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Metakaolin-Based Geopolymers for Targeted Adsorbents to Heavy Metal Ion Separation  [PDF]
Francisco J. López, Satoshi Sugita, Motohiro Tagaya, Takaomi Kobayashi
Journal of Materials Science and Chemical Engineering (MSCE) , 2014, DOI: 10.4236/msce.2014.27002

Geopolymer adsorbents were prepared from silica and metakaolin in different Al and Si components and applied for removal of metal ions, Cs+ and Pb2+, from other heavy metal ions mixture. The geopolymer was optimized at Si/Al = 2 as adsorbent, targeting to Cs+ and Pb2+ separation. The binding behavior was well fitted to Langmuir model, which proved that the metakaolin-based geopolymer had multibinding to adsorb ions. The effective adsorption was also observed independent of NaCl concentration for the Cs+ and Pb2+. This meant that the ion adsorption of geopolymers occurred under non-electrostatic mechanism.

A Direct Comparison of Processing Methods of High Purity Rice Husk Silica  [PDF]
Benjamin Iyenagbe Ugheoke,Othman Mamat,B. Ari-Wahjoedi
Asian Journal of Scientific Research , 2013,
Abstract: It is an established fact that rice husk is rich in amorphous silica which when extracted in sufficiently pure form, could be used in several industrial applications and in the manufacture of value added products. Many of the processes employed for the purification of rice husk silica involve the use of strong acid and bases, requiring complex unit operations and extended times, apart from their unfriendliness to environment and personnel. The hydro thermobaric process was developed as a viable alternative to these rice husk silica purification processes. This study reported a performance comparison in terms of product purity, yield, structure and processing time between the newly developed hydro thermobaric and other previously used processes. The new process surpasses others in terms of processing time and yield while being at par with them in terms of product quality and structure.
Investigation of the capability of regenerated rice husk silica to remove hydrogen sulfide pollution  [cached]
Seyed Mahmoud Mehdinia,Puziah Binti Abdul Latif,Hassan Taghipour
Koomesh , 2012,
Abstract: Introduction: The main goal of this study was to investigate the capability of regenerated rice husk silicaafter saturation to remove Hydrogen sulfide (H2S). For this purpose, rice husk silica and regenerated ricehusk silica were used as adsorbents bed in filter.Material and Methods: A poly vinyl chloride filter with one liter of prepared bed was tested. Rice husksilica was prepared in a furnace at temperature of 800 oC for Four hours, after acid leaching. Saturated ricehusk silica was regenerated in a furnace at temperature of 800 oC for Four hours too. Removal efficiency,elimination capacity, and pressure drop were the three parameters to evaluate the filters bed. System wereoperated with empty bed residence time of 60 s and different inlet concentration of H2S from 10 to 300 partper million (ppm).Results: More than 98% of removal efficiency was observed for both packed filters at inletconcentrations of H2S. The maximum elimination capacity was 7.02 gm-3h-1 with H2S mass loading rateof 9.0 gm-3h-1 in the both beds. This study showed that at a 1.0 lmin-1 flow rate and differentconcentration of inlet H2S. There is no significant difference between the rice husk silica and theregenerated rice husk silica beds in the amount of removal efficiency (p< 0.01). Also, there is no significantdifference between these two beds in the amount of elimination capacity at the same condition (p< 0.01).Moreover, this study showed that the amount of pressure drop was undetectable (zero) in both filter’s bed.Conclusion: The results of this study showed the regenerated rice husk silica has the same performanceof the primary rice husk silica, Therefore it can be considered as a suitable and inexpensive bed to removeH2S at low concentration.
Synthesis and characterization of rice husk silica, silica-carbon composite and H3PO4 activated silica
Singh, D.;Kumar, R.;Kumar, A.;Rai, K. N.;
Ceramica , 2008, DOI: 10.1590/S0366-69132008000200011
Abstract: this paper discusses synthesis and characterization of (i) rice husk based nanosilica, (ii) nanosilica carbon composite granules and (iii) phosphoric acid activated ash silica. these have been produced by burning husk in air, charring husk in hydrogen and activating husk silica with h3po4 respectively. x-ray diffraction studies of these products reveal increasing peak width (amorphosity) with decreasing burning temperature. the activated rice husk silica transforms to crystalline product when burnt above 1000 oc. the variation of surface area and pore volume with burning temperature show different behavior for air fired and hydrogen charred products. activation energy associated with change in surface area for air fired and hydrogen charred samples have also been studied. rate of variation in surface area with temperature indicate different trend. the validations of these products have been evaluated by decolorizing capacity of standard molasses and iodine solution. the adsorptive powers of these products have been found to be highest for activated silica and lowest for hydrogenated ash.
