In this study chemical method of dissolution-precipitation was applied to produce amorphous silica nanoparticles from Rice straw ash (RSA), the waste material of Rice cultivation. The morphology, particle size, structure and area of specific surface of synthesized amorphous silica nanoparticles were evaluated using transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and analysis technique for the measurement of the specific surface area of materials (BET). In addition, chemical composition of RSA, used and the synthesized silica nanoparticles was studied by X-ray fluorescence (XRF) spectroscopy. The effects of sodium hydroxide concentration, precipitation reaction temperature and precipitation reaction duration on the area of a specific surface were determined through Design of Experiments (DOE) Technique. Results depicted that silica nanoparticles with particle size of 10-15 nanometers were successfully synthesized. Average area of a specific surface and purity were 327 m2/g and 99.5% respectively. The interactive influence of temperature and duration having the highest effect on the average area of the specific surface.

Purpose The uncontrolled discharge of phosphorus into aquatic environment leads to the deterioration of the water bodies. Additionally, the agricultural crops present inside the La Albufera de Valencia Natural Park, Rice fields mainly, have a high social and environmental value. However, there is a conflict between private interests (farmers) and public interest in the management of agro-waste produced by them. Nowadays, the option used by the farmers is the uncontrolled burning in the own field. The ashes generated during the combustion process could be used to remove phosphorus loading in water bodies of the Natural Park, contributing to its recovery. Methods Adsorption experiments were carried out in batch mode by using different concentrations (5-100 mgP L-1) of sodium phosphate dibasic (Na2HPO4) placed in 100 mL stoppered conical flask with 50 mL of synthetic wastewater and different amounts of adsorbent, during the selected time (5 days). Adsorption studies were performed with doses varying from 5 to 24 g L-1. After finishing the adsorption experiments, the solution was fi ltered through glass microfiber filter (1. 2 µ m). Results The adsorption capacity varies for Rice straw ash from 31. 91% up to 97. 48% and Rice straw ash with HCl from 17. 49% up to 89. 04%. An increase in temperature or dosage had a positive effect in the removal capacity, increasing its adsorption. Removal process of phosphorus was endothermic. Conclusion The use of Rice straw ash could be a solution to reduce the phosphate in water bodies, providing an advantage to the proposed alternative of agro-waste management.

In this study, Rice straw as an abundant and inexpensive raw material was selected to produce soda - anthraquinone pulp. Nano cellulose fiber from Rice straw, cationic starch and cationic ployacrylamide were added to improve the pulp strength. Cationized nano cellulose fibers suspension was mixed with Rice straw pulp at three levels (2, 5 and 10 percent) and mixed for five minutes. Starch and polyacrylamide as cationic chemicals were used to stabilize nano fiber cellulose at 1.5% and 0.2% (based on oven dried pulp) respectively. The result showed that there is a linear change between stock drainage time and paper strengths containing nano cellulose fiber. Tensile and burst strength indices were improved at 18.66% and 18.12% respectively by adding 10% of nano cellulose fiber to suspension treated with cationic polyacrylamide. Furthermore, the two indices increased by 19.35% and 19.24% by adding the maximum amount of nano cellulose fiber (10%) to pulp suspension cationized with cationic starch, respectively. The overall results indicated that nano cellulose fiber had a positive significant effect on the refined and unrefined pulp strengths of Rice straw.

CEHEP and HEP sequences were used for bleaching of Rice straw organosolv pulps and the effects of these sequences were investigated on optical (brightness and opacity) and mechanical (tear index, burst index and breaking length) properties of produced paper sheets. Despite of the significant reduction in mechanical properties, brightness was increased so that it was suitable for writing and printing paper. CEHEP sequence had more increment on brightness and more decrement on mechanical properties than the HEP sequence. The catalytic soda organosolv pulping was used for the pulp production (delignification) from Rice straw via batch process at high temperatures and high pressures. The catalytic pulping of Rice straw was performed in ethanol-water mixtures (50 and 65% w/w) at various cooking times (150 and 180 min). The ratio of cooking liquor to dry mass of Rice straw was 10:1 and the catalyst (soda) was 1(%) dry mass of Rice straw.

In this study, the effect of alkali treatment on the mechanical properties of Rice straw flour-polypropylene composite was investigated. Rice straw flour (40 mesh) was treated with hydroxide sodium 5 and 10% in two times, once for 45 and another time for90 min respectively. The composites were made from Rice straw flour as filler (30%), polypropylene (65%) as matrix and maleic anhydride (5%) as coupling agent. In order to blend the raw materials of internal mixer a Haake HBI system 90 machines and make standard samples testing an injection molding were applied. The results of this study suggest that treatment of Rice straw flour with alkali 5% concentration increases tensile modulus and impact strength which increase with time prolongation. However, treatment of Rice straw flour with alkali 10% concentration decreases these properties even with the increasing of time. Furthermore, the increasing of alkali concentration and treatment time resulted in an increase in the tensile strength of composites.

Introduction: Rice husk (RH), the outer covering of Rice grains that obtained during the milling process, is one of the main agricultural residues. It mainly consists of cellulose, hemicelluloses, lignin, silica and minor other mineral composition. Societies often dispose of the Rice husk waste using open burning that leads to environmental pollution and damages to the land and the surrounding area in which it was dumped.

Annually huge amount of un-used Rice straw after Rice harvesting were burned due to no specific utilization. Whereas, based on the biorefinery concept there is possibility to use these agricultural residues for production of high value added products. So, this study was aimed to extract the silica from the Rice straw (Oryza Sativa var Indica) as one of the important agro-industrial residues in the country and its capabilities for production of silica nanostructures based on the mentioned concept. After washing, drying and grinding of Rice straw samples, some of them were separately leached with a hydrochloric acid and some ones with a sulphuric acid at concentration of 0. 5 M for 30 min with constant stirring. Afterwards, the silica content of acid-leached and un-leached Rice straw samples was measured in a muffle furnace with varying temperatures at 500, 600, 700, 800 and 900° C for 2 h. The results were obtained from Energy Dispersive X-ray (EDX) and X-ray Fluorescence (XRF) demonstrated the maximum presence of silica into the Rice straw ash. Two of aforementioned spectroscopy methods explored the higher content and purity of acid-leached Rice straw samples in comparison to un-leached Rice straw ones. The Field Emission Scanning Electron Microscopy (FESEM) images demonstrated that the prepared silica nanostructures had a spherical shape and their average particle sizes were 30 nanometer for un-leached Rice straw samples and less than 12 nanometer for acid-leached ones.

Deterioration of concrete structures in sulfate environments is a well-known phenomenon. Cement chemistry is an important parameter in coping with sulfate attack. C3A and CA (OH)2 lead to expansion, cracking and strength reduction. The use of Rice husk ash (RHA) can improve the sulfate resistance of concrete. It was observed that the sulfate resistance of blended cements was significantly higher in sulfate environments. This study investigates the effect of RHA replaced by cement on the durability of concrete due to sulfate attack. Three RHA replacement levels were considered in the study which is 7%, 10% and 15% by the weight of cement. After the specified initial moist curing period (28 days), concrete specimens were immersed in sodium sulfate & magnesium sulfate solution. The degree of sulfate attack was evaluated by measuring the compressive strength reduction of concrete cubes and their weight losses in both continuous immersed and wetting-drying conditions. Expansion observed in the ordinary Portland cement mortar prisms was larger than expansion for the RHA mortar prisms. Moreover, microstructure of the mortar and concrete incorporating Rice Husk ash were studied through SEM tests.