Sediment Microbial Fuel Cells Research Articles

Effect of wastewater containing mixture of nanoparticles on organic matter removal, power generation, and biofilm integrity in sediment microbial fuel cell

ABSTRACT Industrial wastewaters from the cosmetic industry contain high organic strength and mixture of nanoparticles (NPs). Sediment microbial fuel cell (MFC) is an emerging nature-based technology that can treat complex wastewaters. The aim of this study is to understand the effect of a binary mixture of zinc oxide (ZnO) and copper oxide (CuO) NPs (concentration: 1 + 1 and 10 + 10 mg/L) on the organic matter removal, power generation, and biofilm health of sediment MFCs after a long-term operation of 120 days. The high chemical oxygen demand (COD) removal (>95%) observed for all reactors signified the minimal impact of 10 mg/L NP mixture on treatment. The dissolved organic carbon (DOC) removal from the sediment was reduced by 8% due to NPs. NPs also led to 42.2% higher anode extracellular polymeric substances (EPS) and 46.65% lesser cathode EPS generation. The maximum power density of 0.29 mW/m2 was obtained for the 10 mg/L NP reactor, with the average being 23% higher than the no-NP control reactor. This was the first study to explore the effect of the mixture of NPs on the performance of an MFC. The results indicated that sediment MFCs can sustain high mixture concentrations of NPs. Furthermore, variation of parameters can aid in establishing the feasibility of this technology for treating wastewater with NPs.

Sediment microbial fuel cells capable of powering outdoor environmental monitoring sensors

In this study, Sediment Microbial Fuel Cells (SMFCs) prototypes have been developed to operate under open-air conditions and power sensors for environmental monitoring. Two SMFCs with a volume of 50 l each, consisting of two types of anodic materials – graphite and coke, were operated on-field for over a year. The electrical outputs have been recorded and compared with the measured environmental parameters such as temperature, light illumination, atmospheric pressure, humidity, etc. The statistical analysis of the obtained data shows that temperature changes between 0 and 14 °C do not affect the power achieved. On the contrary, the sunlight irradiation showed a second-order polynomial correlation with the current generated by the SMFCs, increasing the latter during the days. The cathode reactions significantly impacted the power density achieved by both explored SMFCs and the system's sustainability. The metallurgical coke is suggested to be used as an inexpensive and convenient anode material for SMFCs giving compatible results to the widely used graphite.

PTFE-based hydrophobic layers influence bioelectrical performance of sediment microbial fuel cells with floating air-cathode

Sediment microbial fuel cells (SMFC) provide scalable power generation, but their low performance is primarily due to poor oxygen reduction reaction (ORR) at cathode. The study aims to improve ORR efficiency by constructing triple-phase interphase (TPI) with multiple hydrophobic polytetrafluoroethylene (PTFE) layers on floating air-cathode. Multiple PTFE layers of 0 (HL0), 1 (HL1), 2 (HL2), 3 (HL3), 4 (HL4), 5 (HL5) and 6 (HL6) are coated on single-sided cathode by brushing method. HL3 generates the highest output current of 204 mA, which is three times higher than control case (HL0). The polarization test shows that HL3 achieves the highest maximum power of 48.88 mW/m2, which corresponds to a 6.8-fold increase compared to HL0 (7.06 mW/m2). HL4 performance improves over time but requires long start-up time before increase in bioelectricity production was achieved. Hydrophobic PTFE layer increases the maximum power density of floating air-cathode, mitigates cathodic limitations and improves SMFC performance.

Improvement of Power Density and COD Removal in a Sediment Microbial Fuel Cell with α-FeOOH Nanoparticles

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m2 of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal.

