Pradip Sarawade - Academia.edu (original) (raw)

Papers by Pradip Sarawade

Applied Surface Science, Feb 1, 2010

The influence of annealing conditions on the properties of reinforced silver-embedded silica matr... more The influence of annealing conditions on the properties of reinforced silver-embedded silica matrix was systematically investigated in the present study. The samples were prepared via a recently reported method using sodium silicate as a silica precursor. Aluminium ions were used to reinforce and improve the chemical durability of silver-embedded silica; and the mole ratio of the precursors was fixed at Al/Ag = 1. The properties of the final product were examined in relation to its counterparts; namely pure silica, aluminium-embedded silica (without silver), and silver doped silica (without aluminium). The materials were heat treated at the range of 600-1000 °C under the constant supply of argon (inert atmosphere). The properties of the final product were compared with those of the previously reported materials prepared via the same method but calcined in air. The current material was found to have pure silver nanoparticles (without AgCl nanoparticles) while the previous material had both silver and AgCl nanoparticles. The results demonstrate that materials with more desirable properties can be obtained by this newly developed technique while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

Chemistry of Materials, 2015

In this research, a facile route was used to prepare silver nanoparticle-coated precipitated sili... more In this research, a facile route was used to prepare silver nanoparticle-coated precipitated silica using sodium silicate, a cheap precursor. Precipitated silica (PS) was synthesized by dropping 8% H 2 SO 4 into a mixed solution of sodium silicate 24% (Na 2 O·3.4SiO 2 ) and NaCl 4%; under constant stirring. The precipitated silica was then modified by simultaneous addition of 3-aminopropyltriethoxysilane (3-APTES) and 8% H 2 SO 4 . The resulting material was aged at 80 • C for 1 h to produce amino-functionalized precipitated silica (AFPS). Silver nanoparticle-coated precipitated silica (Ag-NPS) was synthesized by adding silver nitrate (AgNO 3 ). The synthesis procedure also involved mixing for 2 h and dropping 0.05 M sodium borohydride (NaBH 4 ). The final products, namely, PS, AFPS, and Ag-NPS were characterized using BET analyzer, FE-SEM, TEM and XRD. Silver nanoparticles with an average size ranging from 18 to 25 nm were found mostly coated on the exterior layer of the precipitated silica. The synthesis method reported in this work is facile and might be used for large-scale industrial production of inexpensive Ag-NPS.

We studied the effects of various surfactants on the shape and morphology of three metal organic ... more We studied the effects of various surfactants on the shape and morphology of three metal organic frameworks (MOFs), i.e., Co-MOF, Cu-MOF, and In-MOF, which were synthesized under microwave irradiation. The as-synthesized materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen sorption. The effects of microwave irradiation time, temperature, and surfactant template were investigated. The synthetic parameters, including the type of surfactant template and the reaction temperature, played crucial roles in the size, shape, and morphology of the MOF microcrystals. We also evaluated these MOFs as sorbents for capturing CO 2 . Of the synthesized materials, Cu-MOF demonstrated the highest CO 2 capture capacity, even at atmospheric pressure and ambient temperature.

ACS Sustainable Chemistry & Engineering, 2013

We observed that support morphology has dramatic effects on the performance of nitridated silica ... more We observed that support morphology has dramatic effects on the performance of nitridated silica as a base. By simply replacing conventional silica supports (such as SBA-15 and MCM-41) with fibrous nanosilica (KCC-1), we observed multifold enhancement in the catalytic activity of the nitridated solid base for Knoevenagel condensations and transesterification reactions. This enhancement of the activity can be explained by amine accessibility, which is excellent in KCC-1 due to its open and flexible fibrous structure, that facilitates penetration and interaction with basic amine sites.

