A dual-chamber microbial fuel cell with conductive film-modified anode and cathode and its application for the neutral electro-Fenton process

This study reports on the modification of the anode and the cathode in a dual-chamber microbial fuel cell (MFC) with a polypyrrole (PPy)/anthraquinone-2,6-disulfonate (AQDS) conductive film to boost its performance and the application of the MFC to drive neutral electron-Fenton reactions occurring in the cathode chamber. The MFC equipped with the conductive film-coated anode and cathode delivered the maximum power density of 823 mW cm⁻² that was one order of magnitude larger than that obtained in the MFC with the unmodified electrodes. This was resulted from the enhanced activities of microbial metabolism in the anode and oxygen reduction in the cathode owing to the decoration of both electrodes with the PPy/AQDS composite. The MFC with the modified electrodes resulted in the largest rate of H₂O₂ generation in the cathode chamber by the two-electron reduction of O₂. The increase in the concentration of H₂O₂ was beneficial for the enhancement in the amount of hydroxyl radicals produced by the reaction of H₂O₂ with Fe²⁺, thus allowing an increased oxidative ability of the electro-Fenton process towards the decolorization and mineralization of an azo dye (i.e., Orange II) at pH 7.0.     

Modification of β‐cyclodextrin for rapidly decolorizing the dye‐containing wastewaters by flocculation

To strengthen the role of polymer bridging during the flocculation process and thus raise the speed of decolorizing the dye‐containing wastewaters, β‐cyclodextrin–acrylamide–[2‐(Acryloyloxy)ethyl] trimethyl ammonium chloride copolymer (poly[AM(β‐CD)‐AETAC]) with relatively high intrinsic viscosity (84.3 mL g^?1) and cationicity (24.5%) was prepared by solution polymerization. The successful preparation of copolymer was demonstrated by FT‐IR and ¹H‐NMR characterizations. Its excellent decolorization performances as a new flocculant were evaluated with the C.I. reactive orange 5 (RO 5) and C.I. reactive blue 19 (RB 19) solutions using a jar test method. Both the nature of anionic dyes and the pH of dye solutions influence the decolorization effectiveness. For both the RB 19 and RO 5 solutions (0.10 g L^?1), it can be rapidly decolorized in a wide range of pH (2–7) and flocculant concentration (0.12–0.26 g L^?1). For the given dye/flocculant solution system, both charge neutralization and polymer bridging contribute to the decolorization mechanism. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39940.     

A comparative study of azo dye decolorization by electro‐Fenton in two common electrolytes

BACKGROUND: This study compared the decolorization behaviors of a model azo dye of methyl red in Na₂SO₄ and NaCl media by electro‐Fenton process, in which FeSO₄ was added into the solution, while H₂O₂ was efficiently generated on a graphite–polytetrafluoroethylene cathode. Parameters such as pH, cathodic potential, electrolyte concentration, and initial dye concentration as well as the treatment time were investigated to disclose different decolorization behaviour. RESULTS: Decolorization in NaCl medium had an advantage over that in Na₂SO₄ medium not only in performance but also in its suitability for application, which seemed less sensitive to variations in parameters and thus broadened the optimal performance range. In NaCl medium, indirect oxidation by active chlorine contributed greatly to the decolorization, and the removal of methyl red obeyed pseudo‐first‐order kinetics. CONCLUSION: Electro‐Fenton oxidation in the present system in the presence of NaCl would is a promising procedure for azo dye waste‐water treatment. Copyright © 2009 Society of Chemical Industry     

Electrochemical characteriztion of the bioanode during simultaneous azo dye decolorization and bioelectricity generation in an air-cathode single chambered microbial fuel cell

To achieve high power output based on simultaneously azo dye decolorization using microbial fuel cell (MFC), the bioanode responses during decolorization of a representative azo dye, Congo red, were investigated in an air-cathode single chambered MFC using representative electrochemical techniques. It has been found that the maximum stable voltage output was delayed due to slowly developed anode potential during Congo red decolorization, indicating that the electrons recovered from co-substrate are preferentially transferred to Congo red rather than the bioanode of the MFC and Congo red decolorization is prior to electricity generation. Addition of Congo red had a negligible effect on the Ohmic resistance (R_ohm) of the bioanode, but the charge-transfer resistance (R_c) and the diffusion resistance (R_d) were significantly influenced. The R_c and R_d firstly decreased then increased with increase of Congo red concentration, probably due to the fact that the Congo red and its decolorization products can act as electron shuttle for conveniently electrons transfer from bacteria to the anode at low concentration, but result in accelerated consumption of electrons at high concentration. Cyclic voltammetry results suggested that Congo red was a more favorable electron acceptor than the bioanode of the MFC. Congo red decolorization did not result in a noticeable decrease in peak catalytic current until Congo red concentration up to 900 mg l⁻¹. Long-term decolorization of Congo red resulted in change in catalytic active site of anode biofilm.     

