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The Cr(III) removal (3585 mg L−1) from real tanning discharges is herein conducted using an electro-precipitation process in a rotating cylinder electrode (RCE) reactor. A 1018-type carbon steel anode and two different cathodes (TiO2/RuO2 or 316L stainless steel, 316L SS) are tested within this process, using three current densities (10, 20 and 30 mA cm−2), and two initial pH values for the real solution. A synthetic solution is initially evaluated to analyze more ideal conditions in the reactor. The Cr(III) electroprecipitation is not favorable in the original pH of the real tannery wastewater (∼3.55) unlike the synthetic solution (pH 2.8), presumably since the Fe-Cr interaction is hindered by impurities in the solution, whereby the pH of the real discharge needs to be modified to pH 5 or 6. Residence times of 4800 (80 min) and 3600 s (60 min) using 30 mA cm−2 are enough to remove all the Cr concentration at pH 5 and 6, respectively. Energy consumptions of 10 and 7.5 kWh m−3 are calculated for these treatments, respectively. The precipitates are mainly comprised of Cr2FeO4(s) (Chromite) regardless of the experimental condition used in the removal process, followed by minor traces of Cr ( OH ) 3 ( s ) and CrO ( OH ) ( s ) . A reaction mechanism is proposed for the Cr(III) electro-precipitation relying on the thermodynamic diagrams, and characterizations of the precipitates.

Performance of lithium ion batteries whose electrodes are composed of particles of different sizes is studied. Simplified model developed in (Henquin and Aguirre, AIChE J. 2015; 61:90–102) is extended and the simulations are compared with experiments from the literature so as to validate this new model. The differences in current density observed in particles of different sizes, which are in contact, depend on particle size and state of charge. Internal particle to particle discharge currents are observed during relaxation times. A parametric study of the applied current and particle sizes of electrodes is performed to evaluate cell performance, with emphasis on cell voltage and final capacity measurement. The evolution of reaction rates on the surface of electrode particles and their corresponding states of charge are depicted. An analysis of relaxation times in terms of cell voltage, current density, equilibrium potentials, and overpotentials is included. © 2017 American Institute of Chemical Engineers AIChE J, 2017

The optimal design of Li-ion whole-cells is presented for different discharge operating constraints: constant current (CC), constant power (CP), and constant resistance (CR). In addition, a new Optimal Theoretical Operation Policy (OTOP) is derived resorting to Variational Calculation. When applied to cell discharge, this policy relates equilibrium voltage, applied current, and discharge time. The considered design variables comprise electrode thicknesses, porosity volume fractions, total solid volume fractions, and cell mass. The objective of the optimal design formulation is to maximize the total specific energy delivered for a set of given discharge time values with the aim of relating delivered energy to delivered power. The simultaneous optimization of multiple design variables under different operating conditions is efficiently achieved by using a simple phenomenological mathematical model that predicts the main aspects of these systems. The importance of this procedure is reflected in remarkable improvements to total specific energy delivered. The optimized whole-cell designs gained average improvements of more than 40%, depending on time discharge, when compared to the initial design taken from the literature; and when the optimal designs obtained under the different operating conditions are compared, an additional specific energy is obtained (OTOP results in the best operating condition, followed by CR, CC, and CP, with average differences of 7, 8, and 15%, respectively). Fil: Aimo, Corina Eva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; Argentina Fil: Henquín, Eduardo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina Fil: Aguirre, Pio Antonio. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; Argentina

A simplified electrochemical model is developed as a rapid tool to describe and maximize the specific capacity of Li+ ion cell fabrication through the variation of active (LiFePO4)/inactive (carbon conductor and binder) ratios. The model is able to capture the cooperation arising between liquid and solid phases determining cell performance. Thus, the capacity of first-principle models is extended for the first time to not only account for C-rates, but also electrode composition. The simplified nature of this model is obtained through the correct application of integral current balances, theoretical equations to adjust the conductivity of the electrolyte phase, and material balances in both the electrolyte phase and the solid phase of the electrode agglomerates. The model demands very low computational costs, whereby it can be efficiently solved in a spreadsheet. Simulations of experimental discharge plots reveal that the model adequately describes the cell behaviors at different composite contents and C-rates, using a minimum number of kinetic and transport parameters. The magnitudes of these parameters controlling cell performance depending on electrode composition are discussed.

The discharge and charge processes operation of lithium ion batteries is addressed. A simple phenomenological model is developed in order to predict all variables values. A set of algebraic and differential equations is derived taking into account salt and Lithium balances in electrodes, in the separator, and in particles. Balances are developed for finite volumes and appropriate average values of several variables such as concentrations, current densities, and electrochemical reaction rates are introduced. Definitions of current densities regarding volume fractions are critical issues in computations. Experimental values taken from the literature for discharge processes are predicted very accurately. Constant salt concentration in the separator can be assumed and consequently the model can be analytically solved. Charge and discharge times, initial cell capacity, lost capacity and relaxation times are estimated from simple equations. The limiting processes in cell discharge can be determined. Energy efficiency and capacity usage are quantified for cycles Fil: Henquín, Eduardo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo y Diseño (i); Argentina Fil: Aguirre, Pio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo y Diseño (i); Argentina