以化學活化法製備咖啡渣活性碳及其應用研究

Abstract

本研究回收再利用廢棄咖啡渣，經過碳化與KOH、NaOH兩種化學活化法製備活性碳，並探討其對亞甲基藍之吸附效率。實驗之浸漬比分別為0.5、1、2、3 ，以KOH活化法之活性碳各別命名為CGK0.5、CGK1、CGK2、CGK3，以NaOH活化法之活性碳各別命名為CGN0.5、CGN1、CGN2、CGN3。KOH與NaOH活化法在浸漬比為3時，分別獲得最高比表面積為2470 m2/g以及1968 m2/g。以BET表面積儀量測活性碳之比表面積、孔隙容積、孔徑分佈，再以SEM觀察外觀之變化，隨著浸漬比越高，活性碳之比表面積與孔體積也隨之增加。 透過界達電位分析，KOH與NaOH活化法製備之活性碳零點電位約為2。吸附反應中，不同pH值對於任何參數之影響是不大的，浸漬比才是此吸附反應重要之關鍵因素。 在吸附動力學中，NaOH活化法與KOH活化法之活性碳吸附特性皆是符合擬二階動力學模式，其中CGN3吸附速率是最快的，約在60分鐘內即把300 ppm之亞甲基藍完全吸附，效果明顯優於CGN0.5、CGN1、CGN2以及所有KOH活化法之活性碳。等溫平衡吸附模式中，KOH活化法與NaOH活化法之活性碳吸附特性皆是符合Langmuir等溫平衡吸附模式。當浸漬比為0.5與1時，KOH活化法之Qmax比起NaOH活化法具有較大之優勢，但效率並不佳。當浸漬比達到2與3時，KOH活化法與NaOH活化法之Qmax皆達到一定吸附容量水準，其中以CGK3與CGN3之效率最佳。 將廢棄的咖啡渣拿來碳化及活化進而製備成活性碳，其中CGK2、CGK3、CGN2、CGN3為良好之吸附劑，吸附效率佳，本研究落實資源回收再利用之精神，創造一個新的經濟價值，對於環境友善且不浪費資源。

In this study, the coffee grounds were recycled and reused. The activated carbon was prepared through carbonization and KOH and NaOH chemical activation methods. The adsorption efficiency of methylene blue was investigated. For the impregnation ratios with 0.5, 1, 2, and 3, the activated carbons of the KOH activation method are named as CGK0.5, CGK1, CGK2, and CGK3, respectively. Similarly, the activated carbons by the NaOH activation method are named as CGN0.5, CGN1, CGN2, CGN3.The KOH and NaOH activation method achieved the highest specific surface area of 2470 m2/g and 1968 m2/g at the impregnation ratio of 3, respectively. The specific surface area, pore volume, and pore size distribution of the activated carbon were measured by the specific surface area analyzer, and the appearance was observed by SEM. As the impregnation ratio was higher, the specific surface area and pore volume of the activated carbon were increased. The point of zero charge for activated carbon prepared by KOH or NaOH activation method is about 2. In the adsorption reaction, the influence of different pH values is not significant, and the impregnation ratio is an important key factor for this adsorption reaction. In the adsorption kinetics, the activated carbon adsorption characteristics by both activation method were in accordance with the pseudo second-order model, in which the adsorption rate of CGN3 was the fastest, and 300 ppm of methylene blue was completely adsorbed within about 60 minutes. The adsorption efficiency is significantly better than those of CGN0.5, CGN1, CGN2 and all KOH activated carbons. In the adsorption isothermal, KOH and NaOH activated carbons were in accordance with the Langmuir model. For the impregnation ratio with 0.5 and 1, KOH activated carbons had greater advantages than that of NaOH activated carbons, but the adsorption efficiency are not good enough. For the impregnation ratio reaches 2 and 3, the Qmax of the KOH and the NaOH activated carbons were promising, and the adsorption efficiency of CGK3 and CGN3 were the best. The coffee grounds can be carbonized and activated to prepare activated carbon. Among all the adsorbents, CGK2, CGK3, CGN2, and CGN3 are better adsorbents because of the high specific surface area and the adsorption efficiency. This study implements the spirit of recycling and reuse of waste, which is friendly to the environment and reduces waste.