水溶液中二甲雙胍降解之研究：電高級氧化 vs.輝光放電電解

Degradation of metformin in aqueous solutions: electrochemical advanced oxidation vs. glow discharge electrolysis

楊長祐(Yang Chang-You)

指導教授 ： 黃國林

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2020年)

https://doi.org/10.6346/NPUST202000438

摘要

藥品使用的增加促進它們進入水生環境中。這些藥品屬於新興污染物，會對生態和人類健康帶來不利影響，而抗糖尿病藥物-二甲雙胍(Metformin (Met))是在水生環境中以異常濃度檢測到的一個實例。該事實表明常規廢水處理不能有效地消除這種化合物。本研究以接觸輝光放電電解(contact glow discharge electrolysis，CGDE)與電氧化降解Met，探討降解Met較佳之操作參數，並將其用於降解添加在醫療廢水之Met。進行LC-MS/MS、HPLC分析探討電化學降解Met之中間產物及推測其降解路徑，並配合UV、螢光激發-放射矩陣光譜、自由基及Microtox®毒性等分析，評估電解水特性，以供後續研究及應用之參考。
研究結果顯示，接觸輝光放電電解在酸性條件下容易造成電極的損耗，而以摻硼鑽石電極BDD為陽極、Cu為陰極在1 M Na2SO4電解質溶液下，接觸輝光放電降解有較佳的Met的降解效能與TOC去除率。在循環伏安法分析中，使用BDD電極為工作電極，未發現Met氧化峰。使用BDD電極電化學降解Met的速率隨著電流密度增加而上升，而提升溫度無助於增加Met的去除率，提高電解質NaCl濃度雖然有助於Met的降解，但增加了氨氮、硝酸鹽氮以及亞硝酸鹽氮產物的濃度，而較佳操作條件為NaCl = 0.1 M、BDD陽極面積 = 4 cm2，鈦陰極面積 = 4cm2、電流密度 = 0.25 A/cm2及溫度 = 25°C。於此電解條件之UV-vis分析結果顯示，在降解2.5min時出現385 nm吸收峰為Met之中間產物脫氫-1,2,4-三唑(cyclic dehydro-1,2,4-triazole-derivative)；降解10分鐘時，出現波長292 nm之OCl- 吸收峰，其強度隨著降解時間的增加。添加Met於醫療廢水之螢光激發-放射矩陣(EEM)光譜分析結果顯示，在電解0分鐘時，在區域I(類酪氨酸)/II(色胺酸類有機化合物)及區域IV(類色胺酸)分別出現高強度螢光峰，其強度隨著電解時間的增加而減弱，且於電解30分鐘後消失。電氧化降解Met之主要中間產物為N-氰基-N，N-二甲基-2-氰基-1,1-二甲基胍(N-cyano-N,N-diMethyl- 2-cyano-1,1-diMethyl guanidine)(m/z = 113 )、1,1-二甲基胍(1,1 DiMethylguanidine)(m/z = 88)、胍(Guanidine)(m/z= 60 )、羧酰亞胺基胍(Carboximidoylguanidine)(m/z = 85 )及質荷比(m/z) = 128、116、164之化合物。在120分鐘電解過程中，電解水之Microtox®毒性TU值隨時間增加而增加。使用對苯二甲酸為化學探針，可間接偵測到氫氧自由基 (速率常數 = (2.34‒8.65)×10-3 s-1)；使用DMPO為自旋捕捉劑（spin trap），進行電子自旋共振(electron spin resonance (ESR))分析，主要偵測到DMPOX訊號。

關鍵字

二甲雙胍 ； 接觸輝光放電電解 ； 電化學降解 ； 摻硼鑽石電極電極 ； 紫外-可見分光光譜分析

並列摘要

The increasing use of pharmaceutical products increases their release into aquatic environment. These contaminants, regarded as emerging pollutants, usually induce adverse ecological and human health effects. Metformin (Met) (antidiabetic drug) is one example that has been detected in the aquatic environment at unusual concentrations. This fact indicates that conventional wastewater treatment is inefficient on eliminating this compound. In this study, we explored the contact glow discharge electrolysis (CGDE) and the electrochemical degradation of Met under different operating parameters, and then used the better operating condition to test the degradation of Met in medical wastewater. LC-MS and HPLC analyses were performed to determine the intermediates (products) and pathways of Met electro-degradation. Moreover, UV, fluorescence excitation-emission matrix (EEM), free radical and Microtox® toxicity tests were conducted to evaluate the characteristics of water matrices during Met electro-degradation.
The results showed that CGDE might cause electrode erosion in acidic solutions. The CGDE using boron-doped diamond (BDD) s anode/Cu cathode showed the best Met degradation and TOC removal in 1 M Na2SO4 electrolyte solution. No Met oxidation peak was observed on the BDD electrode in cyclic voltammetry analysis. The rate of electrochemical degradation of Met using BDD anode/Ti cathode increased with the increase of current density, but increasing temperature did not increase the removal rate of Met. Although increasing NaCl concentration increased the electro-degradation of Met, ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen concentration increased. The better operating parameters of Met electro-degradation were: NaCl = 0.1 M, BDD anode area = 4 cm2, titanium cathode area = 4 cm2, current density = 0.25 A/cm2, and e temperature = 25°C. At this operating condition, the results of UV-vis analysis showed that the absorption peak at 385 nm was contributed by Met dehydro-1,2,4-triazole (cyclic dehydro-1,2,4-triazole-derivative) (intermediate) at 2.5 min electrolysis; at 10 min, an OCl- absorption peak appeared at 292 nm and its intensity increased with the increase of degradation time. The results of fluorescence excitation-emission matrix (EEM) spectroscopic analysis of medical waste water , before electrolysis two high intensity fluorescent peaks appeared in regions I (tyrosine-like)/II (tryptophan-like organic compounds) and IV (tryptophan-like acid), respectively, and their intensities decreased with increasing time and they disappeared after 30-min electrolysis. The major intermediates of Met electrochemical degradation were N-cyano-N, N-dimethyl-2-cyano-1,1-dimethylguanidine (m/z = 113), 1,1-bis methylguanidine (m/z = 88 ), guanidine (m/z=60), carboximidoguanidine (m/z = 85) and the compounds with mass-to-charge ratio (m/z) values of 128, 116, and 164. During 120-min electrolysis, the Microtox® TU value increased with increasing electrolysis time. Terephthalic acid could be used as a chemical probe to indirectly detect the formation of hydroxyl radical (rate constant = (2.34‒8.65)×10-3 s-1), while only DMPOX signals were observed in electron spin resonance (ESR) analysis using 5,5-Dimethyl-1-pyrrolidine-N-oxide (DMPO) as a spin trap.

並列關鍵字

Metformin ； contact glow discharge electrolysis(CGDE) ； Electrochemical degradation ； Boron doped diamond (BDD) ； Ultraviolet-visible (UV-Vis) analysis

參考文獻

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