| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 106 === Industrial dyes are common pollutants in the environment, mainly from the Dye processing of textiles. Methylene blue (MB) is one of them of dye. Activated carbon (AC) has microporous structure and high surface area. AC adsorption is a cost-effective treatment technology in pollution treatment. Thus, the removal of color produced by MB in wastewater can usually achieved by AC adsorption, but spent AC is another environmental issue. Sodium persulfate (Na2S2O8, SPS, E0 = 2.01V) can be thermally activated to produce sulfate radicals (SO4-·, E0 = 2.4V), which are potentially capable of destroying pollutants sorbed on the surface of AC to regenerate spent AC. Therefore, the objectives of this study include (1) examining MB adsorption kinetics and adsorption isotherm behavior and (2) exploring MB adsorption efficiencies of thermally activated SPS regeneration of spent AC.
According to the results of the first research objective, the MB adsorption kinetics well fit the pseudo second-order model. The adsorption behavior satisfied better for the Freundlich isotherm model than the Langmuir model, the parameters obtained with the Freundlich model were used for discussion. With increasing numbers of AC regeneration, both n and KF parameters of Freundlich model increased and indicated possible reduction of the adsorption capacity. However, the results of the second research objective showed that adsorption efficiencies actually increased with increasing numbers of regeneration and the averaged adsorption capacity remained nearly 73% of the original capacity among 4 regenerations. The reasons are possibly due to the increase of the oxygen-containing functional groups on AC by persulfate oxidation. Therefore, the MB adsorption was caused by chemical adsorption instead of physical adsorption, which were demonstrated by the results of Fourier transform infrared spectroscopy and specific surface area analysis. These results confirmed that persulfate oxidative regenerated ACs still retain adsorptive capability in removing contaminants.
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