奈米碳管的高比表面積與微孔體積，使其成為一熱門的吸附材料，其表面官能基與污染物之替代基會影響吸附機制，通常吸附機制的探討是利用傳統批次吸附實驗結果推測得知，耗費時間較長且不易直接判斷。因此，本研究將單壁奈米碳管經硝酸純化過後，製作成奈米碳管修飾電極，利用電化學方法探討奈米碳管對2-硝基酚(2-NP)、4-硝基酚(4-NP)及銅(Cu(II))之含苯環異構物與重金屬之交互作用。經由碳管定性分析的結果發現，純化後之碳管表面及頂端會產生破壞及開口，且含氧官能基有增加的趨勢，進而增加了碳管表面的帶電性。奈米碳管修飾電極對K3Fe(CN)6具有一定的催化能力，與玻璃碳電極相比增加了電極反應的可逆性，整體反應為擴散控制，經推算後得知奈米碳管修飾電極之反應有效面積為0.235 cm2。 2-NP與4-NP在解離前後有不同的循環伏安分析結果，NP的解離使得電雙層變化與濃度的相關性比在未解離時顯著，又兩者因替代基在鄰位與對位而導致有不同的吸附行為，4-NP較2-NP容易有規則的以π-π作用力堆疊在碳管表面，為多層的排列方式，且隨4-NP濃度提高而增加電容值，其4-NP之替代基也增加了電子活性反應面積。當pH=8時，Cu(II)的沉澱物被碳管吸附而遮蔽了表面官能基，因而減少電容值。Cu(II)與2-NP同時存在時會影響彼此循環伏安分析之結果，且Cu(II)的存在幫助了2-NP吸附在碳管上，當pH=8時，兩者形成錯合物且因空間障礙而遮蔽碳管上之官能基。同時分析Cu(II)與4-NP的氧化還原峰在pH=5時可清楚分辨，且會單獨競爭碳管上之吸附位置；而當pH=8時，Cu(II)的訊號則不明顯，不同型態之Cu(II)吸附在碳管上後平衡了碳管表面的負電荷，使得4-NP有更大的機會被吸附在碳管上。Carbon nanotubes (CNTs) are popular adsorbents due to high surface area and large micropore volume. The mechanisms of organic compounds adsorption on CNTs are usually investigated by the batch adsorption experiments, which are time-consuming and dubious. The objective of this work was to investigate the adsorption of 2-, 4-NP and Cu(II) on single-walled carbon nanotubes, (SWCNTs) modified electrode via electro-chemical analysis. The cyclic voltammetric study of 2- and 4-NP showed that, after the dissociation of 2- and 4-NP, the effects of concentration on the double layers structure became more important. Also, 2- and 4-NP had different adsorption behaviors because of the location of nitro- groups of them. 4-NP may have more ordered multi-layered structure on the surface of SWCNTs by stronger π-π interactions. Thus, the electrical capacity increased with increasing concentration of 4-NP and the electroactive area was increased by the nitro groups. When Cu(II) and 2-NP coexist, the adsorption of 2-NP on the SWCNTs was enhanced, which may be attributed to the formation of 2-NP / Cu(II) complex. However, Cu(II) and 4-NP had strong competition on the adsorption site at solution pH of 5. When the solution pH was 8, the redox peaks of Cu(II) were not obvious, which indicates that the adsorption of free Cu(II) ions were limited. Also, because the charges on the SWCNTs surfaces were balanced by various cupric species, the adsorption of 4-NP was enhanced.
