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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. [ABSTRACT FROM AUTHOR]

Environmental restoration because of the occurrence of harmful organic substances in our environment has received widespread attention amongst the researchers. Wastewater containing nitro-aromatic compounds and organic dyes are recently recognized as a new danger due to their toxicity towards all forms of living organisms. It is urgently needed to remove organic dye from our water systems in an efficacious manner for the purpose of both drinking and wastewater management. Binary MoS2 nanosheets@ZIF-8 nanocomposite was synthesized by hydrothermal method. The characterization techniques such as PXRD, XPS, EDS, FE-SEM, TEM, UV-DRS and PL were performed to investigate the structure, composition, morphology and optical properties of the synthesized nanocomposite. The catalytic activity of MoS2 nanosheets@ZIF-8 was tested by reduction of Picric acid (PA) in presence of NaBH4 and the photocatalytic degradation of Crystal Violet (CV) under visible-light which is not reported in any literature till date, to check the application of the synthesized nanocomposite for wastewater remediation. Original ZIF-8 had a band gap of 5.2 eV, however incorporation of MoS2 nanosheets on the ZIF-8 phase narrowed down the band gap of the MoS2 nanosheets@ZIF-8 composite to 3.2 eV. MoS2 nanosheets@ZIF-8 composite showed significantly high degradation of CV ~ 96% under visible light at optimum conditions of catalyst amount = 16 mg, dye concentration = 25 ppm and pH = 10. The degradation of CV followed first order kinetics with a first order rate constant of 0.0947 min−1. The as-synthesized catalyst showed good recyclability by showing a degradation efficiency of 85% till the fifth cycle. In addition to the photocatalytic degradation of CV, the MoS2 nanosheets@ZIF-8 displayed significantly high catalytic activity for the reduction of PA in presence of NaBH4 with a reduction efficiency of 96.26% and an apparent rate constant value of 2.7 × 10–3 s−1 in 20 min. The MoS2 nanosheets@ZIF-8 nanocomposite emerged as promising material with high catalytic activity in applications involving wastewater management. [ABSTRACT FROM AUTHOR]

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Conversion of carbon-rich waste biomass into valuable products is an environmentally sustainable method. This study accentuates the synthesis of novel SnO2 QDs@g-C3N4/biochar using low-cost sawdust by applying the pyrolysis method. Morphology, structure, and composition of the synthesized SnO2 QDs@g-C3N4/biochar nanocomposite were characterized using SEM (scanning electron microscope), TEM (transmission electron microscope), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), FT-IR (infrared spectroscopy) and PL (photoluminescence) spectroscopy. The average diameter of the SnO2 QDs was measured from TEM and found to be 6.79 nm. Optical properties of the as-synthesized SnO2 QDs@g-C3N4/biochar were characterized using UV–visible spectroscopy. The direct band gap of synthesized SnO2 QDs@g-C3N4/biochar nanocomposite was calculated from Tauc's plot and found to be 2.0 eV. The fabricated SnO2 QDs@g-C3N4/biochar photocatalyst exhibited outstanding photocatalytic degradation efficiency for the removal of Rose Bengal (RB) and Methylene Blue (MB) dye through the Advanced Oxidation Process (AOP). The synthesized photocatalyst showed a degradation efficiency of 95.67% for the removal of RB under optimum conditions of 0.3 mL H2O2, photocatalyst dosage of only 0.06 gL−1, and 15 ppm initial RB concentration within 80 min, and 94.5% for the removal of MB dye with 0.5 mL of H2O2, 0.08 gL−1 of the fabricated photocatalyst and 6 ppm of initial MB concentration within 120 min. The photodegradation pathway followed the pseudo-first-order reaction kinetics with a rate constant of 0.00268 min−1 and 0.00163 min−1 for RB and MB respectively. The photocatalyst can be reused up to the 4th cycle with 80% efficiency. [ABSTRACT FROM AUTHOR]