| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 88 === Bleaching of sesame oil with acid activated rice hull ash was investigated. Lovibond color indices of sesame oils before and after bleaching with the activated ash were determined to calculate the bleaching efficiency of the ash. The effects of the conditions of acid activation and the conditions of bleaching were studied. The conditions of acid activation studied were: ratio of rice hull ash/acid, activation temperature, agitation speed of activation and pH value of rice hull ash. The conditions of bleaching studied were: ratio of rice hull ash/sesame oil, bleaching temperature, agitation speed of bleaching and bleaching time.
The study was divided into two parts. The first part was one factorial experiment and the other part was the method of experimental design.
Experimental results of the first part indicated that ratio of rice hull ash/acid, agitation speed of activation and pH value of ash almost have no effect on the bleaching efficiency. Increase of activation temperature increases bleaching ability of the ash when the temperatures are low. The influence becomes insignificant when it is over 30℃. Increase of the ratio of rice hull ash/acid increases the bleaching efficiency. Increasing bleaching temperature may also promote bleaching efficiency. However, the bleaching efficiency decreases, when the temperature is over 120℃. Agitation speed of bleaching may increase the bleaching efficiency, however, the effect is insignificant. No effect is found when it is over 80rpm. On the other hand, the bleaching efficiency is found to keep constant initially. When it is over 60 min, the bleaching efficiency decreases with the increase of bleaching time. Still, the effect is not important.
Planning of experimental design method was not well. Consequently, the results obtained was not perfect. However, following results were observed. Only seven factors such as ashing temperature, ashing time, concentration of activation agent, pH value of rice hull ash, ratio of rice hull ash/sesame oil and bleaching temperature should be considered in the experimental design method. The interaction between two factors shown below should be considered in the experimental design method: ashing temperature and ashing time; pH value of rice hull ash and ratio of rice hull ash/sesame oil; pH value of rice hull ash and bleaching temperature; ratio of rice hull ash/sesame oil and bleaching temperature.
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