Optimisation of the electrochemical and UV combined treatment to remove colour and organic halogenated compounds of textile effluents

Different electrochemical oxidation and UV irradiation treatment conditions were studied to improve the removal of colour and organic halogenated compounds of textile effluents wastewater so as to minimise their environmental impact. Synthetic dyeing effluents containing a reactive dye (CI Reactive Black 5, Procion Crimson H-EXL, Procion Navy H-EXL, Procion Yellow H-EXL and Procion Blue H-EXL) and Na2SO4 as dyeing electrolyte were studied. Ti/Pt oxides electrodes at different current densities (3, 6, 12, 24 and 40 mA/cm2) and three UV irradiation lamps (6 and 9 W; 254, 360 and 365 nm maximum emission) were used. Results showed that total colour and organic halogenated compounds removal were achieved by UV irradiation after electrochemical treatment. A clear influence of current density and the type of UV lamp on colour removal was found, being the submerged lamps into the dye solution the most efficient. Kinetic constants of the UV irradiation step were calculated.

► Total colour removal can be achieved by UV irradiation after an EC treatment.
► UV irradiation after EC treatment improves halogenated compounds removal.
► UV irradiation allows application of low current densities in the EC treatment.
► Intensity, application position and λ of the UV light influence UV efficiency.