Methylene blue decolorization and mineralization by means of electrochemical technology at pre-pilot plant scale: Role of the electrode material and oxidants

In this work, a synthetic effluent containing methylene blue has been treated by electrochemical oxidation (EO) process at pre-pilot plant scale using a filter-press electrochemical cell reactor. Electrochemical experiments were carried out using Ti/Pt and Ti/IrO₂-Ta₂O₅ anodic materials in the presence or absence of chloride ions to study the influence on the decolorization and mineralization of the different oxidant species electrogenerated in situ. The electrochemical experiences have been carried out at different applied current densities (j = 20, 40 and 60 mA cm^-2) to evaluate the effect of this controlling parameter on the degradation efficiency and the operational energy consumption. Under optimal treatment conditions of 40 mA cm^-2 in 0.05 M of Na₂SO₄ at pH 6.0, solutions of 100 mg L^-1 of methylene blue were completely decolorized obtaining 86.0 % of COD abatement after 360 min of electrolysis. The determination of energy consumption allowed to estimate operational costs about 13.36 US$ m^-3. The results obtained provide valuable information regarding the EO process scaling-up, aiming the application of electrochemical technologies to treat actual effluent at real scale.