微生物硫化物移除燃料電池: 產電效能與機制

Abstract

因為惡臭ヽ腐蝕性以及對生物的毒性，含硫廢水被廣泛地引起重視。在這個研究中,吾人利用硫酸鹽還原菌群來啟動微生物硫化物去除電池, 並且透過更換人工廢水配方以及線性掃描伏安法ヽ循環伏安法ヽ交流阻抗分析等電化學方法去研究其產電機制。 實驗結果顯示, 大部分在微生物硫化物去除電池中的細菌並不能直接的利用固態電極當成它的電子接受者, 需要透過硫酸根/硫化物當作單一方向的電子中介體, 才能把它的電子傳遞到電極上。首先, 透過乳酸當作電子提供者, 硫酸鹽還原菌把硫酸鹽還原成硫化物, 硫化物會攜帶著電子到鄰近的硫化物氧化菌, 被它氧化成元素硫沉積在電極上並且丟出電子給電極。 在三天的批次實驗中, 多達77.9 % 的硫酸根可以被轉化成元素硫並且同時有300 mV 的電壓輸出(外接電阻為1000 ohm)。 這些沉積的元素硫有回收再利用的可能性, 讓微生物硫化物去除電池能夠在處理含硫廢水並且產電的同時, 更具成本效益。 並且可以將此技術與其他新興的生物電化學技術做結合, 可以更進一步產出像是氫氣ヽ過氧化氫或是鹼性液體等有較高價值的化學品, 或者像是海水淡化等一般需要高耗能高成本的程序，進一步提升此技術的競爭性 此外, 吾人還另外研究了不同接踵策略對微生物硫化物去除電池的影響。結果顯示，接踵處於對數生長期的硫酸鹽還原菌群到反應器中並且啟動時, 不論是啟動成功率ヽ穩定性以及電壓輸出都有顯著的提升。然而，此假說尚須更進一步研究去佐證。

Sulfur-containing wastewater has received many attentions due to the corrosive, toxic and stinking properties of sulfide. This work startup microbial sulfate/sulfide removal cells (MSRC) using sulfate reducing bacteria consortia. Mechanism of electricity production is also been studied by means of changing recipe of media or electrochemical analysis methods, including linear sweep voltammetry(LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The result showed that most of the bacteria in MSRC can’t directly use solid anode as electron acceptor. They need to utilize sulfate/sulfide as a single direction electron mediator. Firstly, the sulfate-reducing bacteria (SRB) used lactate as electron donor and reduced the sulfate to sulfide, which was then oxidized to deposited elementary sulfur (S0) by neighboring sulfide oxide bacteria (SOB) and delivered the electron to the electrode. With this process, both sulfate and sulfide can be converted to S0 via SRB and SOB with a maximum 77.9 % conversion rate with stable 300 mV voltage outputs based on 1000 ohm external resistance in 3 days tests. The deposited S0 can be potentially recycled as a resource, which lead the MSRC to be a more cost-effective technology to treat sulfate/sulfide laden wastewater with electricity production simultaneously. By combination of MSRC and other technologies based on bioelectrochemcial system, more valued added process or product can be obtained such as hydrogen, hydrogen peroxide, caustic solution or desalination of sea water. Furthermore, different strategies to startup MSRC were also been tested. The start-up rate, stability and electricity performance can be largely raised with strategy to inoculate the pre-culture sulfate reducing consortia in log phase at MSRC startup. However, further research is needed to support this hypothesis.