Evaluation of low-cost carbon/metal electrodes as cathodes and anodes in sediment microbial fuel cells

In the present study, influence of different anode and cathode materials including carbon felt, carbon cloth, and several metal electrodes with or without carbon cloth covering on sediment microbial fuel cell (SMFC) performance was investigated. Results suggested that stainless steel poorly performed as cathode electrode whereas it exhibited reasonable performance as anode. In SMFCs with carbon felt cathode, anodes including 400 series stainless steel mesh and 300 series stainless steel plate, both covered with carbon cloth, led to higher maximum power densities of 88 and 87 mW/m−2, respectively, compared with carbon felt, carbon cloth, 400 series stainless steel mesh, 300 series stainless steel mesh covered with carbon cloth, and copper plate covered with carbon cloth (power densities of 40, 74, 53, 68, and 47 mW/m−2, respectively). They also resulted in higher loss on ignition (LOI) removals of 9.4 % and 8.7 %, respectively. Cyclic voltammetry results showed that stainless steel plate covered with carbon cloth produced the highest redox current that was two times that of the carbon cloth. In addition, electrochemical impedance spectroscopy indicated lower charge transfer resistance in the SMFC with anodes including 400 series stainless steel mesh (20.6 Ω) and 300 series stainless steel plate (25.7 Ω), both covered with carbon cloth, compared to other anode materials. These findings suggest that stainless steel electrodes covered with carbon cloth provide SMFCs with improved electrochemical characteristics that enhance their electricity production and organic matter removal.

The impact of bottom water light exposure on electrical and sediment remediation performance of sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) generate bioelectricity from benthic sediments and thus providing both bioelectricity generation and sediment remediation. However, the high internal resistance of the cathode leads to a low power output, which requires research on cathode treatment. In this study, we explored the influence of light irradiation on bioelectricity production and nutrient removal in the SMFC system. The microcosm experiment of the SMFC system was designed with artificial illumination of 500 lux (light-SMFC) and compared with dark conditions of 15 lux (dark-SMFC), which showed that the current increases during photoperiods. The study reveals that light-illuminated SMFC consistently produced the highest voltage, with the highest voltage (553 mV) being 1.3 times higher than the dark-SMFC (440 mV). The polarization curves show a significant reduction in internal cathodic resistance under light condition, resulting in increased voltage generation. The light-SMFC exhibits the highest maximum power density of 35.93 mW/m2, surpassing the dark SMFC of 31.13 mW/m2. It was found that light illumination in the SMFC system increases oxygen availability in the cathodic region, which supports the oxygen reduction reaction (ORR) process. At the same time, the high bioelectricity output contributes to the highest sediment remediation by greatly reducing the chemical oxygen demand (COD) and phosphate (PO4–P) concentrations. The study highlights the potential of light illumination in mitigating cathodic limitation to improve SMFC performance and nutrient removal.

Voltage recovery from frozen microbial fuel cells in the laboratory and outdoor field reactors

Extreme temperature variations are a problem that must be faced in the practical application of microbial fuel cells (MFCs), but MFCs are not extensively described for low and even freezing temperatures. This study assessed the effect of low-temperature shock on the power generation performance and microbial community structure of MFCs. Two scales of MFCs, the small (mL-MFC) and the large (L-MFC), were constructed in the laboratory and their performance was evaluated before and after freezing at −18 °C. The experimental results demonstrate that both MFCs were capable of rapidly restoring their voltage to the previous level after thawing. For the mL-MFC (rGO/Ag), the power density recovered from 194.30 ± 10.84 mW/m2 to 195.57 ± 4.02 mW/m2 after thawing. For L-MFC (carbon felt electrodes), the power density increased significantly from the initial 1.79 mW/m2 to 173.90 mW/m2 after thawing, but the performance degradation problem after reactor amplification still needs to be solved. The sediment microbial fuel cell (SMFC) was successfully constructed and operated in a natural outdoor environment to maintain high voltage output after the period of frost. Microbial analysis indicated after the frost period, psychrotolerant microorganisms enriched on the anode, such as Flavobacterium and Psychrobacter, while the relative abundance of anaerobic methanogenic bacterium decreased. Overall, freeze-thaw operations had a non-negative impact on the performance of MFCs and provided some references for their practical applications.

