Three activated carbons (ACs) were prepared using NaOH (N) as an activating agent. Hy-drofluoricacid pre-leached rice husk was used as a precursor. After leaching, the precursor was washed with distilled water, dried, crushed, and then sieved; a size fraction of 0.3-0.5 mm was selected for carbonization in the absence of air at 600°C. The carbonization prod-uct (LC) was mixed with NaOH at ratios of 1:2, 1:3, and 1:4 (wt of LC: wt of NaOH) and the produced ACs after activation at 800°C were designated NLC21, NLC31, and NLC41, respectively. Surface and textural properties were determined using nitrogen adsorption at -196°C, scanning electron microscopy images, thermogravimetric analysis, and Fourier transform infrared spectra . These ACs were used as adsorbents for lead(II) from aqueous solutions. The effects of the textural properties and the chemistry of the carbon surfaces were investigated and the impact of the operation conditions on the capacity for lead(II) sorption was also considered. Modificationof NLC41 with H2O2 and HNO3 gave two other adsorbents, HNLC41 and NNLC41 respectively. These two new samples exhibited the highest removal capacities for lead(II), i.e.117.5 and 128.2 mg/g, respectively. The adsorption data fittedthe Langmuir isotherm and the kinetic adsorption followed pseudo-second order kinet-ics. The thermodynamic parameters have been determined and they indicated a spontaneous endothermic process.

Activated carbon (AC) was synthesized from rice husks using the chemical activation method with KOH, NaOH, a combination of (NaOH + Na2CO3), and a combination of (KOH + K2CO3) as the chemical activating reagents. The activated carbon with the highest surface area (around 2000m2/g) and high porosity, which allows the absorption of a large number of ions, was applied as electrode material in electric double layer capacitors (EDLCs). The AC for EDLC electrodes is required to have a high surface area and an optimal pore size distribution; these are important to attain high specific capacitance of the EDLC electrodes. The electrodes were fabricated by compounding the rice husk activated carbons with super-P and mixed with polyvinylidene difluoride (PVDF) at a weight ratio of 83:10:7. AC electrodes and nickel foams were assembled with potassium hydroxide (KOH) solution as the electrolyte. Electrochemical measurements were carried out with a three electrode cell using 6 M KOH as electrolyte and Hg/HgO as the reference electrode. The specific capacitance strongly depends on the pore structure; the highest specific capacitance was 179 F/g, obtained for the AC with the highest specific surface area. Additionally, different activation times, levels of heating, and chemical reagents were used to compare and determine the optimal parameters for obtaining high surface area of the activated carbon.

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified N2. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 m2/g).

Dye removal from waste water via adsorption by activated carbons (ACs) developed from agricultural wastes represents an ideal alternative to other expensive treatment options. Physical and chemical ACs were prepared from rice husks. The textural properties of the ACs were characterized by Brunauer-Emmett-Teller-N2 adsorption and scanning electron microscopy. The chemistry of the carbon surface was investigated by Fourier transform infrared spectroscopy, base and acid neutralization capacities, pH of the active carbon slurry, and pHpzc. The adsorption capacities of the ACs for the basic dye (methylene blue) and acid dye (acid green 25) were determined using parameters such as contact time, pH, and temperature. NaOH-ACs showed the highest surface area and total pore volume, whereas steam-ACs showed the lowest ones.

