Preparation of porous ceramic RHA aggregates and its application in treating wastewater from textile industries

• Main Authors: Tasy, Jyh-Ching, 蔡志清
• Other Authors: Kan-Sen Chou
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/40523433332275050937

碩士 === 國立清華大學 === 化學工程學系 === 85 === In this study, the main raw material was rice hull ash (RHA) which was wet-mixed with kaoline (as sintered aids) and starch (as both binder and pore former).The mixture, was then by dried, molded and fired to obtain porous aggregates having desired strength and porosity for adsorption applications. The adsorptive capacities of these aggregates were then measured toward treating wastewater form textile industries to evaluate its efficiency for such an application. The following results were observed: (1) By washing with boiling acid and calcining at 600^C, an amorphous white ash with 236m2/g surface area was formed. (2) For black-aggregates heated under deficient oxygen condition, it showed better sintering, smaller weight loss in flowing water, and larger surface areathan samples heated in air. Samples with more starch (less kaoline) exhibitedlarger surface area, get lower mechanical strength. We found the optimal composition to be kaoline:starch:ash=0.9:0.3:2 (sample B6) which showed porosity of 69%, surface area of 106m2/g and strength of 124psia. (3) For white-aggregates containing more ash (less kaoline), it showed lower strength, higher weight loss in flowing water and larger surface area. The optimal composition was found to be kaoline:starch:ash=1:0.1:5 (sample W2-1) which had porosity of 73%, surface area of 85m2/g and strenngth of 119 psia. (4) From the adsorption experiments, we found that : (a) white ash offered the largest surface area and adsorption capacity, but its aggregates were more suitable in engineering application; (b) the white-aggregates which showed lower rates of loss in both surface area (2.4<8.7%) and capacity (3<12%) through the recycle test than black-aggregates, even thought they have less initial surface area and capacity, the white-aggregates were optimalones for the long term engineering applications. (5) Esterification and rehydration can be applied to modify the surface properties of these samples. As the extent of esterification was increased, it became less hydrophilic and more organophilic, and therefore exhibited a larger capacity toward oil(C24H38O4). On the contrast, as the extent of hydration was increased, the samsample becamemore hydrophilic and showed higher capacity toward molecules found in wastewater from textile industries.