| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 97 === Abstract
Applying recycled industrial solid waste to pollution control has be widely investigated, which is considered as a clean technology able to solve both concerned environmental problems including pollutants removal and solid waste disposal. It has been reported that the chitosan converted from chitin can be applied as an efficient adsorbent for varieties of heavy metals. It also has been found that crab shell, one of the most common seafood wastes, contains natural chitin abundantly. Accordingly, this study attempts to apply wasted crab shell as an adsorbent for removing lead ion from artificial lead-containing wastewater in a fluidized bed reactor in which lead precipitates and crystallizes on the crab shell surface. Many tasks were conducted in this study for evaluating the lead adsorption capacities by both original crab shell and NaOH treated crab shell, which includes conducting both lead adsorption experiments in both batch and fluidized reactors and. Several operational parameters such as, solution pH level, water flow velocity and the presence of carbonate in the adsorption system were tested in the study.
Some important experimental results were observed in this study. The results indicate high adsorption capacity of lead in high pH-level conditions and the NaOH-treated crab shell achieving higher adsorption capacity than the original crab shell. The adsorption capacity of lead by NaOH-treated crab shell can be as high as 714.3 mg-Pb/g-crab as solution pH= 5.0. It is also observed that the lead adsorption by the crab shell basically follows a first-order reaction relationship based on adsorption dynamic analyses. Higher adsorption rate is observed in higher pH conditions. For the adsorption of lead in the fluidized bed reactor, the lead removal ratio is affected by solution pH, water flow rate and added concentration of Na2CO3. It has better to control solution pH between 5 and 7, and the molar ratio of carbonate to lead equal to 6.0.
Observation and analysis by SEM-EDS, NaOH modified crab shell surface cellular structure to be more obvious, the surface of media after the fluidized crystallization is more tighter than the original shell. The component proportion of lead increases, the surface layer is covered by the crystal, but the component Ca in original crab shell is very trace.
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