可可莢殼酸洗前處理對其衍製活性碳特性之影響

本研究以可可莢殼(CPH)作為製備活性碳之前驅料源，而為了提高對活性碳(AC)的吸附能力，實驗以酸洗前後做為比較，藉由近似分析、元素分析及熱重分析比較其酸洗前後之物性差異。再將酸洗前處理所得之產品(CPH-A)施以物理活化來製備高比表面積的活性碳產品(AC-CPH-A)，並進一步比較其孔洞性值。從研究結果可發現酸洗處理可以去除90%以上主要由鉀鹽礦物組成之灰分。研究結果也近一步表明，酸處理會使孔洞更加發達，進而使得比表面積和孔體積的增加。像是從650℃所衍製的活性碳中可發現，BET比表面積從1.1 m2/g (AC-CPH-650)上升至355.8 m2/g (AC-CPH-A-650)。並且隨著活化溫度的提高及活化時間增加，雖其產率變小，但其孔洞特性呈現升高的正相關性，即得到的比表面積值也越高，最高可達1,464 m2/g (AC-CPH-A-900-120)，顯見酸洗前處理料源、活化溫度與停留時間皆會對製作活性碳之特性有相當的影響。最後將以可可莢殼酸洗後衍製之活性碳於不同劑量及起始染料濃度條件下，進行對甲烯藍染料之吸附效能分析，發現起始濃度越高其平衡吸附量也越大，並且可可莢殼所製活性碳具有比商業化活性碳更好的吸附效能。

關鍵字

可可莢殼；酸洗處理；物理活化；活性碳；孔洞性質

並列摘要

In order to enhance adsorption capacity of activated carbon (AC) from cocoa pod husk (CPH), CPH was first leached by acid and then used as a precursor (CPH-A) for preparing ACs by physical activation at activation temperature of 650-900℃ and holding time of 0-120 min in this work. Based on the proximate analysis, mineral compositions, thermogravimetric analysis and thermochemical properties, the differences between CPH and CPH-A were investigated. The chemical and pore properties of the resulting ACs were further studied. The results showed that the pre-treatment of CPH with hydrochloric acid led to removal of over 90% of the ash content in the CPH, mainly composed of potassium minerals. The Brunauer-Emmet-Teller (BET) surface area of the AC derived from CPH-A at 650℃ is 355.8 m2/g (AC-CPH-A-650), significantly larger than that (i.e., 1.1 m2/g) of the AC derived from CPH (AC-CPH-650). The higher activation temperature (e.g., 900℃) and longer holding time are beneficial to the pore development of the resulting AC, but have relatively low yields. The maximal BET surface area reached 1,464 m2/g for AC-CPH-A-900-120. As compared to commercial AC, the resulting AC indicated better equilibrium adsorption capacities under various initial methylene blue concentrations.