PEDOT was synthesized by chemical polymerisation and characterised for its electrochemical insights. Three different anode configuration, namely graphite plate (GP), carbon cloth (CC) and graphite felt (GF) were then loaded with a fixed amount of PEDOT (2.5 mg/m(2)) denoted as GP-P, CC-P and GF-P respectively. The PEDOT coating improved the electrochemical characteristics and electron transfer capabilities of the anodes. They also contributed for enhanced MFC performances with maximum energy generation along with coulombic efficiency than the unmodified anodes. The morphological characteristics like higher surface area and open structure of felt material promoted both microbial formation and electrochemical active area. A maximum current density of 3.5A/m(2) was achieved for GF-P with CE and COD of 51% and 86% respectively. Thus, the GF-P anode excelled among the studied anodes with synergetic effect of PEDOT coating and structural configuration, making it as a potential optimum anode for MFC application.
The occurrence of n-alkanoic acids, amides, and nitriles in samples of aerosol particulate matter from Kuala Lumpur and Santiago suggests that emissions from cooking and biomass burning are the primary sources of these organic markers in the atmosphere. It is proposed that fatty acids react with ammonia during biomass burning or combustion to produce amides and nitriles, which can be applied as useful biomarker tracers. To test this hypothesis, nonadecanoic acid and hexadecanamide were used as reactants in hydrous pyrolysis experiments. These experiments produced amides and nitriles and indicated that ammonia is an essential agent in their formation. Thus amides and nitriles are of utility as indicators for input from combustion and biomass burning in the ambient atmosphere.
Sago hampas is a starch-based biomass from sago processing industries consisted of 58% remaining starch. This study has demonstrated the bioconversion of sago hampas to volatile fatty acids (VFAs) by Clostridium beijerinckii SR1 via anaerobic digestion. Higher total VFAs were obtained from sago hampas (5.04 g/L and 0.287 g/g) as compared to commercial starch (5.94 g/L and 0.318 g/g). The physical factors have been investigated for the enhancement of VFAs production using one-factor-at-a-time (OFAT). The optimum condition; 3% substrate concentration, 3 g/L of yeast extract concentration and 2 g/L of ammonium nitrate enhanced the production of VFAs by 52.6%, resulted the total VFAs produced is 7.69 g/L with the VFAs yield of 0.451 g/g. VFAs hydrolysate produced successfully generated 273.4 mV of open voltage circuit and 61.5 mW/m2 of power density in microbial fuel cells. It was suggested that sago hampas provide as an alternative carbon feedstock for bioelectricity generation.
This study investigates the role of plant (Elodea nuttallii) and effect of supplementary aeration on wastewater treatment and bioelectricity generation in an up-flow constructed wetland-microbial fuel cell (UFCW-MFC). Aeration rates were varied from 1900 to 0mL/min and a control reactor was operated without supplementary aeration. 600mL/min was the optimum aeration flow rate to achieve highest energy recovery as the oxygen was sufficient to use as terminal electron acceptor for electrical current generation. The maximum voltage output, power density, normalized energy recovery and Coulombic efficiency were 545.77±25mV, 184.75±7.50mW/m3, 204.49W/kg COD, 1.29W/m3 and 10.28%, respectively. The variation of aeration flow rates influenced the NO3- and NH4+ removal differently as nitrification and denitrification involved conflicting requirement. In terms of wastewater treatment performance, at 60mL/min aeration rate, UFCW-MFC achieved 50 and 81% of NO3- and NH4+ removal, respectively. E. nuttallii enhanced nitrification by 17% and significantly contributed to bioelectricity generation.
This work studied the performance of a laboratory-scale microbial fuel cell (MFC) using a bioanode that consisted of treated clinoptilolite fine powder coated onto graphite felt (TC-MGF). The results were compared with another similar MFC that used a bare graphite felt (BGF) bioanode. The anode surfaces provided active sites for the adhesion of the bacterial consortium (NAR-2) and the biodegradation of mono azo dye C.I. Acid Red 27. As a result, bioelectricity was generated in both MFCs. A 98% decolourisation rate was achieved using the TC-MGF bioanode under a fed-batch operation mode. Maximum power densities for BGF and TC-MGF bioanodes were 458.8 ± 5.0 and 940.3 ± 4.2 mW m-2, respectively. GC-MS analyses showed that the dye was readily degraded in the presence of the TC-MGF bioanode. The MFC using the TC-MGF bioanode showed a stable biofilm with no biomass leached out for more than 300 h operation. In general, MFC performance was substantially improved by the fabricated TC-MGF bioanode. It was also found that the TC-MGF bioanode with the stable biofilm presented the nature of exopolysaccharide (EPS) structure, which is suitable for the biodegradation of the azo dye. In fact, the EPS facilitated the shuttling of electrons to the bioanode for the generation of bioelectricity.
