Mechanical agitation and ultrasound constructed in situ Fenton system: The role of atomic hydrogen for Fe(III) reduction

It has been reported that the ultrasonic agitation coupled system (US/A) has higher oxidation efficiency than the pure ultrasonic system (US), and the atomic hydrogen (H) and hydroxyl radicals (OH) produced by H2O cracking and in situ hydrogen peroxide (H2O2) can be significantly detected. In order to utilize the residual H2O2 and explore the role and fate of H, US/A/Fe(III) as an in situ Fenton oxidation system, was constructed in this study. The experimental results proved that the system can generate H2O2 in situ, and adding Fe(III) could significantly promote the oxidation of refractory organic pollutants. Quenching tests, probes experiments and EPR test were performed to successfully monitor the existence of OH. The contribution of H to Fe(III) reduction was speculated and confirmed. In addition, the kinetic model showed the decomposition rate of water molecule and the reduction rate of Fe(III) by H under different ultrasonic power. The effects of the factors (pH, coexisting substance, and actual water environment) on degrading organic pollutants were evaluated. Therefore, this work provides new strategy and mechanistic insight into in situ Fenton technique by coupling ultrasonic agitation and Fe(III) without external oxidants.