Improved electricity production from sewage sludge under alkaline conditions in an insert‐type air‐cathode microbial fuel cell

BACKGROUND: Electricity can be generated directly from sewage sludge with a microbial fuel cell (MFC), combining degradation of organic matter. This study constructed a novel insert‐type air‐cathode microbial fuel cell (ITAC‐MFC) as an alternative to a sediment‐type MFC and a two‐chambered MFC for the generation of bioelectricity and the degradation of sewage sludge organic matter. Meanwhile, a pH adjustment was carried out to enhance substrate bioavailability of sludge and to suppress methane production in the MFC. RESULTS: A maximum power density of 73 ± 5 mW m^?2 was obtained at sludge pH 10.0, much higher than those of 33 ± 3 and 4 ± 0.5 mW m^?2 obtained at pH 8.0 and 6.0, respectively. It was observed that the soluble chemical oxygen demand (SCOD) of sewage sludge at pH 10.0 was almost three times greater than that at pH 6.0. At the same time, the total chemical oxygen demand (TCOD) removal and coulombic efficiency (CE) at pH 10.0 were also much higher than at the other two conditions. CONCLUSIONS: The results demonstrated that improved electricity production and organic degradation could be achieved by maintaining the sludge pH at 10.0 in an MFC. ITAC‐MFC offers an attractive alternative for the environmentally‐friendly removal of organic matter in sewage sludge. Copyright © 2011 Society of Chemical Industry     

Treatment of the real boiler cleaning wastewater in an anaerobic fluidized bed microbial fuel cell: Organic matter degradation,bioelectrochemistry, and kinetics

A single chambered air cathode anaerobic fluidized bed microbial fuel cell (AFB‐MFC) was simultaneously used to dispose of the real boiler cleaning wastewater (BCW) containing a high concentration of citric acid and to generate renewable energy. At the temperature of 40 °C and flow rate of 5.22 mL/s, the removal efficiency and power density were improved in AFB‐MFC with the abiotic cathode of the Pt/C modified carbon cloth. With the real boiler cleaning wastewater fed as substrate, the maximal removal efficiency of chemical oxygen demand (COD) in AFB‐MFC was up to 90 %, which was higher than the corresponding value of 84 % obtained in the anaerobic biological fluidized bed reactor (ABFBR). The maximum voltage and the maximum power density were 424.6 mV and 18.68 mW/m², respectively, when the external resistance was 5000 Ω. Furthermore, the Haldane inhibition model was well fitted with experiment data (R² = 0.97–0.98) in AFB‐MFC/ABFBR. The inhibition of citric acid degradation in ABFBR was stronger than that of AFB‐MFC. The bioelectrochemical system of AFB‐MFC not only improved the charge transfer and but also accelerated the reaction rate of citric acid. The reduction of the ferric ion and oxidation of ferrous ion in AFB‐MFC played important roles in the degradation reaction of critic acid.     

Enhanced Performance of Micro‐Electro‐Mechanical‐Systems (MEMS) Microbial Fuel Cells Using Electrospun Microfibrous Anode and Optimizing Operation

In this work, a microfabricated anode based on gold coated poly(ϵ‐caprolactone) fiber was developed that outperformed gold microelectrode by a factor of 2.65‐fold and even carbon paper by 1.39‐fold. This is a result of its ability to three‐dimensionally interface with bacterial biofilm, the metabolic “engines” of the microbial fuel cell (MFC). We also examined unavoidable issues as the MFC is significantly reduced in size (e.g. to the microscale); (1) bubble production or movement into the microchamber and (2) high sensitivity to flow rate variations. In fact, intentionally induced bubble generation in the anodic chamber reduced the MFC current density by 33% and the MFC required 4 days to recover its initial performance. Under different flow rates in the anode chamber, the current densities were almost constant, however, the current increased up to 38% with increasing flow rate in the cathode.     

