One-step co-precipitation synthesis, characterization, and enhanced photocatalytic performance of CaO/TiO2-supported γ-Al2O3 nanocomposites (NCs) in wastewater treatment

Abstract

Hybrid nanocomposites (NCs) have garnered significant attention for their potential applications, including photocatalysis, energy storage, and gas-sensing. This study reports the preparation, characterization, and photocatalytic activity of calcium oxide/titanium dioxide/gamma alumina (CaO/TiO₂/γ-Al₂O₃) NCs fabricated through a one-step co-precipitation processes. Different analytical tools, including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL), ultraviolet-visible spectroscopy (UV-Vis), and dynamic light scattering (DLS), were carefully applied to examine the structural, morphological, and optical properties of the obtained NPs and NCs. The XRD results exhibited an important improvement in the crystallinity and phase purity of γ-Al₂O₃ NPs with supporting CaO NPs and TiO₂ NPs. TEM and SEM analyses verified that the synthesized NPs and NCs have a spherical morphology with a decrease in particle size from 9.50 ± 1.2 nm to 8.21 ± 2.1 nm after the addition of CaO NPs. EDX analysis revealed the presence of the elements calcium, titanium, aluminum and oxygen (Ca, Ti, Al, and O) within the CaO/TiO₂/γ-Al₂O₃ NCs. Raman and FTIR spectra determined the functional groups of the prepared samples. The reduction of the PL intensity indicates that the recombination of the electron–hole pairs is decreased upon adding CaO NPs and TiO₂ NPs. DLS results showed the surface charge and particle distribution of the synthesized NPs and NCs. The degradation of methylene blue (MB) dye under ultraviolet UV irradiation for 200 min was employed to examine the photocatalytic activity of these samples. As shown in the results, the photocatalytic activity of γ-Al₂O₃ NPs, TiO₂/γ-Al₂O₃ NCs, and CaO/TiO₂/γ-Al₂O₃ NCs reached up to 45%, 79%, and 98%, respectively. It can be observed that the CaO/TiO₂/γ-Al₂O₃ NCs achieved higher degradation than the individual samples. These improvements in the observed photocatalytic performance can be linked to various parameters, including the charge separation and increased surface area. The incorporation of CaO and TiO₂ into γ-Al₂O₃ enhances its photocatalytic efficiency by improving charge separation and expanding the surface area. They also promote light absorption and surface reactivity, which help suppress and increase the number of available active sites. These results highlight that the CaO/TiO₂/γ-Al₂O₃ NCs can enhance photocatalytic performance, especially the degradation of organic pollutants in wastewater. This study is an important step toward further research to apply these NCs in medical therapy.