**7. References**

Baker, R. (2002). Future direction of membrane gas separation technology. *Ind. Eng. Chem. Res.,* Vol.41, pp. 1393-1411

*A* membrane area [m2] or concentration wave amplitude

*M* initial concentration of K2CO3 in solution [kmol/m3]

*R* formation/consumption rate of a component [kmol/(m3s)]

**6. List of symbols** 

*C* concentration [kmol/m3] *D* diffusivity [m2/s]

*d* width/half-width of peak *H* thickness of membrane [m]

*k* reaction rate constant

*P* permeability coefficient *p* gas partial pressure [Pa] *q* volume of gas [m3]

*S* solubility [kmol/(m3Pa)]

*A, B* gas mixture components

*α* selectivity/separation factor

*Res.,* Vol.41, pp. 1393-1411

*Φ* contributions of a component into permeation flux

Baker, R. (2002). Future direction of membrane gas separation technology. *Ind. Eng. Chem.* 

*Δ* asymmetry parameter

*μ* molar mass [kg/kmol]

*L* length [m]

*m, n* integer number

*T* temperature [K]

**Subscripts/Superscribts**  ∞ infinite dilution

*d* downstream *liq* liquid phase *mem* membrane phase *SS* steady state *US* unsteady state *u* upstream *W* water

*γ* parameter

*φ* phase shift

frequency

**7. References** 

**Greek** 

*t* time [s] *x* coordinate [m]

*K* reaction equilibrium constant

*I* ionic strength of solution [kg ion/m3] *J* gas flow rate [kmol/s] or [m3/s] *j* pulse response function [kmol/(m2s2)]


**11** 

*Iran* 

**Effect of Mass Transfer on** 

*Babol Noshirvani University* 

**Performance of Microbial Fuel Cell** 

Mostafa Rahimnejad, Ghasem Najafpour and Ali Asghar Ghoreyshi

As the energy sources decrease and the climate conditions change, demand for new and clean sources of energy has increased (Hong et al., 2009; Li et al., 2010a). Fuel cells , as a high efficiency energy converting device, have attracted more and more attention recently with low/zero emission (Liu et al., 2006). Moreover, conventional sewage treatment requires high energy and capital cost so there is great interest for finding clean and sustainable energy with very low or zero emission and cost effective that is an alternative for treatment

Microbial fuel cells (MFCs) are one kind of fuel cell and also new source of energy. In MFCs, electrons are supplied from chemical bonds with the aids of microorganisms. Then the produced electrons are transported to anode surfaces and protons are moved through proton exchange membrane or salt bridge toward cathode (Wen et al., 2009). The electron flows through an electrical external circuit while anode is connected to cathode. The flow of electron has a current (I) and power (P) is resulted. The reduction of organic substances in anode was catalyzed by the living organism in anode chamber (Chen et al., 2008; Rahimnejad et al., 2009) Traditional MFC is consist of two separated chambers named cathode and anode ones. Oxidation of substrate by microorganisms leads to generation of electrons and protons in anaerobic anode compartment. (Rahimnejad et al., 2009). A typical biological fuel cell is

Several parameters affect on the performance of MFC, namely microbial inoculums, chemical substrates, mass transfer area, absence or existence of proton exchange materials, mechanism of electron transfer to the anode surface ,cell internal and external resistance, solution ionic strength, electrode materials and the electrode spacing (Park and Zeikus,

Direct electron transfers from anaerobic anode chamber to anode surface had shown to take place only at very low efficiency (Park et al., 2000; Lovley, 2006) . Electron transfer efficiencies in MFCs would be improved with the use of suitable electron mediators. Most MFCs use electron mediator component to improve the output of the cells. It has been reported in the literature that mediators are artificially added to anode chamber, such as Methylen blue (MB), Neutral red (NR), Thionin, Ferricyanide, Humic acid or Methyl viologen (Kim and Lee). The presence of artificial electron mediators are essential in some of MFCs to improve the performance of MFCs (Park and Zeikus, 1999; 2000) . But recently,

2000; Gil et al., 2003; Rosenbaum et al., 2007; Zhang et al., 2007; Li et al., 2010b)

**1. Introduction** 

technology (Appleby, 1988; Min et al., 2005).

shown schematically in Fig.1.

