Ultraviolet- and visible-light photocatalytic and sonophotocatalytic activities toward Congo red degradation using Ag/Mn3O4 nanocomposites

Herein, silver/manganese(II,III) oxide (Ag/Mn3O4) composites were used as photocatalysts to degrade the Congo red (CR) dye through photocatalysis (light) and sonophotocatalysis (light + ultrasound) under ultraviolet (UV)and visible-light irradiation. Mn3O4 was prepared via a conventional sol-gel method, and the composites containing Ag were synthesized with various Ag-to-Mn3O4 molar ratios via a hydrothermal technique. The assynthesized photocatalysts were characterized by X-ray diffraction, X-ray fluorescence, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, surface plasmonic resonance, Raman spectroscopy, nitrogen adsorption-desorption isotherm measurements, scanning electron microscopy, and transmission electron microscopy. The characterization results revealed that the Mn3O4 nanoparticles were successfully coupled with Ag nanoparticles and that the concentration of Ag nanoparticles influenced the composites' physicochemical properties. The catalytic activity was observed under optimum pH conditions. A substantial enhancement of the removal of CR was observed when ultrasound was used during the photodegradation process. The samples exhibited excellent stability in four-cycle reusability tests. The addition of a scavenger was also studied to observe the contribution of reactive species.

Automated summary

Silver/manganese(II,III) oxide composites were used as photocatalysts to degrade CR dye, with the addition of ultrasound significantly enhancing the removal rate. The composites showed good stability and could be reused multiple times.