E and B Nanotech. Co.

Ansan, South Korea

E and B Nanotech. Co.

Ansan, South Korea
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Shao G.N.,Hanyang University | Shao G.N.,University of Dar es Salaam | Kim Y.,Hanyang University | Imran S.M.,Hanyang University | And 5 more authors.
Microporous and Mesoporous Materials | Year: 2013

The textural properties of TiO2-SiO2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and (3) forming the TiO2 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 TiO2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N2 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 m2/g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm3/g) and ethanol as a medium to form the TiO2 sol (TSCES, 1.85 cm3/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. © 2013 Elsevier B.V.


Quang D.V.,Hanyang University | Quang D.V.,Vietnam Academy of Science and Technology | Lee J.E.,Hanyang University | Kim J.-K.,E and B Nanotech. Co. | And 3 more authors.
Powder Technology | Year: 2013

Thiol-functionalized silica that has been used to remove heavy metal from an aqueous solution and support metallic nanoparticles is usually synthesized by reflux in an organic solvent containing 3-mercaptopropyltrimethoxysilane (MPTMS). In this paper, we report a gentle method for grafting thiol-functional groups onto silica gel by an aging process that does not require mixing and refluxing in an organic solvent. Silica gel was synthesized by a sol-gel method from H2SO4 (40%) and sodium silicate, which was crushed into beads with sizes ranging from 180 to 450μm. Silica beads (50g) were mixed with 75mL of a functionalization solution consisting of MPTMS, H2O, and C2H5OH and aged at 50°C for 36h in a box dryer. The success of the functionalization process was confirmed by FT-IR, BET, SEM and elemental analyses. The functionalization solution was percolated into pores and thiol-functional groups were grafted onto the surface and pore walls of the silica beads. The ability of these functionalized silica beads to adsorb silver ions was determined by the Langmuir isotherm equation with a maximum adsorption of 75.8mg/g. Silver nanoparticles with sizes ranging from 2 to 6nm formed by chemical reduction were located inside the pores and on the surfaces. © 2012 Elsevier B.V.


Quang D.V.,Hanyang University | Quang D.V.,Vietnam Academy of Science and Technology | Kim J.K.,E and B Nanotech. Co. | Sarawade P.B.,Hanyang University | And 2 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2012

In the present research, amino-functionalized silica materials were synthesized to develop absorbents for removing copper (II) ions from water. Three kinds of silica with various BET surface areas and pore volumes (331.4m 2/g, 460.1m 2/g, 717.7m 2/g and 1.38cm 3/g, 1.06cm 3/g, 0.57cm 3/g, respectively) were used to determine an optimum material. 3-Aminopropyltrimethoxysilane (3-APTMS) and N-[3-(trimethoxysilyl)propyl]-ethylenediamine (MSDA) are two amino-functional moieties grafted onto silica surfaces. A maximum copper absorption of 33.45mg/g was confirmed using the amino-functionalized material at an initial 3-APTMS concentration of 2.52mmol/g. Silica with a BET surface of 331m 2/g and a pore volume of 1.38cm 3/g demonstrated a good copper absorption capacity. Interference species such as pH, NH 3 and EDTA were also studied in this work. © 2011 The Korean Society of Industrial and Engineering Chemistry.


Sarawade P.B.,Hanyang University | Kim J.-K.,EandB Nanotech. Co. | Hilonga A.,Hanyang University | Quang D.V.,Hanyang University | Kim H.T.,Hanyang University
Applied Surface Science | Year: 2011

The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m2/g) and small pore volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, pore volume, pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N2 physisorption isotherm; pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed. © 2011 Elsevier B.V. All rights reserved.


Sarawade P.B.,Hanyang University | Kim J.-K.,EandB Nanotech. Co. | Hilonga A.,Hanyang University | Quang D.V.,Hanyang University | Kim H.T.,Hanyang University
Microporous and Mesoporous Materials | Year: 2011

Highly porous hydrophilic and hydrophobic silica xerogels were synthesized by surface modification of silica hydrogels at ambient pressure drying. The silica hydrogels were prepared by a sol-gel polymerization of an inexpensive silica precursor (sodium silicate) under atmospheric conditions. In order to minimize shrinkage due to drying, the hydrogel surface was modified using trimethylchlorosilane (TMCS) in the presence of ethanol/n-hexane solution before ambient pressure drying (APD). Properties of the final product were investigated using Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Analysis (TG-DTA), and nitrogen physisorption studies. The final product was observed to have an extremely high specific surface area (783 m2/g) and a large cumulative pore volume (2.74 cm3/g). Highly porous hydrophilic xerogels were obtained after heat-treating the modified xerogels. At temperatures above 450 °C the surface alkyl groups (CH3) were significantly oxidized and, consequently, the properties of the resulting xerogels were altered. Products obtained via the proposed inexpensive approach have superior properties and the method exploits an inexpensive silica source (sodium silicate). Thus it is feasible for large-scale economic industrial production. © 2010 Elsevier Inc. All rights reserved.


