Experimental study and mathematical modeling of the electrochemical degradation of dyeing wastewaters in presence of chloride ion with dimensional stable anodes (DSA) of expanded meshes in a FM01-LC reactor

In the present work an experimental study and mathematical modeling of 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 carried out. As anode five titanium expanded meshes coated with IrO2-SnO2 doped with Sb2O5 and five stainless steel expanded meshes as cathode were used. 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. The transient mathematical model for FM01-LC reactor takes into account the liquid flow pattern through axial dispersion coefficient (Dax), the electro-oxidation (pseudo first order kinetic) of chloride ions in the anode side (CCl−), the electrochemical reduction of chlorine oxidizing species (Cox) 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 (CCOD) and the color decay (Ccol). It was observed that the proposed mathematical model describe adequately the experimental evolution of different chemical species (CCl−, CCOD, and Ccol). Also the constant values determined under conditions here worked: kCl−=(3.2·103to4.9·103)s−1; kox=3.5·105to4.6·105s−1;kCOD=1.16·105to4.7·105m3mol−1s−1;kcol=1.2·103to9.98·103m3mol−1s−1; are in good agreement with the values reported in other previous works.