Synthesis and characterization of bismuth gadolinium oxide/g-C3N4 heterojunction nano photocatalyst for efficient sunlight-driven purification of wastewater containing malachite green dye

Abstract

In this research, considering the problem of water pollution, efficient bismuthate nanostructures have been designed to destroy organic pollutants; and in the following, suitable strategies to improve the photocatalytic efficiency have been presented and analyzed. In this regard, BiGdO₃ nanoparticles were prepared by auto-combustion route using sucrose as fuel. A series of techniques including X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), Diffuse Reflectance Spectroscopy (DRS) to analyze the morphology, phase purity and optical properties of BiGdO₃ (BGO) samples are employed. Then, the obtained bismuthate nanostructures with an average size of 34.84 nm are used to form BiGdO₃/g-C₃N₄ (BGO/CN) nanocomposites with different content. According to BET analysis, the specific surface area of BGO/CN nanocomposites was found as 5.18 m²g⁻¹. According to DRS data, the BGO band gap (2.78 eV) decreases to 2.45 eV with CN incorporation. The obtained pure BGO nanostructures are studied in malachite green (MG) decomposition. Under optimal conditions , 0.10 g BGO degrades 97.27 % of 20 ppm MG. To investigate the photocatalytic ability of nanocomposites and to improve the use of sunlight, a comparative study is conducted between the light sources. Experimental results show that BGO/CN nanocomposites show higher pho tocatalytic activity (98.36 %) than pure BiGdO₃ and g-C₃N₄. In addition, the photodegradation mechanism of BGO/CN by scavenging experiments introduces •OH active radicals as the main factor in the photocatalytic process.