A carbonaceous sorbent was prepared from rice husk via sulphuric acid treatment. After preparation and washing, the wet carbon with moisture content 85% was used in its wet status in this study due to its higher reactivity towards Cr(VI) than the dry carbon. The interaction of Cr(VI) and the carbon was studied and two processes were investigated in terms of kinetics and equilibrium namely Cr(VI) removal and chromium sorption. Cr(VI) removal and chromium sorption were studied at various initial pH (1.6-7), for initial Cr(VI) concentration (100 mg/l). At equilibrium, maximum Cr(VI) removal occurred at low initial pH (1.6-2) where, Cr(III) was the only available chromium species in solution. Cr(VI) removal, at such low pH, was related to the reduction to Cr(III). Maximum chromium sorption (60.5 mg/g) occurred at initial pH 2.8 and a rise in the final pH was recorded for all initial pH studied. For the kinetic experiments, approximate equilibrium was reached in 60-100 hr. Cr(VI) removal data, at initial pH 1.6-2.4, fit well pseudo first order model but did not fit pseudo second order model. At initial pH 2.6-7, Cr(VI) removal data did not fit, anymore, pseudo first order model, but fit well pseudo second order model instead. The change in the order of Cr(VI) removal process takes place in the pH range 2.4-2.6 under the experimental conditions. Other two models were tested for the kinetics of chromium sorption with the data fitting well pseudo second order model in the whole range of pH. An increase in cation exchange capacity, sorbent acidity and base neutralization capacity was recorded for the carbon sorbent after the interaction with acidified Cr(VI) indicating the oxidation processes on the carbon surface accompanying Cr(VI) reduction.

The present study set out to investigate the adsorption of Cd(II) ions in an aqueous solution by using Peanut Husk Biochar (PHB). An FT-IR analysis revealed that the PHB contained carboxylic and carbonyl groups, O-H carboxylic acids, and bonded-OH groups, such that it could easily adsorb heavy metals. The adsorption of Cd(II) using PHB proved to be a better fit to the Langmuir isotherm than to the Freundlich isotherm. The maximum Langmuir adsorption capacity was 33.89 mg/g for Cd(II). The negative value of ΔGo confirm that the process whereby Cd(II) is adsorbed onto PHB is feasible and spontaneous in nature. In addition, the value of ΔGo increase with the temperature, suggesting that a lower temperature is more favorable to the adsorption process. The negative value of ΔHo indicates that the adsorption phenomenon is exothermic while the negative value of ΔSo suggests that the process is enthalpy-driven. As an alternative to commercial activated carbon, PHB could be used as a low-cost and environmentally friendly adsorbent for removing Cd(II) from aqueous solutions.

The objective of this study was to examine the torrefaction process of three lignocellulose biomasses (rice husks, coffee shell, and wood) produced in Vietnam. Three different torrefaction temperatures ranging from 200oC to 300oC and three residence times of 20, 40, and 60 min were considered. The result showed that temperature had a higher effect on torrefaction process of biomass than residence time. Based on the findings of this study, a residence of 40 min could be suggested for an effective and proper torrefaction process to recycle the agricultural biomass and wood at 300oC. The torrefied products become fuel sources which can be applied to replace with fossil fuels.

Soil-Cement is an outstanding paving material, as it is economic, easy to construct and environmental-friendly due to its usage of natural soil. However, compared to current methods of paving, soil-cement shows low strength and low resistance on cracking, so it is necessary to supplement those drawbacks by use of some admixtures. This paper attempts to take an in-depth study of material characteristics of soil-cement mixtures with rice husk ash which is discarded as waste to enhance the strength and durability of soil-cement. To figure that out, XRF analysis was performed. From the XRF analysis results of the chemical content in rice husk ash, SiO2 is contained as much as 64.85%. Though SiO2 content is major in the rice husk ash, it is less than the amount expected. It is due to incineration temperature and time away from ideal environment for maximum SiO2 content. In addition, it figured out the strength property and durability of rice husk ash added soil-cement mixture by compressive strength test. The compressive strength test of soil-cement mixtures showed the highest strength with 10% of rice husk ash added. This suggests rice husk ash has high potential as one of pozzolanic materials.

Currently, Eco-friendly construction materials are widely utilized for reducing CO2 emission in construction. Furthermore various engineering fibers are also added for improving a brittle behavior in concrete. In the paper, concrete specimens with 10% and 20% replacement ratio with RHA (Rice Husk Ash) are prepared, and engineering behaviors in RHA and OPC concrete are evaluated with different addition of coconut fiber from 0.125~0.375% of volume ratio. Several basic tests including compressive strength, tensile strength, flexural strength, impact resistance, and bond strength are performed, and crack width and deflections are also measured in flexural test. RHA is evaluated to be very effective in strength development and 0.125% of fiber addition leads significant improvement in tensile strength, ductility, and crack resistance. RHA and coconut fiber are effective construction material both for reutilization of limited resources and performance improvement in normal concrete.

