Development of a novel and robust CuO-Co3O4@Biochar nanocomposite using Terminalia chebula leaf extract for reduction of nitro compounds and photodegradation of single and binary mixture of organic contaminants

In this work, Terminalia chebula leaf extract was used to synthesize CuO-Co₃O₄ nanoparticles, which were then embedded in a rice straw biochar. This new biochar-based nano-catalyst is used to photocatalytically degrade a variety of dyes (Eosin Y, Trypan Blue, Crystal Violet, Methylene Blue, Brilliant Green), as well as a binary mixture of Eosin Y and Trypan Blue dyes. It is also used for the catalytic reduction of nitro compounds (4-NP, 3-NP, and Picric acid). To ascertain the structure, composition, and morphology of the CuO-Co₃O₄@BC photocatalyst, various analytical techniques were employed, including Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) spectra, Energy Dispersive X-ray analysis (EDX), Brunauer–Emmett–Teller (BET) analysis, and High-Resolution Transmission Electron Microscopy (HRTEM). The optical properties of the nanocatalyst sample were accurately assessed by the use of UV-Diffuse Reflectance Spectroscopy (UV-DRS). The as-synthesized nanocatalyst’s photocatalytic capacity was assessed by observing dye degradation in the presence of visible light. It suggests a significant reduction in the rate of recombination of electrons and holes and therefore better charge separation from the catalyst optical properties. It was discovered that the efficient photocatalytic activity of the nanocatalyst had been brought about as a result of the synergistic interactions that had occurred between the different moieties. The growing organic water pollutants Trypan Blue were found to deteriorate to 96.80 ± 1.25% in 21 min and Eosin Y to 98.12 ± 1.42% in 30 min by the photocatalyst under visible light irradiation. For the photodegradation, pseudo-first-order kinetics were employed, with specific reaction rate constant of 0.1068 min⁻¹ and 0.1429 min⁻¹ for EY and TB, respectively. Studies have also been conducted to determine the effects of additional variables on deteriorating performance, such as water matrices, beginning concentration, catalyst dose, and contact length. With high catalytic characteristics, the developed CuO-Co₃O₄@BC catalyst completes the reduction reactions of 4-NP, 3-NP, and Picric acid in 3, 2.5, and 5 min, respectively. An affordable CuO-Co₃O₄@BC is a potential catalyst for turning harmful nitro chemicals into useful products. It also serves as a nano photocatalyst that is stable, can be used again, and is cost-effective.