以幾丁聚醣吸附雙成分金屬離子之平衡模式

Equilibrium Modeling of Adsorption of Binary Metals from Aqueous Solution on Chitosan Beads

邵惠珍(Huei-Jen Shao)

指導教授 ： 莊瑞鑫

元智大學/工程學院/化學工程與材料科學學系/碩士(2000年)

摘要

本文是以顆粒狀幾丁聚醣於30℃時，在不同pH(2.5~5)和濃度下(0.77~17 mol/m3)，吸附重金屬-銅、鎳、鋅，並先於單金屬系統下建立一吸附模式，以預測雙金屬下的吸附量。在吸附模式中，考慮了H+和金屬離子的競爭吸附，另外銅離子的水合反應也被列入考慮，根據這些反應的平衡常數及質能均衡式計算後，可得到反應後的pH值和吸附量。
比較雙金屬下的理論吸附量和實驗值後，可以發現有的實驗值與理論值間呈現正偏差；有些則為負偏差，這是因為競爭效應的關係，尤其當銅的存在量增加時，競爭效應更為顯著。而經由模式重新計算雙金屬的數據後發現，受到不同離子存在的影響，平衡常數和配位數都與單金屬的情況不一樣。在探討幾丁聚醣於Cu/Ni、Cu/Zn系統下的選擇性時，定義選擇性係數為兩金屬的吸附量之比值除以初濃度的比值，發現選擇係數會介於5~25 (pH = 3~6)之間，這表示兩系統分離效果都很好，但在Ni/Zn系統時選擇性則偏低(1.2~2.6，pH = 2~5)；但由於三種雙金屬系統的選擇係數皆大於1，所以本實驗的幾丁聚醣是有利於分離雙金屬系統。

關鍵字

幾丁聚醣 ； 吸附 ； 平衡模式 ； 金屬 ； 幾丁質 ； 生物性材料

並列摘要

The adsorption of heavy metals such as copper, nickel and zinc at different pH (2.5~5)and concentration (0.77~17 mol/m3) using chitosan beads at 30 ℃was studied. To predict the amount of adsorption in binary metal systems, an equilibrium model for single-metal adsorption system was developed first. In this model, the adsorption of hydrogen and metal ions were competed, and the hydrolysis of copper ion was also considered. According to the equilibrium constants and mass-balance, pH value and the amount of adsorption were obtained after calculation by the computer program.
Comparing the calculated amount of adsorption in binary systems with experimental data, there showed positive deviation in some cases and negative deviation in some cases because of competitive effect, which was increased as increasing the amount of copper. And, the equilibrium constant and coordination number in binary systems were different from those obtained in single systems owing to the appearance of the other species . Selectivity factor of Cu/Ni、Cu/Zn, defined as the ratio of amounts of metal adsorption divided by that of their initial aqueous concentrations, was in a range 5~25 at a pH range 3~6. This represented that the selective separation in these binary systems could be achieved. In the Ni/Zn system, however the value was small (1.2~2.6) at pH range 2~5. Since the selective factor in all three systems were larger than 1, therefore the separation of metals using chitosan beads was forward.

並列關鍵字

Chitosan ； Adsorption ； Equilibrium Model ； Metal ； Chitin ； Biomaterial

參考文獻

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