Powder Technology, 2009

Less aggregated titania-silica composite was developed by a versatile and reproducible method usi... more Less aggregated titania-silica composite was developed by a versatile and reproducible method using relatively cheap precursors. The final product has more suitable properties than the conventional materials. The composite was synthesized by using sodium silicate, as a silica precursor, and freshly prepared TiOCl 2 as a titania source. The final product was obtained after subsequent calcination for 5 h at 300 to 1000°C. The primary particles of the composite, as examined by SEM technique, are generally less aggregated. The XRD patterns for the calcined samples indicate the presence of TiO 2 and there is a significant increase of peak intensity as the calcination temperature increases. EDS and XPS analyses confirmed the formation of pure composite rich in Ti, Si, and O. Nitrogen physisorption studies reveal that the composite is mesoporous and have large BET surface area (~375 m 2 /g). A simple experiment of photoreduction of methyl orange under solar radiation was attempted to demonstrate the reliability and improvement of titania-silica composite in practice. It was found out that its efficiency is high as compared to P-25 TiO 2 under solar light. The results demonstrate that composite with desirable properties for various applications can be obtained via the present route.

Solid State Sciences, 2010

We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambie... more We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid-base sol-gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and cumulative pore volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm 3 ), high surface area (917 m 2 /g), and large cumulative pore volume (2.8 cm 3 /g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG-DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 C. We discuss our results and compare our findings for modified versus unmodified silica beads.

Powder Technology, 2012

In this study a simple and reproducible method was used to develop silver-doped silica powder wit... more In this study a simple and reproducible method was used to develop silver-doped silica powder with antibacterial properties. Silica matrices were 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 (Ag 0 ), silver in ionic state (Ag + ), AgCl nanoparticles, and the mixture of Ag 0 and AgCl. The efficacy of these products were tested against Escherichia coli and the results demonstrate that materials 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.

Powder Technology, 2010

We rapidly synthesized a homogeneous titania-silica composite with properties desired by the pape... more We rapidly synthesized a homogeneous titania-silica composite with properties desired by the paper and paint industries by the sol-gel method in a controlled manner. The composite was synthesized by impregnating TiOCl 2 (titania precursor) into preformed silica networks (SiO 2 trimers). The first step before the formation of high molecular weight polymers in this rapid, versatile, and reproducible method involves the generation of trimers of SiO 2 after the rapid condensation of silicic acid monomers. The latter were formed as a product of the reaction of aqueous sodium silicate solution (SiO 2 /Na 2 O = 3.24) with 2 N HCl. In the second step, TiOCl 2 was added to the SiO 2 trimers at 50°C. The structure of the composite was characterized by FE-SEM, EDS, TEM, XRD, FTIR, and nitrogen physisorption studies. The results demonstrated the homogeneous incorporation of titania into silica, which is normally difficult to perform because of the significant differences between the hydrolysis rates of the precursors. The maximum BET surface area, average diameter of the pores, and the maximum pore volume obtained were 739 m 2 /g, 27.4 Å, and 0.29 cm 3 /g respectively. The composite has superior oil absorption (240 ml/100 g) compared to that of the conventional pure TiO 2 (100 ml/100 g) filler. It also shows significant photocatalytic ability. The materials prepared via the proposed method are potential candidates for large scale commercial production.

Powder Technology, 2010

A hydrophobic mesoporous silica powder was prepared by surface modification of a sodium silicate-... more A hydrophobic mesoporous silica powder was prepared by surface modification of a sodium silicate-based wet-gel slurry. The effects of the volume percentage (%V) of trimethylchlorosilane (TMCS), used as surface-modifying agent, on the physicochemical properties of the silica powder were investigated. We observed that as the %V of TMCS in the simultaneous solvent exchange and surface modification process increased, so did

Microporous and Mesoporous Materials, 2013

The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three ... more The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and forming the TiO 2 sol in ethanol medium. The sol-gel process was exquisitely used to form the composites using cost effective precursors. Initially, the precipitated hydrogels were washed with water or alcohol to evaluate the influence of washing on the dried hydrogels. Consequently, two composites were formed differently in the presence of stearic acid (SA) as a surfactant and the other by forming TiO 2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N 2 physisorption studies, FTIR, TGA, SEM, XRF and HRTEM. The BET surface area of the sample obtained after washing the hydrogels with ethanol (TSCE) was the largest (594 m 2 /g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm 3 /g) and ethanol as a medium to form the TiO 2 sol (TSCES, 1.85 cm 3 /g) were relatively superior to those obtained under influence of changing washing solvent. Photocatalytic decolorization of methylene blue by the composites calcined at 800°C revealed that the TSCES-800 possessed the highest activity of all the composites due to its superior properties.

