Effect of thermal treatment of rice husk ash on surface properties of hydrated portland cement-rice husk ash pastes

Portland cement was mixed with rice husk ash (RHA) fired at 450, 700 and 1000C, in ratios of 5, 15 and 25% of RHA by mass. Cement-RHA pastes were made by using a water/solid mixture ratio of 0.30 by mass and then cured for various hydration periods within the range 3 to 90 days. The surface properties of the hydrated samples were studied by means of the nitrogen adsorption technique. The results indicated that the hydrated cement-RHA samples made from rice husks fired at 450 and 700C gave higher values of surface area than that for the hydrated cement-RHA sample made from rice husks fired at 1000C. The surface area and pore volume results could be related to the pore structure of the silica produced in the RHA, as controlled by its predicted degree of crystallinity.     

Rice husk ash as an adsorbent for methylene blue—effect of ashing temperature

Utilization of one waste material to control pollution caused by another is of high significance in the remediation of environmental problems. Rice husk, an abundantly available agricultural waste, can be used as a low cost adsorbent for dyes and heavy metals in effluent streams. The possible utilization of rice husk ash as an adsorbent for methylene blue dye from aqueous solutions has been investigated. Ash samples from husks of two origins were prepared at different temperatures and their physical, chemical spectroscopic and morphological properties were determined. XRD, FTIR and SEM were some of the techniques adopted for the characterization. The samples were also analyzed for bulk density, pH, nitrogen adsorption properties and lime reactivity. Experiments of methylene blue adsorption on the ash samples were conducted using batch technique and a comparative study was made. Results were analyzed using linear, Langmuir and Freundlich isotherms. The values of separation factor indicate that most of the ash samples do adsorb the dye molecules, but in varying quantities. Calcination at 900^∘C reduces the adsorption capacity of the ash to a great extent. Regression analysis shows that the experimental data fits both Langmuir and Freundlich isotherms for certain concentration limits. The adsorbate species are most probably transported from the bulk of the solution into the solid phase through intra-particle diffusion process. Kinetics of adsorption was found to follow pseudo second order rate equation with R ²∼ 0.99. The highest adsorption capacity (Q ₀) achieved is found to be ∼690 mg/g, which is even higher than the values reported for activated carbon from rice husk. The adsorption capacity of the ash samples are in good agreement with their surface area and pore volume.     

Effect of removing silica in rice husk for the preparation of activated carbon for supercapacitor applications

The significant influence of silica inside rice husk in the preparation and electrochemical performances of activated carbon are investigated. The removing of silica results in high mesoporous ratio and good rate capability.     

A review on recent advances in the comprehensive application of rice husk ash

Research on Chemical Intermediates - Rice husk ash, which is rich in non-crystalline silica, is a by-product material obtained from the combustion of rice husk. Because rice husk ash is available...     

Ionic conductivity enhancement in the solid polymer electrolyte PEO9LiTf by nanosilica filler from rice husk ash

Rice husk ash is a cheap raw material available in abundance in rice-growing countries. It contains around 85–90 % amorphous silica. Rice husk ash, when subjected to a simple chemical precipitation method, will produce nanosilica which can be used for many industrial and technological applications. In this work, we have successfully synthesized nano-sized silica from local rice husk ash and prepared the nanocomposite solid polymer electrolyte, PEO₉LiTf:SiO₂. The resulting electrolyte has been characterized by X-ray diffraction, differential scanning calorimetry, atomic force microscopy, Fourier transform infrared spectroscopy, and complex impedance spectroscopy. The electrolyte shows about a 12-fold increase in ionic conductivity at room temperature due to the silica filler. In the nanocomposite electrolyte, nanosilica particles obtained from rice husk ash behaved very similarly to the commercial grade nanosilica and had a size distribution in the 25- to 40-nm range. As already suggested by us and by others, the O^2? and OH^? surface groups in the filler surface interact with the Li⁺ ions and provide hopping sites for migrating Li⁺ ions through transient H bonding, creating additional high-conducting pathways. This would contribute to a substantial conductivity enhancement through increased ionic mobility. An additional contribution to conductivity enhancement, particularly at temperatures below 60 °C, appears to come from the increased fraction of the amorphous phase, as evidenced from the reduced crystallite melting temperature and the reduced enthalpy of melting due to the presence of the filler.     

