ahmed hussien - Academia.edu (original) (raw)
Papers by ahmed hussien
Journal of Porous Materials, 2001
Mesoporous silica has been prepared by leaching of the Al 2 O 3 component from mechanically amorp... more Mesoporous silica has been prepared by leaching of the Al 2 O 3 component from mechanically amorphized kaolinite. The kaolinite was amorphized by grinding in a planetary ball mill for 1 h. After grinding the amorphized kaolinite was chemically treated with dilute sulfuric acid at 90 • C for varying times. The influence of the leaching time on the porous properties and structure of the silica was studied by XRD, XRF, FTIR and BET adsorption methods. The specific surface areas of the leached samples were found to vary from 312 m 2 /g to 284 m 2 /g. The pore size distribution, calculated by the BJH method based on N 2 gas isotherms, showed a unimodal pore size distribution with an average pore size of about 3.8 nm. The total pore volume of the porous silica varied from 0.28 ml/g to 0.312 ml/g, with a uniform pore size distribution in the mesopore regions. New applications exploiting the characteristic pore size of this material are to be expected.
Thermochimica Acta, 2003
The mechanochemical activation of a high defect kaolinite has been studied using a combination of... more The mechanochemical activation of a high defect kaolinite has been studied using a combination of high-resolution thermogravimetry and DRIFT spectroscopy. The effect of grinding causes a decrease in the dehydroxylation temperature and an increase in the amount of adsorbed/coordinated water. The temperature of dehydration also increases with grinding time. It is proposed that this dehydroxylation occurs through a homogenous process involving proton transfer through point heating. The amount of adsorbed water decreases with the increase in temperature of the thermal treatment.
Chemical Activation of a Kaolinite under Acid and Alkaline Conditions
Chemistry of materials, 2002
... Carolina Belver, Miguel Angel ... The alkaline treatments were carried out with 1 M and 5 M K... more ... Carolina Belver, Miguel Angel ... The alkaline treatments were carried out with 1 M and 5 M KOH solutions, the treatments with the concentrated solution, both at room temperature and, especially, under reflux, led to the dissolution of the metakaolins and to the formation of well ...
Kinetics of kaolinite dehydration and its dependence on mechanochemical activation
Journal of Thermal …, 1988
For the mechanochemical activation of two processes can be considered: the structural disordering... more For the mechanochemical activation of two processes can be considered: the structural disordering of laminar crystals, and the formation of molecular dense aggregates from small particles. The activation energy of the dehydration is shown to decrease if the first process ...
The influence of surface-active agents on kaolinite
Journal of Colloid and Interface Science, 1979
The influence of surfactants (CTAB and SDS) on suspensions of monoionic kaolinite (Na+ and H+ for... more The influence of surfactants (CTAB and SDS) on suspensions of monoionic kaolinite (Na+ and H+ form) was investigated by adsorption, sedimentation, turbidity, electroosmosis, and rheological measurements, at pH = 3.3 and 10.0. Only small differences are found between the Na+ and H+ forms of the kailinite. The data can be accounted for satisfactorily by a mathematical model based on the DLVO theory for face-face, edge-edge, and edge-face interactions, if some assumptions on the local ψδ potentials near edge and face type surfaces are introduced.
Enhanced fluoride sorption by mechanochemically activated kaolinites
Journal of Hazardous Materials, 2008
Kaolinite clay obtained from the mines was processed and studied for its fluoride sorption capaci... more Kaolinite clay obtained from the mines was processed and studied for its fluoride sorption capacity. The surface area of the clay mineral was increased from 15.11 m2/g (raw) to 32.43 m2/g (activated) by mechanochemical activation. Batch adsorption studies were conducted to optimize various equilibrating conditions like the effect of contact time, dosage, pH for both raw and micronized kaolinites (RK and MK). The effect of other interfering anions on the defluoridation capacity (DC) of the sorbents was studied. Sorption of fluoride by the sorbents was observed over a wide pH range of 3–11. The studies revealed there is an enhanced fluoride sorption on MK. FTIR and XRD were used for the characterization of the sorbent. The surface morphology of the clay material was observed using SEM. The adsorption of fluoride was studied at three different temperatures, viz., 303, 313 and 323 K. The sorption data obtained at optimized conditions were subjected to Freundlich and Langmuir isotherms. Sorption intensity (1/n) (0.770–0.810) has been evaluated using Freundlich isotherm, whereas the values of sorption capacity Q0 (0.609, 0.714 and 0.782 mg/g) and binding energy b (0.158, 0.145 and 0.133 L/mg) at three different temperatures have been estimated using Langmuir isotherm. Adsorption process was found to be controlled by both Freundlich and Langmuir isotherms. Thermodynamic studies revealed that the sorption of fluoride on MK is endothermic and a spontaneous process. The kinetic studies indicate that the sorption of fluoride on MK follows pseudo-first-order and intraparticle diffusion models.
