Preparation of BiFeO3 and photodegradation of tetracycline pollutant in the UV-heterogeneous Fenton-like system

Box-Behnken modeling and optimization of visible-light photocatalytic removal of methylene blue by ZnO-BiFeO3 composite

Box-Behnken experimental design was utilized to model and optimize the photocatalytic removal of methylene blue (MB) using ZnO-BiFeO₃ composite under visible light (LED). Three catalysts with different ZnO:BiFeO₃ molar ratios (2:1, 1:2, and 1:1) were synthesized successfully using the hydrothermal method. The structural, morphological, and optical properties of the synthesized photocatalysts were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectra (FT-IR), Ultraviolet Visible Spectrometer (UV-vis), Transmission Electron Microscopy(TEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Photoluminescence (PL) Spectrophotometry. FESEM showed the relatively uniform distribution of BiFeO₃ crystalline particles on ZnO ones. UV-vis analysis showed that the photocatalytic performance of pure ZnO and BiFeO₃ under visible light irradiation is weak, while ZnO-BiFeO₃ with a 2:1 molar ratio composite with a bandgap of about 2.37 eV showed high performance. This improved photocatalytic activity may be due to the heterogeneous synergistic effect of the p-n junction. In order to optimize the experimental conditions, four factors of initial MB concentration (5 to 20 mg/L), pH (3 to 12), catalyst dosage (0.5 to 1.25 mg/L), and light intensity (4 to 18 W) were selected as independent input variables. Box-Behnken experimental design method (BBD) suggested a quadratic polynomial equation to fit the experimental data. The results of the analysis of variance (ANOVA) confirmed the goodness of fit for the suggested model (predicted- and adjusted-R² 0.99). The optimum conditions for maximizing the photocatalytic MB degradation were found to be an initial MB concentration of 11 mg/L, pH of 11.7, catalyst dosage of 0.716 mg/L, and light intensity of 11.4 W. Under the optimum conditions, the highest photocatalytic MB degradation of 62.9% was obtained, which is in reasonable agreement with the predicted value of 69%.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

A serious threat to human health and the environment worldwide, in addition to the global energy crisis, is the increasing water pollution caused by micropollutants such as antibiotics and persistent organic dyes. Nanostructured semiconductors in advanced oxidation processes using photocatalysis have recently attracted a lot of interest as a promising green and sustainable wastewater treatment method for a cleaner environment. Due to their narrow bandgaps, distinctive layered structures, plasmonic, piezoelectric and ferroelectric properties, and desirable physicochemical features, bismuth-based nanostructure photocatalysts have emerged as one of the most prominent study topics compared to the commonly used semiconductors (TiO₂ and ZnO). In this review, the most recent developments in the use of photocatalysts based on bismuth (e.g., BiFeO₃, Bi₂MoO₆, BiVO₄, Bi₂WO₆, Bi₂S₃) to remove dyes and antibiotics from wastewater are thoroughly covered. The creation of Z-schemes, Schottky junctions, and heterojunctions, as well as morphological modifications, doping, and other processes are highlighted regarding the fabrication of bismuth-based photocatalysts with improved photocatalytic capabilities. A discussion of general photocatalytic mechanisms is included, along with potential antibiotic and dye degradation pathways in wastewater. Finally, areas that require additional study and attention regarding the usage of photocatalysts based on bismuth for removing pharmaceuticals and textile dyes from wastewater, particularly for real-world applications, are addressed.

Removal of Tetracycline Hydrochloride from Water by Visible-Light Photocatalysis Using BiFeO3/BC Materials

It is widely considered that photocatalysis is an effective and eco-friendly method of dealing with organic pollutants dissolved in water. Nonetheless, photocatalysts still have some drawbacks, such as poor visible-light absorption, easy recombination of photogenerated charge carriers, and limited active sites. In this study, bismuth ferrite coupled with biochar material (BiFeO3/BC) was simply synthesized, and its photocatalysis reactivity was systemically examined under an irradiation of λ > 400 nm. The experimental results showed that under a relatively acidic environment, the removal rate of tetracycline hydrochloride reached 95%. Using a variety of characterization investigations, we analyzed the morphology structure and chemical composition of BiFeO3/BC. In consideration of simple preparation and high respondence toward visible light, further explorations of BiFeO3/BC and its properties and optimized degradation conditions are worthwhile.