A critical assessment and new research directions of rice husk silica processing methods and properties
Iyenagbe B. Ugheoke
Maejo International Journal of Science and Technology , 2012,
Abstract: A review of production and properties of silica produced from rice husk is carried out withassessment of processing and manufacturing methods and suggestion of new research directions withrespect to the processing methods. It was revealed that the structural nature of the silica produced fromrice husk is independent of the purification methods but largely dependent on the incinerationtemperature used in the production process. Also, it was established that without pre-treatment,incineration of rice husk results in the production of silica of low purity, surface area and whiteness.The paper concludes by advocating the use of a novel process called hydro thermo-baric process, forproducing high-purity reactive nano-silica from rice husk. This novel process, has the advantages ofhigh volume production, versatility of application of its product through varying any of its processparameters and being environmentally benign compared to other processes.
Mesoporous Silica from Rice Husk Ash  [cached]
V.R. Shelke,S.S. Bhagade,S.A. Mandavgane
Bulletin of Chemical Reaction Engineering & Catalysis , 2010,
Abstract: Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as aconcrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc.Sodium silicate is produced by reacting rice hull ash (RHA) with aqueous NaOH and silica is precipitatedfrom the sodium silicate by acidification. In the present work, conversion of about 90% of silica containedin RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The resultsshowed that silica obtained from RHA is mesoporous, has a large surface area and small particle size.Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usuallycontains carbon particles. Activated carbon embedded on silica has been prepared using the carbon alreadypresent in RHA. This carbon shows good adsorption capacity. 2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010)[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010). Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2): 63-67. doi:10.9767/bcrec.5.2.793.63-67]
Production of silica gel from residual rice husk ash
Lima, Samantha Pinheiro Buás de;Vasconcelos, Raimundo Pereira de;Paiva, Otávio Augusto;Cordeiro, Guilherme Chagas;Chaves, Márcia Rodrigues de Morais;Toledo Filho, Romildo Dias;Fairbairn, Eduardo de Moraes Rego;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000100014
Abstract: this paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. measurements of the chemical composition, x-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. the compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. the results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.
Properties of silica from rice husk and rice husk ash and their utilization for zeolite y synthesis
Saceda, Jan-Jezreel F.;Leon, Rizalinda L. de;Rintramee, Kamolwan;Prayoonpokarach, Sanchai;Wittayakun, Jatuporn;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000800018
Abstract: this study compared properties of silica (sio2) from rice husk (rh) and rice husk ash (rha) extracted by acid- and heat-treatment. the sio2 from rh was in amorphous phase with nearly 100% purity while that from rha was in crystalline phase with 97.56% purity. both extracted sio2 were used in the synthesis of zeolite nay but that from rh was better due to the efficiency in product recovery and simplicity of extraction. after the nay was exchanged to nh4y and calcined to convert to hy, the product did not carry over the textural properties of the parent nay and nh4y.
Synthesis of silica nanoparticles from Vietnamese rice husk by sol--gel method
Van Hai Le, Chi Nhan Thuc and Huy Ha Thuc
Nanoscale Research Letters , 2013, DOI: 10.1186/1556-276X-8-58
Abstract: Silica powder at nanoscale was obtained by heat treatment of Vietnamese rice husk following the sol--gel method. The rice husk ash (RHA) is synthesized using rice husk which was thermally treated at optimal condition at 600[degree sign]C for 4 h. The silica from RHA was extracted using sodium hydroxide solution to produce a sodium silicate solution and then precipitated by adding H2SO4 at pH = 4 in the mixture of water/butanol with cationic presence. In order to identify the optimal condition for producing the homogenous silica nanoparticles, the effects of surfactant surface coverage, aging temperature, and aging time were investigated. By analysis of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the silica product obtained was amorphous and the uniformity of the nanosized sample was observed at an average size of 3 nm, and the BET result showed that the highest specific surface of the sample was about 340 m2/g. The results obtained in the mentioned method prove that the rice husk from agricultural wastes can be used for the production of silica nanoparticles.
Leandro Ludue?a,Diana Fasce,Vera Alejandra Alvarez,Pablo Marcelo Stefani Mail
BioResources , 2011,
Abstract: The present work deals with the use of multiple-step procedures to obtain valuable sub-products, including nanocellulose, from rice husk. Each sub-product was characterized after every step by analyzing the chemical composition (mainly based on thermogravimetric analysis, Fourier transformed infrared spectra, and X-ray diffraction) and morphology (using visual observations and scanning electron microscopy). The results clearly showed that the selected procedure gave the possibility to separate silica in the first step and then to purify the resultant material, leading to nanocellulose production. All acquired sub-products can be used as additives and fillers in a very wide range of applications. The obtained results will be useful both from technological and academic points of view, mainly for people working in the field of biocomposites. The final material could give added value to a raw biomass material source such as rice husk.
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