The effect of dehydroxylation/amorphization degree on pozzolanic activity of kaolinite
Cement and Concrete Research, 2003
The effect of heat treatment parameters on the dehydroxylation/amorphization process of the kaoli... more The effect of heat treatment parameters on the dehydroxylation/amorphization process of the kaolinite-based materials such as natural and artificial kaolin clays with different amounts of amorphous phase (metakaolin) was investigated. The procedure for quantitative estimation of amorphous phase in the heat-treated kaolinite materials was developed. The process of dehydroxylation/amorphization of kaolinite was characterized by DTA/TGA with mass-spectrometry and X-ray powder diffraction. The influence of the heat treatment temperature and content of the amorphous phase on pozzolanic activity was studied. Finally, the relationships between the chemical activity, activity strength index and the amorphous phase content were found and discussed. The results obtained are important for an optimization of the process of the metakaolin large scale production and it's use as an active pozzolanic admixture.
Clay Minerals, 1992
Depending on the preparation temperature and the origin of the raw mineral, the products obtained... more Depending on the preparation temperature and the origin of the raw mineral, the products obtained by thermal activation of kaolinite lead, by hydrothermal treatment with sodium hydroxide at 102~ either to zeolite 4A, or to cubic zeolite P, or to a mixture of cubic and tetragonal zeolite P. The change in the type of zeolite obtained was explained on the basis of a radical change of the zeolite nucleation process due to either the presence of soluble potassium or high silica content resulting from dehydration of muscovite (an impurity in the raw-kaolinite), or from "segregation" associated with the first step of the metakaolinite to mullite transformation. These phenomena occur at a lower calcination temperature with poorly-crystallized kaolinite, and iron in such a sample promotes a sensitive decrease in the formation rate of zeolite crystals. Such results could be used to characterize the crystallinity of kaolinites.
Journal of Porous Materials, 2001
Mesoporous silica has been prepared by leaching of the Al 2 O 3 component from mechanically amorp... more Mesoporous silica has been prepared by leaching of the Al 2 O 3 component from mechanically amorphized kaolinite. The kaolinite was amorphized by grinding in a planetary ball mill for 1 h. After grinding the amorphized kaolinite was chemically treated with dilute sulfuric acid at 90 • C for varying times. The influence of the leaching time on the porous properties and structure of the silica was studied by XRD, XRF, FTIR and BET adsorption methods. The specific surface areas of the leached samples were found to vary from 312 m 2 /g to 284 m 2 /g. The pore size distribution, calculated by the BJH method based on N 2 gas isotherms, showed a unimodal pore size distribution with an average pore size of about 3.8 nm. The total pore volume of the porous silica varied from 0.28 ml/g to 0.312 ml/g, with a uniform pore size distribution in the mesopore regions. New applications exploiting the characteristic pore size of this material are to be expected.
Thermochimica Acta, 2003
The mechanochemical activation of a high defect kaolinite has been studied using a combination of... more The mechanochemical activation of a high defect kaolinite has been studied using a combination of high-resolution thermogravimetry and DRIFT spectroscopy. The effect of grinding causes a decrease in the dehydroxylation temperature and an increase in the amount of adsorbed/coordinated water. The temperature of dehydration also increases with grinding time. It is proposed that this dehydroxylation occurs through a homogenous process involving proton transfer through point heating. The amount of adsorbed water decreases with the increase in temperature of the thermal treatment.
Chemical Activation of a Kaolinite under Acid and Alkaline Conditions
Chemistry of materials, 2002
... Carolina Belver, Miguel Angel ... The alkaline treatments were carried out with 1 M and 5 M K... more ... Carolina Belver, Miguel Angel ... The alkaline treatments were carried out with 1 M and 5 M KOH solutions, the treatments with the concentrated solution, both at room temperature and, especially, under reflux, led to the dissolution of the metakaolins and to the formation of well ...
