以幾丁聚醣混合矩陣式基材及磺化幾丁聚醣基材作為銅離子吸附劑之評估

Abstract

本研究以天然高分子-幾丁聚醣做為研究對象，分別製備包埋離子交換樹脂之混合矩陣式基材及具有磺酸根官能基的磺化幾丁聚醣基材，並探討其對銅離子之移除效果。 本研究成功地將離子交換樹脂(Amberjet 1200H, Rohm & Haas)均勻分散包埋於幾丁聚醣立體結構中，製成幾丁聚醣混合矩陣式基材(Chitosan mixed matrices)。在微觀上，幾丁聚醣基材的雙連續結構使其具有高比表面積(72.26m2/g)，可有效提升混合矩陣式基材對銅離子之吸附量。混合矩陣式基材具有多孔性的幾丁聚醣立體結構，銅離子能流經基材內部與幾丁聚醣之胺基或包埋的離子交換樹脂之磺酸根官能基反應。經由銅離子吸附實驗證實混合矩陣式基材能有效提升幾丁聚醣基材於低濃度時之銅離子吸附能力，並具有應用於處理大範圍離子濃度的潛力。由等溫吸附實驗可知，幾丁聚醣混合矩陣式基材對銅離子之吸附行為以Langmuir模型及Freundlich模型皆能適切描述。 在磺化幾丁聚醣基材(Sulfonic chitosan matrix, SCM)部分，本研究先以epichlorohydrin對幾丁聚醣基材進行交聯，再以1,3-propane sultone(1,3-PS)經由異相磺化反應將丙基磺酸根官能基(-(CH2)3SO3H)接枝於幾丁聚醣之胺基上，並以不同體積比之1,3-PS/乙醇溶液與幾丁聚醣基材反應製備不同磺化程度的幾丁聚醣基材。經由元素分析儀鑑定得知以50mL 1,3-PS(無乙醇溶液)進行3小時磺化程序的幾丁聚醣基材之磺化率約為100.00%；而幾丁聚醣基材與不同體積比(0.1/50、0.5/50及2.5/50)之1,3-PS/乙醇溶液反應後之磺化率分別為35.05%、57.40%及96.05%。電子顯微鏡照片顯示幾丁聚醣基材於交聯及磺化反應後表面結構發生合併且部分面積被緻密層所覆蓋。基材表面結構合併情形與緻密層覆蓋面積隨著磺化程度的增加而增大。磺化幾丁聚醣基材對初濃度100mg/L之銅離子溶液的吸附量(14.5mg/g)較未磺化的幾丁聚醣基材(28.4mg/g)低，且銅離子吸附量隨幾丁聚醣基材的磺化率升高而降低。可能原因為幾丁聚醣基材於磺化後分子量增加，使相同重量之磺化幾丁聚醣基材與磺化前相較，具有較少的官能基能與銅離子反應；另外交聯反應降低磺化幾丁聚醣基材之-NH2官能基密度，且磺化幾丁聚醣基材的緻密結構造成基材的比表面積降低，都是幾丁聚醣基材於磺化後對銅離子吸附量降低的可能原因。

In this study, chitosan mixed matrices and sulfonic chitosan matrices were prepared for copper ion adsorption process. Ion exchange resins (Amberjet 1200H, Rohm & Haas) were incorporated into the stereo structure of chitosan matrices to fabricate chitosan mixed matrices. The porous structure of chitosan matrices could make the copper ion solution flowing though the matrices. The copper ions would be easily caught by the amino groups of chitosan matrices or sulfonic groups of ion exchange resins. The specific surface area of chitosan mixed matrices are 72.26m2/g due to the formation of bi-continuous structure, which has considerable surface area and can enhance the copper ion adsorption capacities. Results of copper ion adsorption experiments showed that adsorption capacities of chitosan matrices were obviously improved at low ion concentrations and could be utilized in various ranges of ion concentrations. The copper ion adsorption isotherm of chitosan mixed matrices fitted well with both Langmuir and Freundlich models. In sulfonation process, chitosan matrices were cross-linked and sulfonated by epichlorohydrin(ECH) and 1,3-propane sultone(1,3-PS) solutions respectively. Chitosan matrices with different degree of sulfonation can be composed by reacting chitosan matrices with different volume ratio of the 1,3-PS/EtOH solution. By the results of elementary analysis, the degree of sulfonation of sulfonic chitosan matrices (without EtOH) was 100.00%. The sulfonic chitosan matrices which reacted with 0.1/50, 0.5/50 and 2.5/50 of volume ratio of 1,3-PS/EtOH solutions were 35.05%, 57.40% and 96.05% respectively. SEM images revealed that the external structure of sulfonic chitosan matrices were suppressed and sheltered by dense layer after cross-linking and sulfonation processes. The results of copper ion adsorption experiments showed that the copper ion adsorption capacity of sulfonic chitosan matrix (14.5mg/g) is lower than that of chitosan matrix (28.4mg/g) at an initial ion concentration of 100mg/L. The possible reasons may include: 1) Based on the same weight of chitosan adsorbents, increasing molecular weight of matrices after sulfonation process could decrease the number of functional groups feasible reacting with copper ions; 2) Cross-linking process decrease the density of amino groups available chelate with copper ions; 3) Structure transformation of the sulfonic chitosan matrices could decrease the attainable surface area for adsorption processes.