Crystallite growth of rice husk ash silica

The effect of temperature of firing and time of annealing on crystallite size of silica obtained by burning boiled rice husk was studied by the X-ray broadening technique. The results showed that nuclei of disordered cristobalite were present in ash silica, and crystallite growth was governed by two processes, namely nucleation and growth taking place simultaneously with a rate varying with the temperature of treatment. The nucleation process manifested itself in the low temperature range of 800–900°C, while growth was more pronounced in the temperature range 1000–1100°C, occurring with different activation energies of 81.3 and 52.4 cal mole^?1, respectively. Both processes occurred with the same intensity at 964°C. A growth process and crystal perfection followed with an activation energy of 36.8 cal mole^?1.     

Preparation of super-hydrophobic white carbon black from nano-rice husk ash

Nano-rice husk ashes were prepared by burning rice husk with a self-propagating method. The white carbon black with high purity was prepared by an alkali dissolving–acid reaction method from nano-husk ash. The super-hydrophobic SiO₂ films were prepared by the sol–gel method using hexamethyldisilazane as a modifier. The effects of the pH and reaction time in the acid reaction process on the purity of the white carbon black, and the effect of the modifier on the hydrophobic property of SiO₂ films were studied. The performances were characterized by XRD, BET, SEM, IR, and contact angle analyzer. The results showed that the purity of white carbon black reached 98.48 % when the NaOH solution with the rice husk ash was heated for 2 h at 90 °C, then the pH of the solution was adjusted by sulfuric acid to 3, and the acid reaction time was 2 h. The contact angle of SiO₂ films was more than 160° when volume ratio of the modifier to silica–sodium hydroxide mixed solution was 0.15. The mechanism of the modifier on SiO₂ surfaces is a graft copolymerization. The hydrophobic groups in the modifier replace the hydroxy groups on SiO₂ surfaces and make SiO₂ surfaces present super-hydrophobicity.     

Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica

Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.     

Preparation and characterization of rice husk/ferrite composites

<正>A novel ferrite composite using rice husk as substrate has been prepared via high temperature treatment under nitrogen atmosphere.The rice husk substrate consists of porous activated carbon and silica,where spinel ferrite particles with average diameter of 59 nm are distributed.The surface area of the composite is greater than 170 m~2 g~(-1) and the bulk density is less than 0.6 g cm~(-3).Inert atmosphere is indispensable for the synthesis of pure ferrite composites,while different preparation temperatures of above 600℃result in composites with similar structures and morphologies.Due to the presence of ferrite particles,this novel composite shows enhanced adsorption ability for acid orangeⅡ.     

Immobilization of dihydrogen phosphate onto rice husk ash as a highly efficient and green catalyst for the synthesis of symmetrical N,N′-alkylidene bisamides

Research on Chemical Intermediates - The preparation and characterization of an environmentally-benign and low-cost catalyst consisting of KH2PO4 supported on silica from rice husk ash is reported....     

Understanding rice hull ash as fillers in polymers: A review

The polymer industry has a newfound interest in fillers from industrial by-products and other waste materials having potential recyclability. This new class of fillers includes fillers from natural sources (e.g., natural fibers), industrial by-products (e.g., saw dust, rice husks) and a recent entry in the form of silica ash – an industrial waste material –obtained by burning rice husks. Rice hulls possess an unusually high percentage of `opaline silica'. Its annual worldwide output is more than 80 million tons, which corresponds to 3.2 million tons of silica. Silanol groups present on the surface of rice hull ash can positively influence its reinforcing character ash as a filler, however, being hydrophilic, it suffers fromfiller-aggregation and moisture absorption. Present article reviews the performance of rice husk ash, or silica ash, in polymeric composites. This paper emphasizes the need for better characterization of silica ash to obtain an in-depth understanding of its behaviour with the view to identifying suitable modifications to improve its performance as a filler. It is emphasized that poor understanding of silica ash as a filler is linked to the lack of surface characterization, since its behaviour is significantly linked to its surface properties. Based on this analysis, a new approach to silica ash modification is proposed.     

