含幾丁聚醣吸附劑的製備與特性研究：重金屬移除

Abstract

銅和汞這二種重金屬被認為是有毒的。銅雖是一種人體必需的元素，但過量或急速給予銅卻會對人體造成傷害，甚至死亡。汞無法被生物分解而且會累積在生物體內，造成各種疾病和不適。近年來大家對於這類議題普遍的關注引發了廣泛的相關研究，以便開發出從水溶液中移除這類潛在毒害物質的新技術。ㄧ種令人信賴的方法是利用生物高分子作為累積金屬的吸附劑，花費可負擔的成本即可降低重金屬離子濃度至環境可接受的範圍。幾丁聚醣 (chitosan) 是由存在於真菌、昆蟲及甲殼類體內的幾丁質 (chitin) 經過N-去乙醯化 (N-deacetylation) 反應而成的天然陽離子型生物高分子。幾丁聚醣以它多功能的特性及多方面的應用著稱。並且，幾丁聚醣已被證實可有效的從水溶液中移除多種金屬。由於幾丁聚醣有生物可分解性、親水性、具有官能基、天然來源等特性，因此和其他傳統物質比較起來是非常有潛力開發作為吸附劑的物質。 本研究的目的是探討含幾丁聚醣材料於移除水溶液中重金屬的應用，並探討其吸附金屬的行為。本論文中實驗工作分成三個章節： (1) 為了同時符合實用性及成本性，我們成功製備出部分去乙醯化蟹殼(幾丁聚醣)。藉由批次式吸附實驗，我們得以比較部分去乙醯化幾丁聚醣及市售螯合性樹脂對於二價銅離子的吸附效果。並且由批次式吸附實驗，我們得以比較此二種吸附劑的導電度移除效果。 (2) 將經過戊二醛交聯處理的幾丁聚醣包埋固定於藻酸鈣膠球內，我們製備出含幾丁聚醣藻酸膠球 (AGCC: alginate gel containing chitosan)，並可應用於移除水溶液中之二價汞離子。實驗顯示AGCC膠球兼具高吸附能力 (667 mg / g) 及快速達到吸附平衡 (60 min) 的二個優點。 (3) 我們以活性碳及幾丁聚醣成功製備出一種複合碳吸附劑：含幾丁聚醣及活性碳藻酸膠球 (GCA: alginate gel containing chitosan and activated carbon)。二種材料的組合使得GCA膠球具備：對於二價汞離子的更高吸附能力 (576 mg / g)、且可快速達到吸附平衡 (70 min)。因為含有活性碳顆粒，GCA膠球並可廣泛的應用於各種水處理(例如：飲用水處理)。

Heavy metals, such as copper and mercury, may be regarded as toxic. Although copper is an essential element for human, large and acute doses can be harmful, even fatal, effects. Mercury is not biodegradable and tends to accumulate in living organisms, causing various diseases and disorders. In recent years, widespread concern over these issues has lead to extensive research in developing effective alternative technologies for the removal of these potentially damaging substances from solutions. One promising technique for accumulating metals is using biopolymers as adsorbents, which can reduce heavy metal concentrations to environmentally acceptable levels at affordable costs. Chitosan is a natural cationic biopolymer formed by the N-deacetylation of chitin, which is present in fungi, insects, and crustaceans. Besides its versatile properties and numerous applications, chitosan has been shown to effectively remove several metals from aqueous solutions. Chitosan is a very promising material as adsorbent when compared with other conventional ones because of its advantages such as biodegradability, hydrophilicity, presence of functional groups, and natural origin. The objective of this study is to investigate the application of chitosan containing material for the heavy metal removal from solutions, and its metal adsorption behavior. The experimental work in this dissertation was divided into three chapters: (1) The partially deacetylated crab shell (chitosan) was successfully prepared to meet the requirement of both feasibility and cost. By carrying out the batch type adsorption experiments and the breakthrough experiments, we compare the Cu2+ adsorption of partially deacetylated chitosan and a commercial chelating resin. We also compare the conductivity removal of these two adsorbents by using the batch type adsorption experiments. (2) Alginate gel containing chitosan (abbreviated as AGCC) was prepared by immobilizing glutaraldehyde-crosslinked chitosan into calcium alginate gel bead via entrapment, and used for the removal of Hg2+ ions from aqueous solutions. Both high uptake capacity (667 mg / g) and fast time (60 min) to equilibrium were demonstrated as the excellent characteristics of AGCC. (3) A composite carbon adsorbent, alginate gel containing chitosan and activated carbon (abbreviated as GCA), was successfully prepared. The combination of these two materials, activated carbon and chitosan, resulted in high adsorption capacity (576 mg / g) and fast time (70 min) to reach adsorption equilibrium for Hg2+. GCA could be applied to a great variety of water treatment (e.g. drinking water) due to the contained activated carbon.