Enhanced photocatalytic degradation of reactive blue 21 dye and textile dyeing effluent by synthesized SmFeO3-rGO photocatalyst in combination with ultrasonication: Characterization and performance evaluation

Abstract

This research aimed to synthesize SmFeO3 and SmFeO3-rGO photocatalysts via an ultrasound-assisted sol-gel technique. The synthesized photocatalysts were characterized through various analytical technique including XPS, XRD, FESEM with EDX, FTIR, PL, UV-DRS LC-MS, Mott Schottky Plot, and BET analysis. The study evaluated the photocatalytic degradation efficiency of Reactive Blue 21 (RB21) using these synthesized photocatalysts, and the influence of operating factors such as solution pH, catalyst dose, and initial dye concentration. In order to enhance the activity of the photocatalyst, a combination of ultrasonication (US) and ultraviolet (UV) irradiation, were used, and their respective results have been reported in the present study. The RB21 degradation followed first-order kinetics, achieving a rate constant of 8.7 × 10−3 min−1. Over 68.82 % degradation was noted under optimal conditions, utilizing 20 mg/L SmFeO3 catalyst at a pH of 7.1. Using SmFeO3-rGO with an optimal molar ratio of rGO to SmFeO3 (1:1) achieved over 92.37 % degradation in 120 min. However, the sonophotocatalytic approach resulted in 99.41 % degradation within 30 min. The mineralization of textile dyeing effluents using sonophotocatalytic method observed significant COD and TOC reductions of 78.3 % and 75.9 % respectively in 30 min treatment. The SmFeO3-rGO nanophotocatalyst exhibited reliable degradation performance across five cycles. The LC-MS analysis provides a detailed view into the degradation pathway of RB21 through sonophotocatalysis. The combined ultrasonication and photocatalytic oxidation strategy yielded superior energy efficiency (4.45 × 10−6 mg/J) as compared to UV, US, and UV + SmFeO3-rGO methods.