Optimization of the Performance of Ultrasonic Irradiation for the Treatment of Textile Wastewater: Synergetic Effect of US and Advanced Oxidation

摘要

Acoustic cavitation and the physical effects of ultrasound have gained recently much attention as promising techniques for the degradation of recalcitrant organics in water such as dye. This article primarily focuses on the removal of Indigo dye substances from real textile wastewater samples using standalone ultrasonication and advanced oxidation-assisted ultrasonication. The ultrasonic treatment was optimized using a central composite design (CCD) (29 experiments, 4 factors) as a response surface methodology. Various design experimental factors (frequency, pH, initial concentration, and temperature) were investigated. The design response considered was the COD removal after 2 h of sonication. The optimal values of frequency, pH, initial concentration, and temperature were 578 kHz, 2, 1000 mg/L, and 35℃ respectively. At the aforementioned optimal factors, the US showed ultimate COD and decolorization efficiency of 16% and 59%, respectively. To get more details, a kinetic model for the rate of COD removal using non-linear regression analysis was developed and the validity of the model was tested. The rate of COD removal followed pseudo-first-order kinetics for the sonicated textile wastewater. Moreover, the dye degradation intermediate products were identified by GC-MS analysis. The results showed that both Indigotine and Indigo carmine were broken down into smaller chemical compounds. Finally, the decolorization efficiency of dyes using oxidation-assisted US (H_2O_2 and Fenton process) and using physicochemical treatment (coagu-lation/flocculation) was measured. A maximum decolorization efficiency of 94% was achieved in the sample treated by Sono-Fenton using 15 mM ferrous sulfate.