添加石墨粉對固定化微生物燃料電池產電效能之影響

Abstract

微生物燃料電池的特點是處理廢水的同時也可以產電，兼具環保及產能的雙重意義。本研究採用不需曝氣的空氣陰極式微生物燃料電池，以碳布為陽極材料，白金鈦網為陰極，菌種則是取自三段式豬糞尿水處理系統之厭氧污泥。實驗時以固定化技術將菌種和石墨粉包埋於醋酸纖維中，經裁切成適當大小後，均勻填充於陽極槽內，並分別以人工廢水及豬糞尿水為基質進行試驗，本研究之目的係探討不同石墨粉添加量及有機負荷率對微生物燃料電池效能之影響。 實驗結果顯示，以人工廢水為基質的試驗中，除了無添加石墨粉的固定化細胞是在4 gL-1d-1有機負荷中有最大功率密度56.9 mW/m2外，其餘試驗最大功率密度皆隨著有機負荷的增加而提昇，最大功率密度的最佳值113 mW/m2出現於使用3 g石墨粉之固定化細胞(3 g石墨粉/10 g菌種)且有機負荷在8 gL-1d-1時；當有機負荷為2 gL-1d-1時有最大的庫倫效率，而無添加石墨粉之固定化細胞(0 g石墨粉/10 g菌種)，有最佳值1.8%。 以豬糞尿水為基質的試驗是採用添加3 g石墨粉(3 g石墨粉/10 g菌種)之固定化細胞，其最大庫倫效率1.5%出現在6 gL-1d-1有機負荷時，平均的庫倫效率均較人工廢水為佳；最大功率密度的最佳值75.6 mW/m2則出現於2 gL-1d-1有機負荷時；在COD去除率部分，高有機負荷(8 gL-1d-1)時驟降至剩下18.1％，而人工廢水則仍有51％，此係因為豬糞尿水中可生物降解之COD含量明顯低於人工廢水。 本研究成功地證實了添加石墨粉於固定化細胞中可以促進空氣陰極式微生物燃料電池的產電效能，同時以豬糞尿水做為進流基質也確實可行。

The microbial fuel cell (MFC) is a technology which could simultaneously treat the wastewater and also produce the electricity, with significant meaning in both environmental protection and energy production. This study adopted an air-cathode microbial fuel cell, no aeration requirement, using carbon cloth as the anode and platinum titanium net as the cathode, the anaerobic sludge of a three-stage swine wastewater treatment system was used as the seeding bacteria. The sludge and graphite powder were immobilized by entrapping with the cellulose acetate, after cutting into the proper size, these immobilized cells were packed homogeneously in the anodic compartment. Experiments were conducted using both the synthetic and swine wastewater as substrate. The objective of this study is to investigate the effect of different amount of graphite powder addition and the organic loading rate. Experimental results showed, in tests of using synthetic wastewater as substrate, the maximum power density was increasing when organic loading rate increased except the test of not adding graphite powder when making the immobilized cells. The maximum power density of 113 mW/m2 was observed at the loading rate of 8 gL-1d-1 with 3 g of graphite powder addition. The maximum coulombic efficiency of 1.8% was observed at the organic loading rate of 2 gL-1d-1, with no addition of graphite powder when making the immobilized cells. The tests of using swine wastewater as substrate used 3 g graphite powder when making the immobilized cells. The maximum coulombic efficiency of 1.5% was occurred at the organic loading rate of 6 gL-1d-1. However, its average coulombic efficiency was better than those tests of using synthetic wastewater as substrate. The optimal value 75.6 mW/m2 of the maximum power density was achieved at the organic loading rate of 2 gL-1d-1. Comparing the COD removal efficiency, the test of using the swine wastewater dropped down to only 18% at a loading rate of 8 gL-1d-1, while the synthetic wastewater test still maintained a COD removal efficiency of 51% at the same loading rate, for it had much higher biodegradable COD than the swine wastewater. This study successfully proved that addition of graphite powder when making the immobilized cells did improve the electricity production for the air-cathode microbial fuel cell and it was feasible using the swine wastewater as the substrate.