本研究以不同組合之新型吸附劑來去除鎘金屬，分別探討不同控制變因對於去除效率之影響，實驗進行在不同pH值及溫度下，並且模擬等溫、動力吸附模式，最後進行SEM及BET分析來印證新型吸附劑表面孔洞大小及多寡對於鎘去除效率之影響。 其中影響鎘金屬吸附之因素：(1) pH值(2)溫度(3)官能基(4)零電位點等，而實驗結果顯示本研究最佳吸附pH值及溫度分別為7及35℃，吸附最佳之新型吸附劑比例為Fe(OH) 3：PSF：CH2Cl2=1：1.5：18。在相同的含鐵量下，在吸附20 ppm 鎘溶液100 mL 3小時後，其去除率可達100 %。動力吸附模式模擬結果顯示四種新型吸附劑皆以擬二階反應模式最符合，其線性回歸R2值皆大於0.995以上。經由SEM儀器(掃描式電子顯微鏡)分析得知，當增加二氯甲烷比例之新型吸附劑，所照射出了孔洞較深也較大，當增加PSF(聚碸)之新型吸附劑，其孔洞較為淺也較少。使用BET儀器(比表面積分析儀)分析得知，新型吸附劑比例為Fe(OH) 3：PSF：CH2Cl2=1：1.5：18，其BET值為18.1822 m2/g，HIOPs之BET值為3.2 m2/g，兩者相比之下，新型吸附劑之BET值為HIOPs的 6倍。 在本研究中，BET值越高，其去除效率越好。在相同含鐵量下，增加二氯甲烷比例，可以增加新型吸附劑之孔洞多寡，對於去除效率具有正面的影響。 In this study, several new adsorbents prepared with different iron oxides/foaming agent /dichloromethane ratios, iron sources (HIOPs and ferrihydrate), and foaming agents (PS versus PSF) were employed to remove cadmium. Adsorption test were conducted under different pH and temperatures, and sorption results were modeled with various adsorption isotherms and kinetic models. Finally, SEM and BET analysis were used to confirm the size and new adsorbent surface morphology which might affect the removal efficiency of cadmium.
The results of this study show that the best pH and temperature for cadmium adsorption were 7 and 35 oC, respectively. The new adsorbent (dosage = 1.5g) prepared with Fe(OH)3: PSF: CH2Cl2 ratio of 1:1.5:18 exhibits the best performance, achieving completely removal of cadmium with initial concentration of 20 ppm at 3 hours of reaction time. Kinetic modeling reveals that adsorption of the four new adsorbents for cadmium follows pseudo- second-order rate model with linear regression R2 values of greater than 0.995. SEM analysis reveals that new adsorbent has bigger and deeper pores with increasing dichloromethane ratio. When the ratio of foaming agent in the new adsorbent is increased, the pore becomes smaller and shallower. The new adsorbent prepared with Fe(OH)3: PSF: CH2Cl2 ratio of 1:1.5:18 has BET surface area of 18.1822 m2/g which is six times high than HIOPs (of 3.2 m2/g). Increasing dichloromethane ratio will increase pore number of the new adsorbent and BET value resulting in better cadmium removal efficiency.