Sarawade P.B.,Hanyang University | Kim J.-K.,E and B Nanotech. Co. | Hilonga A.,Hanyang University | Kim H.T.,Hanyang University
Solid State Sciences | Year: 2010

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/cm3), high surface area (917 m2/g), and large cumulative pore volume (2.8 cm3/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. © 2010 Elsevier Masson SAS. All rights reserved.


Sarawade P.B.,Hanyang University | Kim J.-K.,E and B Nanotech. Co. | Hilonga A.,Hanyang University | Kim H.T.,Hanyang University
Journal of Hazardous Materials | Year: 2010

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H2SiF6) and 100 ml, 0.297 M Na2CO3 to generate the alkaline aqueous slurry. Silica was separated from the slurry by filtration and the sodium fluoride was extracted from the aqueous solution by evaporation method. The obtained mesoporous silica was characterized by N2 absorption/desorption (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results confirm that the separation of silica and NaF was successful and the final products have high purity. The silica product was found to have an average pore diameter of 4.14 nm and a high surface area (up to 800 m2/g). 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. © 2009 Elsevier B.V. All rights reserved.


Sarawade P.B.,Hanyang University | Kim J.-K.,EandB Nanotech. Co. | Hilonga A.,Hanyang University | Quang D.V.,Hanyang University | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2011

This work demonstrates the synthesis of hydrophilic and hydrophobic high surface area silica aerogel beads with a large pore volume. Wet gel silica beads were modified and heat-treated under atmospheric pressure after modification of the surface by trimethychlorosilane (TMCS). The effects of heat treatment on the physical (hydrophobicity) and textural properties (specific surface area, pore volume, and pore size) of silica aerogel beads were investigated. The results indicated that hydrophobicity of the silica aerogel beads can be maintained up to 400 °C. The hydrophobicity of the silica aerogel beads decreased with increasing temperature in the range of 200-500 °C, and the beads became completely hydrophilic after heat treatment at 500 °C. The specific surface area, cumulative pore volume, and pore size of the silica aerogel beads increased with increasing temperature. Heating the TMCS modified bead gel at 400 °C for 1 h resulted in silica aerogel beads with high surface area (769 m2/g), and large cumulative pore volume (3.10 cm3/g). The effects of heat treatment on the physical and textural properties of silica aerogel beads were investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric and differential analysis (TG-DTA), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer, Emmett and Teller (BET) and BJH nitrogen gas adsorption and desorption methods. © 2011 Elsevier B.V. All rights reserved.


Sarawade P.B.,Hanyang University | Kim J.-K.,E and B Nanotech. Co. | Hilonga A.,Hanyang University | Kim H.T.,Hanyang University
Powder Technology | Year: 2010

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 the specific surface area and cumulative pore volume of the resulting silica powder. Hydrophobic silica powder with low tapping density (0.27 g/cm3), high specific surface area (870 m2/g), and a large cumulative pore volume (2.2 cm3/g) was obtained at 10%V TMCS. Surface silanol groups of the wet-gel slurry were replaced by non-hydrolysable methyl groups (-CH3), resulting in a hydrophobic silica powder as confirmed by FT-IR spectroscopy and contact angle measurements. We also employed FE-SEM, EDS, TG-DTA, and nitrogen physisorption studies to characterize the silica powders produced and to compare the properties of modified and unmodified silica powders. Moreover, we used a spray-dying technique in the present study, which significantly reduced the overall processing time, making our method suitable for economic and large-scale industrial production of silica powder. © 2009 Elsevier B.V. All rights reserved.


Hilonga A.,Hanyang University | Kim J.-K.,E and B Nanotech. Co. | Sarawade P.B.,Hanyang University | Kim H.T.,Hanyang University
Powder Technology | Year: 2010

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 TiOCl2 (titania precursor) into preformed silica networks (SiO2 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 SiO2 after the rapid condensation of silicic acid monomers. The latter were formed as a product of the reaction of aqueous sodium silicate solution (SiO2/Na2O = 3.24) with 2 N HCl. In the second step, TiOCl2 was added to the SiO2 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 m2/g, 27.4 Å, and 0.29 cm3/g respectively. The composite has superior oil absorption (240 ml/100 g) compared to that of the conventional pure TiO2 (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. © 2010 Elsevier B.V. All rights reserved.

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