Rice Hull Ash Research Articles

Thermoelectric Properties of Porous β-SiC Fabricated from Rice Hull Ash

Beta-SiC powder was synthesized by carbothermal reduction of silica contained in rice hull ash, and porous ceramics were fabricated by conventional sintering. Electrical conductivity and Seebeck coefficient were measured as functions of temperature under Ar atmosphere to evaluate their applicability to thermoelectric energy conversion. Thermoelectric properties of β-SiC ceramics fabricated from rice hull ash were comparable to those fabricated from a commercial high-purity powder.

Phospholipid adsorption onto rice hull ash from soy oil miscellas

Phospholipid was adsorbed from soy oil miscellas by rice hull ash, with small doses of adsorbent binding most efficiently. Adsorption increased with residual phosphorus, suggesting that less accessible adsorption sites were being used as residual values increased, probably due to the heterogeneous nature of the ash. Binding of phospholipid was enhanced by isopropanol, as has been found for adsorption on silicic acid.

Desorption of soy oil lutein from rice hull cristobalite with polar solvents

AbstractThe effectiveness of sequential isopropanol/hexane washes of increasing polarity for desorbing soy oil pigment (lutein) from alkaline and acid rice hull ash was studied. Increasing the polarity promoted desorption of pigment. However, the amount of pigment desorbed with each extraction decreased after washing with 2% isopropanol. More lutein was desorbed as the amount of adsorbed lutein increased. Desorption from acid ash was greater than that from alkaline ash, which may be due to the absence of potassium from acid ash. The data suggest that the adsorption sites, occupied by lutein, are not all equally accessible to isopropanol, probably because of the irregular structure of the ash.

Evaluation of soy oil lutein isotherms obtained with selected adsorbents in hexane miscellas

Bleaching of soy oil hexane/miscellas by adsorption of the lutein was examined. Quantitative differences in the adsorption behavior between a bleaching clay, alkaline rice hull ash and acid rice hull ash were measured by comparing the constants,K andn, of Freundlich isotherms. All the isotherms were dose‐dependent withK being inversely related andn directly related, to adsorbent mass. Overall, the bleaching clay performed better than the ashes. Alkaline ash had a largerK value than acid ash, but then value of acid ash was greater.Equations of lutein adsorption were derived based on initial concentrations on lutein and the amount adsorbed per gram. Logarithmic plots produced constants,Ki and ni which were the intercept and slope, respectively. As adsorbent dose increased,Ki decreased andni increased for each adsorbent studied. These findings may have applications in the processing of dilute miscellas where low temperature, low viscosity oil refining is desired.

Preparation of SiCl<sub>4</sub> from Rice Hull Ashes (Part 2)

In order to produce SiCl4 efficiently from active SiO2 in rice hulls, rice hull ash, combustion waste of rice hull, was chlorinated under the coexistence of alkaline and alkaline earth additives such as potassium compounds in the temperature range of 600° to 1000°C. These additives changed to chlorides under the condition of chlorination. Potassium compounds accelerated the chlorination of the rice hull ash. Other alkaline and alkaline earth compounds such as lithium, sodium, magnesium and calcium inhibited the chlorination. The acceleration effect of potassium in the chlorination of SiO2 was explained by assuming that the diffusion of K+ ion in SiO2 lattice caused the distortion of SiO2 lattice and the chlorinating species such as chlorinated carbon were easy to diffuse in SiO2 lattice. The inhibitory efffect of other elements was interpreted in terms of the absence of SiO2 lattice distortion, since the ionic radii of these elements are smaller than that of K+. It is also inferred that the melts of these chlorides covered the contact points of SiO2 and C.

Preparation of SiCl<sub>4</sub> from Rice Hull Ashes (Part 3)

The chlorination of a mixture of rice hull ashes and carbon containing alkaline and alkaline earth salts was investigated by FT-IR-PAS. It was thought that the relative ratio of totally symmetric SiO4 stretching vibration (ν1) to antisymmetric SiO4 degenerate stretching vibration (ν3) in infrared frequencies for SiO2 whose constituent oxygen atoms occupy the corners of a tetrahedron shows structural changes of SiO2 network. The results of ν1/ν3 of SiO2 before and after chlorination showed that the values of ν1/ν3 increased and the chlorination was accelerated because K+ increased. The ν1/ν3 of SiO2 by addition of Na+, Mg2+ and Ca2+ was smaller than that of K+ and these additives did not accelerate the chlorination. KCl, NaCl, MgCl2 and CaCl2 which formed during the chlorination melted at 900°C.

