Phase Transformation of Amorphous Rice Husk Silica

Rivas, Ana; Vera, Grace; Palacios, Víctor; Cornejo, Mauricio; Rigail, Andrés; Solórzano, Guillermo

doi:10.1007/978-981-10-4819-7_2

Cited by 6 publications

(9 citation statements)

References 21 publications

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“…It was found in previous work [6] that in Sample 1, the first trace of crystallization appears at 900°C and became entirely crystalline at 1200°C, when heated continuously. On the other hand, in isothermal annealing, it starts to transform from amorphous to crystalline after 6h at 800°C and the transformation is completed after 2h at 900°C.…”

Section: B Scanning Electron Microscopy (Sem) Of Rh In the Asreceivementioning

confidence: 65%

“…Scans were taken with a 2θ, step size of 0,017 and a counting time per step of 0,1s using a Cu-Kα radiation source (λ=1.542 Å). The isothermal crystallization results were then compared with those obtained by continuous heating carried out in situ, from room temperature up to 1450°C [6].…”

Section: Methodsmentioning

confidence: 99%

“…Thus, for those applications, it is of great interest to establish the most favorable conditions to keep the RHA silica in the amorphous state. In recent studies [6], the authors evaluated the evolution of silica crystallization by continuous heating in situ from room temperature to 1450°C, highlighting the effect of impurity levels in this process. The transition temperature could also be affected by the heating mode.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Rice Husk and the Crystallization Process of Amorphous Silica from Rice Husk Ash

Rivas¹,

Vera²,

Palacios³

et al. 2016

Proceedings of the 14th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Engineering Innovati

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Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies. Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies..

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Section: B Scanning Electron Microscopy (Sem) Of Rh In the Asreceivementioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Rice Husk and the Crystallization Process of Amorphous Silica from Rice Husk Ash

Rivas¹,

Vera²,

Palacios³

et al. 2016

Proceedings of the 14th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Engineering Innovati

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“…Silicon is by far the most abundant element among the inorganic matter both in RH and RS [58,59,72,[98][99][100][101]. Ca, Mg, K, Na, P, S, Cl, and Al are also included but to a far lesser extent [59,73,98,99,[102][103][104][105]. Association of these ash forming elements as well as their distribution in the biomasses have a major impact on ash melting behavior [106] and consequently determine the remaining silica purity and quality [105,[107][108][109].…”

Section: Fuel Properties Of Rice Husk and Rice Strawmentioning

confidence: 99%

Generation of High Quality Biogenic Silica by Combustion of Rice Husk and Rice Straw Combined with Pre- and Post-Treatment Strategies—A Review

et al. 2019

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Utilization of biomass either as a renewable energy source or for the generation of biogenic materials has received considerable interest during the past years. In the case of rice husk (RH) and rice straw (RS) with high silica contents in the fuel ash, these approaches can be combined to produce high-grade biogenic silica with purities >98 wt % from combustion residues. The overall process can be considered nearly neutral in terms of CO2 emission and global warming, but it can also address disposal challenges of rice husk and rice straw. For the resulting biogenic silica, several advanced application opportunities exist, e.g., as adsorbents, catalysts, drug delivery systems, etc. This article provides a comprehensive literature review on rice husk and rice straw combustion as well as applied strategies for raw material pre-treatment and/or post-treatment of resulting ashes to obtain high quality biogenic silica. Purity of up to 97.2 wt % SiO2 can be reached by combustion of untreated material. With appropriate fuel pre-treatment and ash post-treatment, biogenic silica with purity up to 99.7 wt % can be achieved. Studies were performed almost exclusively at a laboratory scale.

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“…It has been reported previously (de Souza et al, 2002) for rice husk ash that potash-rich silicate glass is produced in liquid phase, and which participates in the sintering process. Additionally, the presence of significant amounts of potash achieves the conversion of amorphous silica into cristobalite at temperatures higher than 800ºC (Rivas et. al., 2018).…”

Section: Microscopic Characterization Of Dried Elephant Grass Leaves mentioning

confidence: 99%

Microscopic Chemical Characterization and Reactivity in Cementing Systems of Elephant Grass Leaf Ashes

et al. 2018

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Many agrowastes are being used for energy production by combustion in power plants. This process generates huge amounts of ash, which has a potential pozzolanic activity for blending with Portland cement or hydrated lime. In this paper, the ash obtained from elephant grass (Pennisetum purpureum Schum var. purple) leaves (EGLs) was studied, including the silicon content and its distribution, the presence of other compounds, and in addition, the presence of silica bodies (phytoliths). Combustion temperatures of 450 and 650°C produced an unaltered inorganic skeleton (spodogram), whereas at 850°C, there is a sintering process because of high potassium content in the ash. Phytoliths and different types of hairs were identified, and they contained high percentages of silica. Magnesium (mainly as periclase) was distributed in the most porous parts in the interior of the leaves. The silica can react with calcium hydroxide (pozzolanic reaction) forming calcium silicate hydrates (observed by field-emission scanning electron microscopy and thermogravimetric analysis). Fixed lime percentages at 28 curing days (63%) indicated the high reactivity of EGL ashes in calcium hydroxide pastes due to the pozzolanic reaction. This study demonstrates the possibility of the reuse of ashes from EGLs for the production of environmental-friendly cements.

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Phase Transformation of Amorphous Rice Husk Silica

Cited by 6 publications

References 21 publications

Characterization of Rice Husk and the Crystallization Process of Amorphous Silica from Rice Husk Ash

Characterization of Rice Husk and the Crystallization Process of Amorphous Silica from Rice Husk Ash

Generation of High Quality Biogenic Silica by Combustion of Rice Husk and Rice Straw Combined with Pre- and Post-Treatment Strategies—A Review

Microscopic Chemical Characterization and Reactivity in Cementing Systems of Elephant Grass Leaf Ashes

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