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Ansan, South Korea

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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