多孔聚苯胺-稻壳基白炭黑复合物的制备及循环伏安特性

以工业生产废弃的稻壳灰为原料,采用化学沉淀法制备了大孔径多孔稻壳基白炭黑,并在多孔白炭黑(RHSi)分散体系中,采用原位聚合法制备了聚苯胺(PAn)-稻壳基白炭黑复合物.采用热重分析、傅里叶红外光谱、透射电镜、低温氮吸附法和循环伏安法研究了复合物的结构及电化学性能.结果表明:聚苯胺-稻壳基白炭黑复合物具有多孔聚集体结构.当m_(PAn)/m_(RHSi)＝0.434时,复合物的比表面积为42.1 m~2/g,最可几孔径约为22 nm,适宜负载生物大分子,且在酸性及中性溶液中具有良好的电化学可逆性.     

Thermal analysis and X-ray diffraction of untreated coffee’s husk ash reject and its potential use in ceramics

The agro and industrial activities are actually responsible for the production of large amounts of solid wastes in Brazil. The use of industrial wastes as alternative raw materials into ceramic products has been widely developed. The typical materials used in the ceramic formulations present a large diversification of chemical compositions, what allow the incorporation of different types of waste materials in the ceramic mixture. Brazil produces a massive amount of coffee and the lack of adequate landfill areas available to dispose the coffee’s husk ash reject material are causing an ambiental problem for the agro-industry. This work describes research carried out on the thermal characterization and X-ray diffraction of coffee’s husk ash reject and its possible use in the ceramic industry.     

Influence of cross profile of PE fibers on thermal properties of materials

Molecular sieves MCM-41 were synthesized from rice husk ash (RHA) as alternative sources of silica, called RHA MCM-41. The material was synthesized by a hydrothermal method from a gel with the molar composition 1.00 CTMABr:4.00 SiO₂:1.00 Na₂O:200.00 H₂O at 100 °C for 120 h with pH correction. The cetyltrimethylammonium bromide (CTMABr) was used as a structure template. The material was characterized by X-ray powder diffraction, FTIR, TG/DTG, and surface area determination by the BET method. The kinetics models proposed by Ozawa, Flynn–Wall, and Vyazovkin were used to determine the apparent activation energy for CTMA⁺ species decomposition from the pores of MCM-41 material. The results were compared with those obtained from the MCM-41 synthesized with silica gel. The synthesized material had specific surface area, size, and pore volume as specified by mesoporous materials developed from conventional sources of silica.     

One-step synthesis of solid sulfonic acid catalyst and its application in the acetalization of glycerol: crystal structure of cis-5-hydroxy-2-phenyl-1,3-dioxane trimer

A one-pot method was employed to immobilize sulfonic acid onto silica obtained from rice husk ash using 3-(mercaptopropyl)trimethoxysilane to form a solid catalyst denoted as RHASO₃H. BET measurements of the catalyst showed the surface area to be 340 m² g^?1 with the average pore volume of 0.24 mL g^?1 and the pore diameter of 2.9 nm. Acidity test of cation exchange capacity and pyridine adsorption studies revealed the presence of Br?nsted acid sites on the catalyst surface. The catalyst was used in the acetalization reaction of glycerol with benzaldehyde. Under optimized conditions, the reaction showed the maximum conversion of 78 % after 8 h with 67 % selectivity towards the five membered ring isomer. Variation in the glycerol concentration had a significant effect on the reactants conversion. A single crystal X-ray study of one of the products proved the existence of a unique trimer formed by hydrogen bonding by the six-membered cis-isomer. The catalyst was several times recycled without any loss of its catalytic activity.     

Synthesis of phthalazine compounds using heterogeneous base catalyst based on silica nanoparticles obtained from rice husk

Research on Chemical Intermediates - In this study, the nanoparticles of amorphous silica were easily extracted from low-cost rice husk ash. They were functionalized with 3-(chloropropyl)...     