Photocatalytic Degradation of Two Commercial Reactive Dyes in Aqueous Phase Using Nanophotocatalysts

This study involves the photocatalytic degradation of Reactive Black 5 (RB5) and Reactive Orange 4 (RO4) dyes, employing heterogeneous photocatalytic process. Photocatalytic activity of different semiconductors such as titanium dioxide (TiO₂) and zinc oxide (ZnO) has been investigated. An attempt has been made to study the effect of process parameters through amount of catalyst, concentration of dye, and pH on photocatalytic degradation of RB5 and RO4. The experiments were carried out by varying pH (3–11), amount of catalyst (0.25–1.5 g/L), and initial concentration of dye (10–100 mg/L). The optimum catalyst dose was found to be 1.25 and 1 g/L for RB5 and RO4, respectively. In the case of RB5, maximum rate of decolorization was observed in acidic medium at pH 4, whereas the decolorization of RO4 reached maximum in basic region at pH 11. The performance of photocatalytic system employing ZnO/UV light was observed to be better than TiO₂/UV system. The complete decolorization of RB5 was observed after 7 min with ZnO, whereas with TiO₂, only 75% dye degraded in 7 min. In the case of RO4, 92 and 62% decolorization was noticed in the same duration.     

Enhancing the stability of power generation of single‐chamber microbial fuel cells using an anion exchange membrane

BACKGROUD: A decreased power density could be observed in a single‐chamber microbial fuel cell (MFC) with a cation exchange membrane (CEM), as a result of pH‐associated problem and a precipitated salt‐associated problem, due to the transport of cations other than protons through the membrane to the cathode. To inhibit cation transport and enhance the stability of power generation, an anion exchange membranes (AEM) was applied in a single‐chamber MFC. RESULTS: After 70 days' operation, the power density dropped 29% in the MFC with an AEM (AMFC), smaller than 48% in the MFC with a cation exchange membrane (CMFC). The reason for this difference lay in internal resistance development. Membrane resistance in the AMFC remained the same but that in the CMFC was increased by 67 Ω, and the cathode resistance increase in the AMFC was 54 Ω, while that in the CMFC was 123 Ω. The precipitated cations on the cathode catalyst surface in the CMFC, which accounted for the resistance increase, were up to 84 times larger than that in the AMFC. CONCLUSION: Because of its capacity for inhibiting cations, the AMFC possessed more stable membrane and cathode resistances; thus an enhanced power generation was obtained. Copyright © 2009 Society of Chemical Industry     

Simultaneous nitrification and denitrification with electricity generation in dual‐cathode microbial fuel cells

BACKGROUND: Nitrogen removal using microbial fuel cells (MFCs) is of great interest owing to the potential benefits of bioenergy production. In this study, simultaneous nitrification and denitrification in dual‐cathode MFCs was investigated. RESULTS: The dual‐cathode MFCs investigated were capable of generating electricity and removing nitrogen, influenced by operating methods, nitrogen loading rates and external resistance. Depending on the ammonium concentration in the anode chamber, 84–97% of the ammonium nitrogen was removed via nitrification in the aerobic cathode. The removals of nitrate and total nitrogen were relatively low (～50%) at the influent ammonium concentration of 80 mg NH₄⁺‐N L^?1, but were significantly improved to more than 90% at a lower ammonium input (40 and 20 mg NH₄⁺‐N L^?1). When the electrode couples were electrically connected for different purposes, with high power output from the anode/aerobic cathode and high current generation from the anode/anoxic cathode, nitrogen removal was also improved. An investigation of aeration suggested that factors other than carbon supply, possibly inefficient reactor configuration, also limited the performance of the developed MFC. CONCLUSION: The experimental results demonstrated that the proposed pathway was feasible with effective nitrogen and organic removal. This study provided valuable information for the further development of a continuously operated dual‐cathode MFC system. Copyright © 2011 Society of Chemical Industry     

Cost analysis for the degradation of highly concentrated textile dye wastewater with chemical oxidation H2O2/UV and biological treatment

The efficiency and cost‐effectiveness of H₂O₂/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200–300 mg g^?1 of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g^?1 RB5 for 2.1 g L^?1 versus 354 W h g^?1 RB5 for 0.5 g L^?1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g^?1 overall mineralization, 500 mg g^?1 of the DOC had to be oxidized in the H₂O₂/UV stage. A cost analysis showed that although the capital costs are much less for a H₂O₂/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H₂O₂/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost‐effective in this case when mineralization is desired. Copyright © 2006 Society of Chemical Industry     

