Rice husks as a source of high purity silica

Riveros, Héctor G.; Garza, C.

doi:10.1016/0022-0248(86)90233-2

Cited by 32 publications

(17 citation statements)

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“…The ash of RH contains 87-97 wt% of silica in a hydrated amorphous form (Chen and Chang 1991) which is a good precursor for chemical synthesis involving silicate sources. Pure silica up to 99.98% can be obtained from rice husk ash (RHA) (Riveros and Garza 1986). Other than that, RHA can be used as an alternative source for active silica production (Della et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of zeolites NaA and NaY from rice husk ash

et al. 2011

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In this study, both zeolites NaA and NaY were synthesized from rice husk ash (RHA) by a simple conventional hydrothermal route. Rice husk (RH) was used as a silicate source to produce various zeolites. The hydrothermal route was conducted via a seeding technique involving the preparation of two separate gels, i.e. colloidal seed and feedstock gel. The zeolite was first produced using commercially available chemicals and followed by the replacement of the commercial silicate sources with RHA derived silicate. The RHA silicate was obtained by combusting the RH at different temperatures and durations i.e. 450°C for both 2 and 6 hours, as well as 750°C for 6 hours. Zeolite NaY (faujasite) was successfully synthesized with commercial chemical seed and RHA derived feedstock gel. On the other hand, using RHA silicate in both colloidal seed and feedstock gel would give only zeolite NaA. Elemental, structural and morphological analyses of RHA and zeolites were carried out with X-ray fluorescence (XRF) spectrometer, X-ray diffractometer (XRD) and scanning electron microscopy (SEM).Keywords Zeolite NaA · Zeolite NaY · Rice husk ash · Silicate sources Electronic supplementary material The online version of this article (

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Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of zeolites NaA and NaY from rice husk ash

et al. 2011

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“…Other authors used thermal treatments at different temperatures and atmospheres with or without pretreatments 4,8,9,12,13 .…”

Section: Riverosmentioning

confidence: 99%

Characterization of Silica Produced from Rice Husk Ash: Comparison of Purification and Processing Methods

et al. 2017

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As a byproduct of the combustion of rice husk to generate energy, rice husk ash (RHA) is formed by silica and carbon, apart from small amounts of other constituents. Several treatments can be used to increase the purity of the silica obtained, or even produce pure silica. The present study tested the efficiency of different techniques to obtain silica, characterizing and comparing the silicas obtained from RHA. A literature review was conducted, and then selected techniques were used to produce silica, which was characterized by XRF, XRD, particle sizing, specific weight, specific surface area, total carbon, and SEM. The literature review showed that most techniques include a pretreatment like acid or alkaline leaching followed by thermal treatment to increase the amount of silica produced by reduction of carbonaceous materials. The results showed that it is possible to produce silica from RHA using simple methods, and that these produced silica with purity above 98%. The treatments that afforded the best results were acid leaching followed by thermal treatment at 800ºC, and alkaline extraction at low temperature, with silica purity of 99.3% and 99.6%, respectively.

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“…RHA samples were reacted with sodium hydroxide with a molar ratio SiO 2 / NaOH of 1:2 in reflux at 100°C for 1 hr or until no silica residue to select optimal condition. The solution of sodium silicate are designated as SSi 2 , SSi 4 and SSsi 5 according to the type of RHA of RHA 2 , RHA 4 , and RHA 5 , respectively . The RHA and sodium silicate were characterized by X Ray Diffraction (XRD) Cu-Kαpw 3050/60-2006, Fourier Transform Infra Red (FTIR) (Jasco FT/ IR 460 plus, and Scanning Electron Microscope (SEM) JOEL JEM-100S.…”

Section: Methodsmentioning

confidence: 99%

“…There are several methods for the extraction of silica from biomass. Many authors, [4][5][6][7] have suggested that acid preliminary treatment before thermal treatment is a reasonable method for natural silica extraction. The high purity of silica and low mineral impurity are retrieved by boiling in hydrochloric solution for 1 h followed by burning in the atmosphere at 650-700 °C for 4 h [5].…”

Section: Introductionmentioning

confidence: 99%

A Low Cost Conversion Method of Agro-Residue to Coagulant Aid

Abo-El-Enein

Eissa²,

Diafullah

et al. 2008

The International Conference on Chemical and Environmental Engi

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Rice is one of the major crops grown throughout the world, it covers 1% of the earth's surface and is a primary source of food for billions of people Globally, approximately 600 million tons of rice paddy is produced each year. On average 20% of the rice paddy is husk, giving an annual total production of 120 million tons. In Egypt, the annual rice production is about 5,700,000 tons, equivalent to 200,000 tons of rice husk ash .After the separation of the rice from the paddy, one -third of the mass remains as a waste material ..Many workers have tried to use this agricultural waste to produce useful materials such as silica, zeolite, silica gel silicon carbide, activated carbon and sodium silicate notation coagulant aid. Rice husk ash is one of the most silica rich raw materials containing about 90-98% silica (this quantity depends on the soil type, plant variety and climatic conditions, geological factor, type of ground, near of harvest, sample preparation and analysis method..etc.The chemical process discussed below not only provides a solution for waste disposal but also recovers a valuable silica product, together with certain useful associate recoveries The activated silica or sodium silicate is one of the four basic types of coagulants aids beside pH adjusters, clay and polymers which increase a stability of coagulant and can unite with the positively charged aluminum or with iron flocs, resulting in a larger, denser lamellar floc that settles faster and enhances enmeshment. The objectives of this study were to :produce rice husk ash (RHA) from rice husk, produce sodium silicate, and characterizations of new materials obtained by FTIR, XRD, and SEM. Under the study condition it was found that selected sample (optimum condition),of RHA which is designated as RHA 5 obtained by calcination of untreated RH at 650 º C in semi closed system. FTIR shows signals at 1098 and 800 cm -1 for Si-O and O-Si-O respectively; XRD shows a sharp signal (amorphous silica ) at 2θ =22º and SEM examination indicate that rectangular particles should be distinguished. whereas RHA 5 used in manufacturing of sodium silicate which is designated as Ssi 5 and identified by XRD with its characteristic peak at 2θ about 28º, FTIR shows signals at (1443,994) for Si-O-Si, NFTIR shows signal at 7326 for overtone OH stretching Si-OH.

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Rice husks as a source of high purity silica

Cited by 32 publications

References 4 publications

Synthesis and characterization of zeolites NaA and NaY from rice husk ash

Synthesis and characterization of zeolites NaA and NaY from rice husk ash

Characterization of Silica Produced from Rice Husk Ash: Comparison of Purification and Processing Methods

A Low Cost Conversion Method of Agro-Residue to Coagulant Aid

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