Synergetic decolorization of azo dyes using ultrasounds, photocatalysis and photo-fenton reaction

Antonis Maroudas; Pavlos K Pandis; Anastasia Chatzopoulou; Lambros-Roland Davellas; Georgia Sourkouni; Christos Argirusis

doi:10.1016/j.ultsonch.2020.105367

Synergetic decolorization of azo dyes using ultrasounds, photocatalysis and photo-fenton reaction

Ultrason Sonochem. 2021 Mar:71:105367. doi: 10.1016/j.ultsonch.2020.105367. Epub 2020 Oct 20.

Authors

Antonis Maroudas¹, Pavlos K Pandis¹, Anastasia Chatzopoulou¹, Lambros-Roland Davellas¹, Georgia Sourkouni², Christos Argirusis³

Affiliations

¹ School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechneiou St., Zografou Campus, 15780 Athens, Greece.
² Clausthal Centre for Materials Technology (CZM), Clausthal University of Technology, Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany.
³ School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechneiou St., Zografou Campus, 15780 Athens, Greece; Clausthal Centre for Materials Technology (CZM), Clausthal University of Technology, Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany. Electronic address: amca@chemeng.ntua.gr.

Abstract

In the present work, ultrasound irradiation, photocatalysis with TiO₂, Fenton/Photo-Fenton reaction, and the combination of those techniques were investigated for the decolorization of industrial dyes in order to study their synergy. Three azo dyes were selected from the weaving industry. Their degradation was examined via UV illumination, Fenton and Photo-Fenton reaction as well as ultrasound irradiation at low (20 kHz) and high frequencies (860 kHz). In these experiments, we investigated the simultaneous action of the ultrasound and UV irradiation by varying parameters like the duration of photocatalysis and ultrasound irradiation frequency. At the same time, US power, temperature, amount of TiO₂ photocatalyst and amount of Fenton reagent remained constant. Due to their diverse structure, each azo dye showed different degradation levels using different combinations of the above-mentioned Advanced Oxidation Processes (AOPs). The Photo-Fenton reagent is more effective with US 20 kHz and US 860 kHz for the azo dyes originated from the weaving industry at pH = 3 as compared to pH = 6.8. The combination of the Photo-Fenton reaction with 860 kHz ultrasound irradiation for the same dye gave an 80% conversion at the same time. Experiments have shown a high activity during the first two hours. After that threshold, the reaction rate is decreased. FT-IR and TOC measurements prove the decolorization due to the destruction of the chromophore groups but not complete mineralization of the dyes.

Keywords: AOPs; Azo dyes; Organic pollutants; Photo-Fenton; Sonophotocatalysis.