On-Line Monitoring of Minor Oil Spills in Seawater Using Sediment Microbial Fuel Cells: A Preliminary Study

In recent years microbial fuel cells have been studied for their biosensing properties. Consequently, sediment microbial fuel cells (sMFCs) have been found to be able to detect minor oil spills in freshwater. However, it was previously unknown whether sMFC properties as a biosensor would be able to produce the same results in a saltwater environment. Therefore, sMFCs at various external resistances (220 Ω, 300 Ω, 430 Ω, 510 Ω, 1000 Ω and 2000 Ω) were assembled to assess their ability to detect oil in seawater. The results indicated that an ER of 1k Ω is optimal for sMFC power generation, and that as oil was added to the cathode of the sMFCs, there was a clear and gradual decrease in the voltage output due to the oil’s interference with oxygen dissolvability in seawater; However, the relationship between the change in voltage and change in time was less linear than the change observed in previous studies, and inconsistent across the different voltages. The variation observed may be due to the absence of a catalyst, such as platinum, which would have sped up the rate of the decrease in voltage. This study illustrates that sMFCs provide a cost effective and environmentally friendly method to detect minor oil spills in seawater.

Cross-linked Polypyrrole@Co3O4 for boosting bioenergy output and regulating electroactive microflora in sediment microbial fuel cells

Sediment microbial fuel cell (SMFC) has been regarded as a promising device for simultaneously bioenergy supply and bioremediation, but the low power density and less research on bioremediation still hinders its practical application. As the carrier of exoelectrogens, anode is closely related to above characteristics of SMFC. Thus, the modification of anode is a reliable way to improve SMFC performance. In this paper, the graphite plate (GP) is modified with polypyrrole/Co3O4 composite (PPy@Co3O4) by electrodeposition to obtain a high capacitive and conductive electrode. SMFC equipped with PPy@Co3O4-GP shows maximum power density of 247.89 mW/m2, nearly 1.94 times higher than blank control group (127.61 mW/m2). The microflora analysis exhibits that PPy@Co3O4-GP has great screening ability for electroactive microbes, and forming electroactive functional microflora involved with Sulfurovum and Streptococcus. The results of sediment composition show that PPy@Co3O4-GP has good bioremediation potential. This work provides an easy and reliable surface modification method for the development of high-performance bioenergy harvesting and bioremediation SMFC anodic materials.

Migration of various ions based on pH shifts triggered by the application of sediment microbial fuel cells.

Sediment microbial fuel cells (SMFCs) represent a technology that can enhance sediment quality through processes such as nutrient suppression while simultaneously generating electricity from microorganisms. Despite its importance in elucidating the principles of nutrient suppression, the complex behavior of various ions within this context has been rarely explored. Herein, we applied an SMFC and systematically evaluated alterations in ion concentrations in interstitial and overlying waters. The SMFC deployment substantially decreased Na+ concentrations and increased Cl- levels in the interstitial water. This intriguing phenomenon was attributed to reactions driven by the electrodes. These reactions induced remarkable shifts in pH. Consequently, this pH shift triggered the leaching of heavy metals, particularly Fe, and decreased HCO3- concentrations within the interstitial water, thereby inducing the migration of other ions, including Na+ and Cl-, as compensation. Moreover, the PO43- concentration in interstitial water showed an increasing trend upon SMFC application, which contradicts the results of several previous reports. This increase was primarily attributed to the release of PO43-caused by the leaching of Fe salts, which was triggered by the pH shift. These findings provide new insights into sediment improvement research through SMFCs, enhancing our understanding of the fundamental principles and broadening the potential applications of this technology.

