A sustainable route for the preparation of activated carbon and silica from rice husk ash
ABSTRACT An environmentally friendly and economically effective process to produce silica and activated carbon form rice husk ask simultaneously has been developed in this study. An extraction yield of silica of 72-98% was obtained and the particle size was 40-50 nm. The microstructures of the as-obtained silica powders were characterized by X-ray diffraction (XRD) and infrared spectra (IR). The surface area, iodine number and capacitance value of activated carbon could achieve 570 m(2)/g, 1708 mg/g, 180 F/g, respectively. In the whole synthetic procedure, the wastewater and the carbon dioxide were collected and reutilized. The recovery rate of sodium carbonate was achieved 92.25%. The process is inexpensive, sustainable, environmentally friendly and suitable for large-scale production.
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ABSTRACT: In the present study, rice husk ash (RHA, a solid waste from agriculture) was served as the support for loading calcined eggshell (another material derived from waste source) to prepare solid base catalyst. This catalyst was then applied for catalytically converting palm oil into biodiesel. The effects of catalyst preparation conditions (such as rice husk treatment temperature, the loading of calcined eggshell on the RHA, and the calcination temperature of eggshell-loaded RHA), reaction conditions (such as reaction time, methanol-to-oil molar ratio and catalyst loading) and the catalyst reusability were carefully studied. The experimental results revealed that 30% RHA800-800 exhibited the highest catalytic activity. More specifically, when the reaction was carried out with a reaction time of 4 h, methanol-to-oil molar ratio of 9:1, and catalyst loading of 7 wt.%, the biodiesel yield could reach 91.5%. Besides, after reused for more than 8 cycles, the catalyst could still possess a rather high biodiesel yield (above 80%).Fuel Processing Technology 05/2015; 133. DOI:10.1016/j.fuproc.2015.01.005 · 3.02 Impact Factor
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ABSTRACT: The overall valorization of rice husk char obtained by flash pyrolysis in a conical spouted bed reactor (CSBR) has been studied in a two-step process. Thus, silica has been recovered in a first step and the remaining carbon material has been subjected to steam activation. The char samples used in this study have been obtained by continuous flash pyrolysis in a conical spouted bed reactor at 500°C. Extraction with Na2CO3 allows recovering 88% of the silica contained in the rice husk char. Activation of the silica-free rice husk char has been carried out in a fixed bed reactor at 800°C using steam as activating agent. The porous structure of the activated carbons produced includes a combination of micropores and mesopores, with a BET surface area of up to 1365m(2)g(-1) at the end of 15min.Bioresource Technology 07/2014; 170C:132-137. DOI:10.1016/j.biortech.2014.07.073 · 5.04 Impact Factor
Conference Paper: PRODUCTION AND CHARACTERISATION OF AMORPHOUS SILICA FROM RICE HUSK WASTE[Show abstract] [Hide abstract]
ABSTRACT: Rice covers about 1% of the earth's surface. Rice husk is the major by-product of the rice-processing industries which must be appropriately managed. On average 20% of the rice paddy is husk. The major constituents of rice husk are cellulose, lignin and silica. During growth, rice plants absorb silica and other minerals from the soil and accumulate it into their structures. Its composition varies with the diversity, climate and geographic location of growth. The high grade of silica in the husk opens a possibility for its valorisation. Through thermal treatment by calcination, with or without energy recovery, the ash obtained is constituted by amorphous silica with high porosity having potential application as ligand in construction materials, catalyst support, metals adsorbent, insulation or ceramics, among others. In the research developed, the rice husk was processed by washing, acid leaching and calcination in order to produce an ash, which was characterized aiming at assessing possible valorising solutions. The chemical treatment involved water washing for partial purification of the husk, and leaching with diluted sulphuric acid solution, allowing obtaining high metals removal efficiency, decreasing at least 90% of the initial content of contaminants (K, Fe and Mn). After calcination at 540ºC for organics decomposition, the final ash consisted in white colour amorphous silica as confirmed by XRPD analysis, being characterized by SEM to evaluate the microstructure. The results showed that after calcination the rice husk ash had a very porous, alveolar and even tracery morphology, which seems promising for applications requiring high reactivity, such as in construction materials and technical ceramics.4th International Conference on Engineering for Waste and Biomass Valorisation, Porto - Portugal; 09/2012