Preparation Of Porous Silica Research Articles

Preparation of porous silica from natural chlorite via selective acid leaching and its application in methylene blue adsorption

Preparation of porous silica from natural chlorite via selective acid leaching and its application in methylene blue adsorption

Preparation of mesoporous silica from a Nigerian talc ore by acetic acid treatment

A study on the preparation of porous silica from a Nigerian talc ore by acetic acid leaching was investigated. The initial and leached talc products were characterized by Energy Dispersive X-ray fluorescence EDXRF , X-ray diffraction XRD , Scanning Electron Microscopy SEM with Energy Dispersive spectroscopy EDS and the N2 adsorption techniques. The influence of acetic acid concentration, reaction temperature and particle size on the ore leaching kinetics were examined. The results of the dissolution rates were found to be significantly influenced by leachant concentration, temperature and decreasing particle size. The dissolution mechanism process followed the diffusion control shrinking core model with the calculated activation energy of 34.53 kJ/mol supporting the proposed mechanism. The leached product has a specific surface area increased to 2.056 m2 /g from the initial ore surface area of 0.15 m2 /g. At optimal leaching conditions, the pore size distribution calculated by Barret-Joyner-Halenda BJH method based on N2 gas isotherms showed the presence of peaks from micropores and mesopores formation, indicating the porous nature of the leached product.

Synthesis of Porous Silica via Styrene Natural Rubber Template: The Effect of Calcination

This paper discussed the preparation of porous silica using styrene natural rubber (SNR) sacrificial template. The preparation of porous silica based on SNR template involved three steps which were the synthesis of SNR, the formation of SNR/silica, and the formation of porous silica. The SNR sacrificial template was synthesized using styrene as monomer and deproteinized natural rubber (DPNR) latex as based material. The effects of different silica loading and mixing methods were studied to produce SNR/silica films. Calcinations process was carried out to remove SNR to produce porous silica structure. The increasing of silica loadings enhanced the porosity of the template structure. The shaker mixing method produced better porous structure compared to the mechanical stirring and the magnetic stirring methods. The porous structure was analyzed via SEM which the optimum silica loading was obtained at 15 % of silica loading.

Preparation of Porous Silica by Acid Dissociation of Thermally Activated Kaolinite

Preparation of porous silica from thermally activated kaolinite was investigated by using acid dissociation process, and the relationship between structural transformation and acid dissociation properties of aluminium were elucidated. AlVI transfers into AlV and AlIV when kaolinite changes into metakaolinite during thermal activation. AlV is dissoluble in acid, while AlVI, AlIV are difficult to be dissolved into acid, therefore, the coordinations of aluminium affect acid dissociation of alumina markedly. Mesoporous silica is made by acid dissociation alumina of metakaolinite, and the specific surface area of porous silica is determined by acid dissociation ratio of alumina. The dissociation ratio of aluminum is up to 97% when kaolinite is activated at 900°C for 15 min. Specific surface area of the porous silica material is 357 m2/g, the pore volume is 0.43 cc/g, and BJH pore diameter is 2.18 nm. The pore is found to be in the worm-like shape by high resolution TEM analysis.

Preparation of Porous Silica by Microemulsion Coupling with Sol-Gel Method

A novel method of microemulsion coupling with sol–gel process was used for preparation of porous silica using tetraethyl orthosilicate as silicon source. Effect of solvent and catalyst on the surface texture properties was investigated respectively. The results showed that porous silica with large specific surface area (738.65 m2/g) and high pore volume (2.01 cm3/g) was obtained. However, the mesopores in silica were arranged in disorder and showed great ununiformity in shape and arrangement. To obtain porous silica with desired texture properties, an appropriate dosage of ethanol and higher HCl concentration were needed.

