| Summary: | 碩士 === 中原大學 === 化學研究所 === 92 === The extraction efficiencies and performance evaluations for the application of a mesoporous molecular sieves, MCM-41, on heavy metal remediation were studied in this research. With its high surface area, MCM-41 is a good candidate for physisorbing and/or chemisorbing heavy metals and organometals. The effect of modifying the MCM-41 surface on the extraction efficiencies and performance was also undertaken by chemically changing the surface functional group to amino or EDTA ligands.
MCM-41, MCM-NH2, and MCM-EDTA were used as adsorbent with solutions including tin, tributyltin chloride, lead acetate, zine acetate, and cadmium acetylacetonate. Heavy metals and organometals were quantitated by ICP-AES, GFAAS and SPME/GC methods. The results show that the order of extraction efficiency is MCM-EDTA > MCM-NH2 > MCM-41, indicating that the covalent grafting of ligating NH2 and COOH functional groups on the MCM-41 surface could enhance chemisorption.
The adsorbing efficiency of the metals is affected by pH value due to the charge of the surface of the adsorbate and the morphology of the functional group. Adsorption capacity of MCM-EDTA was found to decrease with increase in pH value, which is very likely due to dissociation of EDTA from the MCM surface. For organometal adsorption, the most significant effects come from hydrophobic interaction and physisorption. Thus, unmodified MCM-41 also shows high adsorption efficiency for organometals.
Duplicate studies on the extraction efficiency of lead acetate yield relative standard deviations of 0.0 to 10.7 %, indicating satisfactory reproducibility. Matrix spike studies were done on cadmium acetylacetonate and zinc acetate besides lead acetate. The matrix spike recovery results are 94.5, 97.1, and 104.5%, respectively, indicating that the matrix does not have major interfering capacity.
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