| Summary: | 碩士 === 國立中央大學 === 環境工程研究所 === 100 === This study investigated the feasibility of synthesizing activated carbon-zeolite composites (AC-Z composites), using primarily sewage and water purification sludge as starting silicon, aluminum and carbon sources; and the AC-Z composites as synthesized in this study were evaluated for their adsorption behavior of Cd, Cu and methylene blue (MB), in hope that such composites could be applied to remove organic and inorganic pollutants simultaneously.
Firstly, the starting sludges as received were pretreated by drying and/or incineration to provide the dry sewage sludge (DSS) and the water purification sludge ash (WPSA), respectively, for the subsequent study. Secondly, it is supposed that the silicon and aluminum sources are provide by both DSS and WPSA, and the carbon source solely by DSS, and that the molar ratio of Si/Al and carbon content can affect the synthesis of zeolite and production of activated carbon; therefore, starting materials with various Si/Al ratio and carbon content were prepared by a mix design of DSS and WPSA (i.e., DSS:WPSA=1:9, 3:7 and 5:5). Thirdly, the synthesis of AC-Z composites were conducted by an alkali fusion, followed by a hydrothermal process.
The results indicate that the resultant ACZ1090 composite ( i.e., DSS:WPSA=1:9 for the starting mixture) was confirmed to contain trace amount of activated carbon and single-phased Na-A zeolite as main phase; in contrast, ACZ3070 composite, 2.75% activated carbon and Na-X zeolite as main phase; and ACZ5050 composite, 4.14% activated carbon and Na-X zeolite also as main phase. The results suggest that the activated carbon content in the resultant composites increased with increasing mix portion of DSS; and the theoretical Si/Al ratio of the starting mixture increased with the increasing portion of DSS (i.e., from 1.57 to 1.93), it seemed that with the increasing Si/Al ratio, the main crystal phase of in the resultant composites shifted from Na-A type to Na-X type.
The resultant AC-Z composites were evaluated for their adsorption of MB, Cu(II) and Cd(II). The adsorption of MB, Cu(II) and Cd(II), respectively, in a single component system, was found well fitted with the Langmuir model. The maximum adsorption of MB, Cu(II) and Cd(II), in a single component system was found to be 0.10, 0.68 and 0.49 mmole/g, respectively for ACZ1090 composite; and in comparison, 0.11, 0.64 and 0.50 mmole/g, respectively, for ACZ3070 composite; and 0.14, 0.56 and 0.45 mmole/g, respectively, for ACZ5050 composite. All the adsorption performance was comparable to that of the commercial grade 4A zeolite and 13X zeolite. However, the adsorption of MB, Cu(II) and Cd(II), in a multi-component system showed decreased adsorption quantity for the tested adsorbates, possibly due to the competition among the adsorbates. It was found that the selectivity for the tested adsorbates in decreasing order was Cu(II)>Cd(II)>MB.
This work demonstrated that it is feasible and beneficial to synthesize activated carbon-zeolite composites (AC-Z composites) with primarily sewage and water purification sludge as starting silicon, aluminum and carbon sources. The results may contribute to the recycling of water treatment sludges and the production of green activated carbon-zeolite composites.
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