Siberian Federal University

This study investigated the levels of generation of sulfate radical anion (SO4•–) and hydroxyl radical (•OH) under irradiation of deionized (DW) and natural surface water (NW) with single- and dual- frequency ultrasound at 120 kHz and 1.7 MHz with and without potassium persulfate. 4-chlorobenzoic acid (4-CBA) was used as a radical trapping agent. The degradation rate of 4-CBA increased in the raw 120 kHz<1.7 MHz<120 kHz+1.7 MHz, reaching a steady-state concentration •OH of 2.25×10–14 and 1.18×10–14 Mol/L in DW and NW, respectively. Despite the inhibition of radical generation in NW, dual- frequency ultrasound-activated persulfate was found to be the most efficient system. The competitive kinetics with methanol and tert- butanol revealed a predominant contribution •OH (on average 70 %) over SO4•– in both DW and NW. The obtained results indicate the prospects of using persulfate activated by dual-frequency ultrasound for developing novel methods of removal of organic pollutants from natural water and wastewater