Treatment of vegetable oil industry wastewater and bioelectricity generation using microbial fuel cell via modification and surface area expansion of electrodes
Kamyar Yaghmaeian, Ahmad Rajabizadeh, Farshid Jaberi Ansari, Sebastià Puig, Roohallah Sajjadipoya, Abbas Norouzian Baghani, Narges Khanjanid and Hossein Jafari Mansoorian
To read and cite the full paper, please visit:
doi.org/10.1002/jctb.7301
First published:14 March 2023
WHAT'S IT ABOUT?
In recent years, there has been growing interest in harnessing microorganisms for simultaneous wastewater treatment and renewable bioelectricity production. Microbial fuel cell (MFC) technology can convert the chemical energy stored in organic matter in wastewater into electricity, using bacteria as a catalyst.
Researchers in Iran have developed a novel and cost-effective anode catalyst (TiO2-HX@MWCNT-COOH-Al2O3) that can improve and stabilise the power generation performance of MFCs treating vegetable oil industry wastewater. The choice of anode material is key to dictating the efficiency and cost-effectiveness of MFCs, as it is the site at which bacteria grow and form a biofilm.
The team also investigated modification of the cathode to identify a cost-effective alternative to platinum. Carbon felt modified with powdered activated carbon (PAC) originating from Bambuseae (a family of bamboo plants) was found to be effective.
From the editor of Journal of Chemical Technology and Biotechnology
Professor Dionissios Mantzavinos
Vice-Rector Academic & Int’l Affairs
University of Patras
Journal of Chemical Technology and Biotechnology (JCTB) is an interdisciplinary journal concerned with the application of scientific discoveries and advancements in chemical and biological technology that aim towards economically and environmentally sustainable industrial processes.
JCTB, originally published as the Journal of the Society of Chemical Industry back in 1882, attracts authors and readers from the whole spectrum of applied chemical and biochemical sciences and, in this respect, the review article of Lu and Lu just epitomises this approach.
Waste valorisation alongside process optimisation to produce high-value products – microbial astaxanthin, in this case – is a win-win scenario, which can simultaneously address environmental problems (i.e. wastewater treatment) and produce natural astaxanthin, typically employed in aquaculture, at an affordable cost.
Research questions that have been addressed include the type of astaxanthin-rich microbial strains, accumulation processes, specific growth conditions and cultivation models.
Recalling George Bernard Shaw’s quote that ‘science never solves a problem without creating ten more’, the proposed methodology may suffer certain drawbacks, such as safety risks of microbial biomass, due to heavy metals bioaccumulation, and ecological disasters, due to coupling waste treatment with microorganisms cultivation. Such potential obstacles need serious attention from the research community.
ABSTRACT
BACKGROUND: This study evaluates the treatment of vegetable oil industry wastewater using dual-chamber microbial fuel cells (MFCs) via modification and surface area expansion of cost-effective electrodes. The modified electrodes were applied as both the anode and cathode to investigate their treatment capacity and electrochemical performance. Carbon paper anodes were modified using TiO2-HX@MWCNT-COOH-Al2O3 composite. Activated carbon powders originating from Bambuseae were used as the low-cost catalyst for the carbon felt cathode. The synthesized catalysts were characterized by Field-Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) techniques. The electrochemical properties of the MFCs were investigated by Electrochemical Impedance Spectroscopy (EIS).
RESULTS: The highest average removal efficiencies of COD (chemical oxygen demand), BOD5 (5-day biochemical oxygen demand), NH4+ (ammonium), NH3− (nitrate), TSS (total suspended solids), and VSS (volatile suspended solids) were 94 ± 3% (33 kgCODrem/m3.d), 89 ± 1% (12 kgBODrem/m3.d), 87 ± 1% (0.24 kgNH4+-Nrem/m3.d), 74 ± 3% (0.05 kgNO3−-N/m3.d), 79 ± 2% (1 kgCODrem/m3.d), and 65 ± 3% (0.73 kgCODrem/m3.d), respectively. The highest average power density of 30 ± 5 W/m3 was obtained when treating vegetable oil industry wastewater. The highest average coulombic efficiency (CE) of 85 ± 3% and energy efficiency (EE) of 35 ± 2% were achieved. The EIS results showed that the high conductivity and large unique surface area significantly enhanced the charge transfer efficiency on the electrode surface.
CONCLUSION: The results indicated that the TiO2-HX@MWCNT-COOH-Al2O3 composite can be used to reinforce the performance of MFCs.
MEET THE RESEARCHERS
Hossein Jafari Mansoorian
Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran
Why are microbial fuel cells (MFCs) attracting the attention of researchers for wastewater treatment applications?
