• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.3 no.2
• /
• pp.146-155
• /
• 2002

Surface complexation models employ mass law equations to describe the reaction of surface functional groups with ions in the solution and also Gouy-Chapman theory to consider the electrostatic effects in the surface reactions. In current surface complexation models, however, the coulombic factors used are not wholly consistent with the Gouy-Chapman model of the surface. This study was to provide the derivation of the coulombic term usually employed and then a revised coulombic term completely consistent with Gouy-Chapman Theory. The electrical potential energy. zF${\psi}$, in current surface complexation models is not consistent with the Gouy-Chapman theory with the potential gradient close to the charged surface but with the Donnan model with the uniform potential. Even though the new coulombic factor yielded lower surface potential, it provided worse fits for acid-base titration data of the goethite suspensions.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.317-320
• /
• 2013

• Journal of Microbiology and Biotechnology
• /
• v.11 no.5
• /
• pp.863-869
• /
• 2001

A systematic study of microbial fuel cells comprised of alkalophilic Bacillus sp. B-31 has been carried out under various operating conditions. A significant amount of electricity was generated when redox mediators were used. Among the phenothiazine-type redox dyes tested, azure A was found to be the most effective both in maintaining a high cell voltage and for the long-term operation. The maximum efficiency was and for the long-term operation. The maximum efficiency was obtained at ca. $50^{\circ}C$ giving an open circuit voltage of 0.7V. A small change in temperature did not significantly affect the cell performance, but a rapid decrease in performance was observed below $20^{\circ}C$ and above $70^{\circ}C$. It was noticeable that fuel cell efficiency and discharge pattern depended strongly on the carbon source used in the initial culture medium. Regardless of the initial carbon sources, only glucose and trehalose were utilized as substrates. Galactose, however, was not substantially utilized except when galactose was used in the initial medium. Glucose, in particular, showed $87\%$ coulombic efficiency, which was the highest value ever reported, when Bacillus sp. was cultured in a maltose-containing medium. This study demonstrates that highly efficient microbial fuel cells can be constructed with alkalophilic microorganisms by fine-tuning the operating conditions and by carefully selecting carbon sources in the initial culture medium.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2648-2651
• /
• 2008

In AC electrowetting, it has been reported that there is a flow inside droplets. The flow characteristics such as flow rate, direction and the pattern of streamline are altered according to the frequency range of applied voltage. However, the mechanism of the flow has not been explained yet. This work is concentrated on investigation of the flow mechanism when high-frequency voltage is applied to droplets. We propose that this phenomenon arises from the electro-thermal flow. A numerical analysis is performed for the needle-electrode-plane geometry in which the Coulombic force term is included in the Navier-Stokes equation. According to our analysis, electrical charge is generated due to conductivity gradient which is originated from the nonuniform Joule heating of fluid medium. The result of the analysis is compared with experimental result.

• Membrane Journal
• /
• v.27 no.5
• /
• pp.415-424
• /
• 2017

Commonly cation exchange membranes have been used for vanadium redox flow batteries. However, a severe vanadium ion cross-over causes low energy efficiency. Thus in this study, we prepared 3 different anion exchange membranes to investigate the effect on the membrane properties such as vanadium ion cross-over and long term stability. The base membranes were prepared by an electrolyte pore filling technique using vinyl benzyl chloride (VBC), divinylbenzene (DVB) within a porous polyethylene (PE) substrate. Then 3 different functional amines were introduced into the base membranes, respectively. These resulting membranes were evaluated by physico-chemical properties such as ion exchange capacity, dimensional stability, vanadium ion cross-over and membrane area resistance. Conclusively, TEA-functionalized membrane showed longest term stability than other membranes although all the membranes are similar to coulombic efficiency.