Sediment microbial fuel cell with biochar-modified cathode for remediation of black-odorous water sediments and analysis of microbial community

Sediment microbial fuel cells (SMFCs) generate electricity through microbial degradation of organic matter in sediments, and the cathode catalyst used for the oxygen reduction reaction is a key factor affecting the performance of SMFCs. To improve power production in SMFCs and remediate black-odorous water sediments, this study modifies the cathode carbon felt of the SMFC system with Enteromorpha prolifera (EP) biochar with high N and P content. The study demonstrated that the SMFC system with the modified cathode carbon felt (C-800℃/CF) exhibited superior power generation capabilities, achieving a maximum power density of 219.44 mW·m−2. Over 25 days of operation, the anode biofilm effectively degraded around 78.15% of total organic carbon, 79.55% of acid volatile sulfide, 74.78% of total nitrogen, 80.58% of ammonia nitrogen, and 77.46% of total phosphorus in the sediment. In addition, microbial community analysis showed that functional bacteria Thiobacillus, Acidaminobacter, Sulfurimonas, Bacteroidetes_vadinHA17, and Sideroxydans were the dominant genera in the anode biofilm.

Sediment microbial fuel cell monitoring repeated Cr(VI) shocks in different wetlands for a year: Performance and mechanism

Cr(VI) is a major heavy metal contaminant that poses great threats to aquatic ecosystems and human health. To guarantee the safety of water quality, the development of in-situ and online sensors for monitoring Cr(VI) contamination events is crucial. In this work, sediment microbial fuel cell (SMFC) based sensors using floating cathode as sensing element were operated in outdoor environment for one year to monitor repeated Cr(VI) shocks in wetlands constructed with coastal alkaline soil (YC), paddy of acidic soil (YT), and paddy of neutral soil (NJ). K2CrO4 solutions were added to the cathode four times in January, March, June, and September, respectively. Results showed that each Cr(VI) addition triggered a voltage peak and the voltage increments were linearly correlated with Cr(VI) concentrations within the range of 5–120 mg L−1 Cr(VI). The highest sensitivity was observed for YC (1.2 mV L mg−1) and YT (1.4 mV L mg−1) in June and for NJ (1.2 mV L mg−1) in September. XPS analysis demonstrated the reduction reaction of Cr(VI) to Cr(III) on the cathode might contribute to the generation of voltage peaks. Despite repeated shocks, Cr(VI) was immobilized in the soil and completely reduced to low-toxic Cr(III) with the consumption of soil organic matter, and the diversity and abundance of exoelectrogenic bacteria-associated genera were not inhibited. As a result, stable operation of the SMFC sensors was ensured. The SMFC sensors exhibited great potential for in-situ and online monitoring of Cr(VI) contamination events across various wetlands.

Utilization of Spent Coffee Grounds for Bioelectricity Generation in Sediment Microbial Fuel Cells.

This study examined the utilization of spent coffee grounds with different aqueous extraction methods for the bioelectricity generation from coastal benthic sediment through a sediment microbial fuel cell (SMFC) system. Different methods for the aqueous extraction of SCGs were evaluated, including rinsing and drying of the SCG (SMFC-CRD), immersion, rinsing and drying (SMFC-CRID), drying alone (SMFC-CD), and untreated SCG (SMFC-C). The caffeine concentration in the SCG was significantly reduced using pretreatments, with SMFC-CRID achieving the lowest concentration of 0.021 ± 0.001 mg/g. SMFC-CRD contributed to the generation of the highest current density of 213.7 mA/m2 during closed-circuit operation and exhibited the highest power density of 96.9 mW/m2 in the polarization test, due to the suitable caffeine content of 0.275 ± 0.001 mg/g in the SCG. This study could provide a cost-effective method for reusing SCGs (i.e., 128 g) while generating bioelectricity as an alternative energy source. These results suggest that pretreatment with SCGs is essential for achieving optimal power density and reducing the caffeine concentration in the SMFC system.

