Anodic oxidation of a simulated effluent containing Reactive Blue 19 on a boron-doped diamond electrode

An electrochemical oxidation using a boron-doped diamond electrode has been tested for the treatment of solutions miming a real wastewater, containing the Reactive Blue 19 dye, taken after the rinse and softening bath from a typical reactive dyes process. This effluent is a complex mixture of dyes, electrolytes at high concentration, mainly chlorides or sulphates and carbonates together with dyeing auxiliaries.Electrolyses were conducted in an undivided electrolytic cell under galvanostatic conditions.The effect of carbonate has been extensively investigated as well as pH, temperature and current density. The efficiency of the process has been evaluated in terms of colour, chemical oxygen demand (COD) and total organic carbon (TOC) removal.Results show that colour removal was negatively affected by carbonates and favoured by both chlorides and additives while complete mineralisation was found to mainly depend only on temperature. The study of current density effect supports the hypothesis that discoloration mainly occurs via indirect oxidation mediated by electrogenerated active chlorine while COD and TOC removal is carried out by direct oxidation by means of hydroxyl radicals produced at BDD surface.

► Anodic oxidation of a simulated dyeing effluent.
► Colour removal mainly occurs via active chlorine oxidation.
► Carbonates negatively affect discoloration.
► Oxidation and complete mineralisation mediated by hydroxyl radicals.
► Mineralisation significantly enhanced by higher temperature.