Materials Letters, 2012

Here we report the preparation of micrometer-sized highly nanoporous, relatively trasperant silic... more Here we report the preparation of micrometer-sized highly nanoporous, relatively trasperant silica aerogel beads with high surface area as well as large pore volume with sizes ranging from 165 to 395 μm. The wet micrometer-sized silica hydrogel beads were prepared through hydrolysis and polycondensation of sodium silicate as a silica precursor. A hydrophobic micro-silica aerogel nanoporous bead was synthesized by simultaneous solvent exchange surface modification process of as synthesized micron sized silica hydrogel bead at an ambient pressure. Hydrophilic micron-sized silica aerogel beads with relatively more textural properties (surface area, pore volume and pore size) with its counterpart were obtained by heating the synthesized hydrophobic micro-silica aerogel beads at 395°C for an hour. This study demonstrates a robust approach to high porous hydrophobic and hydrophilic micro-silica aerogel beads with a myriad of potential applications in various fileds such as catalysis, biomolecule immobilization, chromatographic separation, and CO 2 absorption. This proposed synthesis, which exploits a low-cost silica source (water-glass), is suitable for large-scale industrial production of highly porous hydrophobic and hydrophilic micro-silica aerogel beads at an ambient pressure.

Materials Letters, 2012

The aim of this study is to identify an acid precursor that is most desirable for the synthesis o... more The aim of this study is to identify an acid precursor that is most desirable for the synthesis of sodium silicate-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 N 2 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 m 2 /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 from desirable precursors. This approach to the synthesis of silica with desirable properties without involving sacrificial templates (surfactants) will be convenient for many applications and suitable for large-scale economic industrial production.

Materials Letters, 2012

Here, we report on the synthesis of silver nanoparticles (Ag-NPs) manipulating the pores of silic... more Here, we report on the synthesis of silver nanoparticles (Ag-NPs) manipulating the pores of silica beads (SBs) with sizes ranging from 0.5 to 1 mm. Silver ions were occluded inside the pores of SBs and in situ reduced to Ag-NPs using Sodium borohydride (NaBH 4 ). SBs with different average pore diameters from 3.8 to 20 nm were used to assess the effect of their pore sizes and porous structures on the formation of Ag-NPs. Obtained results revealed that the silver amount occluded inside pores increases along with the increase of total pore volume. The particle sizes of the synthesized Ag-NPs mainly distribute from 8 to 15 nm and vary with the pore sizes and porous structure.

Korean Journal of Chemical Engineering, 2012

We report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste ma... more We report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste material (hexafluorosilicic acid, H 2 SiF 6 ) of phosphate fertilizer industry and sodium silicate (Na 2 O·SiO 2 ). 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 N 2 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.

Korean Journal of Chemical Engineering, 2010

The experimental results of aging time and temperature on the textural properties of water-glass ... more The experimental results of aging time and temperature on the textural properties of water-glass (sodium silicate)-based silica aerogels are reported and discussed. Aging of the hydrogel for different times and temperatures led to an ability to increase the stiffness and strength of the networks. These improvements enabled the gel to withstand ambient pressure drying (APD) and, consequently, preserve the highly porous silica network without collapse. The pore size and volume increased with increasing aging temperature and time, while the specific surface area decreased. Monolithic aerogels with extremely low bulk density (~0.069 g/cm 3 ), high specific surface area (820 m 2 g −1 ), large cumulative pore volume (3.8 cm 3 g −1 ), and high porosity (~96%) were obtained by aging at 60 o C for 18 hours. Therefore, easy synthesis of monolithic silica aerogels at ambient pressure is achievable using a relatively inexpensive silica precursor (sodium silicate).