Effect of submerged and floating cathodes on sustainable bioelectricity generation and benthic nutrient removal in sediment microbial fuel cells

Sediment microbial fuel cells (SMFC) are a potential alternative for benthic sediment remediation in bioelectricity generation. The cathodic oxygen reduction rate is an important limiting factor in SMFC. This study aims to evaluate the effects of submerged and floating cathodes on bioelectricity generation and benthic nutrient removal in SMFC. Based on the generated current density, SMFC with a wick-air cathode, 10 cm from the top sediment surface and partially submerged in water and exposed to air (SMFC-CW) was found to be superior to those with bottom cathode, 1 cm from the top sediment surface (SMFC-C1), a middle cathode, 5 cm from the top sediment surface (SMFC-C5), and a floating cathode, 10 cm from the top sediment surface and placed under the overlying surface water (SMFC-C10). In the polarization test, SMFC-CW contributed to the lowest concentration loss with a maximum current density of 236.4 mA/m2. The overshoot phenomenon in SMFC-C1 is not a good indicator of the SMFC system, despite the generation of a high maximum power density. This study has shown that a large pH difference between the anodic and cathodic regions in SMFC-CW is important for bioelectricity generation as it was observed that the internal resistance of SMFCs changes. SMFC-CW showed the largest reduction in phosphate concentration, from 0.61 mg/L to 0.14 mg/L. These results provide a simple strategy for sustainable bioelectricity generation in SMFC systems while remediating benthic sediments.

On-Line Monitoring of Minor Oil Spills in Seawater Using Sediment Microbial Fuel Cells: A Preliminary Study

In recent years microbial fuel cells have been studied for their biosensing properties. Consequently, sediment microbial fuel cells (sMFCs) have been found to be able to detect minor oil spills in freshwater. However, it was previously unknown whether sMFC properties as a biosensor would be able to produce the same results in a saltwater environment. Therefore, sMFCs at various external resistances (220 Ω, 300 Ω, 430 Ω, 510 Ω, 1000 Ω and 2000 Ω) were assembled to assess their ability to detect oil in seawater. The results indicated that as oil was added to the cathode of the microbial fuel cells, there was a clear and gradual decrease in the voltage output due to the oil’s interference with oxygen dissolvability in seawater; However, the relationship between the change in voltage and change in time was less linear than the change observed in previous studies, and inconsistent across the different voltages. The variation observed may be due to the absence of a catalyst, such as platinum, which would have sped up the rate of the decrease in voltage. This study illustrates that sediment microbial fuel cells provide a cost effective and environmentally friendly method to detect minor oil spills in seawater.

The Effect of Illumination, Electrode Distance, and Illumination Periods on the Performance of Phototrophic Sediment Microbial Fuel Cells (PSMFCs)

Microbial fuel cells (MFCs) can potentially be used to overcome issues with battery powered light buoys and their frequent maintenance. In this study, a phototrophic sediment microbial fuel cell (PSMFC) was chosen, as the microalgae provide oxygen to be reduced on the cathode and to release the necessary nutrients for the bacteria on the anode. To achieve this, we studied the effect of illumination, the period of the illumination, and the distance between 9-cm2 stainless steel mesh electrodes on the performance of the MFC. The illuminated cells were able to produce higher OCP (max. 205.2 mV) and higher power density (max. 0.68 mW/m2). However, the highest current was achieved during the unilluminated variation (max. 5.3 μA unilluminated and 3.3 μA illuminated). Prolonged illumination produced a higher OCP, current, and power density. A longer electrode distance produced a higher OCP, power density, and current. SEM analysis showed that biofilm formation tended to be scattered at lower electrode distance and more clumped (filling the anode area) at higher electrode distance. Through FTIR analysis, it was found that all MFC variations had the same organic matter, but a more concentrated organic content was found in the MFC at longer electrode distances.

Energy harvesting from plants using hybrid microbial fuel cells; potential applications and future exploitation.

