A study on the degradation of direct pink by the low-frequency ultrasonic irradiation

The ultrasonic degradation of direct pink was investigated in this study. Parameters affecting ultrasonic degradation degree such as ultrasonic power, pH, bubbling gas and the presence of inorganic salts, were examined. The results showed that the addition of inorganic salts (NaCl, CuSO₄) facilitated the degradation of direct pink while the addition of K₂CO₃ inhibited it. The degradation degree was enhanced significantly in the presence of saturated gases as listed here in decreasing order of effectiveness: argon > air > oxygen > nitrogen. The degradation degree of direct pink was largely influenced by pH value and boosted by acidic condition. The optimum degree could be achieved when pH value was 3.0 or when the sound power was 150 W. However, the degradability decreased notably in alkaline condition. Also, ultrasound/H₂O₂ technology was used, and the results showed that ultrasound/H₂O₂ has a better effect on the degradation than ultrasound alone or with H₂O₂ oxidation. After 120 minutes, the degradation degree could reach 78.0% under the optimum conditions, when the ultrasonic power was 150 W, 50 μL H₂O₂, CuSO₄ and argon atmosphere being added and the initial pH value of the model dye was 3.0.