Environmental applications of ultrasound activated persulfate/peroxymonosulfate oxidation process in combination with other activating agents

Ultrasonically activated persulfate (S2O82-, PS) or peroxymonosulfate (HSO5-, PMS) processes have sparked a lot of interest in the degradation of emerging contaminants in the recent years, because of their excellent potential and adaptability. In this review, the synergistic effects of ultrasound (US) and other activating agents such as heat, ultraviolet light (UV), electricity, and heavy metals were analyzed in order to make recommendations for commercial exploitation. Several designs of ultrasonic reactors in the direct or indirect mode of operation were discussed with possible use in the activation of PS/PMS for the degradation of refractory compounds. Applications of suitable sonoreactor configurations for PS/PMS activation in water treatment, disinfection, wastewater treatment (synthetic/real wastewater), soil, and sludge treatment were presented. It has been elucidated that the selection of optimized designs of sonoreactor considering the various parameters including geometric (type of acoustic device, number of transducers, configuration/arrangement of transducers) and operating parameters (power dissipation, irradiating frequency, duty cycle) is important to maximize the efficacy for PS/PMS activation. A systematic insight into the mechanism of US and PS/PMS combination as well as the synergistic effect of US/other activating agents on PS/PMS activation is also highlighted in this review. The work has clearly elucidated the key process intensification benefits in terms of higher oxidation capacity, reduced treatment times and cost of operation based on expected synergism in various combinations.