Browsing by Author "Elineema, Gideon"
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Item BET Study of Silver-Doped Silica Based on an Inexpensive Method(Materials Letters, 2012-04-28) Hilonga, Askwar; Kim, Jong-gil; Sarawade, Pradip B.; Quang,Dang Viet; Shao, Godlisten N.; Elineema, Gideon; Kim, Hee TaikThe aimof this study is to identify an acid precursor that ismost desirable for the synthesis of sodiumsilicate-based silver-doped silica for large-scale industrial production. The final products were developed based on the presence of silver (silver-doped silica) or the absence of silver (pure silica). The properties of the obtained final products were examined using the BET method. This method involves characterization based on N2 physisorption studies to determine the surface area, pore diameter, and pore volume. Various graphs were plotted using the obtained data to describe the pore size distribution, isotherms, and the properties of hysteresis loops. Silver-doped silica with a BET surface area of up to 357 m2/g and a pore size of 5.4 nm was obtained using the most desirable precursors—sodium silicate and sulfuric acid. This is an unprecedented step toward synthesis of silver-doped silica fromdesirable precursors. This approach to the synthesis of silica with desirable propertieswithout involving sacrificial templates (surfactants) will be convenient for many applications and suitable for large-scale economic industrial production.Item Characterization of Calcium-Doped Silica Gel Prepared in an Aqueous Solution(Resources Processing, 2012-02-20) Quang, Dang Viet; Park, Jin Koo; Kim, Jong-gil; Elineema, Gideon; Shao, Godlisten N.; Lee, Jae Eun; Kim, Hee TaikIn this study, calcium-doped silica was prepared by modifying sodium silicate-based silica gel in an aqueous solution of Ca(OH)2. Silica gels with less than 1 mm in size with different pH values were treated in Ca(OH)2 solution at concentrations ranging from 2 to 20 g/L and aged at 25, 60, and 90°C for 40 min. The BET surface area of the silica gel decreased while its pore size increased considerably after modification in Ca(OH)2 solution. The pH of 5% calcium-doped silica in water ranged from about 8.5 to 10, depending on the pH of silica gel, the aging temperature, and the concentration of the Ca(OH)2. When the concentration of the Ca(OH)2 solution was 20%, needle-like crystals of calcium silicate hydrate formed over the surface of silica gel.Item Influence of titania content on the mesostructure of titania–silica composites and their photocatalytic activity(Powder Technology, 2012-08-28) Shao, Godlisten N.; Hilonga, Askwar; Jeon, Sun Jeong; Lee, Jae Eun; Elineema, Gideon; Quang, Dang Viet; Kim, Jong-Kil; Kim, Hee TaikTitania–silica composites (TSC) with various Ti/Si ratios were synthesized via sol–gel process using less expensive precursors; sodium silicate solution as a silica source and titanium oxychloride as a titania source. The influence of varying Ti content in the composites was examined by FTIR, SEM, TEM, DTA/TGA, N2 physisorption studies, XRF and XRD. The BET surface area of the raw materials increased with increasing Ti/Si ratio up to 2.9 (461 m2/g) but further increase of Ti content beyond that ratio yielded compositeswith decreased surface area. The effect of aging evaluated in the samplewith Ti/Si=2.9 revealed that aging the composite for 2 h yields titania–silica powderwith the highest surface area (461 m2/g). The FTIR analysis displayed the presence of a vibration band at 945 cm−1, assignable to hetero linkage of the Si–O–Ti depicting the incorporation of TiO2 into SiO2 to form a composite.Moreover, photodegradation of methyl orange (MO) by the samples calcined at 800 °C showed that the TSC-5-800 (Ti/Si=5.6) exhibited the highest maximum photocatalytic activity of all the composites.Item Peptization technique in the synthesis of titania–silica composites and their photocatalytic properties(Chemical Engineering Journal, 2012-05-18) Shao, Godlisten N.; Hilonga, Askwar; Kim, You Na; Kim, Jong-gil; Elineema, Gideon; Quang, Dang Viet; Jeon, Sunjeong; Kim, Hee TaikA comparative study of titania–silica composite (TSC) synthesized via peptization sol–gel method was conducted. Typically, titanium hydroxide gel (Ti(OH)4) was formed by condensation of titanium oxychloride solution using adequate amount of ammonium hydroxide solution. The preformed gel was peptized either in silicic acid (SA) or nitric acid (NA) to form a sol. The composite was characterized by XRD, FTIR, SEM, TEM, TGA, and N2 physisorption studies. The XRD patterns and the TEM micrographs confirmed that thermal-derived samples of the composite, formed using silicic acid as a silica source and peptizing agent (TSC–SA), yielded TiO2ASiO2 composite with a single-phase (anatase phase); while a mixture of both anatase and rutile phases were observed in the composite (TSC–NA), where nitric acid was used as a peptizing agent. FTIR analysis showed the vibration band assignable to the TiAOASi bond at 945 cm 1, suggesting that titania was incorporated into silica to form a composite. Furthermore, a simple experiment of photodegradation of methyl orange in the presence of sunlight was performed to demonstrate the practical efficacy of the composites synthesized via this method. The results indicated that the calcined samples of TSC–NA-800 had the highest activity due to its superior properties.Item Quantitative Recovery of High Purity Nanoporous Silica from Wste Products of the Phosphate Fertilizer Industry(2012-06-12) Elineema, Gideon; Kim, Jong-gil; Hilonga, Askwar; Shao, Godlisten