Journal of Non-Crystalline Solids, 2010

In this study we have examined the properties of sodium alumino silicate (SAS) synthesized by sim... more In this study we have examined the properties of sodium alumino silicate (SAS) synthesized by simultaneous addition of sodium silicate and aluminate under controlled reaction conditions. The varied conditions include the concentration of the reactants and the pH (low, neutral, and high); while the stirring speed, precipitating temperatures, and the drying conditions were kept constant. XRD, SEM, and EDS results indicate that the materials developed were amorphous and have irregularly-textured particles. They were rich in Si, Al, O, and Na; and had Na/Al molar ratios of about 0.4 to 1. The SiO 2 :Al 2 O 3 molar ratio in the final product ranges from 2.2 to 5.8 as determined by EDS. FTIR studies confirmed the formation of Si-O-Al bond. Nitrogen physisorption studies were done to examine the surface area and porosity of the final product. The SAS samples examined have bulk density greater than 2.5 g/cm 3 , pore volume up to 0.85 cm 3 /g, and the pore diameters between 13 to 20 nm. The BET surface area ranges from 80 to 318 m 2 /g, and oil absorption from 75 to 200 ml/100 g. The products obtained have desirable properties and are expected to be a potential low-cost alternative as functional fillers for paper and paint industries.

Applied Surface Science, Feb 1, 2010

The influence of annealing conditions on the properties of reinforced silver-embedded silica matr... more The influence of annealing conditions on the properties of reinforced silver-embedded silica matrix was systematically investigated in the present study. The samples were prepared via a recently reported method using sodium silicate as a silica precursor. Aluminium ions were used to reinforce and improve the chemical durability of silver-embedded silica; and the mole ratio of the precursors was fixed at Al/Ag = 1. The properties of the final product were examined in relation to its counterparts; namely pure silica, aluminium-embedded silica (without silver), and silver doped silica (without aluminium). The materials were heat treated at the range of 600-1000 °C under the constant supply of argon (inert atmosphere). The properties of the final product were compared with those of the previously reported materials prepared via the same method but calcined in air. The current material was found to have pure silver nanoparticles (without AgCl nanoparticles) while the previous material had both silver and AgCl nanoparticles. The results demonstrate that materials with more desirable properties can be obtained by this newly developed technique while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

Chemistry of Materials, 2015

In this research, a facile route was used to prepare silver nanoparticle-coated precipitated sili... more In this research, a facile route was used to prepare silver nanoparticle-coated precipitated silica using sodium silicate, a cheap precursor. Precipitated silica (PS) was synthesized by dropping 8% H 2 SO 4 into a mixed solution of sodium silicate 24% (Na 2 O·3.4SiO 2 ) and NaCl 4%; under constant stirring. The precipitated silica was then modified by simultaneous addition of 3-aminopropyltriethoxysilane (3-APTES) and 8% H 2 SO 4 . The resulting material was aged at 80 • C for 1 h to produce amino-functionalized precipitated silica (AFPS). Silver nanoparticle-coated precipitated silica (Ag-NPS) was synthesized by adding silver nitrate (AgNO 3 ). The synthesis procedure also involved mixing for 2 h and dropping 0.05 M sodium borohydride (NaBH 4 ). The final products, namely, PS, AFPS, and Ag-NPS were characterized using BET analyzer, FE-SEM, TEM and XRD. Silver nanoparticles with an average size ranging from 18 to 25 nm were found mostly coated on the exterior layer of the precipitated silica. The synthesis method reported in this work is facile and might be used for large-scale industrial production of inexpensive Ag-NPS.

