| 摘要: | 本研究從文獻中得知幾丁質的應用非常廣泛，使用在食品、醫學、美容、環境...等用途，而幾丁質經由去乙醯後的幾丁聚醣具有良好的吸附效果，運用在環境上可以吸附水中之重金屬離子，經由螯合作用易與重金屬離子形成配位鍵。另外幾丁質結構類似於纖維素，在地球上含量是非常豐富，是自然界上第二多高分子纖維，它來自於甲殼類動物如:蝦、蟹、等節肢動物。本實驗使用微量之幾丁聚醣附著於石英砂探討其吸附Cu2+效果，並且使用不同之自然砂土如高嶺土（Kaolinite）、膨潤土（Bentonite），改變幾丁聚醣型態，探討不同黏土聚合吸附劑之吸附能力，進而探討等溫吸附Langmuir Isotherm、Freundlish Isotherm之適用性及動力吸附（擬一階動力吸附、擬二階動力吸附）之探討。
本實驗在不同吸附劑應用於吸附平衡的試驗中發現：不同比例之膨潤土-幾丁聚醣與高嶺土-幾丁聚醣均可在不同之銅離子濃度下，於4小時的接觸時間中達到吸附平衡。此外，各吸附劑對於銅離子之吸附情形，由實驗數據得知：在單一使用幾丁聚醣、膨潤土及高嶺土之狀態下，以Chitosan > Bentonite> Kaolinite；若利用不同比例之高嶺石與膨潤土固化於幾丁聚醣對於Cu2+的吸附能力，排序如下：1:5 > 1:10 > 1:20。
不同比例之膨潤土-幾丁聚醣與高嶺土-幾丁聚醣吸附劑皆符合Langmuir等溫吸附模式，R2值均可達0.986以上，各吸附劑之最大吸附量依黏土與幾丁聚醣不同之結合比例1:5、:10、1:20分別為16.78、12.69、12.15（mg Cu2+/g CCB）及11.24、9.36、6.88（mg Cu2+/g CCK）。此外，在Freundlich等溫吸附式中，所有吸附劑之n值均大於1，亦驗證此吸附劑有利於金屬吸附現象的發生。
以動力吸附模式探討，不同比例之膨潤土-幾丁聚醣與高嶺土-幾丁聚醣吸附劑，其動力吸附方程式皆符合擬二階動力學模式（解析偏差值較符合，R2>0.999），吸附動力模式符合化學性吸付模式（Chemical Adsorption），顯示水中銅離子與石英砂─幾丁聚醣吸附劑表面之官能基原子間發生電子的交、轉移或共有，形成吸附化學的吸附作用。
Because of the dramatic develop of industry, heavy metal pollution has become a global environmental considerations. The heavy metals in the soil and groundwater have endangered our environment and human body by direct or indirect pathway. Thus, how to solve efficiently the heavy metal pollution in groundwater has become the most essential issue around the world. Theoretically, the strategy for groundwater remediation cloud be divided in two categories, “control” and “treatment”. The treatment methods for groundwater contaminated site cloud be divided in two technologies, including the “ex-situ” and “in-situ” remediation. The most widely application based on the idea of in-situ remediation in US is permeable reactive barrier, due to its economical efficiency in treating large contamination area, and was widely accepted as an efficiency technology for groundwater remediation.
This research is based on the ideal of green design and using biodegradable material (Chitosan) coated with nature materials, such as kaolinite and bentonite. First of all, this research will perform the process optimization for this biodegradable adsorbent. The optimized adsorbents will execute the adsorption experiment, and evaluate the isothermal studies (Langmuir Isotherm、Freundlish Isotherm) and kinetic study (Pseudo-first order and Pseudo-second order kinetic model) for Cu ions.
In terms of the adsorption capacity and the ability to adsorb Cu2+ ions in aqueous medium, when used alone, is chitosan > bentonite > kaolinite. However, when clay materials (either bentonite or kaolinite) were coated with chitosan, the adsorption capacity and Cu2+ removal were significantly enhanced. Bentonite and kaolinite was coated with chitosan at 1:20, 1:10 and 1:5 chitosan-to-clay ratios. The equilibrium time was four hours. Equilibrium data fits very well to the Langmuir isotherm model, which indicates that the adsorption of copper ions was monolayer on homogeneous adsorption sites. Chitosan coated bentonite had a higher adsorption capacity for copper ions of 12.1507 mg/g, 12.6904 mg/g and 16.7785 mg/g compared to 6.8823 mg/g, 9.3633 mg/g, and 11.2360 mg/g for chitosan coated kaolinite for 1:20, 1:10 and 1:5 chitosan-to-clay ratios, respectively. Experimental data followed pseudo-second order kinetic model, which suggests that the chemical sorption is the rate limiting step, instead of mass transfer. |
