Effect Of Pretreatment On Properties Of Rice Husk Ash

Rice husk ash (RHA) is an agricultural waste material which has great industrialvalue. The main composition of RHA is silica. There are also some metal oxides andunburned carbon in RHA. High purity amorphous silica nano-particles can be obtainedby combusting rice husk at low temperature which has good future of industrialapplication. However, with the increasing of combustion temperature, the black carbonresidue content of RHA increases and the amorphous silica becomes into the quartzcrystal, which could reduce RHA activity. Therefore, it was pointed out that highactivity and purity RHA can be obtained by combusting rice husk which has beensoaked in acid.Based on the above, the effects of different methods and combustion conditionson the properties of RHA were studied. The research methods were all follow, ricehusk pretreated with3kinds of acid (hydrochloric acid, sulfuric acid and acetic acid) indifferent concentrations (1%,2.5%,5%and10%) for different time (0.5h,1h and2h),then the rice husk pretreated with acid combusted at different temperature (600,700,800and900℃) for different time (0.5h,1h) in two combustion equipments (mufflefurnace and fluidized bed). The microstructure and elemental composition of RHAwere tested by XRF, SEM and EDS.Firstly, comparing RHA obtained from origin rice husk with that from acidpretreated rice husk, the reasons of high content of carbon residue and surfacecrystallization in RHA were analyzed. It was found that pretreatment could improvethe performance of RHA, and increase the purity of silica. The effects of3kinds ofacid pretreatment were discussed. It was found that hydrochloric acid pretreatmenteffect was the best. And then, the effect of pretreatment conditions and combustionconditions on the microstructure and elemental composition of RHA were also studied.There were critical conditions during pre-treat process which could affect the RHAcharacteristics. In addition, there weren’t relevance between combustion conditionsand RHA characteristics. Finally, RHA characteristics obtained by combusting ricehusk pretreated in fluidized bed were compared with that in muffle furnace. Variationsof Si and K in RHA obtained by combusting different acid pretreatment rice husk influidized bed were also studied.Moreover, using XRF analysis results as a reference, relevant error of EDS testdata was analyzed. The error range of testing methods also was obtained, and theadvisability of data analysis in this thesis was discussed.