Matched MeSH terms: Bioelectric Energy Sources/microbiology*
Microbial fuel cells (MFCs) represent one of the most attractive and eco-friendly technologies that convert chemical bond energy derived from organic matter into electrical power by microbial catabolic activity. This paper presents the use of a H-type MFC involving a novel NAR-2 bacterial consortium consisting of Citrobacter sp. A1, Enterobacter sp. L17 and Enterococcus sp. C1 to produce electricity whilst simultaneously decolourising acid red 27 (AR27) as a model dye, which is also known as amaranth. In this setup, the dye AR27 is mixed with modified P5 medium (2.5 g/L glucose and 5.0 g/L nutrient broth) in the anode compartment, whilst phosphate buffer solution (PBS) pH 7 serves as a catholyte in the cathode compartment. After several electrochemical analyses, the open circuit voltage (OCV) for 0.3 g/L AR27 with 24-h retention time at 30 °C was recorded as 0.950 V, whereas (93%) decolourisation was achieved in 220-min operation. The maximum power density was reached after 48 h of operation with an external load of 300 Ω. Scanning electron microscopy (SEM) analysis revealed the surface morphology of the anode and the bacterial adhesion onto the electrode surface. The results of this study indicate that the decolourisation of AR27 dye and electrical power generation was successfully achieved in a MFC operated by a bacterial consortium. The consortium of bacteria was able to utilise AR27 in a short retention time as an electron acceptor and to shuttle the electrons to the anode surface for bioelectricity generation.
Matched MeSH terms: Bioelectric Energy Sources/microbiology*
One of the biggest challenges of using single-chamber microbial fuel cells (MFCs) that utilize proton-exchange membrane (PEM) air cathode for bioenergy recovery from recalcitrant organic compounds present in wastewater is mainly attributed to their high internal resistance in the anodic chamber of the single microbial fuel cell (MFC) configurations. The high internal resistance is due to the small surface area of the anode and cathode electrodes following membrane biofouling and pH splitting conditions as well as substrate and oxygen crossover through the membrane pores by diffusion. To address this issue, the fabrication of new PEM air-cathode single-chamber MFC configuration was investigated with inner channel flow open assembled with double PEM air cathodes (two oxygen reduction activity zones) coupled with spiral-anode MFC (2MA-CsS-AMFC). The effect of various proton-exchange membranes (PEMs), including Nafion 117 (N-117), Nafion 115 (N-115), and Nafion 212 (N-212) with respective thicknesses of 183, 127, and 50.08 μ, was separately incorporated into carbon cloth as PEM air-cathode electrode to evaluate their influences on the performance of the 2MA-CsS-AMFC configuration operated in fed-batch mode, while Azorubine dye was selected as the recalcitrant organic compound. The fed-batch test results showed that the 2MA-CsS-AMFC configuration with PEM N-115 operated at Azorubine dye concentration of 300 mg L-1 produced the highest power density of 1022.5 mW m-2 and open-circuit voltage (OCV) of 1.20 V coupled with enhanced dye removal (4.77 mg L h-1) compared to 2MA-CsS-AMFCs with PEMs N-117 and N-212 and those in previously published data. Interestingly, PEM 115 showed remarkable reduction in biofouling and pH splitting. Apart from that, mass transfer coefficient of PEM N-117 was the most permeable to oxygen (KO = 1.72 × 10-4 cm s-1) and PEM N-212 was the most permeable membrane to Azorubine (KA = 7.52 × 10-8 cm s-1), while PEM N-115 was the least permeable to both oxygen (KO = 1.54 × 10-4) and Azorubine (KA = 7.70 × 10-10). The results demonstrated that the 2MA-CsS-AMFC could be promising configuration for bioenergy recovery from wastewater treatment under various PEMs, while application of PEM N-115 produced the best performance compared to PEMs N-212 and N-117 and those in previous studies of membrane/membrane-less air-cathode single-chamber MFCs that consumed dye wastewater.
