利用幾丁聚醣改質濾材於管柱中吸附與回收銅金屬之研究

The Column Study of Copper Adsorption and Recovery in Aqueous Solution Using Chitosan Modified Filter Media

本研究利用具備生物可分解特色的生物高分子聚合物（Biopolymer）幾丁聚醣（Chitosan）結合不同自然物質來過濾含銅溶液，幾丁聚醣主要由幾丁質經去乙醯化所製成，且幾丁聚醣表面因具有胺基官能基故可與重金屬離子相互作用，進而形成吸附機制。本實驗以節省經濟成本為概念，將幾丁聚醣固化於不同天然物質形成吸附劑如:石英砂Chitosan Coated Sand （CCS）、膨潤土Chitosan Coated Bentonite（CCB） 、高嶺土Chitosan CoatedKaolin（CCK）。此外，回收銅的實驗參數為流量5ml/min、吸附劑厚度3 公分、並配置不同之Cu2+濃度:200、1000mg/L，在不同pH（3、4、5）下應用管柱實驗中比較吸附劑之吸附率，同時選擇最高吸附率之吸附劑進行反洗脫附實驗，並計算吸附貫穿時間與耗竭時間之濃度。研究結果得知，CCK、CCB、CCS 在pH3、Cu2+濃度為200、1000mg/L時對於銅離子去除率最佳，分別為 68.6%>58.9%>56.1%（200mg/L）；5 6 . 2 3%> 4 8 . 3 1%> 4 5 . 11%（ 1 0 0 0mg / L） 。質量傳遞區（ Zm ） 分別為1.4<2.3<2.37（200mg/L）；1.88<2.32<2.47（1000mg/L）。此外，應用Thomasmodel 實驗結果顯示、吸附劑參數R2 值均可達0.85 以上，且經由Thomasmodel 之預測曲線與實驗曲線亦可證明此三種吸附劑均有利於金屬吸附現象之發生。另外，在pH1 的狀態下進行脫附試驗，CCK 之脫附率可達82.13%以上，由證明Cu2+離子可經脫附作用回收，但由於CCK的表面被強酸破壞，導致幾丁聚醣滲透於酸中，因而無法進行第二次吸附。

Chitosan, a deacetylated product of chitin, is a well-known biopolymer that has high chelation capacity for heavy metals due to its functional amine groups.In this study, the removal of copper from aqueous solution using differentadsorbents such as chitosan-coated bentonite （CCB）, chitosan-coated kaolinite （CCK） and chitosan-coated sand （CCS） under fixed bed conditions was investigated. Under a constant flow rate of 5 mL/min and bed height of 3 cm, the effect of initial solution pH （pH 3 to 5） and initial concentration （200 and 1000 mg/L） on the % Cu2+ removal, breakthrough time, exhaustion time and length of the mass transfer zone was examined. The % Cu2+ removal, breakthrough time and exhaustion time were observed to increase with decrease in initial concentration and lower pH. On the other hand, a shorter mass transfer zone is observed at lower initial concentration and pH. The results show that the best Cu2+ removal is obtained at pH 3, where the removal rate of CCK, CCB andCCS could be arranged in the order of: 68.6%> 58.9%> 56.1% and 56.23%>48.31%> 45.11% at 200 and 1000 mg/L, respectively. The length of the mass transfer zone （Zm） has the following values: 2.37 > 2.3 > 1.4 at 200 mg/L and2.47 > 2.32 > 1.88 at 1000 mg/L for CCK, CCB and CCS. Under 200 and 1000 mg/L, it is observed that CCK having the smallest value of Zm would lead to a better removal rate for Cu2+ in comparison to CCB and CCS. The Thomas model was applied to the experimental data in order to predict breakthrough curves and describe the dynamics of the fixed bed. Thomas model shows to be a good fit in describing the breakthrough curves under different pH and initial concentration, due to its high correlation coefficient values （R2 > 0.85）. In addition, the experimental fixed bed data shows a good agreement with the predicted data derived from the Thomas model. Desorption studies were performed using HCl （pH=1） as a desorbing agent, where 82.13% Cu2+ was recovered. During desorption, the CCK beads were observed to be damaged due to HCl solution causing the dissolution of chitosan. The kaolinite particles were observed to be washed out from the column, which prevents a second adsorption cycle to take place.