Energy generation, storage and consumption are topics that are increasingly prevalent within modern research fields and are of global interest and importance. The use of fossil fuels, especially oil and gas, has accelerated in recent years and this has triggered a global energy crisis. Renewable bioenergy is viewed as one of the ways to alleviate the current global warming crisis. Major efforts are devoted to developing alternative electricity production methods. New electricity production from renewable resources without a net carbon dioxide emission is much desired. Microbial fuel cell (MFC) technology is a prospective technology that purifies wastewater and converts the energy stored in chemical bonds in organic compounds to electrical energy using microorganisms as catalysts. In other words, MFCs utilise the bio-catalytic capabilities of viable microorganisms and can use a range of organic fuel sources, converting the energy stored in the chemical bonds to generate an electrical current. This is instead of relying for example, on the use of metal catalysts. Microorganisms, such as bacteria, can generate electricity by utilising organic matter and biodegradable substrates such as wastewater, whilst also accomplishing biodegradation/treatment of biodegradable products, such as municipal wastewater, industrial wastewater, animal waste, plant waste, food waste, landfill leachate. Therefore, this technology has generated considerable interest among academic researchers in recent years.
Why are the properties of MFC electrodes significant and how can modified electrodes be used to improve the performance of MFCs in wastewater treatment strategies?
Electrodes are the key component in deciding the performance and cost of MFCs. Electrode design is the greatest challenge in making MFCs a cost-effective and scalable technology. The anode of MFCs serves as an attachment carrier of microorganisms and plays a vital role in the extracellular electron transfer between the electroactive bacteria and solid electrode surface for bioelectricity production in MFCs. In this regard, it is of crucial importance to develop a novel anode material with synergistic effects between the properties of anode surface and microorganisms. A desirable anode should have the following properties:
- Good conductivity to speed up the electron transfer rate
- Excellent biocompatibility and low bio-toxicity for microbes
- Higher specific surface area to provide more microbe attachment and catalytic activity sites
- Chemical stability and anti-corrosion resistance
- Flexibility and durability
- Low economic cost and convenience to commercial application
In order to improve bacterial adhesion and efficient electron transfer on the electrode surface, it should be modified and its surface area increased to ensure efficient current collection and power yield through the decomposition of organic compounds in the wastewater. As a result, wastewater treatment is also improved by this strategy.
How can the findings from this study contribute to future wastewater treatment strategies?
MFCs can potentially be used for different applications. MFCs undoubtedly have potential in terms of energy recovery during wastewater treatment. They may occupy a market niche in terms of a stand-alone power source and in the direct treatment of wastewater. As aforementioned, when MFCs are used in wastewater treatment, a large surface area is needed for biofilm to build up on the anode. In other words, a good configuration for electrodes must provide a large surface area for bacterial adhesion and ensure efficient current collection. Based on the results of this study, the TiO2-HX@MWCNT-COOH-Al2O3 structure of this composite is a suitable candidate for modifying the anode and greatly enhances the electroactivity of the electrode. PAC originating from bambuseae can be a good alternative for platinum to avoid the expensive costs associated with the use of a platinum catalyst. Therefore, both composites can work together as a good catalyst in the application of microbial fuel cells individually or in combination with other processes for both wastewater treatment and bioelectricity generation.
How scalable is MFC technology for wastewater treatment and bioelectricity generation?
MFCs are a novel bioelectrochemical device that integrates wastewater treatment and bioelectricity generation. A tremendous breakthrough has been made regarding power output in MFCs from few mW⋅cm-2 or mW.cm-3, to several W⋅cm-2 or W.cm-3, an improvement of three orders of magnitude owing to continuous efforts of researchers. Notably, there are still a considerable number of MFC researchers working on the development of high-performance electrode materials. After obtaining superior anode electrodes, it is necessary to strengthen the long-term performance study of electrodes in real wastewater treatment to investigate the stability, durability, mechanical properties, and secondary pollution of anode electrodes. Although some basic knowledge has been gained in MFC research, there is still a lot to be learned in the scale-up of MFCs for large-scale applications. Therefore, a considerable in-depth analysis needs to be carried out to realise the large-scale practical applications of MFCs.
Where does research need to focus next to overcome the challenges and limitations of MFC wastewater treatment?
Since traditional wastewater treatment has various limitations, sustainable implementations of MFCs might be a feasible option in wastewater treatment as well as green electricity production, bio-hydrogen synthesis, carbon sequestration, and environmentally sustainable sewage treatment. For MFCs to be a viable option for wastewater treatment, they need to be scaled up to accommodate large volumes of incoming wastewater, which has proven challenging for several reasons, including minimising the distance between the anode and cathode to reduce electrical losses and being cost-competitive with other treatment technologies. The materials used are expensive, including membranes to separate the electrodes, which are prone to fouling, and a catalyst to produce enough power. Further research should also pay attention to new MFC materials to make wastewater treatment more effective. Finally, it is necessary to better understand the nature and function of electrode materials. Multiform wastewaters can be significantly degraded by advancing MFCs alone or integrating them with other processes.
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