| 摘要: | 近年來，幾丁聚醣(β-(1-4)-N-acetyl-D- glucosamine)是廣泛受到矚目與多元運用的生物聚合物，並且具有：生物相容性、生物降解性、再生性，生物活性及無毒性等特點；此外，幾丁聚醣為幾丁質去乙醯化之多醣體，而幾丁質含量為全球僅此次於纖維素之聚合物，可由蝦蟹及菌類中提煉出；眾多文獻指出：幾丁聚醣對於重金屬離子及染料具有良好的吸附能力。但是，若單純使用幾丁聚醣應用於汙染物之去除，其價格昂貴，不符實場應用之經濟效益，所以，本研究為降低其應用成本，利用了自然界、易取得之不同載體，如：膨潤土、高嶺土及石英砂等，作為幾丁聚醣之吸附載體，使之達到降低成本的目的。
本研究利用少量的幾丁聚醣與膨潤土、高嶺土及石英砂參合，形成：幾丁聚醣固化於膨潤土（CCB）、幾丁聚醣固化於高嶺土（CCK）及幾丁聚醣固化於石英砂（CCS）等吸附劑，對五價砷進行吸附。此外，本研究先以BET、TGA 及FT/IR 等分析了解吸附物的特性，並探討在不同反應時間（0.5,1, 2, 4, 6, 12, 24 小時），不同起始濃度（50, 100, 500, 1000 ppb）及不同溫度下（25, 35, 45, 55°C）各吸附劑之吸附效益；此外，進一步探討動力吸附（pseudo-first order、 pseudo-second order and intraparticle diffusion models），等溫吸附（Langmuir、Freundlich 及Dubinin-Radushkavich）及吸附熱力學IV等模式演算。結果顯示：不同吸附物劑皆在12 小時候達到達吸附平衡；在動力吸附方面，所有吸附劑皆遵循擬二階動力模式，各吸附物之R2 值依序如下：活性碳（AC）（0.9064< R2< 0.9987）、純幾丁聚醣（0.9213< R2< 0.98）、CCB（0.9575< R2< 0.9988）、CCK（0.9916< R2< 0.998） 及CCS（0.794< R2<0.9991）。此外，在等溫吸附方面：各吸附物在Langmuir 模式下具有較高的R2值（0.94~0.99），而各吸附物的最大吸附能力分別為AC（11.41553μg/g），純幾丁幾丁聚醣（23.31002 μg/g），CCB（67.11409μg/g），CCK（68.96552μg/g）及CCS（16.77852μg/g）；再者，Freundlich 模式中的n 值皆大於1，表示各個吸附劑皆遵循物理吸附。在吸附熱力學方面：活性碳及純幾丁聚醣皆為非自發性反應、CCB 和CCK 為自發性；但CCB 在35℃時為非自發性，而CCS 在25℃時為自發性隨著溫度的升高轉變成非自發性。
In recent years, chitosan (β-(1-4)-N-acetyl-D- glucosamine) is a very popular and well known polymer owing to its many advantages, such as biocompatibility, biodegradability, renewability, bioactivity, and non-toxicity. Chitosan is a polysaccharide formed by the deacetylation of chitin, and chitosan is the second most abundant natural polymer, which is obtained from shrimps, crabs, and fungi. Many literatures have indicated that chitosan was excellent in removing heavy metal ions and dyes. However, pure chitosan is very expensive. Lowering the cost of chitosan is recommended in future application. To support chitosan, the usage of different carriers such as bentonite, kaolinite, and quartz sand were applied to reach the goal of this study. In this experiment, small amount of chitosan was coated on the bentonite, kaolinite and quartz sand to form Chitosan coated bentonite (CCB), Chitosan coated kaolinite (CCK), and Chitosan coated sand (CCS). BET, TGA, and FT/IR analysis were firstly implemented to characterize the adsorbents. Effect of adsorbing time (0.5, 1, 2, 4, 6, 12, 24 hours), initial concentration (50, 100, 500, 1000 ppb), and temperature (25, 35, 45, 55°C) were evaluated. Kinetic studies (pseudo-first order, pseudo-second order, and intraparticle diffusion models), II equilibrium studies (Langmuir, Freundlich, and Dubinin-Radushkavich isotherm), and thermodynamic studies were executed and confirmed the research results. This research indicates the equilibrium time of different adsorbents at different initial concentrations was about 12 hours. The kinetic study exhibits all adsorbents approximately follow pseudo-second order, with the R2 ranges as follows: Active Carbon (AC) (0.9064< R2< 0.9987), pure chitosan (0.9213< R2< 0.98), CCB (0.9575< R2< 0.9988), CCK (0.9916< R2< 0.998), and CCS (0.794< R2< 0.9991). Langmuir isotherm of the different adsorbents has best R2 (0.94~0.99). The maximum adsorption capacity of adsorbents (AC, pure chitosan, CCB, CCK and CCS) are 11.416 μg/g, 23.310μg/g, 67.114μg/g, 68.966 μg/g, and 16.779 μg/g respectively. Moreover, the n of all adsorbents in the Freundlich isotherm are all greater than 1 which verifies that all adsorbents follow physical sorption. Thermodynamic studies determined that AC and pure chitosan are non- spontaneous, CCK and CCB are spontaneous, but the CCB is non- spontaneous at 35°C; CCS is spontaneous when the temperature is 25°C but becomes non-spontaneous at higher temperatures. |