Single chambered up-flow membrane-less microbial fuel cell (UFML MFC) was developed to study the feasibility of the bioreactor for decolorization of Acid Orange 7 (AO7) and electricity generation simultaneously. The performance of UFML MFC was evaluated in terms of voltage output, chemical oxygen demand (COD) and color removal efficiency by varying the concentration of AO7 in synthetic wastewater. The results shown the voltage generation and COD removal efficiency decreased as the initial AO7 concentration increased; this indicates there is electron competition between anode and azo dye. Furthermore, there was a phenomenon of further decolorization at cathode region which indicates the oxygen and azo dye are both compete as electron acceptor. Based on the UV-visible spectra analysis, the breakdown of the azo bond and naphthalene compound in AO7 were confirmed. These findings show the capability of integrated UFML MFC in azo dye wastewater treatment and simultaneous electricity generation.
An air-cathode MFC-adsorption hybrid system, made from earthen pot was designed and tested for simultaneous wastewater treatment and energy recovery. Such design had demonstrated superior characteristics of low internal resistance (29.3Ω) and favor to low-cost, efficient wastewater treatment and power generation (55mW/m(3)) with average current of 2.13±0.4mA. The performance between MFC-adsorption hybrid system was compared to the standalone adsorption system and results had demonstrated great pollutants removals of the integrated system especially for chemical oxygen demand (COD), biochemical oxygen demand (BOD3), total organic carbon (TOC), total volatile solids (TVS), ammoniacal nitrogen (NH3-N) and total nitrogen (TN) because such system combines the advantages of each individual unit. Besides the typical biological and electrochemical processes that happened in an MFC system, an additional physicochemical process from the activated carbon took place simultaneously in the MFC-adsorption hybrid system which would further improved on the wastewater quality.
Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity
generation. However, the choice of the electrode material and its design is critical and directly affect their performance.
As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power
output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF)
was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs.
The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2
and 827.25 mW/m2
,
respectively, which were higher than MFC-CS (641.95 mA/m2
and 260.14 mW/m2
) and MFC-GF (728.30 mA/m2
and 307.89
mW/m2
). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and
MFC-GF anode, also supported by cyclic voltammetry test.
Thriving oil palm agroindustry comes at a price of voluminous waste generation, with palm oil mill effluent (POME) as the most cumbersome waste due to its liquid state, high strength, and great discharge volume. In view of incompetent conventional ponding treatment, a voluminous number of publications on non-conventional POME treatments is filed in the Scopus database, mainly working on alternative or polishing POME treatments. In dearth of such comprehensive review, all the non-conventional POME treatments are rigorously reviewed in a conceptual and comparative manner. Herein, non-conventional POME treatments are sorted into the five major routes, viz. biological (bioconversions - aerobic/anaerobic biodegradation), physical (flotation & membrane filtration), chemical (Fenton oxidation), physicochemical (photooxidation, steam reforming, coagulation-flocculation, adsorption, & ultrasonication), and bioelectrochemical (microbial fuel cell) pathways. For aforementioned treatments, the constraints, pros, and cons are qualitatively and quantitatively (with compiled performance data) detailed to indicate their process maturity. Authors recommended (i) bioconversions, adsorption, and steam reforming as primary treatments, (ii) flotation and ultrasonication as pretreatments, (iii) Fenton oxidation, photooxidation, and membrane filtration as polishing treatments, and (iv) microbial fuel cell and coagulation-flocculation as pretreatment or polishing treatment. Life cycle assessments are required to evaluate the environmental, economic, and energy aspects of each process.
Complete degradation of azo dye has always been a challenge due to the refractory nature of azo dye. An innovative hybrid system, constructed wetland-microbial fuel cell (CW-MFC) was developed for simultaneous azo dye remediation and energy recovery. This study investigated the effect of circuit connection and the influence of azo dye molecular structures on the degradation rate of azo dye and bioelectricity generation. The closed circuit system exhibited higher chemical oxygen demand (COD) removal and decolourisation efficiencies compared to the open circuit system. The wastewater treatment performances of different operating systems were ranked in the decreasing order of CW-MFC (R1 planted-closed circuit) > MFC (R2 plant-free-closed circuit) > CW (R1 planted-open circuit) > bioreactor (R2 plant-free-open circuit). The highest decolourisation rate was achieved by Acid Red 18 (AR18), 96%, followed by Acid Orange 7 (AO7), 67% and Congo Red (CR), 60%. The voltage outputs of the three azo dyes were ranked in the decreasing order of AR18 > AO7 > CR. The results disclosed that the decolourisation performance was significantly influenced by the azo dye structure and the moieties at the proximity of azo bond; the naphthol type azo dye with a lower number of azo bond and more electron-withdrawing groups could cause azo bond to be more electrophilic and more reductive for decolourisation. Moreover, the degradation pathway of AR18, AO7 and CR were elucidated based on the respective dye intermediate products identified through UV-Vis spectrophotometry, high-performance liquid chromatography (HPLC), and gas chromatograph-mass spectrometer (GC-MS) analyses. The CW-MFC system demonstrated high capability of decolouring azo dyes at the anaerobic anodic region and further mineralising dye intermediates at the aerobic cathodic region to less harmful or non-toxic products.