This research investigated the feasibility of rice husk (RH) as a biosorbent for the removal of anions from aqueoussolution. RH-g-GMA-Am biosorbent, which possesses anionic exchangeable function, was prepared through graftpolymerization of glycidyl methacrylate (GMA) in the presence of N,N'-methylene-bis-acrylamide as a cross-linker usingpotassium peroxydisulphate as a redox initiator and subsequent amination reaction using ethylenediamine (EDA),diethylenetriamine (DETA), dimethylamine (DMA) and trimethylamine (TMA) as a amine source. Fourier transforminfrared (FTIR) and scanning electron microscopy (SEM) analysis as well as the sorption capacity for anions verifiedthe presence of grafted GMA polymers and amine groups on the RH surface. The zero point of surface potential ofaminated RH-g-GMA-Am sorbent was 6.4, which facilitated the sorption of anions on the positively charged sorbent atpH<6.4. The sorption capacity of RH-g-GMA-Am depending on the amination chemicals increased in the order:DETA≥EDA>DMA>TMA, i.e., primary amine>secondary amine>tertiary amine. The sorption selectivity of RH-g-GMA-Am sorbent aminated with DETA and EDA in the presence of equimolar anions and at pH 4.7 increased in theorder: SO4>PO4>NO3>F. Furthermore, their sorption capacities for PO4 were much higher than those of commercialanion-exchange resins. The results obtained suggest that the RH-g-GMA-Am biosorbent prepared by the GMA graftcopolymerization and subsequent amination can be used as an effective anion-exchanger comparable to commercial anion-exchange resins.

Since the volume based tipping system was adopted for municipal solid wastes in Korea, the system has been well implied with the positive participation of households. Therefor local governments have started to apply the system to food wastes as well in recent years and each household has put an effort to reduce the generation of food wastes consequently. Another big movement on the management of municipal solid waste has been made, which was intending to utilize wastes to energy resources by converting to solid refuse fuel (SRF). In the meantime the conversion of biomass to energy became an issue to argument national renewable energy. Such motivation made an attempt to utilize fruit husks as SRFs since they has been used to dispose of as food wastes with the payment of tipping fee by households. Thus, in this study, five fruits (mandarine, apple, pear, sweet persimmon and grape) of 6 main consuming fruits in Korea were chosen as tested materials to check out any potentials of biomass SRFs. The basic characteristics of 5 fruit husks after drying naturally were analyzed. Heating values, proximate analysis results were reported and thermo-gravimetric tests were made for suggesting them to combustible wastes or bio-SRFs. The higher heating values of all fruit husks with natural drying showed above 3,000 kcal/kg which is the criterium of SRF and the lower heating values were less than SRF standard due to higher content of moisture. Proximate analysis and thermo-gravimetric data were similar to other biomass fuels like wood and municipal solid waste. It is concluded that such fruit husks could be used as SRFs by adopting an effective drying method in advance.

This research investigated the feasibility of rice husk as a biosorbent for removal of ammonium ion from aqueous solutions. To improve the sorption functionality of rice husk, the carboxyl groups were chemically bound to the surface of the rice husk by graft polymerization of acrylic acid using potassium peroxydisulphate as a redox initiator. The removal of ammonium ion by rice husk grafted with acrylic acid (RH-g-AA) was studied in a batch mode and fixed bed columns. The kinetic and equilibrium data obtained from batch experiments follow the second-order kinetics and fit well with the Langmuir isotherm model. The sorption energy determined from D-R model was 8.61 kJ/mol indicating an ion-exchange process as the primary sorption mechanism. To determine the characteristic parameters of the column useful for process design, four mathematical models; Bed Depth Service Time (BDST), Bohart-Adams, Clark and Wolborska models were applied to experimental data obtained from the fixed bed columns with varying bed heights. All models were found to be suitable for simulating the whole or a definite part of breakthrough curves, but the Wolborska model was the best. The fixed bed sorption capacity determined from the Wolborska model was in the range 33.3 ~ 40.5 mg/g close to the value determined in the batch process. The thickness of mass-transfer zone was calculated to be approximately 40 mm from DBST model. The RH-g-AA sorbent could be regenerated by a simple acid washing process without a serious lowering the sorption capacity or physical durability.

