An investigation on polymer ion exchange membranes used as separators in low-energy microbial fuel cells

Platinum nanoparticles embedded into polyaniline on carbon cloth: improvement of oxygen reduction at cathode of microbial fuel cell used for conversion of medicinal plant wastes into bio-energy

A microbial fuel cell is a biological electrochemical system that extracts electrons stored in organic matter by oxidation using catalytic properties of microorganisms at bioanode. The major problem in such device, is however limited power production due to slow kinetic of oxygen reduction at cathode. It is worthwhile to develop new materials that fulfil these requirements. The polymerization of aniline onto carbon cloth for effective electrodeposition of platinum nanoparticles has been carried out by chronoamperometry and cyclic voltammetry. Three materials were thus elaborated, namely pristine carbon cloth, carbon cloth modified with platinum and carbon cloth modified by polymerization of aniline for immobilization of Pt-nanoparticles. The FTIR spectroscopy analysis revealed characteristic band located in 1720-1650 cm^-1, attributed to imine function, main component in skeleton of polymer PANI chain. The modified materials have been utilized as cathode in cell inoculated with medicinal plant wastes for improvement of oxygen reduction. Modified cathode with CC-PANI-Pt proved higher performances in all respects: increase of cell voltage from 338 to 765 mV and power density from 862 to 1510 mW/m² and abatement of COD of microbial inoculum leachate to 88%. Another feature of cell with modified cathode CC-PANI-Pt, was the enormous electric charge density harvested upon oxidation of 1 mL of acetate 7.62 C/cm² compared to that of cell with pristine CC cathode 0.54 C/cm². Nevertheless, coulombic efficiency for conversion of medicinal plant wastes into bioenergy was relatively lower 9%, making in evidence that elaborated electrochemical device was rather efficient and benificial environmentally than energetically.

Synthesis of nickel-based layered double hydroxide (LDH) and their adsorption on carbon felt fibres: application as low cost cathode catalyst in microbial fuel cell (MFC)

Following their successful utilization as novel bioanodes in Microbial Fuel Cells (MFCs), Layered Double Hydroxide (LDH) were tested in the present investigation, as promising cathodes to reduce electrons coming from oxidation of organic matter in the anode compartment, in the presence of oxygen used as successful oxidant. Therefore, the LDH samples Ni₃Al-LDH with the ionic ratio Ni²⁺/Al³⁺ equal to 3, were synthesized and added by adsorption to Carbon Felt (CF) fibres. They were then stored separately in three electrolyte solutions KCl, NiCl₂ and AlCl₃ used as catholytes in the MFCs. Effects of the active cationic sites located inside the Ni₃Al-LDH on these electrolytes, were discussed in terms of energies produced by these MFCs. The structure and morphology of the synthesized LDH, were studied by using the analytical techniques XRD, FTIRS and SEM, while the electrode performances of the LDH-electrodes were investigated with the electrochemical methods CV and EIS. It was revealed that the CF modified with Ni₃Al-LDH cathode and conditioned in the NiCl₂ electrolyte solution yielded the highest energy harvesting for the MFC (i.e. 3.2 µW/cm²). This power density output was similar to previous clean one-compartment MFC. However, it was less expensive than an Enzymatic Fuel Cell (45 µW/cm²), making in evidence the highest cost of the material. Thus, by taking into account these encouraging findings, the low cost materials used in MFCs held great promise for practical application in electrochemical power devices and therefore fruit waste treatment. Abbreviations: ACFC: Air Cathode Fuel Cell; ADEFC: Alkaline Direct Ethanol Fuel Cell; AFC: Alcaline Fuel Cell; BET: Brunauer-Emmett-Teller; BFC: Biological Fuel Cell; CF: Carbon Felt; CV: Cyclic Voltammetry; DGFC: Direct Glucose Fuel Cell; DMFC: Direct Methanol Fuel Cell; EFC: Enzymatic Fuel Cell; EIS: Electrochemical Impedance Spectroscopy; FC: Fuel Cell; FTIR: Fourier Transform Infra Red spectroscopy; LDH: Layered Double Hydroxide; MEC: Microbial Electrolysis Cell; MFC: Microbial Fuel Cell; Mg-Al- CO 3 2 -LDH: Layered Double Hydroxide Magnesium-Aluminium-Carbonate; Ni-Al-LDH: Layered Double Hydroxide Nickel-Aluminium; OCP: Open Circuit Potential; SEM: Scanning Electron Microscope; TG/DTA: ThermoGravimetric and Differential Thermal Analysis; XRD: X-Ray Diffraction.

Scratching and transplanting of electro-active biofilm in fruit peeling leachate by ultrasound: re-inoculation in new microbial fuel cell for enhancement of bio-energy production and organic matter detection

OBJECTIVE

An electro-active biofilm of Fruit Peeling (FP) leachate was formed onto the Carbon Felt (CF) bio-anode in a Microbial Fuel Cell (MFC), after functioning for a long time. The electro active-biofilm thus formed was then scratched by ultrasound and re-inoculated in a new leachate to be transplanted onto the bio-anode. This procedure allowed the microbial electron charge transfer and therefore the enhancement of the bio-energy production of the fuel cell.

RESULTS

By using the repetitive mechanical biofilm removal, re-suspension and electrochemically facilitated biofilm formation, the voltage was substantially increased. In effect, the voltage of the 1st G of biofilm, rose gradually and reached its maximum value of 65 mV after 10 days. Whilst the 2nd generation allowed to obtain the maximum voltage 276 mV and without any lag time. The DCO abatement using the 1st G biofilm was 68% greater than the 3rd G 26%. Besides, the electrochemical impedance spectroscopy characterization and cyclic voltammetry of bio-anode with 2nd G biofilm confirmed the ability of electro-active biofilm formation on a new support. The biofilm transplanted showed thus greater kinetic performance, with reduced lag time demonstrating the interest of the selection that took place during the formation of successive biofilms.

CONCLUSIONS

Despite the transplantation of the electro-active biofilm onto the bio-anode, the MFC still produced relatively lower power output. Nevertheless, it has been tested successfully for monitoring and detecting the oxidation of sodium acetate substrate in the very wide concentration range 0.0025-35 g/l.