A recent rise in crab aquaculture activities has intensified the generation of waste shells. In the present study, the waste shells were utilized as a source of calcium oxide to transesterify palm olein into methyl esters (biodiesel). Characterization results revealed that the main component of the shell is calcium carbonate which transformed into calcium oxide when activated above 700 degrees C for 2 h. Parametric studies have been investigated and optimal conditions were found to be methanol/oil mass ratio, 0.5:1; catalyst amount, 5 wt.%; reaction temperature, 65 degrees C; and a stirring rate of 500 rpm. The waste catalyst performs equally well as laboratory CaO, thus creating another low-cost catalyst source for producing biodiesel. Reusability results confirmed that the prepared catalyst is able to be reemployed up to 11 times. Statistical analysis has been performed using a Central Composite Design to evaluate the contribution and performance of the parameters on biodiesel purity.
A double-chambered membrane microbial fuel cell (MFC) was constructed to investigate the potential use of natural microflora anaerobic palm oil mill effluent (POME) sludge and pure culture bacteria isolated from anaerobic POME sludge as inoculum for electricity generation. Sterilized final discharge POME was used as the substrate with no addition of nutrients. MFC operation using natural microflora anaerobic POME sludge showed a maximum power density and current density of 85.11mW/m(2) and 91.12mA/m(2) respectively. Bacterial identification using 16S rRNA analysis of the pure culture isolated from the biofilm on the anode MFC was identified as Pseudomonas aeruginosa strain ZH1. The electricity generated in MFC using P. aeruginosa strain ZH1 showed maximum power density and current density of 451.26mW/m(2) and 654.90mA/m(2) respectively which were five times higher in power density and seven times higher in current density compared to that of MFC using anaerobic POME sludge.
Matched MeSH terms: Bioelectric Energy Sources/microbiology*
In this study, fatty acid methyl esters (FAME) have been successfully produced from transesterification reaction between triglycerides and methyl acetate, instead of alcohol. In this non-catalytic supercritical methyl acetate (SCMA) technology, triacetin which is a valuable biodiesel additive is produced as side product rather than glycerol, which has lower commercial value. Besides, the properties of the biodiesel (FAME and triacetin) were found to be superior compared to those produced from conventional catalytic reactions (FAME only). In this study, the effects of various important parameters on the yield of biodiesel were optimized by utilizing Response Surface Methodology (RSM) analysis. The mathematical model developed was found to be adequate and statistically accurate to predict the optimum yield of biodiesel. The optimum conditions were found to be 399 degrees C for reaction temperature, 30 mol/mol of methyl acetate to oil molar ratio and reaction time of 59 min to achieve 97.6% biodiesel yield.
The industrial contamination of marine sediments with mercury, silver, and zinc in Penang, Malaysia was studied with bio-remediation coupled with power generation using membrane less open (aerated) and closed (non-aerated) sediment microbial fuel cells (SMFCs). The prototype for this SMFC is very similar to a natural aquatic environment because it is not stimulated externally and an oxygen sparger is inserted in the cathode chamber to create the aerobic environment in the open SMFC and no oxygen supplied in the closed SMFC. The open and closed SMFCs were showed the maximum voltage generation 300.5 mV (77.75 mW/m2) and 202.7 mV (45.04 (mW/m2), respectively. The cyclic voltammetry showed the oxidation peak in open SMFCs at +1.9 μA and reduction peak at -0.3 μA but in closed SMFCs oxidation and reduction peaks were noted at +1.5 μA and -1.0 μA, respectively. The overall impedance (anode, cathode and solution) of closed SMFCs was higher than open SMFCs. The charge transfer impedance showed that the rates of substrate oxidation and reduction were very low in the closed SMFCs than open SMFCs. The Nyquist arc indicated that O2 act as electron acceptor in the open SMFCs and CO2 in the closed SMFCs. The highest remediation efficiency of toxic metals [Hg (II) ions, Zn (II) ions, and Ag (I) ions] in the open SMFCs were 95.03%, 86.69%, and 83.65% in closed SMFCs were 69.53%, 66.57%, and 65.33%, respectively, observed during 60-80 days. The scanning electron microscope and 16S rRNA analysis showed diverse exoelectrogenic community in the open SMFCs and closed SMFCs. The results demonstrated that open SMFCs could be employed for the power generation and bioremediation of pollutants.