Mass housing based on traditional design and indigenous materials for passive cooling in the tropical urban climate of the Philippines

This paper presents two low-cost houses which result from the adaptation of traditional Philippine architectural designs and the use of indigenous building materials that are aesthetically and bioclimatically acceptable for mass housing in a tropical urban environment. The increasing cost of energy and concern about indoor environment in a developing country has led to studies for design criteria appropriate for the hot, humid climate of Metro Manila and, at the same time, for the low-income family housing program or mass housing. The Bahay Kubo (nipa hut) and the Bahay na Bato (house of stone) were the subjects of study regarding traditional design for passive cooling. Coco-timber, rice-hull ash (RHA), ordinary portland cement (OPC) and bamboo were the indigenous materials chosen owing to their excellent thermal qualities. The combination of traditional design and indigenous materials resulted in houses with an acceptable internal bioclimatic environment, which are economically affordable and are appealing for low-income families in the tropical urban areas. Maximum benefits from natural ventilation and sun-shading were achieved by collating wind direction and speed data, solar charts and elements of the traditional Filipino house. The use of building materials that are low-cost, but are thermally congruent for passive cooling in urban areas, enhanced affordability for mass housing. Indigenous materials, considered culturally unacceptable for urban mass housing, are innovatively used to make them aesthetically acceptable in urban areas. The result is the plan and construction of model houses as a showcase for the design and technology and viability of affordable houses for the general public in a tropical environment.

Competitive adsorption of lutein from soy oil onto rice hull ash

Adsorption of lutein from crude soybean oil onto acid ash prepared from rice hulls displayed Freundlich‐type isotherms. Different isotherms were obtained depending on the amount of adsorbent used. Addition of isopropanol to the miscella and water deactivation of the adsorbents decreased lutein adsorption. These observations suggested competitive adsorption based on polarity. Triglycerides were adsorbed to a greater extent than lutein, probably due to their larger concentrations. These findings parallel the adsorption behavior of silicic acid.

X‐ray diffraction and scanning electron microscope studies of processed rice hull silica

The structure and composition of processed rice hull ash were studied to better understand its adsorption of the soy oil components, lutein and free fatty acids. The silica‐rich ash was composed largely of low order cristobalite and tridymite in the form of opal CT, with variable particle size. On heating of the ash there was conversion to a more ordered form of opal C, fusing of particles, and loss of potassium. Acid washing, following heating, also removed potassium and slightly reduced particle size further. Crystal form, particle size, particle fusion and potassium content may be important factors influencing ash adsorption of soy oil components.

Adsorption of soy oil free fatty acids by rice hull ash

AbstractStudies demonstrated that free fatty acids can be adsorbed from a soybean oil/hexane miscella by inorganic rice hull ash. A 1% dose was effective in diminishing free fatty acid concentrations but acid activation reduced the adsorption. Binding of free fatty acids followed a Freundlich isotherm with smaller doses of ash adsorbing more efficiently. Addition of isopropanol to the miscella promoted the adsorption, while water deactivation of the ash had no effect, possibly because water occupied sites not accessible to free fatty acids. Impaired adsorption behavior of ash heated above 700°C could have been due to disruption of the crystal form. The adsorption behavior of rice hull ash may be more fully understood with a better knowledge of adsorbent structure.

Soy oil lutein adsorption by rice hull ash

AbstractRice hull material was converted to an adsorbent of the soy oil pigment, lutein, by a combination of ashing and acid activation. Pigment was adsorbed from a 20% (v/v) soy oil/hexane miscella. The most effective ashing temperature was 500°C. Five percent acid activation significantly promoted adsorption of the ash, but greater acid activation did not increase adsorption capacity very much. In the system studied, the performance of activated ash was comparable to that of activated bleaching earth. Nonactivated ash also had an ability to bind lutein but was less effective than activated adsorbent. The absorbance spectrum of the residual lutein was not altered by rice hull ash, but was changed when exposed to bleaching clay.

