Colour removal from effluents with adsorbing structures generated by electrocoagulation using aluminum and iron electrodes
The presence of dyes in industrial effluents represents a serious issue in many countries. This type of effluent is mainly discharged by textile and pulp and paper mill industries. The discharge of such effluents causes excessive oxygen demand in the receiving water and the effluents need to be treated before any discharge. This study describes a new option for the removal of this type of pollutant, which is the decolourization with adsorbing structures generated by electrocoagulation using aluminum and iron electrodes. Three solid structures have been produced in a 10-2 mol NaCl•L-1 electrolyte solution. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses have shown that the structures produced using aluminum electrodes are constituted of bayerite (Al(OH)3), whereas the structures produced using iron electrodes are principally composed of magnetite (Fe3O4) and lepidocrocite (γ-FeO(OH)). The structures generated with both types of electrodes notably contain bayerite and goethite (α-FeO(OH)). Dye removal assays have been carried out in acid (pHi = 4.8) and alkaline (pHi = 9.8) solutions artifically polluted by diazoic dye ([Blue Trypan]i = 3.75 mg•L-1). The results demonstrated very high dye (94-99%) and COD (≤ 96%) removal yields, these removal percentages being sensitive to the solution pH.