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Abstract: Silica with 98% purity was prepared from rice husk by acid leaching and used as a silica source for the syntheses of zeolite beta (Beta) under hydrothermal conditions with gel Si/Al ratios of 8, 13, 15, 20, 50, 100, 150, and 200. Based on powder X-ray diffraction patterns, samples with gel Si/Al ratios of 8–20 contained only the pure phase of Beta and the highest relative crystallinity was observed in the Beta with gel Si/Al ratio of 13. This sample was further characterized by scanning electron microscopy, particle size analyzer and N2 adsorption analysis. The Beta particles were sphere shaped with the average particle size of 1.5μm and a surface area of 670m2 g−1. The samples with gel Si/Al ratios ranging from 50 to 200 showed mixed phases of Beta and ZSM-12, and the latter phase was more dominant as the Si/Al ratio increased. [Copyright &y& Elsevier]

Adsorption is one of the methods used to reduce free fatty acid in feedstock oils with high acid content that are used for the production of biodiesel. This work investigated MCM-41 synthesized from rice husk silica for the adsorption of oleic acid in isooctane. The adsorption conformed to the Langmuir isotherm model and equilibrium adsorption capacities at 25.0°C were 277.8 mg/g for as- synthesized MCM-41 and 270.3 mg/g for template- removed MCM-41. The determined free energy and enthalpy of adsorption showed that the adsorption was spontaneous and exothermic. Adsorption of oleic acid in soy bean oil was also demonstrated. Results showed that as-synthesized MCM-41 was a better adsorbent than template-removed MCM-41 for oleic acid removal from soybean oil. [ABSTRACT FROM AUTHOR]

Photocatalysts were prepared by using TiO2 at 10 and 30 wt% grafted on rice husk silica (RHS) and zeolite NaY. The photocatalysts were characterized by X-ray diffraction and N2 adsorption-desorption analysis. The TiO2 in the anatase phase was well dispersed on the external surface area of the supports. Paraquat adsorption on the catalysts (determined before the photocatalytic testing) mainly occurred on the supports. The adsorption on the TiO2/NaY was much higher than that on the TiO2/RHS. In photocatalytic testing, both the 10 and 30% TiO2/NaY catalysts were not active probably due to high adsorption of the paraquat on the supports. In contrast, both of the TiO2/RHS catalysts were active and the best photocatalyst was the 30% TiO2/RHS. The supported catalyst showed a higher activity than the bare TiO2 indicating the enhancement from the dispersion of the RHS. Moreover, the photocatalytic degradation of paraquat on the 30% TiO2/RHS was similar to commercial TiO2 (P25) with the same TiO2 content. [ABSTRACT FROM AUTHOR]

The goal of this work was to utilize rice husk silica (RHS) and porous materials synthesized with RHS, including mesoporous material (MCM-41) and microporous materials (zeolite NaY and NaBEA), for adsorption of herbicide paraquat. The adsorption occurred although cation exchange and the capacity decreased in the following order: NaY>NaBEA> MCM-41>RHS, consistent with the amount of Al. The adsorption on all adsorbents fitted well with the Langmuir model and the maximum adsorption capacity of 185.2 mg/g-adsorbent was obtained on NaY. In addition, blue dye in commercial grade paraquat did not interfere with paraquat adsorption. Although MCM-41 was the most efficient adsorbent for the blue dye, RHS was favorable in terms of production cost. A mixture of NaY and RHS is recommended for simultaneous adsorption of paraquat and blue dye. [ABSTRACT FROM AUTHOR]