探討微生物電解池對產氫效率及碳捕捉的優化條件

Abstract

微生物電解池為一種新興的綠色能源科技，陽極的產電微生物能將廢水中之有機質代謝產生氫離子以及電子，分別透過陽離子交換膜和外電路傳送到陰極，另外藉由一外部電源施加電壓，並藉由陽極提供一部分電位，使陽極產生之氫離子與電子在陰極結合產生氫氣，此技術除了能處理廢水，同時還能產生無碳燃料氫能源。另外透過陰極合成海水中存在之無機碳成分，可不須透過額外之二氧化碳進料來源，即能將其與鈣離子反應生成碳酸鈣，實現產生氫能源的同時，也能進行碳捕捉，轉化成有價化學品再利用。 本實驗採集台北市迪化污水廠之污泥，在H-type雙槽式微生物電解池進行產氫及碳捕捉實驗，實驗運行過程中持續監測電化學活性以及水質變化。透過實驗結果顯示，當施加0.6 ~ 1.0 V之電壓時，其中以含有活性碳及鎳元素塗層之陰極電極表現最為突出，擁有比其他兩組未含有鎳元素之電極更高之電流密度以及產氫效能，尤其在施加電壓為0.6 V時，產氫速率分別高於未經過任何前處理以及僅含有活性碳塗層之陰極電極的66.5倍和12.5倍，由此可見鎳元素可作為析氫反應良好之催化劑。透過反應在陰極槽產生之鹼度，成功使陰極液為人工海水中之鈣離子與其反應為氫氧化鈣，再與碳酸氫鈉反應生成碳酸鈣，沉澱在電極表面與反應槽底部。水質分析部分，在水力停留時間為兩天之下，不同之施加電壓與COD去除率間並無明顯差異，均介於50 ~ 70%之間，而當水力停留時間為三天時，COD去除率均達到74%以上。

Microbial electrolysis cell (MEC) are an emerging green energy technology. The exoelectrogens at the anode chamber oxidize the organic matter to produce protons and electrons, which are transferred to the cathode through a cation exchange membrane and an external circuit, respectively. An external power source is used to apply voltage, and part of the potential is provided by the anode, allowing the protons and electrons produced by the anode to generate hydrogen gas in cathode. This technology not only treats wastewater but also generates green energy resource. Additionally, inorganic carbon in the artificial seawater reacts with calcium ions to form calcium carbonate, eliminating the need for extra carbon dioxide. This process allows for simultaneous hydrogen production and carbon capture, converting captured carbon into valuable chemicals for reuse. In this experiment, the sludge was collected from the Dihua Wastewater Treatment Plant in Taipei City. It was used in an H-type dual-chamber microbial electrolysis cell to conduct hydrogen production and carbon capture experiments. During the experiment, electrochemical and water quality changes were continuously monitored. The results showed that when a voltage of 0.6 to 1.0 V was applied, the cathode electrode with activated carbon and nickel coating performed the best, exhibiting higher current density and hydrogen production efficiency compared to the other two electrodes without nickel. When the applied voltage was 0.6 V, the hydrogen production rate was 66.5 times and 12.5 times higher than those of the untreated cathode electrode and the cathode electrode with only activated carbon coating, respectively. This indicates that nickel is an excellent catalyst for the hydrogen evolution reaction. Additionally, the alkalinity generated in the cathode chamber successfully reacted with calcium ions in the artificial seawater to form calcium hydroxide, which then reacted with sodium bicarbonate to produce calcium carbonate. The calcium carbonate precipitated on the electrode surface and at the bottom of the cathode chamber. Regarding water quality analysis, with a hydraulic retention time of two days, there was no significant difference in COD removal rate across different applied voltages, with rates ranging between 50% and 70%. When the hydraulic retention time was increased to three days, the COD removal rate reached above 74%.