Preparing spherical lignin from rice husk

Lignin is one of the important branched amorphous polymers, which generally has the irregular and fractal morphology. The preparation of regular sphere of lignin needs long steps and special conditions. In this study, the regular sphere of lignin can be simply prepared from rice husk (RH) under certain conditions. Namely, RH is mixed with 35 % ethanol aqueous solution in the proportion of 1:10 (g:mL), non-isothermally heated to 493 K and kept for 5 h. After filtration and air-drying at room temperature, the regular lignin sphere with the diameter of 100–400 nm is obtained. The regular sphere of lignin has the potential utilization in fields such as reactive functional materials, photo sensing materials and surface active materials in cosmetics. The mechanism of formation of the regular spherical lignin is proposed and discussed in this paper.     

Chlorine-free extraction of cellulose from rice husk and whisker isolation

This work reports the isolation of cellulose whiskers from rice husk (RH) by means of an environmental friendly process for cellulose extraction and bleaching. The multistep process begins with the removal of pectin, cutin, waxes and other extractives from rice husk, then an alkaline treatment for the removal of hemicelluloses and lignin, and a two-step bleaching with hydrogen peroxide/tetra-acetylethylenediamine (TAED), followed by a mixture of acetic and nitric acids, for further delignification of the cellulose pulp. The techniques of infrared absorption spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), modulated differential scanning calorimetry (MDSC) and X-ray diffraction (XRD) showed that the overall process is adequate to obtain cellulose with high purity and crystallinity. This cellulose was submitted to sulfuric acid hydrolysis with the aim to isolate the whiskers. They showed the typical elongated rod-like aspect as revealed by transmission electron microscopy (TEM) and atomic force microscopy (AFM).     

Sorption of cadmium from aqueous solution using pretreated rice husk

The sorption of Cd(II) from aqueous solution by rice husk, a surplus agricultural byproduct was investigated. Some simple and low-cost chemical modifications resulted in increasing the sorption capacity of raw rice husk (RRH) from 8.58 mg/g to 11.12, 20.24, 16.18 mg/g and reducing the equilibrium time from 10 h of RRH to 2, 4 and 1 h for epichlorohydrin treated rice husk (ERH), NaOH treated rice husk (NRH), sodium bicarbonate treated rice husk (NCRH), respectively. The effect of pH, sorption kinetics and isotherms were studied in batch experiments. Good correlation coefficient was obtained for pseudo second-order kinetic model, which agreed with chemisorption as the rate-limiting mechanism. Sorption isotherm test showed that equilibrium sorption data were better represented by Langmuir model than the Freundlich model. The highly efficient low cost and the rapid uptake of Cd(II) by NCRH indicated that it could be an excellent alternative for the removal of heavy metal by sorption process.     

Phenolic compounds present in rice husk

In a study on the phenolic distribution of rice husk (lemma, palea, rachilla and sterile lemmas), seven phenolic acids were detected in the alkali and alcoholie extracts. The total quantity of phenolic compounds in the husk differed with cultivars; however, no qualitative difference was noticed.     

Fast pyrolysis of rice husk: Product yields and compositions

A series of pyrolysis oils and chars were prepared from agricultural by-product rice husk by the lab-scale fast pyrolysis system using induction heating. The effect of process parameters such as pyrolysis temperature, heating rate, holding time, nitrogen gas flow rate, condensation temperature and particle size on the pyrolysis product yields and their chemical compositions was examined. The maximum oil yield of over 40% was obtained at the proper pyrolysis conditions. The chemical characterization by elemental, calorific, spectroscopic and chromatographic studies showed that the pyrolysis oils derived from the fast pyrolysis of rice husk contained considerable amounts of carbonyl groups and/or oxygen content, resulting in low pH and low heating values.     

Consistent production of kojic acid from Aspergillus sojae SSC-3 isolated from rice husk

Molecular Biology Reports - A consistent kojic acid producing fungal strain has been isolated from rice husk using glucose-peptone medium. The isolate was identified as Aspergillus sojae SSC-3 on...     

