Sequential Design of Experiments for Removal of Methylene Blue Dye by Electrocoagulation Associated with Dissolved-Air System

Abstract

The present work presents a strategic sequential experimental planning to evaluate the removal of methylene blue dye from aqueous medium by electrocoagulation combined with dissolved air flotation. Effect of electrode pairs, electrode spacing, contact time, initial pH, voltage, and pressure were optimized according to the following response variables: color, final pH, turbidity, and dye removal. The best-achieved optimized conditions were: 4 pairs of electrodes, 2.5 cm spacing, electrolysis time of 203 min, initial pH 4, voltage of 32 V, and no pressure by dissolved air injection. Among the experimental results, it was possible to obtain a maximum removal of 95.1% of the dye. The analysis of the response surfaces showed that the initial pH has a great influence on the final characteristic of the treated effluent. Through the study of optimization, synthetic effluents have been obtained that meet the discharge standards according to the current Brazilian environmental legislation.