| 摘要: | 因奈米碳管有高的比表面積，可提供較多之吸附位置，且經過改質過之碳管的物化特性會被改變，進而影響吸附污染物之能力。因此，本研究將多壁奈米碳管(A-MWCNT)經過酸、鹼改質劑改質後，在碳管表面鍵結官能基，探討對鄰苯二甲酸二甲酯(DMP)、鄰苯二甲酸二乙酯(DEP)及腐植酸(HA)之含苯環化合物的吸附影響及吸附機制。碳管定性分析之結果發現，經過改質過後之含氧官能基、比表面積及孔洞體積，有增加的趨勢。在SEM及TEM中可看到碳管管壁被破壞程度很嚴重，產生許多缺陷，硝酸改質之碳管(H-MWCNT)的形態短小，氫氧化鉀改質之碳管(K-MWCNT)的管壁及末端受損多，經過高溫裂解速率之快慢依序為K-MWCNT > H-MWCNT > A-MWCNT，殘餘量多寡為K-MWCNT > H-MWCNT ≒ A-MWCNT，表示未改質之碳管純度高，改質後不定型碳增多。 由動力吸附實驗結果可發現，在奈米碳管上達吸附平衡時間所需時間為DEP > DMP > HA，且結果均符合擬二階動力吸附模式。等溫吸附實驗中顯示，碳管的比表面積大小及含氧官能基多寡會影響DMP及DEP之吸附量。比較A-MWCNT、H-MWCNT及K-MWCNT對DMP之吸附量依序為0.20、0.14及0.27 mmol/g，在DEP之吸附量為0.23、0.16及0.28 mmol/g，DEP之吸附量皆較DMP高，和分子形狀及疏水性有關，且二種吸附質的吸附曲線均較符合Freundlich模式。在HA存在下之競爭吸附結果，碳管對DMP及DEP的相對吸附量分別下降22.14－41.01 %、30.20－45.41 %，和HA分子佔去碳管大部分之吸附位置，形成空間障礙有關。綜合上述之結果，奈米碳管的吸附能力會隨改質方式而異。 The adsorption DMP, DEP, and HA by MWCNTs with different surface properties were investigated in this study. The influences of the surface area, pore volume, and functional groups of MWCNTs were observed by modification for MWCNTs. After oxidation, the MWCNTs broke into smaller sizes with defects on their surface. From thermogravimetry analysis, it was shown that the percentages of impurity from the largest to the smallest were K-MWCNT > H-MWCNT > A-MWCNT. The adsorption capacity of DMP, DEP, and HA affected by the molecular shape and hydrophobicity of the molecules as well as the surface area, pore volume, and surface groups of MWCNTs. The adsorption capacity of DEP is larger than that of DMP, because of DEP has larger molecular weight, and logKow value; thus, DEP has higher affinity to the MWCNTs than DMP. The adsorption capacity of A-MWCNT, H-MWCNT, and K-MWCNT were 0.20, 0.14, and 0.27 mmol/g for DMP, respectively, and were 0.23, 0.16, and 0.28 mmol/g for DEP, respectively. With introduction of oxygen-containing surface groups, the hydrophilicity of the MWCNTs increased and steric obstructions were introduced. When humic acid was present, the adsorption of humic acid was favored. Occupation of adsorption sites and steric hindrance resulted in the reducetion of adsorption to 22.14 － 41.01 % for DMP and 30.20 － 45.41 % for DEP. The results suggested that modification of MWCNTs would alter the adsorption behavior. |
