Study On The Comprehensive Utilization Of Rice Hulls

The technologies were studied for the production of activated carbon, an adsorbent for the soy oil industry, sodium silicate and white carbon black from rice hull (RH) or rice hull ash (RHA). And the properties of the finished production were also characterized.The activating effects of different activating agents were compared on the activation efficiendcy to RH and silicon dioxide-freed RH. Zinc chloride was proved to be a better activating agent than phosphoric acid, and the activation conditions was optimized: the RH to zinc chloride ratio 1:2.5, the zinc chloride concentration 60%, activation time 60 min, activation temperature 600. Both RH derived activated carbon products exceeded the first grade of powder activated carbon as specified in Standard LY/T 1281-1998, in terms of the methylene blue decolorizing abilities, though the ash contents were a little higher.RHA was activated with sulfuric acid after treatment with sodium hydroxide solution to produce an adsorbent for the soy oil industry. The factors that influenced the ability of adsorption were investigated. The optimal sodium hydroxide solution concentration and reaction time were determined to be 2mol/L and 2 hours. Consequently, the optimal acid activating conditions, under which the resulting product had greatest adsorption ability of pigment in soy oil, was also determined: H2SO4 concentration 5%(v/v), activation time 4 hours, activation temperature 90 The adsorbent produced under the above mentioned conditions was named ARHA. Activation with water vapor under the optimal conditions (the ratio of silicon dioxide-freed RHA to water 1:15, activation time 900 activation time 1.5 hours), also enhanced the adsorbent's carotene decolorizing ability. The adsorbent produced under the above mentioned conditions was named VRHA. VRHA was superior to activated bleaching clay (ABC) but not as good as ARHA, and the yield of the VRHA decreased to a great extent. Scanning electron microscope (SEM) and pore properties analysis showed that the specific surface area of ARHA was nearly twice that of ABC and the pore size distribution of ARHA was suitable to absorb the pigment in soy oil. In addition, the lower pH value of ARHA compared with ABC might have enhanced the chemisorption ability of ARHA. The cost of decolorizing process was reduced to the maximum extent when a mixture with an ABC to ARHA ratio of 70:30 was used.Sodium silicate and white carbon black were produced from RHA. The optimum sodium hydroxide solution concentration and reaction time were determined separately to be 2mol/L and 2 hours, respectively. The factors that influenced the adsoption of dibutyl phthalate (DBP) property of white carbon black, such as the concentration of sodium silicate, the type and dosage of flocculating agent, the temperature of neutralization, the method of neutralization and the aging time were also investigated. The optimized conditions were: 15 Be sodium silicate solution with 1.5 volumes of saturated sodium chloride solution was gradually neutralized withhydrochloric acid at the temperature no higher than 80, and then aged for 1.5 hour. The adsoption of dibutyl phthalate (DBP) property of production was comparable with the white carbon black as specified in National Standard GB10517-89. The production of white carbon black and ARHA from RHA can bring significant benefit.