Catalytic and kinetic studies of CuFe 2 O 4 as a superior heterogeneous nanocatalyst for dye degradation and Cr(VI) reduction

The contamination of water resources by emerging contaminants, such as heavy metals and textile effluents, poses significant ecological and human health risks. Conventional effluent treatment plants may not effectively degrade all types of pollutants, resulting in the contamination of natural water resources. Photocatalysis, specifically the photo-Fenton reaction, has emerged as an efficient sustainable cost-effective method for the removal of pollutants. In this study, three batches (CF-1, CF-2, and CF-3) of copper ferrite nanoparticles (NPs) were synthesized and used as photocatalysts for the degradation of methylene blue (MB) dye and reduction of hexavalent chromium (Cr(VI)) under visible light. The CF-1, CF-2, and CF-3 required (90, 75, and 60 min.) different periods to reach a nearly similar degradation percentage, i.e., 90%, wherein the CF-3 batch demonstrated better catalytic activity. The successful synthesis of copper ferrite NPs was confirmed by XRD analysis which reveals the CuFe 2 O 4 phase. With the increased concentration of copper, the formation of the CuO phase alongside the CuFe 2 O 4 phase was observed. The CF-3 catalyst had a surface area of 44.496 m 2 /g according to BET studies. The catalyst exhibited a pore radius of 19.175 Å and an adsorption pore volume of 0.109 cc/g, as determined by the BJH method. TEM micrographs showed spherical-shaped NPs with sizes ranging from 55 to 60 nm. The photo-Fenton process was optimized by varying dye concentration, pH, catalyst, and hydrogen peroxide (H 2 O 2 ) dosages for MB degradation. The scavenger study reveals the contribution of the •OH radical over •O 2 − radical in the photo-Fenton process for MB degradation. The reduction of Cr(VI) was optimized by adjusting pH and Cr load. The CF-3 catalyst exhibited almost complete degradation of MB (32 mg/L) within 60 min and reduction of Cr(VI) (100 mg/L) within 20 min. The good reusability of the catalyst exhibits 71.4% MB degradation after four cycles and 78.34% Cr(VI) reduction after five cycles. The regression coefficient ( R 2 ) of the pseudo-second-order reaction was close to 1 and higher than the pseudo-first-order reaction. The catalyst achieved 0.0540 and 0.1047 1/min kinetic constant at pseudo-first-order reaction, while 0.0614 and 0.0497 L/mg.min kinetic constant was achieved at pseudo-second-order reaction for MB degradation and Cr(VI) reduction. These kinetic studies proved that the dye degradation and chromium reduction follow the pseudo-second-order reaction ( R 2 ). The overall study demonstrates the promising potential of magnetic CF-3 nanoparticles as efficient catalysts for industrial applications in dye degradation and Cr(VI) reduction. Graphical abstract