Electricity Generation Using Sediment Microbial Fuel Cells with a Manganese Dioxide Cathode Catalyst

Wastewater treatment plants employ an energetically costly aerobic unit process to remove organic matter from municipal wastewater; this process is known as activated sludge. Microbial fuel cells (MFCs) present an anaerobic, energy-saving approach to wastewater treatment that results in electricity generation. However, MFCs are often limited by internal resistance from membrane fouling and slow cathodic oxygen reduction. This work examined an option to overcome these limitations-- adapting membrane-less sediment microbial fuel cells (SMFCs) for use with wastewater as an organic substrate by using floating carbon cloth air cathodes coated with an oxygen reduction reaction (ORR) catalyst. The performance of a platinum ORR catalyst at the cathode was compared to a manganese dioxide ORR catalyst and several additional cathode materials and reactor configurations were tested to optimize SMFC performance. The MnO2 catalyst, though significantly cheaper than platinum, was unable to sustain consistent high cathode potentials in wastewater over time

Friction coefficient between sea ice and different test surfaces

Among the projects of the scientific program of the F. S. Polarstern expedition of May 1984 along the coast of Labrador, Canada, was the measurement of the kinetic friction factor between various surfaces and sea ice samples collected at the site of the ship trials. The surfaces included a steel sheet coated with Inerta 160 to represent the ship hull, and base steel sheets of two roughnesses. The latter had previously been tested at CRREL with urea-doped ice, which is used as model ice in tests of icebreakers and other structures (Forland and Tatinclaux 1984). A friction test table was specially constructed by the Hamburgische Schiffbau- Versuchsanstalt (HSVA), the organization leading the expedition, and was instrumented on board the Polarstern. The ice samples used in the friction tests were cut from two large ice blocks gathered at the trials site, primarily Hebron Fjord; samples from the same blocks were used in two other projects, which were studies of ice structures (Gow 1984) and ice strength properties (Timco and Frederking, in prep.).NRC publication: Ye

Laboratory and field strudies of ice friction coefficient

Results of laboratory and field tests on the dynamic friction factor between ice (freshwater, urea-doped, and granular or columnar sea ice) and bare or Inerta-coated steel plates of various roughness averages are presented. Laboratory tests were made at three air temperatures, T = -15, -9, and -2 C, with either the ice sample towed over the test plate or a plate sample towed over the ice sheet. All field tests were made at T = -2 C to 0 C. The maximum test velocity was 30 cm/s, and the normal pressure was of the order of 10 kPa. From the test results it is concluded that viscous shear in the meltwater layer between ice and test plate may dominate when the test plate is very smooth, as proposed by Oksanen in his analytical model, but when the material roughness increases, mechanical shear of the ice crystals dominates.NRC publication: Ye

Field tests of the kinetic friction coefficient of sea ice /

"October 1985."Mode of access: Internet

Electricity generation from wastewater using a floating air cathode microbial fuel cell

Recovering energy from wastewater is an important frontier of environmental engineering and science. Of the many proposed strategies, microbial fuel cells (MFCs) provide a direct path to electricity generation. Here, we report MFCs equipped with floating carbon-cloth air cathodes modified with manganese oxide (MnOx) or Platinum nanoparticle oxygen reduction catalysts. The performances of these MFCs were compared using domestic wastewater in a configuration suitable for electricity generation from primary settling tanks. The open-circuit voltages of the Mn-MFCs decreased gradually over time while those of the Pt-MFCs remained stable indicating that Mn leaching from the electrodes was occurring. Over 90% of the MnOx catalyst was solubilized from the cathode surface within the first two weeks of operation. Initially, the Pt-MFCs did not generate as high of a current density as MnOx but after 55 days, Pt-MFCs had a higher average maximum power density during polarization than Mn-MFCs: 65.4 ± 4.6 and 48.4 ± 10.16 mW/m2 (based on anode geometric surface area), respectively. These results show the importance of evaluating promising alternative MFC cathode catalyst like MnOx in actual wastewater since it is difficult to predict how new catalysts designed to decrease cost yet increase the efficiency of the reduction of oxygen will respond in real-world wastewater applications. Keywords: Microbial fuel cell, Biofilm, Wastewater, Energy recovery, Catalys