Preparation of porous silica from chlorite by selective acid leaching

Porous silica was prepared by selective leaching of chlorite and the influence on the porous properties of the product of the acid type and acid concentration, solution temperature and leaching time were investigated. After leaching, only SiO 2 remained, the other components being selectively leached from the sample in the order MgO < Fe 2O 3 < Al 2O 3. The specific surface area of the product obtained by H 2SO 4-leaching was greater than with HNO 3- and HCl-leaching. The highest specific surface area (394 m 2/g) was obtained by leaching the chlorite with 5 N H 2SO 4 at 90 °C for 1.5 h. The pore size distribution of the products showed a maximum at about 5 nm with a pore size much larger than would be expected for selective leaching of the octahedral chlorite sheets. The 29Si MAS NMR spectra of the products showed a stronger Q 4 peak (related to a framework structure unit) than the Q 3 peak (from a layer structure unit), suggesting the presence of a framework structure similar to silica gel rather than the original layered structure. The resultant structure of the silica product results in a lower specific surface area than found in leached vermiculite and phlogopite.

Preparation of porous silica from vermiculite by selective leaching

High surface area silica was obtained by selectively leaching vermiculite. The influence of acid concentration and leaching time on the porous properties of silica was studied. Leaching with 2 M HCl at 80 °C for 2 h produced a maximum value of surface area (672 m 2/g) with total pore volume of 0.44 ml/g. The 29Si MAS NMR spectra of the leached products indicate mainly Q 3 and Q 4 structural units, assigned as layer and framework structures, respectively. The layer structure is responsible for forming micropores and the framework structure forms mesopores. The number of micropores decreased with longer leaching time, the micropores condensing to increase the framework structure. The characteristics of the porous silica obtained from vermiculite are compared with those from other clay minerals.

Effect of grinding on the preparation of porous material from talc by selective leaching

Porous silica has been prepared from various clay min-erals including kaolinite [1], montmorillonite [2] andvermiculite [3] by selective leaching. Selective leach-ingisaprocessforremovingpartofthestartingmaterialby exploiting solubility differences in the leaching so-lution.Thestartingmaterialstobeleachedcanbeeithercrystallineoramorphous.Theuseofamorphous(anhy-drous) starting material has been found to improve theleaching rate in some cases; for example, microporoussilicahasbeenobtainedfromthermallyamorphizedde-hydrated kaolinite (metakaolin) by acid leaching [1, 4].Clay minerals can be amorphized by either heating orgrinding (mechanochemical treatment). It has been re-ported that mechanochemical treatment of various clayminerals brings about changes in their surface struc-ture without recrystallization into new phases [5]. Wehave studied the effect of grinding on the preparationof porous silica from kaolinite and have found similarresults to those obtained by thermal amorphization [6].However,theclaymineralsamorphizedbydehydrationretainedtheirlayeredstructureandconsequentlyexhib-ited high surface areas after leaching, whereas mechan-ically amorphized kaolinite was found to contain bothlayered and framework structures giving rise to bothmicropores and mesopores on leaching. Consequentlythe surface area of the leached product was slightlysmaller than the product from metakaolin.Although there are many reports of the preparationof porous silica from clay minerals by leaching, thepreparation of porous material from talc has not beenreported.Talc(Mg

Preparation of Porous Silica from Mechanically Activated Kaolinite

Mesoporous silica has been prepared by leaching of the Al2O3 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 m2/g to 284 m2/g. The pore size distribution, calculated by the BJH method based on N2 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.

Successive Use of Amphiphilic Block Copolymers as Nanoreactors and Templates: Preparation of Porous Silica with Metal Nanoparticles

A new way for preparation of microporous silica containing metal nanoparticles inside pores is described. Special amphiphilic block copolymers, polybutadiene-b-poly(ethylene oxides), are used in a ...

Molecular Dynamics Simulations of Porous Silica

ABSTRACTWe describe a new simulation method for the preparation of porous silica and present results from molecular dynamics simulations of the structures obtained. We start from a homogeneous liquid phase with reduced atomic charges. The charges are then slowly rescaled and the atoms start clustering to finally form a porous network. We observe that local ordering precedes formation of long range correlations. We investigate physical properties of porous silica such as porosity, internal surface and fractality. They are in reasonable agreement with experimental data, although internal surface and porosity seem to be systematically larger than those found in adsorption experiments. The vibrational and dielectric power spectra show an enhanced intensity in the low frequency region. These modes can be associated with slow dynamics of clusters.