Microbial Fuel Cells (MFC) can be fuelled using biomass derived from dead plant material and can operate on plant produced chemicals such as sugars, carbohydrates, polysaccharides and cellulose, as well as being "fed" on a regular diet of primary biomass from plants or algae. An even closer relationship can exist if algae (e.g., prokaryotic microalgae or eukaryotic and unicellular algae) can colonise the open to air cathode chambers of MFCs driving photosynthesis, producing a high redox gradient due to the oxygenic phase of collective algal cells. The hybrid system is symbiotic; the conditions within the cathodic chamber favour the growth of microalgae whilst the increased redox and production of oxygen by the algae, favour a more powerful cathode giving a higher maximum voltage and power to the photo-microbial fuel cell, which can ultimately be harvested for a range of end-user applications. MFCs can utilise a wide range of plant derived materials including detritus, plant composts, rhizodeposits, root exudates, dead or dying macro- or microalgae, via Soil-based Microbial Fuel Cells, Sediment Microbial Fuel Cells, Plant-based microbial fuel cells, floating artificial islands and constructed artificial wetlands. This review provides a perspective on this aspect of the technology as yet another attribute of the benevolent Bioelectrochemical Systems.

Simultaneous degradation of NSAIDs in aqueous and sludge stages by an electron-Fenton system derived from sediment microbial fuel cell based on a novel Fe@Mn biochar GDC

Electro-Fenton (e-Fenton) reactions boosted using microbial fuel cells (MFCs) can degrade contaminants with high efficiency, the treatment is generally performed in the aqueous phase and the sludge pollution is ignored in such MFCs. In this study, a sediment MFC e-Fenton (SMFC-e-Fenton) system was proposed for the degradation of nonsteroidal anti-inflammatory drugs (NSAIDs) in both aqueous and solid phases. A Fe@Mn-codoped biochar gas diffusion cathode was fabricated to produce hydroxyl radicals without any additional power input. The studied NSAIDs of ibuprofen (IBU), naproxen (NPX), and diclofenac (DCF) exhibited total degradation efficiencies (including aqueous and sludge phase) of 99.1%, 98.5%, and 80.6%, respectively, in the SMFC-e-Fenton system. Compared with sludge anaerobic digestion, the residual amounts of IBU, NPX, and DCF reduced from 10.2%, 24.6%, and 32.2% to 2.7%, 4.4%, and 8.5%, respectively, in the sludge phase. Moreover, the electricity generation and sludge reduction improved owing to the e-Fenton process. Using the SMFC-e-Fenton system, the effects of NSAIDs were reduced and the richness and diversity of the microbial community are maintained, improving the overall system performance. These results demonstrate that the SMFC-e-Fenton method is a high-efficiency, economic and environmental friendly technology for simultaneously treating NSAIDs in the aqueous and sludge phases.

Effect of NH2-MWCNTs/CF anodes on the power generation performance of SMFCs

The carbon nanotube-modified anodes have been widely recognized as one of the most effective methods to improve the conductivity of the anode and enhance the performance of microbial fuel cells. And there are few studies on the effect of amino-functionalized carbon nanotube-modified anodes on the performance of sediment microbial fuel cells (SMFCs) systematically. In this paper, we prepared amino-functionalized carbon nanotube-modified electrodes and constructed SMFCs using them to study the effect of amino-functionalized carbon nanotubes on the power generation performance of SMFCs. The results showed that the highest output voltage of NH2-functionalized multi-walled carbon nanotube (NH2-MWCNT)-modified carbon felt (CF) SMFCs (529.15 mV) was significantly higher than that of CF (474.5 mV). And the power density of SMFCs with 10% NH2-MWCNTs/CF reached a maximum of 58.3 mW/m3. There are because NH2-MWCNTs surface has a larger specific surface area and a porous structure, enhancing electron conduction pathway helps to improve the conductivity of the anode. Therefore, the modification of CF surfaces with NH2-MWCNTs can be used to improve the interfacial properties and positively enhance the power generation performance of SMFCs. This study provides a novel and effective approach to enhance the performance of SMFCs and contributes to the international research on carbon nanotube-modified anodes for energy and environmental applications.

Phosphorus Release from Agricultural Drainage Sediments with Iron-Added Sediment Microbial Fuel Cells

Phosphorus Release from Agricultural Drainage Sediments with Iron-Added Sediment Microbial Fuel Cells