Ultrasound-Promoted Abatement of Formaldehyde in Liquid Phase with Electrospun Nanostructured Membranes: The Synergy of Combined AOPs

Abstract

The present work investigates the effect of ultrasounds in the performance of combined advanced oxidation processes (AOPs) on the degradation of formaldehyde (HCHO)-polluted aqueous solutions for potential application in wastewater treatment. Different heterogeneous nanostructured catalysts based on TiO2 and FeSO4 for photocatalysis and the Fenton process were employed after electrospray deposition on electrospun nanofibrous membranes. Such systems were tested, without the use of any added hydrogen peroxide, by varying the combinations among the selected AOPs in a batch reactor configuration. The results show that, in the absence of a Fenton reaction, ultrasounds provided a significantly increased formaldehyde photocatalytic abatement, probably by increasing the concentration of active species through a different set of reactions while providing a favorable mass transfer regime by the cavitational effect. Due to the faster kinetics of the photo–Fenton process, thanks to its partial homogeneous nature, such a beneficial effect is more limited for the sono–photo–Fenton configuration. On the other hand, the employment of a sono–photocatalytic–Fenton process revealed a synergic effect that provided the best results, reducing the formaldehyde concentration to less than 99% after 240 min. Further analysis showed that, due to a mutual influence, only a tailored TiO2/FeSO4 ratio on the membranes was able to display the best performance.

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Recent Developments in Photoluminescent, Photothermal and Photocatalytic Nanomaterials

“…Thus, the Mo-doped Sv-ZnIn 2 S 4 exhibited a high hydrogen evolution rate of 5739 μmol g −1 h −1 with a high apparent quantum yield of 21.24% at 420 nm. Boaretti et al explored the effects of combinations of different advanced oxidation processes on the degradation of formaldehyde at a low concentration [ 12 ]. They demonstrated that ultrasound treatment improved the kinetics, producing a final abatement of formaldehyde and breaking the bottleneck of photocatalysis.…”