Resource for Alumina

Mark¹,

Anyakwo²,

Onyemaobi³

et al. 2019

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The thermal activation of Ngwo clay from southeastern Nigeria for optimal leaching of alumina was investigated. The clay assayed 24.63% Al 2 O 3 and 52.15% SiO 2 , comprising mainly kaolinite mineral and free silica or quartz. The alumina locked up in the clay structure was rendered acid-soluble by thermal activation which transformed the clay from its crystalline nature to an amorphous, porous phase or metakaolinite. The clay samples were heated at calcination temperatures of 500˚C, 600˚C, 700˚C, 800˚C, and 900˚C at holding times of 30, 60, and 90 minutes. Uncalcined clay samples and samples calcined at 1000˚C (holding for 60 minutes) were used in the control experiments. After leaching the resulting clay calcines in 1 M hydrochloric acid solution at room temperature, it was observed that the clay calcines produced at 700˚C (holding for 60 minutes) responded most to leaching. Samples calcined for 60 minutes also responded better than those held for 30 or 90 minutes. Based on activation energy studies, it was observed that calcines produced at 700˚C (for 60 minutes) had both the highest leaching response (51.84% after 1 hour at leaching temperature of 100˚C) and the lowest activation energy of 25.03 kJ/mol. It is concluded therefore that Ngwo kaolinite clay should be best calcined for alumina dissolution by heating up to 700˚C and holding for 60 minutes at that temperature. The clay deposit has potential for use as alternative resource for alumina production in Nigeria where bauxite is scarce.

show abstract

Kinetic features of phase transformation of kaolinite into metakaolinite for kaolin clays from different deposits

Cited by 9 publications

References 3 publications

The Thermal Activation of Nsu Clay for Enhanced Alumina Leaching Response

The Thermal Activation of Nsu Clay for Enhanced Alumina Leaching Response

Determination of the Calcination Procedure Required to Activate Edda Clay for Optimal Leaching of Alumina

Conditions for Thermal Activation of Ngwo Clay as an Alternative Resource for Alumina

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