| Summary: | 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.
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