活性黑5的生物脱色、复色现象及机理

印染废水问题形势依然严峻,目前常用生物法来治理,筛选高效降解染料的微生物是生物法处理印染废水的关键。本文利用梯度浓度压力驯化法,从印染废水水解酸化反应器中筛选出对染料活性黑5具有良好脱色性能的混合菌群DDMY1。利用该菌群在兼氧条件下对活性黑5进行脱色研究,首先采用拍照方式记录其反复脱色、复色的直观效果,其次运用紫外-可见光分光光度计检测其不同时间、不同状态下脱色液吸光值情况,最后运用气相色谱质谱联用仪和傅里叶变换红外光谱仪等检测方法分析脱色、复色过程中产物情况。结果表明,混合菌群DDMY1对活性黑5的脱色性能显著,24h脱色率能达到97.4%。同时,发现活性黑5的兼氧生物脱色反应可有效反复脱色、复色达17次之多,根据分析测试的结果,初步推测该现象可能是由活性黑5降解产物中的苯胺类物质或萘醌类物质造成的。     

Generation behavior of elctricity in a microbial fuel cell

Electricity generation using a microbial fuel cell (MFC) was investigated with acetate as the fuel and Geobacter sulfurreducens as the biocatalyst on the anode electrode. The voltage and power density behaviors at various external resistances were observed, as were the coulombic efficiency and energy recovery behaviors at various acetate concentrations. A high voltage production was obtained when the pH in the cathode chamber was maintained in the range of 7–8, which is similar to that used in other MFC studies. After 72 hours of operation, the voltage production was decreased by 11.5% with 30 mM tris-HCl and by 33.7% with 10 mM tris-HCl.     

蒽醌染料活性艳蓝KN-R的ACF电极成对电解脱色

在恒电流模式下,采用无隔膜电解槽,同时以活性炭纤维（ACF）为阳极和阴极,研究了不同电流密度下蒽醌染料活性艳蓝KN-R的脱色效果和脱色机制.结果表明：0～0.1 mA·cm^-2时,脱色是由于染料在ACF上的吸附,极化对吸附行为影响不大,脱色率在15%左右;0.2～0.6 mA·cm^-2时,阳极电位达到该染料在ACF上的氧化电位（0.5 V）,阴极电位未达到其还原电位（-0.7 V）,脱色是由于阳极电氧化和阴极吸附,脱色率最高可达52%;0.7～1.0 mA·cm^-2时,发生成对电解,即阳极电氧化和阴极电还原同时使染料脱色,脱色率最高可达83%.     

活性蓝FNR降解脱色菌的培养及其脱色性能的研究

从印染厂的活性污泥中筛选分离出了一株活性蓝FNR染料脱色优势菌株.研究了该脱色菌在不同温度、不同pH值、不同培养时间及不同染料浓度条件下对染料脱色的影响.结果显示,在30℃、120 rpm、染料浓度为5 mg/L、接种量为5 mL、培养基pH值(5～6)、自然的实验条件下,进行脱色培养36小时,其脱色率最高,可达到50％.     

Bacterial decolorization of an azo dye with a natural isolate of Pseudomonas luteola and genetically modified Escherichia coli

The azo dye, Reactive Black B (RBB), was decolorized by a wild‐type isolate (Pseudomonas luteola), an Escherichia coli mutant (E coli NO3), and a recombinant strain (E coli CY1) harboring decolorizing genes from Rhodococcus sp. Decolorization of RBB by P luteola was inefficient with only 65% conversion, while color removal exceeded 90% for the two E coli strains, which were further investigated to determine the decolorization kinetics and operational stability. Kinetic studies applying a Monod‐type model showed that E coli NO3 was a more effective decolorizer for RBB than the CY1 strain. In addition, decolorization of RBB with the NO3 strain could tolerate higher temperatures and was more kinetically favorable over CY1. The optimal pH for decolorization was around 6.0–8.0 for NO3 and 8.0–10.0 for CY1. Decolorization of RBB was inhibited when the dissolved oxygen level exceeded 0.35 mg dm^?3 for both strains. E coli NO3 was more stable during repeated operations, whereas the decolorization activity of E coli CY1 slightly decreased when the strain was used repeatedly. Copyright © 2004 Society of Chemical Industry     

Decolorization of Direct Blue GLL with enhanced lignin peroxidase enzyme production in Comamonas sp UVS

