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Nanoporous Stainless Steel Anode for Enhanced Microbial Fuel Cells
The Freshwater shortage crises are becoming more threatening, and it is inevitable to preserve the water resources that we already have. Adequate wastewater treatment (WWT) ensures avoiding current water resources’ contamination. Unfortunately, energy consumption during WWT is considered a barrier...
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| Format: | Thesis |
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AUC Knowledge Fountain
2019
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| Summary: | The Freshwater shortage crises are becoming more threatening, and it is inevitable to preserve the water resources that we already have. Adequate wastewater treatment (WWT) ensures avoiding current water resources’ contamination. Unfortunately, energy consumption during WWT is considered a barrier, and hence, in process energy production is attracting much attention. Biofuel cells (i.e microbial fuel cells (MFCs)) are one of the systems that are capable of producing electricity during the biodegradation of organic matters. Wastewater is one of the most suitable fuels for MFCs as it is abundant, therefore power production during the WWT process can be considered as sustainable. However, the low power production and high initiation cost of MFCs hinder its usage as a fully operating system. Accordingly, finding efficient, low cost and commercially available materials for the MFC components is a necessity for MFC to be a real-life application. The anode (solid state electron acceptor) where electron transfer from bacteria takes place is one of the crucial compartments of MFC, and improving both the anode material and its surface structure should lead to high possibilities of improvement in MFC performance. The ideal anode electrode should be of low cost, high conductivity, high specific area, biocompatibility, and high chemical and physical stability. Herein, the impact of fabricating nanostructured stainless steel (SS) anodes, annealed in different environments, on MFC performance is explored. In the first part of this research work, the factors controlling the fabrication of nanostructured SS, using anodization in fluoride/sulfuric acid/ethylene glycol based electrolytes, were determined. Based on these factors, the fabrication process was carried out, and the role of the different components of the anodization bath are illustrated along with the effect of the operating factors such as voltage and time. A nanostructured 316L SS samples were successfully fabricated and reported for the first time in the literature. Several surface characterization tests were carried out on the fabricated samples using energy dispersive X-ray spectroscopy (EDX), X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to determine the surface film elemental composition, crystalline phases, and oxidation state of the elements within the film. The electrochemical activity of the samples was evaluated by the potentiodynamic cyclic voltammetry (CV) using ferricyanide/ferrocyanide (Fe(CN)63-/Fe(CN)64-) reversible redox couple to determine the impact of the samples treatment on the surface electron transfer kinetics. Secondly, the fabricated SS samples were used as anodes in dual chamber MFCs inoculated with sludge, using sodium acetate as a substrate and potassium ferricyanide as the oxidant in the cathode. The results obtained were promising, as the MFCs with the as-anodized (AA) SS anode produced a voltage 81 times higher than that produced by the as-received (AR) SS anode. Even though, the CVs using ferricyanide/ferrocyanide redox reaction did not show a significant difference in the produced current between the AR and AA stainless steel samples, supporting that the enhanced power performance in MFCs is due to the enhanced biofilm growth offered by the high specific area of the nanostructured SS. On the other hand, experiments testing the effect of the different annealing atmospheres concluded that the AA-OA anode had the best performance which can be attributed to the increase of Fe2O3 ratio on the surface of the AA-OA sample as confirmed by the XPS results. the anodized sample annealed in O2 (AA-OA) produced the highest power (430 mW/m2) compared to the power produced by the AR and AA anodes (0.01 and 182.4 mW/m2), respectively. |
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