Sonochemical removal of naphthol blue black azo dye: influence of parameters and effect of mineral ions

Sonochemical degradation at 278 kHz of naphthol blue black (NBB, a diazo dye widely used in the textile and soap industries) has been investigated. The effects of different parameters and the influence of mineral matrix (bicarbonates ions and phosphates ions) on its sonodegradation have been evaluated. The influence of parameters linked to the pollutant (concentration: 0.50–97.32 lmol L^-1), to the technique (power: 20–100 W) and to the natural medium (pH 3–10.8; bicarbonate ions; phosphate ions) has been studied. The decolourisation rate of NBB increases when substrate concentration or ultrasound power increases. Bicarbonate ions at natural medium concentration (2.97 mmol L^-1) have a positive influence for low pollutant concentration (0.5–2.0 lmol L^-1), due to carbonate radicals. Phosphate ions may also improve the kinetics, but this effect depends on the pH domains. Furthermore, acid pH (pH 3) has a positive effect for high pollutant concentration, whereas basic pH (pH 10.8) has a positive influence at low pollutant concentration.

Keywords
Naphthol blue black; Azo dye; Ultrasound; Sonochemistry; Bicarbonates ions; Phosphate ions