In the present work a mathematical model to describe the indirect electrochemical oxidation of dyeing wastewaters in presence of chloride ion in a FM01-LC reactor in undivided mode coupled to Continuous Stirring Tank (CST) was implemented. The FM01-LC reactor was modeled with the Nernst-Planck equations in order to takes into account the dispersion, migration, and convection terms; the Poisson equations (through flow mode) for describe the potential distribution in solution, and the electro-oxidation (pseudo first order kinetic) of chloride ions in the anode side (C_Cl^-), the electrochemical reduction of chlorine oxidizing species (C_ox) under mass transport control (mass transfer coefficient) in cathode side; while in the CST the chemical oxidation reactions between active chlorine species and organic matter through homogeneous second order kinetics were considered, which were evaluated through consumption of the chemical oxygen demand (C_COD) and the color decay (C_col). The reactor operated as a batch recirculation system under galvanostatic conditions, the electrolyses were carried out at two current densities, 132 and 200 A m^-2, with 1.0 mM of indigo carmine dye and 0.05 M of NaCl; four liquid flow rates: 0.9, 1.8, 2.7, and 3.6 L min^-1 were used. As anode five titanium expanded meshes coated with IrO₂-SnO₂ doped with Sb₂O₅ and five stainless steel expanded meshes as cathode were used [1].

Figure 1(a) shows the simulation of the (a) chlorine oxidizing species (C_ox) without the presence of dye, and the experimental and mathematical prediction: (b) the chloride ion, C_Cl^-, consumption; (c) the color, C_col, removal, and (d) the chemical oxygen demand, C_COD, decay at four liquid flow rates: 0.9, 1.8, 2.7, 3.6 L min^-1 and a current density of 132 A m^-2 (i=5.0 A).

It can be observed that the proposed mathematical model describe adequately the experimental evolution of different chemical species (C_ox, C_Cl^-, C_COD, and C_col).