We studied the effects of various surfactants on the shape and morphology of three metal organic ... more We studied the effects of various surfactants on the shape and morphology of three metal organic frameworks (MOFs), i.e., Co-MOF, Cu-MOF, and In-MOF, which were synthesized under microwave irradiation. The as-synthesized materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen sorption. The effects of microwave irradiation time, temperature, and surfactant template were investigated. The synthetic parameters, including the type of surfactant template and the reaction temperature, played crucial roles in the size, shape, and morphology of the MOF microcrystals. We also evaluated these MOFs as sorbents for capturing CO 2 . Of the synthesized materials, Cu-MOF demonstrated the highest CO 2 capture capacity, even at atmospheric pressure and ambient temperature.

ACS Sustainable Chemistry & Engineering, 2013

We observed that support morphology has dramatic effects on the performance of nitridated silica ... more We observed that support morphology has dramatic effects on the performance of nitridated silica as a base. By simply replacing conventional silica supports (such as SBA-15 and MCM-41) with fibrous nanosilica (KCC-1), we observed multifold enhancement in the catalytic activity of the nitridated solid base for Knoevenagel condensations and transesterification reactions. This enhancement of the activity can be explained by amine accessibility, which is excellent in KCC-1 due to its open and flexible fibrous structure, that facilitates penetration and interaction with basic amine sites.

Powder Technology, 2009

Less aggregated titania-silica composite was developed by a versatile and reproducible method usi... more Less aggregated titania-silica composite was developed by a versatile and reproducible method using relatively cheap precursors. The final product has more suitable properties than the conventional materials. The composite was synthesized by using sodium silicate, as a silica precursor, and freshly prepared TiOCl 2 as a titania source. The final product was obtained after subsequent calcination for 5 h at 300 to 1000°C. The primary particles of the composite, as examined by SEM technique, are generally less aggregated. The XRD patterns for the calcined samples indicate the presence of TiO 2 and there is a significant increase of peak intensity as the calcination temperature increases. EDS and XPS analyses confirmed the formation of pure composite rich in Ti, Si, and O. Nitrogen physisorption studies reveal that the composite is mesoporous and have large BET surface area (~375 m 2 /g). A simple experiment of photoreduction of methyl orange under solar radiation was attempted to demonstrate the reliability and improvement of titania-silica composite in practice. It was found out that its efficiency is high as compared to P-25 TiO 2 under solar light. The results demonstrate that composite with desirable properties for various applications can be obtained via the present route.

Solid State Sciences, 2010

We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambie... more We report a method to synthesize low-density transparent mesoporous silica aerogel beads by ambient pressure drying (APD). The beads were prepared by acid-base sol-gel polymerization of sodium silicate in aqueous ammonia solution via the ball dropping method (BDM). To minimize shrinkage during drying, wet silica beads were initially prepared; their surfaces were then modified using trimethylchlorosilane (TMCS) via simultaneous solvent exchange and surface modification. The effects of the volume percentage (%V) of TMCS on the physical and textural properties of the beads were investigated. The specific surface area and cumulative pore volume of the silica aerogel beads increased with an increase in the %V of TMCS. Silica aerogel beads with low packing bed density (0.081 g/cm 3 ), high surface area (917 m 2 /g), and large cumulative pore volume (2.8 cm 3 /g) was obtained when 10%V TMCS was used. Properties of the final product were examined by FE-SEM, TEM, BET, and TG-DT analyses. Surface chemical modifications were confirmed by FTIR spectroscopy. The hydrophobic silica aerogel beads were thermally stable up to 411 C. We discuss our results and compare our findings for modified versus unmodified silica beads.

Powder Technology, 2012

In this study a simple and reproducible method was used to develop silver-doped silica powder wit... more In this study a simple and reproducible method was used to develop silver-doped silica powder with antibacterial properties. Silica matrices were 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 (Ag 0 ), silver in ionic state (Ag + ), AgCl nanoparticles, and the mixture of Ag 0 and AgCl. The efficacy of these products were tested against Escherichia coli and the results demonstrate that materials 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.

