Sono-electrochemical decolorization and removal COD of Disperse-yellow-7 dye in aqueous solutions

Abstract

The sono-electrochemical decolourization and removal of disperse yellow 7 (DY7, 4-[4-(Phenylazo) phenylazo]-o-cresol) in aqueous solutions was investigated with different concentrations of NaCl and CaCl₂ (0.02, 0.05, 0.1, and 0.2 mol/L) as electrolytes, treatment times, and DY7 concentrations. The combination of electrochemistry (EC) and ultrasound (US) was called the sono-electrochemical (EC_US) process, and it shows a higher treatment efficiency than each parent technique alone. CaCl₂ is more effective than NaCl at the same concentrations. At the dose of DY7 at 25 ppm, the EC_US method (NaCl or CaCl₂ 0.1–0.2 mol/L, frequency 20 kHz, electrodes of TiO₂ and RuO₂-IrO₂-TiO₂) entirely removed the dye from aqueous solutions (100% colour and 100% COD) within a 45 min treatment. This technique could be a valuable alternative for treating dyeing wastewater or other refractory organic compounds in wastewater.