| Summary: | 碩士 === 國立雲林科技大學 === 工業化學與災害防治研究所 === 91 === The soil contaminated by heavy metals is increasing in Taiwan. The biosorption process for removal of heavy metals from contaminated soil is chosen in this study because it is cost-effective, easy to be commercialized, and does not destroy soil structure. This study includes: (1) soil leaching: it investigates the dependence of the soil leaching effect on the stirring rate, the liquor concentration, the ratio of solvent and soil, the time of soil washing and the value of pH. The results show that the stirring speed should be faster soil for a shorter washing time. At a solvent to soil ratio of 1：8 and a liquor concentration of 0.1M, the maximum yield can be reached when stirring rate was 8000 rpm soil washing time was about 0.5h, and the pH value was 6.0 ; (2) heavy metal biosorption test with immobilized Saccharomyces pombe : the suitable temperature for the cultivation of S. pombe 806 was 30℃. The proper temperature for the S. pombe. ATCC 2476 culture was 29℃ as the rotational speed was 200rpm and pH=5-6. By adding polymer(PVA) and reagent(Epichlorohydin) into Chitosan/Alg to chemically modify and improve the mechanical strength of the immobilized cells. The experimental result shows adsorption capacity and mechanical strength were optional when the immobilized cells were formed with 1.5％ Chitosan +10％Polyvinyl alcohol +10％ Alginate. Besides, pH=4–6 was appropriate for biosorption when the rotational speed was 400 rpm. The outcome reveals that the biosorption capacity was better when Saccharomyces (e.g.: Schizosaccharomyces pombe 806 and Schizosaccharomyces pombe ATCC 2476) was added, especially for the addition of 1g S. pombe 806. Analysis with Langmuir and Freundlich isotherms reveals that the biosorption of metals was monolayer and favorable adsorption. It shows first order model and spontaneous response from Kinetic model. Approximately 93％ of Cd2+ in the solution from washing soil was adsorbed by immobilized Saccharomyces pombe. About 79% of Cd2+ on the immobilized cells was desorbed with 1N HCl. It still was 70% adsorbed when it was desorbed or adsorbed about six times. This indicates that remediation of metal-polluted soil with immobilized yeast is feasible and cost-effective because the reusability of immobilized cells was high.
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