Oxidative Degradation of Basic Red 29 by Persulfate Activated by Sulfur Composite Zinc

Abstract

Herein, a composite zinc formed by ZnO and different zinc sulfur species is synthesized via a simple reduction of zinc sulfate by sodium sulfite under air. The obtained product is found to be very efficient in the activation of persulfate (PS) when compared to commercial ZnO. Diluted PS at 2 mM in homogeneous system allows the degradation of 24.83% of Basic Red 29 (BR29) after 120 min at 40 °C. The addition of 5 mg of the composite zinc increases the yield to 74.89%, while commercial ZnO registers 50.21% under the same conditions. The effectiveness of the composite sample is found to be due to the presence of ZnS and SO32− species that act as dopants for PS activation. The degradation reactions follow the pseudo‐first order with both catalysts. The main components involved in the degradation process are superoxide radical followed by singlet oxygen and then sulfate radical. Further application of ultrasounds at 40 kHz and addition of H2O2 at 1 mM reduces the reaction time for total degradation to 40 min with the composite zinc and 70 min with commercial ZnO.