BACKGROUND: The present work aims to study the production of lignin peroxidase (LiP) enzyme by Comamonas sp UVS using various media, and lignocellulosic waste materials, and its effect on decolorization of Direct Blue GLL (DBGLL). RESULTS: Yeast extract medium was found to be more effective for the production of LiP and also for the decolorization of DBGLL. The bagasse powder along with yeast extract induced LiP activity. Comamonas sp UVS decolorized DBGLL dye (50 mg L^?1) within 13 h at static condition in YE broth. It could degrade up to 300 mg L^?1 of dye within 55 h. The maximum rate (Vmax) of decolorization was 12.41 ± 0.55 mg dye g cell^?1 h^?1 with the Michaelis constant (Km) value as 6.20 ± 0.27 mg L^?1. The biodegradation was monitored by UV‐Vis, GC‐MS and HPLC. CONCLUSION: The use of agricultural by‐products for the activity enhancement of the ligninolytic enzymes is a cost effective process. It also resolves the problem of the disposal of agro‐residues. This system can be applied for the degradation of different recalcitrant compounds. Copyright © 2008 Society of Chemical Industry     

Power Generation and Electrochemical Analysis of Biocathode Microbial Fuel Cell Using Graphite Fibre Brush as Cathode Material

To improve cathodic efficiency and sustainability of microbial fuel cell (MFC), graphite fibre brush (GFB) was examined as cathode material for power production in biocatalysed‐cathode MFC. Following 133‐h mixed culturing of electricity‐producing bacteria, the MFC could generate a reproducible voltage of 0.4 V at external resistance (R_EX) of 100 Ω. Maximum volumetric power density of 68.4 W m^–3 was obtained at a current density of 178.6 A m^–3. Upon aerobic inoculation of electrochemically active bacteria, charge transfer resistance of the cathode was decreased from 188 to 17 Ω as indicated by electrochemical impedance spectroscopy (EIS) analysis. Comparing investigations of different cathode materials demonstrated that biocatalysed GFB had better performance in terms of half‐cell polarisation, power and Coulombic efficiency (CE) over other tested materials. Additionally, pH deviation of electrolyte in anode and cathode was also observed. This study provides a demonstration of GFB used as biocathode material in MFC for more efficient and sustainable electricity recovery from organic substances.     

Effects of Dodecyl Trimethyl Ammonium Bromide Surfactant on Decolorization of Remazol Blue by a Living Aspergillus versicolor Strain

The effect of dodecyl trimethyl ammonium bromide (DTAB) cationic surfactant on Remazol Blue reactive dye bioremoval properties of a growing Aspergillus versicolor strain in a molasses medium was investigated in a batch system as a function of pH, dye and surfactant concentrations. To determine the optimal pH value in the presence of 0.5?mM DTAB pH 3 to 7 was examined and pH 6 was selected. The dye concentrations of 50, 100, 200, 400 and 800?mg/L were examined with 0.5?mM DTAB and maximum decolorization occurred in 100?mg/L dye (98.8?%). The surfactant concentration of 0.1, 0.5, 1 and 2?mM DTAB was performed in 100 and 800?mg/L dye. The effect of surfactant concentration (0.1 to 2?mM DTAB) in a fungal growth experiment has shown that DTAB inhibited fungal growth. The decolorization was increased from 53.6?% (dry weight: 1.31?g/L) to 100?% (dry weight:0.93?g/L) while the surfactant concentrations were increased from 0.1 to 1?mM. A. versicolor (dry weight: 0.93?g/L) showed its maximum dye removal activity, namely 100?% in 100?mg/L dye with 1?mM DTAB at pH 6 in 3?days. The use of surfactants in biological wastewater treatment process will save energy and lower energy costs (such as the required energy for treat techniques) by shortening the incubation period. The results showed that the A. versicolor strain, which produces laccase enzyme, can effectively decolorize reactive dyes by the enhancement of DTAB. Surfactant enhanced decolorization technology is one of the feasible approaches to remove textile dye from wastewater.     

Synthesis of calix[6]arene based XAD‐4 material for the removal of reactive blue 19 from aqueous environments

This study describes the synthesis of calix[6]arene (C6) appended Amberlite XAD‐4 resin and its application for the removal of anthraquinone‐based reactive blue 19 (RB‐19) dye from aqueous environments. The C6‐resin 5 was characterized with various analytical techniques, including Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and elemental analysis. Adsorption experiments were carried out to investigate the effects of the pH, adsorbent dosage, electrolyte, contact time, and temperature on the adsorption of RB‐19 dye onto the C6‐resin 5. From the results, we observed that the percentage adsorption of the RB‐19 dye was highly dependent on the concentration of electrolyte and the pH of the solution. The maximum adsorption was achieved at pH 9. The thermal study demonstrated that the adsorption process was endothermic and spontaneous in nature. The isothermic study showed that the adsorption behavior could be better demonstrated by the Langmuir and Dubinin and Radushkevich isotherm model. From field studies, it has been concluded that C6‐resin 5 is an effective adsorbent for the removal of RB‐19 dye. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 776‐785, 2013