Gd2O3/CdS Nanocomposites were Synthesized for Photocatalytic Elimination of Methyl Blue (MB) Dye Under Visible Light Irradiation

Water contamination with hazardous dyes is a serious environmental issue that concerns humanity. A green technology to resolve this issue is the use of highly efficient photocatalysts under visible light to degrade these organic molecules. Adding composite and modifying shape and size on semiconductor materials are attempts to improve the efficacy of these compositions. The optical, microstructural and photocatalytic features of the compositions were investigated by several characterization procedures such as XRD, XPS, SEM, and TEM. Here, modifies Scherrer equation, Williamson–Hall (W–H), and Halder–Wagner method (H–W) have been used to investigate the crystal size and the micro-strain from the XRD peak broadening analysis. The average crystal size according to Modified Scherrer’s formula was 6.04–10.46 nm for pristine CdS and CdS/Gd2O3@GO, respectively. While the micro-strain (ɛ) corresponds to 3.88, 4.63, 4.03, and 4.15 for CdS, Gd₂O₃, CdS/Gd₂O₃, and CdS/Gd₂O₃@GO. It was also shown that the modest difference in average crystal size acquired by the Modified Scherrer and Halder–Wagner (HW) forms was related to differences in average particle size classification. As a result, the Halder–Wagner method was accurate in estimating crystallite size for the compositions. The average roughness is slightly changed from 4.4 to 4.24 nm for CdS/Gd₂O₃ and CdS/Gd₂O₃@GO, respectively. A kinetics investigation further revealed that the photocatalytic degradation of MB dyes was accompanied by a Langmuir isotherm and a pseudo-second-order reaction rate. The highest adsorption capacity (qe) determined for (type 1) CdS, Gd₂O₃, CdS/Gd₂O₃, and CdS/Gd₂O₃@GO adsorption was 5, 0.067, 0.027, and 0.012 mgg⁻¹, respectively. The R² values originated from the pseudo-second-order (type 2) for CdS, Gd₂O₃, CdS/Gd₂O₃, and CdS/ Gd₂O₃@GO were 0.904, 0,928, 0.825, and 0.977. As a result, the initial sorption rate (h) is altered between types 1 and 2. In type 2, the pseudo-second-order rate constant (k2) ranges from 0.005 for CdS to 0.011 for CdS/Gd₂O₃@GO. The Langmuir Hinshelwood and pseudo-second-order kinetic models describe the photodegradation process. The results demonstrate that the developed compositions can be used as a long-term substance for dye removal.