Abstract: A new method on comprehensive utilization of rice hull ash (RHA) was explored, based on the fact that mineral is highly and homogeneously distributed in RHA and is mainly composed of amorphous SiO₂. RHA was first treated with alkali solution and converted into water glass and desiliconized RHA (DRHA). Then, DRHA was activated with sulfuric acid to prepare a porous decolorizing agent (PRHA) for vegetable oil industry. Factors which influenced the modulus of water glass and decolorizing capability of PRHA were investigated. Different kinds of water glass products in the range of modulus 2.3-3.6 could be prepared by changing NaOH concentration in the range of 2-3 mol/L or reaction time in the range of2-3 h. High desiliconization was beneficial to the formation of porous structure in PRHA. Reacted with 2 mol/L NaOH at 100℃ for 2 h, RHA was converted in water glass of modulus 3.3 and DRHA. Under this condition, SiO₂ was extracted out from RHA by 94.83%. The optimum technology for activating DRHA to prepare PRHA was obtained as follows: sulfuric acid concentration 5%(mass part), activation time 4 h, temperature 90℃. The decolorizing capability of PRHA for soybeans crude oil was 3 times as much as that of activated attapulgite commonly used in vegetable oil industry.

Key words: rice hull ash, decolorizing agent, vegetable oil, water glass, activated attapulgite