This research investigated the feasibility of rice husk as a biosorbent for the removal of heavy metals from aqueous solutions. The carboxyl groups were chemically bound to the surface of the rice husk by graft polymerization of acrylic acid using potassium peroxydisulphate as a redox initiator. The Pb sorption capacity and FT-IR spectra confirmed the presence of carboxyl groups on the structural units of the acrylic acid-grafted rice husk (RH-g-AA). The sorption selectivity of the RH-g-AA for cations under competition with each other was high in the following order: Pb > Cu > Cd ≥ Fe > Mn > Zn > Ni > Mg > K > Cr > Ca. Sorption equilibrium of Pb on RH-g-AA was better described by the Fruendlich isotherm model than the Langmuir isotherm model. The sorption energy obtained from D-R model was 13.13 kJ/mol indicating an ion-exchange process as the primary sorption mechanism. Sorption kinetic data fitted with the pseudosecond- order kinetic model and indicated that both external and intraparticle diffusion took part in sorption processes. The RH-g-AA sorbent could be regenerated for more than 5 times by the washing process with 0.1 M HCl without a serious lowering the sorption capacity.

Expanded rice husk (ERR) is different from commercial rice seedling media in chemical and physical properties such as pH, permeability, and water content. This study was conducted to test a possibility of improving rice seedling growth by improving the texture of ERR as a rice seedling medium. The seedling media used were a commercial seedling medium (CSM), rice husk, and ERR 1, 2, 3, and 4 with different expansion degrees. The pH of the ERHs ranged from 6.3 to 6.8. As the expansion rate increased, ERR particle sizes decreased, and water permeability and absorption rates improved. No significant differences in shoot dry weight and rate of maturity were found among the seedlings cultivated in the different ERH media. However, the mat formation of seedling roots became loose as the expansion rates were decreased. Further studies are necessary to determine the cause of poor root growth in ERH media.

Rice farmers can save labor and expenses by using expanded rice husk (ERH) as a seedling medium since ERH is lighter and cheaper than other commercial seedling media (CSM). This study was carried out to develop a method for rice seedling cultivation using ERH as a seedling medium. It is suggested that a mixture of 60~% of ERH and 40~% of a CSM could be used as a seedling medium; the planting densities would be 240g per tray for infant seedlings and 200 g for young seedlings; and nitrogen (N) would be applied at a rate of 1g per tray for infant seedlings prior to planting and 2g per tray for young seedlings with division. Great care should be taken to use CO(NH2)2 as an N-source fertilizer. These results would lay a foundation for the rice seedling cultivation with ERH as a medium.

The antimicrobial and glucosyltransferase(GTase) inhibition activity were searched for 30 species of various folk drugs and by products of food industry. Among them, two species, gallnut and red grape husk water extracts, were selected for the powerful antimicrobial and GTase inhibition activity. The polyphenol fractions of gallnut and red grape husk were showed very greater antimicrobial activity on both Gram(+) and (-), B. subtilis and E. coli. The minimum antimicrobial activity of gallnut polyphenol fraction were 1.0mg for B. subtilis and 3,0mg for E. coli. Red grape husk was 2.0mg for B. subtilis and 3.0mg for E coli. The polyphenol fractions of gall nut and red grape husk were showed powerful GTase inhibition activity. The concentrations of these fractions for 80% inhibition of GTase activity were 1.0810-3/mg/㎖ and 1.0810-2/mg/㎖, respectively. The most abundant compound in these fraction seems to be polyphenol derivatives. From these results, we think that the gallnut and the red grape husk polyphenol fraction had more antimicrobial and anti-plaque activities than artificial synthetic preservatives as an economic point of view.