| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 87 === Bleaching efficiency of sesame oil by rice hull ash has been examined. Box furnace, bleaching set-up and tintometer were employed to ash rice hull, bleach sesame oil and determine red index of sesame oil, respectively. Elemental analyzer, inductively coupled plasma-mass spectroscopy, surface area meter, X-ray diffractometer and scanning electron microscope were used to determine the composition and the physical properties of rice hull and rice hull ash.
This study was divided into two parts. Effects of ashing temperature and ashing time on the bleaching efficiency were studied in the first part. Rice hull ash was then activated by acid. Effects of acid type, acid concentration and activation time on the bleaching efficiency were studied in the second part.
The results of the first part indicated that bleaching efficiency was elevated and then reduces as the ashing temperature was increased. Maximum bleaching efficiency occurred at 773K. Bleaching efficiency was increased when the ashing time was increased. After 1,800-3,600s it leveled off. The optimal ashing conditions of rice hull were found to be 773K and 1,800-3,600s. Bleaching efficiency was found not to be influenced by specific surface area when the average pore diameter is smaller than 50A. Bleaching efficiency was found to be directly related to surface area when the average pore diameter is greater than 50A.
The results of the second part indicated that acid activation, increase of acid concentration or increase of activation time might elevate bleaching efficiency mildly. The optimal conditions for activation of rice hull ash was found to be 6N sulfuric acid and 3,600s. Acid activation may increase bleaching efficiency from 0% to 43% as the rice hull was ashed under various conditions followed by optimal activation conditions.
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