| Summary: | 碩士 === 中原大學 === 環境工程學系 === 105 === The adsorption of the cationic heavy metals (Cu、Pb、Cd、Ni) and the oxyanion (MnO4-) on Mg-Al layered double hydroxides (Mg-Al LDHs) intercalated with the organic solutes containing sulfur from aqueous solution have been studied. Mg-Al LDHs was prepared by hydrothermal method and then the organic acids were used to intercalate Mg-Al LDHs through a coprecipitation method to form the adsorbents of DS·Mg-Al LDHs, Ethyl xanthate·Mg-Al LDHs and L-cysteine·Mg-Al LDHs. The adsorbents were characterized by XPS, SEM, FTIR, XRD and BET. The maximum adsorption capacities of adsorbents under the given conditions were estimated from Langmuir equation. The adsorption mechanisms of test adsorbents toward the heavy metal ions were examined.
The results indicated that the modified adsorbents could simultaneous adsorb cationic and the anionic heavy metal ions. For Mg–Al LDHs, the adsorption capacities mainly result from the surface precipitation. For·Mg-Al LDHs, Ethyl xanthate·Mg-Al LDHs and L-cysteine·Mg-Al LDHs, the adsorption capacities were mainly attributable to the formation of the DS–metal, Ethyl xanthate–metal and L-cysteine–metal complexes in the interlayers of the Mg–Al LDHs, leading to the high adsorption capacities. The best solution pH values for adsorption of the cationic and anionic heavy metal on adsorbents were pH=5 and pH=4, respectively. The uptake of the cationic heavy metals increased in the order to DS·Mg-Al LDHs > Ethyl xanthate·Mg-Al LDHs > L-cysteine·Mg-Al LDHs> Mg-Al LDHs. The modified adsorbents offered more than 2~6 times higher adsorption capacities, not only for the cationic heavy metals but also to the anionic pollutants.
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