Preparation and Properties of SiO<sub>2</sub> from Rice Hulls

Dry rice hull contains 13-29wt% inorganic matter depending on the species, climate and geographic location. The inorganic matter is composed of silica (87-97wt%) with small amounts of alkali and other trace elements. Properties of ash obtained by combustion of between 400° and 1500°C were investigated. The SiO2 in the rice hull was localized in the outer and inner epidermis of rice hull. The SiO2 in rice hull ash formed by combustion below 800°C of rice hull powder with a particle size below 152μm was amorphous. Particles of the ash having an average diameter of 20μm were aggregates of small particles with a diameter of 2-5μm. At combustion temperatures above 900°C, the SiO2 in rice hull ash consisted of cristobalite and a small amount of tridymite. The surface of ash particles melted and the particles bonded to each other. The particle size was 40-60μm. It was found that potassium contained in the rice hull ash caused surface melting of SiO2 particles and accelerated the crystallization of amorphous SiO2 to cristobalite.

Studies on rice hull ash cement

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Porous kaolinite bead: A novel but economical solid support material for biomass in fluidised bed technology

Porous kaolinite beads were prepared by mixing kaolinite with various proportions of rice hull ash (RHA) and heating in a furnace at 800 °C for five hours. Those with 10 to 60% (w/w) RHA were very porous and had good mechanical strength. The raw materials were inexpensive and their preparation relatively simple, therefore these porous kaolinite beads would be an excellent solid support matrix material for the utilization of biomass in biological fluidised bed (BFB) processes.

Effect of Rice Hull Ash on Root-Knot Nematodes in Tomato

Effect of Rice Hull Ash on Root-Knot Nematodes in Tomato

The engineering properties of rice‐hull‐ash as a soil stabilizer

Click to increase image sizeClick to decrease image size Abstract The study of an effective utilization of rice hull ash, which is produced 100,000 tons per year in Taiwan, becomes necessary. This study investigates the uses of rice hull ash with lime as a soil stabilizer admixture. The primary purposes were to study the compaction characteristics and the factors affecting the strength development of the lime‐ash stabilized sandy and clayey soils. Standard compaction test and undrained direct shear test were carried out. Results showed that adding rice hull ash into a soil increased the effectiveness of lime. Lime‐ash admixture caused the compacted dry density of a soil to decrease but the as‐compacted strength to increase. The shear strength of a lime‐ash stabilized soil increased with curing time, but reduced when soaked. The optimum lime‐ash weight ratio of soils was found to be 1:2 or 1:3. To produce equivalent strength values, the percentage of lime requirement could be reduced by adding rice hull ash.

Use of Rice Hull Ash to Reduce Temperature in High-Strength Mass Concrete

Use of Rice Hull Ash to Reduce Temperature in High-Strength Mass Concrete

Making bricks from rice-hull ash

The fuel ash from rice mills has been used for making building-quality bricks when fully decarbonised, but this is not a simple process. The National Research Centre at Dokki, Cairo, has used the partially decarbonised ash with magnesium oxychloride cement to make light-weight bricks with crushing strengths up to 30 kg/cm2.

Energy and industrial materials from crop residues

Crop residues such as rice hulls and rice straw can be valuable resources for recovery of energy and useful industrial products. By a special process, combustion of rice hulls produces a reactive silica ash which is used for making acid-resistant hydraulic cement and reinforcing filler for rubber. Properties of the hydraulic cements and the rubber filler made from rice hull ash are described.

Ground Rice-Hull Ash as a Filler for Rubber

Abstract A ground rice hull ash prepared by a new burning process has been found to be a moderately reinforcing filler for rubber. This filler, 85-90% amorphous silica and 10-15% carbon, is made by a controlled incineration process in which the bulk of the organic components of the rice hulls is removed, leaving the skeletal silica structure of the hull intact and in the amorphous state. The resultant ash is easily ground to produce fine particles, generally in the range of 0.1-2.0 μm. This filler does not adversely affect either the vulcanization characteristics or the aging of SBR, natural rubber, nitrile rubber, butyl rubber, neoprene, EPDM, and propylene oxide rubber compounds. As it is predominantly silica, it responds effectively to silane coupling agents in improving properties of the rubber compounds. It is concluded that RHA filler is a satisfactory substitute for MT black and that, in blends with blacks, it can be effectively used as a partial replacement for finer and more reinforcing blacks.