- 學位論文
循環伏安法應用於電化學氧化降解反應機制探討
Electrochemical Oxidation Mechanism Study with Cyclic Voltammetry
摘要
本研究為了證實電氧化三途徑中，次級氧化劑會於電化學氧化程序中生成並提高有機物的降解效率，利用循伏安法(cyclic voltammetry , CV)，分析在不同pH值條件下以硫酸鈉、氯化鈉作為輔助電解質時，四環素於工作電極周圍所發生的電化學反應。藉由循環伏安圖所得之峰值電流與掃描速率平方根之間的關係，了解工作電極周圍所發生的反應為擴散控制或是化學反應控制，用以判定是否有次級氧化劑產生。 由循環伏安法分析後發現，以氯化鈉作為輔助電解質時，峰值電流與掃描速率平方根呈非線性關係，表示電極周圍發生化學反應，其原因在於氯離子於電氧化過程中會形成次氯酸根離子氧化四環素；硫酸鈉作為輔助電解質於電氧化過程當中不會有氧化劑產生，但經由循環伏安法分析後發現峰值電流與掃描速率平方根亦呈非線性關係，表示電氧化過程中有其他次要氧化劑如過氧化氫、臭氧、氫氧自由基產生與四環素發生化學反應，證實次級氧化劑會於電化學氧化程序中生成。
並列摘要
This research attempts to confirm the formation of secondary oxidant during an electrochemical oxidation as well as its function of improving the degradation efficiency of the targeted organic, which was initially proposed in the three-pathway theory of electrochemical- oxidation. Cyclic voltammetry (CV) is utilized hereby to analyze the electrochemical reactions of Tetracycline (TC) happened adjacent to the working electrode in different pH environment when using Na2SO4 and NaCl as auxiliary electrolytes, respectively. In a cyclic voltammogram, the relationship between the current peak (Ip) and the square root of scan rate (V^(1/2)) could be used to determine whether the reactions happened around working electrode are diffusion controlled or chemical reaction controlled; in other words, to detect the production of secondary oxidant. The CV analysis indicated a non-linear relationship between Ip and V^(1/2) when NaCl was used as the auxiliary electrolyte. As a result, there was some chemical reactions occurred near the working electrode, whichwould most possibly be the oxidation of TC by hypochlorite which was converted from the Cl-. Theoretically speaking, Na2SO4 should not generate any oxidant during the electro-oxidation; however, a linear relationship still could not be built between Ip and V^(1/2) when Na2SO4 served as the electroylte. The possible scenario is that other secondary oxidants may form during the electro-oxidation including, but not limited to, hydrogen peroxide, ozone and hydroxyl radical, all of which might trigger the oxidation of TC.