Powder Technology, 2010

We rapidly synthesized a homogeneous titania-silica composite with properties desired by the pape... more We rapidly synthesized a homogeneous titania-silica composite with properties desired by the paper and paint industries by the sol-gel method in a controlled manner. The composite was synthesized by impregnating TiOCl 2 (titania precursor) into preformed silica networks (SiO 2 trimers). The first step before the formation of high molecular weight polymers in this rapid, versatile, and reproducible method involves the generation of trimers of SiO 2 after the rapid condensation of silicic acid monomers. The latter were formed as a product of the reaction of aqueous sodium silicate solution (SiO 2 /Na 2 O = 3.24) with 2 N HCl. In the second step, TiOCl 2 was added to the SiO 2 trimers at 50°C. The structure of the composite was characterized by FE-SEM, EDS, TEM, XRD, FTIR, and nitrogen physisorption studies. The results demonstrated the homogeneous incorporation of titania into silica, which is normally difficult to perform because of the significant differences between the hydrolysis rates of the precursors. The maximum BET surface area, average diameter of the pores, and the maximum pore volume obtained were 739 m 2 /g, 27.4 Å, and 0.29 cm 3 /g respectively. The composite has superior oil absorption (240 ml/100 g) compared to that of the conventional pure TiO 2 (100 ml/100 g) filler. It also shows significant photocatalytic ability. The materials prepared via the proposed method are potential candidates for large scale commercial production.

Powder Technology, 2010

A hydrophobic mesoporous silica powder was prepared by surface modification of a sodium silicate-... more A hydrophobic mesoporous silica powder was prepared by surface modification of a sodium silicate-based wet-gel slurry. The effects of the volume percentage (%V) of trimethylchlorosilane (TMCS), used as surface-modifying agent, on the physicochemical properties of the silica powder were investigated. We observed that as the %V of TMCS in the simultaneous solvent exchange and surface modification process increased, so did

Microporous and Mesoporous Materials, 2013

The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three ... more The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and forming the TiO 2 sol in ethanol medium. The sol-gel process was exquisitely used to form the composites using cost effective precursors. Initially, the precipitated hydrogels were washed with water or alcohol to evaluate the influence of washing on the dried hydrogels. Consequently, two composites were formed differently in the presence of stearic acid (SA) as a surfactant and the other by forming TiO 2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N 2 physisorption studies, FTIR, TGA, SEM, XRF and HRTEM. The BET surface area of the sample obtained after washing the hydrogels with ethanol (TSCE) was the largest (594 m 2 /g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm 3 /g) and ethanol as a medium to form the TiO 2 sol (TSCES, 1.85 cm 3 /g) were relatively superior to those obtained under influence of changing washing solvent. Photocatalytic decolorization of methylene blue by the composites calcined at 800°C revealed that the TSCES-800 possessed the highest activity of all the composites due to its superior properties.

Materials Letters, 2012

Here we report the preparation of micrometer-sized highly nanoporous, relatively trasperant silic... more Here we report the preparation of micrometer-sized highly nanoporous, relatively trasperant silica aerogel beads with high surface area as well as large pore volume with sizes ranging from 165 to 395 μm. The wet micrometer-sized silica hydrogel beads were prepared through hydrolysis and polycondensation of sodium silicate as a silica precursor. A hydrophobic micro-silica aerogel nanoporous bead was synthesized by simultaneous solvent exchange surface modification process of as synthesized micron sized silica hydrogel bead at an ambient pressure. Hydrophilic micron-sized silica aerogel beads with relatively more textural properties (surface area, pore volume and pore size) with its counterpart were obtained by heating the synthesized hydrophobic micro-silica aerogel beads at 395°C for an hour. This study demonstrates a robust approach to high porous hydrophobic and hydrophilic micro-silica aerogel beads with a myriad of potential applications in various fileds such as catalysis, biomolecule immobilization, chromatographic separation, and CO 2 absorption. This proposed synthesis, which exploits a low-cost silica source (water-glass), is suitable for large-scale industrial production of highly porous hydrophobic and hydrophilic micro-silica aerogel beads at an ambient pressure.