Kinetics of kaolinite dehydration and its dependence on mechanochemical activation
Journal of Thermal …, 1988
For the mechanochemical activation of two processes can be considered: the structural disordering... more For the mechanochemical activation of two processes can be considered: the structural disordering of laminar crystals, and the formation of molecular dense aggregates from small particles. The activation energy of the dehydration is shown to decrease if the first process ...
The influence of surface-active agents on kaolinite
Journal of Colloid and Interface Science, 1979
The influence of surfactants (CTAB and SDS) on suspensions of monoionic kaolinite (Na+ and H+ for... more The influence of surfactants (CTAB and SDS) on suspensions of monoionic kaolinite (Na+ and H+ form) was investigated by adsorption, sedimentation, turbidity, electroosmosis, and rheological measurements, at pH = 3.3 and 10.0. Only small differences are found between the Na+ and H+ forms of the kailinite. The data can be accounted for satisfactorily by a mathematical model based on the DLVO theory for face-face, edge-edge, and edge-face interactions, if some assumptions on the local ψδ potentials near edge and face type surfaces are introduced.
Enhanced fluoride sorption by mechanochemically activated kaolinites
Journal of Hazardous Materials, 2008
Kaolinite clay obtained from the mines was processed and studied for its fluoride sorption capaci... more Kaolinite clay obtained from the mines was processed and studied for its fluoride sorption capacity. The surface area of the clay mineral was increased from 15.11 m2/g (raw) to 32.43 m2/g (activated) by mechanochemical activation. Batch adsorption studies were conducted to optimize various equilibrating conditions like the effect of contact time, dosage, pH for both raw and micronized kaolinites (RK and MK). The effect of other interfering anions on the defluoridation capacity (DC) of the sorbents was studied. Sorption of fluoride by the sorbents was observed over a wide pH range of 3–11. The studies revealed there is an enhanced fluoride sorption on MK. FTIR and XRD were used for the characterization of the sorbent. The surface morphology of the clay material was observed using SEM. The adsorption of fluoride was studied at three different temperatures, viz., 303, 313 and 323 K. The sorption data obtained at optimized conditions were subjected to Freundlich and Langmuir isotherms. Sorption intensity (1/n) (0.770–0.810) has been evaluated using Freundlich isotherm, whereas the values of sorption capacity Q0 (0.609, 0.714 and 0.782 mg/g) and binding energy b (0.158, 0.145 and 0.133 L/mg) at three different temperatures have been estimated using Langmuir isotherm. Adsorption process was found to be controlled by both Freundlich and Langmuir isotherms. Thermodynamic studies revealed that the sorption of fluoride on MK is endothermic and a spontaneous process. The kinetic studies indicate that the sorption of fluoride on MK follows pseudo-first-order and intraparticle diffusion models.
The effect of dehydroxylation/amorphization degree on pozzolanic activity of kaolinite
Cement and Concrete Research, 2003
The effect of heat treatment parameters on the dehydroxylation/amorphization process of the kaoli... more The effect of heat treatment parameters on the dehydroxylation/amorphization process of the kaolinite-based materials such as natural and artificial kaolin clays with different amounts of amorphous phase (metakaolin) was investigated. The procedure for quantitative estimation of amorphous phase in the heat-treated kaolinite materials was developed. The process of dehydroxylation/amorphization of kaolinite was characterized by DTA/TGA with mass-spectrometry and X-ray powder diffraction. The influence of the heat treatment temperature and content of the amorphous phase on pozzolanic activity was studied. Finally, the relationships between the chemical activity, activity strength index and the amorphous phase content were found and discussed. The results obtained are important for an optimization of the process of the metakaolin large scale production and it's use as an active pozzolanic admixture.
Clay Minerals, 1992
Depending on the preparation temperature and the origin of the raw mineral, the products obtained... more Depending on the preparation temperature and the origin of the raw mineral, the products obtained by thermal activation of kaolinite lead, by hydrothermal treatment with sodium hydroxide at 102~ either to zeolite 4A, or to cubic zeolite P, or to a mixture of cubic and tetragonal zeolite P. The change in the type of zeolite obtained was explained on the basis of a radical change of the zeolite nucleation process due to either the presence of soluble potassium or high silica content resulting from dehydration of muscovite (an impurity in the raw-kaolinite), or from "segregation" associated with the first step of the metakaolinite to mullite transformation. These phenomena occur at a lower calcination temperature with poorly-crystallized kaolinite, and iron in such a sample promotes a sensitive decrease in the formation rate of zeolite crystals. Such results could be used to characterize the crystallinity of kaolinites.