N.; Kim, You Na; Quang, Dang Viet; Sarawade, PB; Kim, Hee TaikThis study reports on the quantitative recovery of high purity nanoporous silica from wastes material (H2SiF6) of the phosphate fertilizer industry and Na2O SiO2. The silica recovered from the wastes was compared with silica from the reaction of H2SO4 and Na2O SiO2 because H2SO4 is commonly used. The product recovered from the wastes material and H2SO4 were 99.3% and 99.1% pure, respectively. The quantity recovered were 22.30 g and 20.11 g, respectively. The product had superior properties suitable for applications such as chromatography, reinforcing material for rubber and plastics. The process may significantly reduce the release of SiF4 gas into the environment.Item Silver-Doped Silica Powder with Antibacterial Properties(Powder Technology, 2011-10-08) Hilonga, Askwar; Kim, Jong-gil; Sarawade, Pradip B.; Quang, Dang Viet; Shao, Godlisten N.; Elineema, Gideon; Kim, Hee TaikIn this study a simple and reproduciblemethodwas used to develop silver-doped silica powder with antibacterial properties. Silicamatriceswere synthesized via a sol–gel route which allows one to easily tailor textural and chemical properties. A wide range of silica-materials/products was obtained via the present route. These are: pure silver nanoparticles (Ag0), silver in ionic state (Ag+), AgCl nanoparticles, and the mixture of Ag0 and AgCl. The efficacy of these products were tested against Escherichia coli and the results demonstrate thatmaterials that are suitable for antibacterial applications were obtained by this newly developed technique while utilizing sodium silicate, which is relatively inexpensive, as a silica precursor. This may significantly boost the industrial production of the inexpensive silver-doped silica products for various applications. A project on other innovative industrial applications of our products is in progress.Item Synthesis of Mesoporous Silica with Superior Properties Suitable for Green Tire(2012-04-26) Hilonga, Askwar; Kim, Jong-gil; Sarawade, Pradip B.; Quang, Dang Viet; Shao, Godlisten N.; Elineema, Gideon; Kim, Hee TaikIn this article we report synthesis of mesoporous silica with superior properties for application in green tire (environmentally friendly tire) as filler. The synthesis was done using a newly innovated apparatus which produce mesoporous silica with superior properties. The desired superior properties are big pore size, optimum BET, large pore volume, uniform properties, and improved performance in real application as tire filler. Mesoporous silica was characterized by BET method and final product with a pore diameter of up to 37 nm was obtained without using surfactants. This is unprecedented step toward synthesis of silica that is suitable for tire industry.Item Two step synthesis of a mesoporous titania–silica composite from titanium oxychloride and sodium silicate(Powder Technology, 2011-11-15) Shao, Godlisten N.; Elineema, Gideon; Quang, Dang Viet; Kim, You Na; Shim, YoungHo; Hilonga, Askwar; Kim, Jong-gil; Kim, Hee TaikMesoporous titania–silica composite (MTSC) with a large surface area (387 m2/g) and large pore volume was synthesized by a two step condensation sol–gel method. Transparent TiO2 sol was formed at room temperature through condensation and peptization of titanium oxychloride solution using ammonium hydroxide and aqueous nitric acid respectively. Sodium silicate was used as a silica source to form a composite with the preformed TiO2 sol. The physical properties of the composite were examined by Fourier Transform infrared (FTIR), BET surface area, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nitrogen physisorption behavior of the synthesized composite was compared to that obtained from grafting and one-pot co-condensation methods using the same precursors in the presence of cetyltrimethylammonium bromide (CTAB). It was found that MTSC synthesized under this method possessed large pore sizes and pore volume but its thermal stability was comparatively low. FTIR spectra showed the formation of a Ti\O\Si bond at 940 cm−1 suggesting that titania was incorporated in silica to form a composite. The XRD patterns showed that the major phase of the titania had an anatase phase up to 900 °C but it transforms into rutile when calcined at 1000 °C. Furthermore the EDS studies of the as-synthesized and calcined samples substantiated the formation of titania–silica composites.Item Two-step rapid synthesis of mesoporous silica for green tire(KOREAN JOURNAL OF CHEMICAL ENGINGERING, 2012-04-17) Hilonga, Askwar; Kim, Jong-gil; Sarawade, PB; Quang, DV; Shao, Godlisten N.; Elineema, Gideon; Kim, HTWe report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste material (hexafluorosilicic acid, H2SiF6) of phosphate fertilizer industry and sodium silicate (Na2O·SiO2). The reaction was performed in a newly innovated manufacturing apparatus. This apparatus produces mesoporous silica with uniform properties through controlled mixing of source materials at predetermined equivalent ratio. The precursors are rapidly mixed within the nozzles to enable uniform control of physical properties of the final product. The obtained mesoporous silica was characterized using N2 physisorption studies, scanning electron microscope (SEM), and EDS. The final product was found to have superior properties that are suitable for green tire (environmentally friendly tire) as inorganic filler. The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries. A project on innovative industrial application of our products for the tire industry is in progress.