Adsorption studies on rice husk: removal and recovery of Cd(II) from wastewater

Adsorption behaviour of Ni(II), Zn(II), Cd(II) and Cr(VI) on untreated and phosphate-treated rice husk (PRH) showed that adsorption of Ni(II) and Cd(II) was greater when PRH was used as an adsorbent. Sorption of Cd(II) was dependent on contact time, concentration, temperature, adsorbent doses and pH of the solution. The Langmuir constants and thermodynamic parameters have been calculated at different temperatures. It was found that recovery of Cd(II) from synthetic wastewater by column operation was better than a batch process.     

Immobilization of invertase on rice husk using polyethylenimine

Washed and dried rice husk was coated with 2% polyethylenimine (PEI). Invertase was immobilized on this support through adsorption followed by cross-linking with 2% glutaraldehyde. Immobilized enzyme was reused for the hydrolysis of sucrose without loss in activity. This approach may serve as a simple technique in the future for the covalent immobilization of enzymes on lignocellulosic supports.     

Adsorption of paraquat using methacrylic acid-modified rice husk

This work investigates the adsorption of paraquat from aqueous medium using a methacrylic acid (MAA)-modified rice husk. The carboxyl groups were chemically bound to the surface of the rice husk by graft copolymerization using Fenton's reagent as a redox initiator. The graft copolymerization was examined to determine the H(2)O(2) concentration and the amount of MAA monomer used. FT-IR spectra confirmed the presence of carbonyl groups on the structural units of the rice husk derivative. The MAA-modified rice husks were hydrolyzed to sodium salt and used to adsorb paraquat. The adsorption was rapid in the first few minutes and quickly reached equilibrium. Equilibrium adsorption data are more consistent with the Langmuir isotherm equation than with the Freundlich equation. The maximum adsorption capacity of modified rice husks was 317.7mg/g-adsorbent. This value clearly exceeds the 60mg/g of Fuller's earth and the 90mg/g of activated carbon, which are the most commonly used binding agents for paraquat.     

Carbon/silica composite fabricated from rice husk by means of binderless hot-pressing

A carbon/silica composite designed for use under compressive loads was fabricated from rice husk (RH), an agricultural waste material. RH was pulverized by using a planetary ball mill, then carbonized and molded into the precursor by means of hot-pressing without using any binders. A compression of 100 MPa was intermittently applied to the RH powder heated from room temperature to 150 °C, and then to 280 °C. The precursor, the bulk density of which was 1.37 g/cm³, was sintered for further densification at up to 1400 °C without compression, in nitrogen gas. The smaller particle size of the pulverized RH was beneficial for densifying the carbon/silica composite and increasing its compressive strength. Sintering at 800 °C for 1 h in nitrogen gas provided the maximum bulk density of 1.52 g/cm³ and the maximum Vickers hardness at the surface of 343 HV. The maximum compressive strength was measured to be 55.7 MPa using a sintering temperature of 1200 °C.     

Evaluation of ultra- and nanofiltration for refining soluble products from rice husk xylan

Liquors from water treatments of rice husks (containing soluble xylan-derived products) were processed with NF and UF membranes for concentrating and removing both monosaccharides and non-saccharide compounds. Among the commercial membranes assayed, the best results were achieved with the 4 kDa polymeric tubular ESP04 (PCI Membranes), and the 1 kDa ceramic monolithic Kerasep Nano (Novasep). Several trade-offs were identified both in membrane selection and in operating conditions. The ESP04 polymeric membrane provided the best fractionation, but lower recovery under comparable experimental conditions, while its fluxes were about half of those of the ceramic Kerasep Nano membrane. Increase in transmembrane pressure resulted in improved product recovery, at the expense of a lower purity. Additional data on product refining by coupling membrane processing with extraction and ion exchange are provided.     

