Inuence of Gel Aging Time on the Properties of Various Silica Aerogels Synthesized from Water Glass 2 2 -1 2 -1 -3

Silica aerogel, a nanoporous material, was produced by using rice husk ash via sol–gel method. The aim of the study is to examine effects of the acid type (acetic, hydrochloric, nitric, oxalic and sulfuric acid), dryer type (air, freeze, oven and vacuum) and the addition of tetraethyl orthosilicate on the structural and physical properties of aerogels produced from rice husk ash. In addition, this is the first study investigating the effect of vacuum oven drying on the structure of rice husk based silica aerogel. Specific surface area and pore size of obtained silica aerogels have been analyzed by the N2 adsorption and desorption measurements at 77 K via Brunauer–Emmett–Teller (BET) and Barrett–Joiner–Halenda (BJH) methods, respectively. Surface functional groups were determined with fourier transform infrared spectroscopy (FTIR). Surface morphology was examined with scanning electron microscopy (SEM). Moreover, density was calculated by tapping method. The results showed that all of the variables had remarkable effects on the final properties of the silica aerogel. The BET specific surface area of the silica aerogels increased with the addition of tetraethyl orthosilicate, while the tapping density decreased. The BET specific surface area and pore size of silica aerogels varied between 140.7–322.5 m2 g−1, and 5.38–12.05 nm, respectively. Silica aerogel which was obtained by using oxalic acid, tetraethyl orthosilicate addition and air dryer had the highest BET specific surface area (322.5 m2 g−1).

Current study aimed to utilize agricultural waste, wheat husk to produce valuable materials. Amorphous silica (~88 % purity) was extracted from acid leached wheat husk, and used in the synthesis of zeolite NaA. Crystallization factors were analysed at different temperatures (40–100 °C) and durations (1–3 days) without using template. Crystallization conditions showed slight effects on the structural properties of the final product. The wheat husk silica based zeolites had a BET surface area and particle size ranging from 0.48 to 1.21 m g and 0.60 to 3.00 µm, respectively. Results indicated that the wheat husk silica can be used to produce advanced materials for various industrial purposes. Keywords Porous material Silica Wheat husk ash Zeolite NaA References 2 −1

Carbon aerogel its fabrication and characterization and its uses in this process were studied for desalinating of saline and brackish water. The carbon aerogel manufacturing process involves the polymerization and pyrolysis of the mixture of resorcinol and formaldehyde. Carbon aerogels were analyzed using BET, BJH, and T-plot after construction. The effect of various parameters (including the influent salt concentration, the intensity of electric current flow, the distance between the electrodes and pH) on salt adsorption were studied. Analysis of BET/BJH shown that the surface of aerogel was 677.8 m 2 /g. much of porosity in the samples of carbon aerogel were between 1-2 nm, namely micro-pour and a similar level 0f 456 m 2 /gr is dedicated to micro-pour, with a correlation coefficient (r) equal to 94.5. According to the results, it seems that carbon aerogel electrodes have a good structure in desalination of brackish and saline water.

Dekker Encyclopedia of Nanoscience and Nanotechnology, Second Edition - Six Volume Set (Print Version), 2004

Applied Surface Science, 2003

Physicochemical pre-treatment of fly ash for nanoporous materials synthesis. Synthesis of zeolites, mesoporous silica, and silica aerogel/foam from fly ash. Synthesis of nanoporous materials using solid wastes as silica and/or alumina sources. Applications of the synthesized nanoporous materials via fly ash recycling for sustainability. g r a p h i c a l a b s t r a c t a b s t r a c t Large quantities of fly ash are discharged as a by-product from coal power plants. Therefore, an effective method to recycle this waste material is necessary. In this regard, the high silica content of fly ash makes it a potential useful source for the synthesis of nanoporous materials, such as zeolites, mesoporous silica or silica aerogels. In this mini review, zeolite synthesis from fly ash was examined by considering the ash composition, pretreatment procedures, and hydrothermal synthesis conditions (substrate composition and synthesis temperature/time) to identify an optimal set of synthesis conditions. These zeolites can be used as adsorbents and ion-exchangers for environmentally hazardous materials including those present in the fly ash itself. The synthesis of mesoporous silica materials with a high surface area and large pore volume derived from fly ash was next assessed for their use as a support and as a surface-functionalized host for capturing the global warming CO 2 and rare earth metal ions. Lastly, the utilization of fly ash for the preparation of silica aerogels or adiabatic foams, which are being considered as a potential building insulation materials, was briefly examined. Cases of synthesizing these nanoporous materials using other solid wastes as silica and/or alumina sources were also examined. The synthesis of diverse porous materials utilizing the waste sources would enable a high level of recycling for a sustainable society with a low environmental burden.

Space 98, 1998

Journal of Porous Materials, 2003

This paper reviews the synthesis and the absorbing properties of the wide variety of porous sorbent materials that have been studied for application in the removal of organics, particularly in the area of oil spill cleanup. The discussion is especially focused on hydrophobic silica aerogels, zeolites, organoclays and natural sorbents many of which have been demonstrated to exhibit (or show potential to exhibit) excellent oil absorption properties. The areas for further development of some of these materials are identified.