稻壳炭基固体酸催化剂的制备及其催化酯化反应性能

以热解稻壳炭为原料, 浓硫酸为磺化剂制备了固体酸催化剂. 采用X射线衍射、X射线光电子能谱、元素分析、孔结构分析和热重-质谱联用等手段对其进行了表征. 以油酸和甲醇的酯化为探针反应, 考察了磺化温度和时间对催化剂活性的影响, 探讨了反应条件对油酸转化率的影响, 并对所制催化剂的稳定性进行了研究. 结果表明, 制备该催化剂的适宜磺化温度和时间分别为90℃和0.25 h, 在该条件下制得的催化剂为无定形碳结构, 磺酸基密度为0.7 mmol/g. 该催化剂表现出较高的催化酯化反应活性, 在催化剂用量为5%、甲醇/油酸摩尔比为4、酯化温度和时间分别为110℃和2 h的条件下, 油酸的酯化率可达98.7%. 该催化剂具有较好的稳定性, 经7次连续反应后, 油酸的酯化率仍可达96.0%.     

Thermal kinetics and morphological investigation of alkaline treated rice husk biomass

Agro waste bio mass are creating challenges for environment in term of air pollution due to improper disposal. Rice milling is the process in which rice husk is produced as by-product. The agro-waste rice husk has tremendous potential to be used either in its raw form or in ash form. The inherent component of this waste cellulose provides enhanced properties in a reinforced composite when used as filler. Rice husk is the hard outer layer and covering rice seed, which makes reinforcement challenging in its original form. Fiber surface treatment significantly improves adhesion with matrix and various thermo chemical properties of filler as well as of composites. NaOH treatment is cost-effective and it ensures the adhesion with matrix by removal of hemicellulose and lignin. The chemical treatment of agro-waste (rice husk) is performed with 5% alkali solutions of NaOH in water. Results are compared with the properties of untreated rice husk for thermal and morphological characterizations. In the present work, we are trying to quantify the impact of chemical treatment on rice husk thermal decomposition and its kinetics. Thermogravimetric analysis and kinetics study of thermal degradation, provide key input towards pyrolysis pattern of rice husk, while FTIR and SEM analysis provide the prospects of this bio filler using a reinforcing agent to develop green composite and productive disposal. The FTIR data helps to find the possibilities of blending different bio fillers and natural fibers to find suitable reinforcing substances. The average activation energy of treated fiber is noted as 137.95 by KAS method and 108.08 by FWO method as compared to 55.56 by KAS method & 54.26 by FWO method for untreated rice husk.     

钾元素对生物质及其三组分热解的影响

采用机械混合法将KCl加入到纤维素、半纤维素、木质素以及稻壳和稻壳模拟物等生物质中,得到了一系列不同K含量的生物质样品,通过热重(TG)实验考察了K元素对生物质热解特性的影响.结果表明,K元素对生物质三组分热解特性的影响比较复杂,纤维素的最大热解失重速率随着KCl添加量的增加而降低,但KCl对半纤维素和木质素热解特性的影响不显著.无论是否添加KCl,模拟生物质的热解特性均可以认为是三组分热解的简单叠加.但酸预处理稻壳三组分间的稳定结构,导致其DTG曲线在300 ℃左右的热解峰由稻壳模拟物的尖峰变为肩峰,其热解焦炭收率也比稻壳模拟物的略低.此外,实验还采用浸渍法向酸预处理稻壳中添加了KCl.TG实验结果表明,K元素的存在对生物质热解具有一定的催化作用,但KCl的添加方式不同,生物质的热解特性有明显差别,生物质样品经机械混合添加KCl后,其热解焦炭收率呈下降趋势(纤维素除外),浸渍法添加的KCl导致酸预处理稻壳的最大热解失重速率和焦炭收率升高.     

Removal of rhodamine B from aqueous solution via adsorption onto microwave-activated rice husk ash

The adsorption of rhodamine B (RhB) onto microwave-activated rice husk ash (ARHA) was conducted to demonstrate the capability of an inexpensive abundant biomaterial as an alternating bio-sorbent for the removal of dye residue from wastewater. Experimental data show that ARHA achieved the maximum adsorption capacity of 21.89 mg/g at pH 5.5 and 303 K. The absorption process was followed pseudo-second-order kinetic model and adsorption equilibrium data were well described by the Freundlich model. Thermodynamic studies indicated that the RhB adsorption onto ARHA was endothermic and spontaneous.