Activation of persulfate with hydrodynamic cavitation in the removal of atrazine: Regulating the concentration of OH and SO4− and the degradation mechanism

Hydrodynamic cavitation (HC) is a promising technology for the removal of organic pollutants because the collapse of cavitation bubbles can generate reactive oxygen species (ROS) from the water molecular. However, the controlled reactive oxygen species (ROS) in the HC process remains a challenge. This study has regulated the dominant radical species in HC-activated persulfate (PDS) systems by adjusting experimental conditions, such as PDS dosage and pH. Atrazine (ATZ) degradation of 95 % was achieved after 180 min in HC-activated PDS of 0.37 mM at pH = 6.8. The mineralization rate of ATZ was 44.9 % due to the synergistic effect of sulfate radical ( SO 4 − ) and hydroxyl radical ( OH). The main degradation pathways of ATZ were dealkylation products and ring-opening products. Increasing the PDS dosage to 3.7 mM, the degradation of ATZ was 94.0 % after 60 min with the dominant radical of SO 4 − , while the mineralization rate of ATZ was only 8.8 %. Correspondingly, when OH was the dominant radical in HC-activated PDS at pH = 3.5, the removal rate and mineralization rate of ATZ reached 97.5 % and 77.4 %, respectively. It is demonstrated that the contribution of ROS was difference in HC-activated PDS systems for the ATZ degradation and mineralization. The controlled strategy of ROS in HC-activated PDS systems offers a promising approach for effectively eliminating various organic pollutants in the wastewater.