Materials Letters, 2012

The aim of this study is to identify an acid precursor that is most desirable for the synthesis o... more The aim of this study is to identify an acid precursor that is most desirable for the synthesis of sodium silicate-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 N 2 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 m 2 /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 from desirable precursors. This approach to the synthesis of silica with desirable properties without involving sacrificial templates (surfactants) will be convenient for many applications and suitable for large-scale economic industrial production.

Materials Letters, 2012

Here, we report on the synthesis of silver nanoparticles (Ag-NPs) manipulating the pores of silic... more Here, we report on the synthesis of silver nanoparticles (Ag-NPs) manipulating the pores of silica beads (SBs) with sizes ranging from 0.5 to 1 mm. Silver ions were occluded inside the pores of SBs and in situ reduced to Ag-NPs using Sodium borohydride (NaBH 4 ). SBs with different average pore diameters from 3.8 to 20 nm were used to assess the effect of their pore sizes and porous structures on the formation of Ag-NPs. Obtained results revealed that the silver amount occluded inside pores increases along with the increase of total pore volume. The particle sizes of the synthesized Ag-NPs mainly distribute from 8 to 15 nm and vary with the pore sizes and porous structure.

Korean Journal of Chemical Engineering, 2012

We report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste ma... more We report a two-step rapid route of synthesizing inexpensive mesoporous silica using the waste material (hexafluorosilicic acid, H 2 SiF 6 ) of phosphate fertilizer industry and sodium silicate (Na 2 O·SiO 2 ). 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 N 2 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.

Korean Journal of Chemical Engineering, 2010

The experimental results of aging time and temperature on the textural properties of water-glass ... more The experimental results of aging time and temperature on the textural properties of water-glass (sodium silicate)-based silica aerogels are reported and discussed. Aging of the hydrogel for different times and temperatures led to an ability to increase the stiffness and strength of the networks. These improvements enabled the gel to withstand ambient pressure drying (APD) and, consequently, preserve the highly porous silica network without collapse. The pore size and volume increased with increasing aging temperature and time, while the specific surface area decreased. Monolithic aerogels with extremely low bulk density (~0.069 g/cm 3 ), high specific surface area (820 m 2 g −1 ), large cumulative pore volume (3.8 cm 3 g −1 ), and high porosity (~96%) were obtained by aging at 60 o C for 18 hours. Therefore, easy synthesis of monolithic silica aerogels at ambient pressure is achievable using a relatively inexpensive silica precursor (sodium silicate).

Journal of Non-Crystalline Solids, 2010

In this study we have examined the properties of sodium alumino silicate (SAS) synthesized by sim... more In this study we have examined the properties of sodium alumino silicate (SAS) synthesized by simultaneous addition of sodium silicate and aluminate under controlled reaction conditions. The varied conditions include the concentration of the reactants and the pH (low, neutral, and high); while the stirring speed, precipitating temperatures, and the drying conditions were kept constant. XRD, SEM, and EDS results indicate that the materials developed were amorphous and have irregularly-textured particles. They were rich in Si, Al, O, and Na; and had Na/Al molar ratios of about 0.4 to 1. The SiO 2 :Al 2 O 3 molar ratio in the final product ranges from 2.2 to 5.8 as determined by EDS. FTIR studies confirmed the formation of Si-O-Al bond. Nitrogen physisorption studies were done to examine the surface area and porosity of the final product. The SAS samples examined have bulk density greater than 2.5 g/cm 3 , pore volume up to 0.85 cm 3 /g, and the pore diameters between 13 to 20 nm. The BET surface area ranges from 80 to 318 m 2 /g, and oil absorption from 75 to 200 ml/100 g. The products obtained have desirable properties and are expected to be a potential low-cost alternative as functional fillers for paper and paint industries.