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This work reports on the synthesis of a series of new sulfonated fluorine-containing aromatic polyamides with increasing degree of sulfonation (DS). The chemical structure of the resulting polymers was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance (1 H NMR) which evidenced the presence of amide and sulfonic groups in the proposed concentrations. Afterwards, we carried out a comparative study of heavy metal ion adsorption in membranes based on these aromatic polyamides. The main purpose was to determine the adsorption capacity of the prepared polymer membranes toward Pb 2þ and Hg 2þ in aqueous media at 30 C and pH neutral. The adsorption kinetics was evaluated with the pseudo-first-order and pseudo-second-order models. The adsorption kinetics in all the polyamide membranes followed the pseudo-second-order rate law for both heavy metal ions. It is observed that the adsorption capacities of all the polyamides toward Pb 2þ ions are higher than those of the Hg 2þ ions, and these capacities increase as the DS increases. The equilibrium adsorption amounts, q e , were 11.87 mg/g for Pb 2þ and 5.17 mg/g for Hg 2þ ions for the highest sulfonated polymer.

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A 3D single cell model of a proton exchange membrane fuel cell (PEMFC) was developed using a computational fluid dynamics software (Fluent 6.3.26). The effect of operating conditions such as pressure, temperature and humidity on the performance of fuel cell was investigated. The study was focused on the activation losses and ohmic resistance. Simulations were performed at three different temperatures 25, 50 and 80 Celsius degrees, at three different gas inlet pressures 1, 2 and 3 atmospheres, and three relative humidity's 25, 50 and 100%. The best results were found when the PEMFC worked at high operating conditions. The analysis showed good agreement with the literature data. The single cell model provided a clear understanding of the influence of operating conditions in the irreversibilities that take place in PEM fuel cells. IntroductionFuel cells convert the chemical energy of hydrogen directly into electricity. Their high efficiency and low emissions promote their use for supplying energy to the next generation of electric vehicles. Their modular design and scalability make them excellent candidates for a variety of applications. The main disadvantages for the massive commercialization are the lack of infrastructure and the high production cost. The design optimization is an important issue that can aid to reduce the production cost of PEMFC systems (1). However, the design optimization requires a good level of knowledge related to the basic processes that take place in PEMFCs. Modeling and Simulation have become in important tools to aid understanding the complex phenomena occurring in the active components of the fuel cell which are very difficult to obtain by experimental studies. Many research efforts have been initiated to develop realistic simulation models. Threedimensional models and detailed discussions about the contribution of mass transport, heat transfer and electrochemical kinetics in PEM Fuel Cells, have been described by H. J. Sung (2), K. W. Lum (3) and T. Berning (4). In this work, we present a model to reproduce and predict the influence of operating conditions like pressure, temperature and humidity on the performance and irreversibilities of fuel cells, considering a straight channel of 50 mm length with a mesh size optimized to reduce the CPU iterations time. ModelingThe single PEM fuel cell model was built in Gambit® 2.4.6 preprocessor. Dimensions and geometry are shown in Table I and Figure 1 respectively.