Heterogeneous photocatalysis with wireless UV-A LEDs

The world is facing a water crisis and 80% of the generated wastewater is released without a proper treatment. Therefore, wastewaters are now seen as a valuable resource. In this line, wastewater treatment and reuse are being implemented globally [1]. Unfortunately, not all industries have an efficient wastewater treatment, being in the best cases only able to comply with the legal limits to discharge into municipal wastewater treatment plants or in natural water streams. Water reuse policies demand high treated water quality, ensuring no harm to human health and ecosystems [2]. To foresee a safe water reuse, Advanced Oxidation Processes (AOPs) seem to be one of the most appropriated technologies to achieve the desired water quality. The use of UV light enhances the system overall efficiency, in which light emitting diodes (LEDs) are rising comparing to traditional UV lamps. Nonetheless, by considering the commonly used wired systems, photons are scattered during the air path diminishing the treatment effectiveness.

In this work, a wireless UV-A LEDs (λ = 365 nm) lab-scale reactor (330 mL) powered by a resonant inductive coupling (RLC) system was built maximizing the UV photon absorption, being the energy inside the photoreactor supplied through a magnetic field generated by induction coils placed on the external wall [2, 3]. To this aim, it was firstly evaluated the best working frequency and then it was investigated the photocatalytic degradation of the textile dye, Reactive black 5, under different TiO₂, H₂O₂ and pollutant concentrations and pH values. The best operating parameters were found to be [TiO₂] = 500 mg L^-1 and [H₂O₂] = 100 mg L^-1, with an Electric Energy per Order (E_EO) of 17.6 kWh m^-3 order^-1. The wireless UV-A LEDs system proved to be efficient in the removal of Reactive black 5 with TiO₂ photocatalysis.

References

[1] R. Simhayov, N. Ohana-Levi, M. Shenker, Y. Netzer, Agric. Water Manag., 275 (2023).

[2] L.C. Ferreira, J.R. Fernandes, J.A. Peres, P.B. Tavares, M.S. Lucas, Environ. Res., 200 (2021) 111430108002.

[3] B. Burek, A. Sutor, D.W. Bahnemann, J.Z. Bloh. Catal. Sci. Technol. 7 (2017) 4977-4983.

Acknowledgments: The financial support was provided by OBTain project (NORTE-01-0145-FEDER-000084) and project INICIO - Setup of research infrastructure for closed circles of water, nutrients and energy in Portuguese agriculture (NORTE-01-0145-FEDER-072685), both co-financed by the European Regional Development Fund (ERDF) through NORTE 2020.