Preparation of carbon black from rice husk by hydrolysis, carbonization and pyrolysis

Carbon black is a form of amorphous carbon that is produced by incomplete combustion of petroleum- or some plant-derived materials and has a number of industrial uses. A process consisting of hydrolysis, carbonization and pyrolysis of rice husk was developed. Under optimal hydrolysis conditions (72 wt.% sulfuric acid, 50 °C, 10 min), a hydrolysis ratio of 52.72% was achieved. After carbonization of the hydrolysis solution by water bath, the solid carbon was further pyrolyzed. As the pyrolysis temperature was increased from 400 to 800 °C, the carbon content increased from 83.41% to 94.66%, the number of O-H, C-H, CO, and CC surface functional groups decreased, and based on Brunauer-Emmett-Teller (BET) results, the specific surface area and pore volume of carbon black increased from 389 to 1034 m²/g and from 0.258 to 0.487 cm³/g, respectively. X-ray diffraction pattern (XRD) and Raman spectroscopy analyses of samples pyrolyzed at 400-800 °C showed a localized graphitic structure. It is possible that the hydrolysis/carbonization/pyrolysis process developed in this study could also be applicable to the preparation of carbon black from other types of biomass.     

改性稻壳焦对糠醛的吸附特性

为了探索生物质焦对糠醛的吸附脱除特性,利用流化床快速热解制得稻壳焦,研究N2、CO2气氛下高温改性方式对稻壳焦孔隙特征与表面性质的影响,以及稻壳焦对糠醛的吸附脱除特性。采用元素分析、N2等温吸脱附、傅里叶红外、Boehm滴定等方法对稻壳焦的孔隙结构与表面化学特性进行表征。结果表明:原始的稻壳焦残留大量有机基团,孔隙结构较差;经N2和CO2高温改性后,稻壳焦表面的含氧酸性官能团大量分解,碱性官能团增加,比表面积和孔结构得到较好的扩充和优化,稻壳焦与糠醛的π-π色散力作用力增强。综合考虑π-π色散力和表面吸附位点的作用,CO2改性的稻壳焦表现出了最好的吸附效果。     

Separation of phthalate esters from bio-oil derived from rice husk by a basification-acidification process and column chromatography

Solid precipitate containing phthalate esters was obtained from rice-husk-derived oil through a basification-acidification process. After separation by column chromatography, the solid precipitate was divided into two mono-component fractions, two bi-component fractions and a tetra-component fraction. The major compounds of the five fractions were all consisted of phthalate esters. Especially, phthalate esters accounted for a proportion higher than 80% in both Fractions I and II. The generation and precipitation mechanisms of phthalate esters were proposed. Phthalate esters were considered to be derived from a series of complicated chemical reactions of small molecules in the biomass pyrolysis process, and precipitated from bio-oil by catalytic hydrolysis and esterification.     

Effect of fluidising velocity on the combustion of rice husk in a bench-scale fluidised bed combustor for the production of amorphous rice husk ash

This study was focused on investigating the optimum fluidising velocity during the combustion of rice husk in a bench-scale fluidised bed combustor (ID 210mm) to obtain low carbon ash in the amorphous form. When all other parameters are held constant, the optimum fluidizing velocity aids in almost complete combustion, thereby releasing the entrapped carbon for further conversion. This results in ash with consistently low carbon content (less than 2wt%). The range of fluidising velocities investigated was from as low as 1.5U(mf) to as high as 8U(mf). It was found that the optimum fluidising velocity was approximately 3.3U(mf) as the mixing of rice husk with the bed was good with a high degree of penetration into the sand bed. The resulting ash retained its amorphous form with low residual carbon content (at 2.88wt%) and minimal sand contamination as shown by the X-ray diffraction analysis.     

Erratum to: Generating broad-spectrum tolerance to ALS-inhibiting herbicides in rice by base editing

Science China Life Sciences -     

Characteristics of rice husk gasification in an entrained flow reactor

Experiments were performed in an entrained flow reactor to better understand the characteristics of biomass gasification. Rice husk was used in this study. Effects of the gasification temperature (700, 800, 900 and 1000 °C) and the equivalence ratio in the range of 0.220.34 on the biomass gasification and the axial gas distribution in the reactor were studied. The results showed that reactions of CnHm were less important in the gasification process except cracking reactions which occurred at higher temperature. In the oxidization zone, reactions between char and oxygen had a more prevailing role. The optimal gasification temperature of the rice husk could be above 900 °C, and the optimal value of ER was 0.25. The gasification process was finished in 1.42 s when the gasification temperature was above 800 °C. A first order kinetic model was developed for describing rice husk air gasification characteristics and the relevant kinetic parameters were determined.