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Nanosized ceria (CeO2) and a graphitic carbon nitride-loaded ceria (CeO2/GCN) nanocomposite were synthesized using a straightforward and efficient method and characterized by XRD, FTIR, SEM, TEM, TGA, and BET analyses. These techniques confirmed that CeO2 was effectively supported on the surface of GCN, with particle sizes of the CeO2/GCN composite in the range of 10–15 nm and a pore size of 3.33 nm. The photocatalytic activity of the CeO2/GCN nanocomposite and CeO2 NPs in the degradation of methyl red dye under sunlight radiation was studied using UV–visible spectroscopy. A noticeable red shift in the CeO2/GCN nanocomposite compared to pure CeO2 NPs suggests a reduction in its band gap energy, calculated at 3.90 eV for CeO2 NPs and 2.97 eV for the CeO2/GCN nanocomposite. This band gap reduction enhances the photocatalytic degradation process, achieving a removal efficiency of 99.92% within a short irradiation time of 40 min for the CeO2/GCN nanocomposite, compared to 69.47% for CeO2 NPs. These findings indicate that graphitic carbon nitride significantly enhances the photocatalytic properties of CeO2 NPs. [ABSTRACT FROM AUTHOR]

In the present work, the adsorption mechanism and capacity of MWCNTs/CoFe2O4 nanocomposite as an adsorbent were investigated. Levofloxacin (LFX), a widely used antibiotic, was selected as a hazardous model contaminant in aqueous solutions. The surface and inner characterization of MWCNTs/CoFe2O4 was obtained via SEM/TEM, XRD, BET/BJH, and pHPZC. These analyses indicated that MWCNTs/CoFe2O4 possess excellent surface and pore characteristics, e.g., specific surface area, pore volume, and mean pore diameter, which were 72 m2/g, 0.51 cm3/g, and 65 nm, respectively. The results demonstrate that by supplementing 1 g/L of MWCNTs/CoFe2O4 at experimental conditions of pH value of 5, temperature of 30 °C, initial LFX concentration of 50 mg/L and mixing time of 90 min, a significant outcome of 99.3% removal was achieved. To identify the phenomenon of adsorption, the thermodynamic parameters of ΔH° and ΔS° were calculated, which indicated that the nature of LFX adsorption onto MWCNTs/CoFe2O4 nanocomposite was endothermic and spontaneous. Nine isotherm models, including four two-parameter and five three-parameter models, were investigated. In addition, the regression coefficient as well as five error coefficient models were calculated for nonlinear isotherm models. According to the goodness of fit tests, the equilibrium data were well coordinated with the Freundlich and Sips isotherms. The kinetics study showed that the LFX adsorption data well fitted with pseudo-second-order model, and the adsorption of LFX molecules occurred through several stages from surface to intraparticle diffusion. In conclusion, the present work evinces that LFX wastewater can be efficiently treated via an adsorption process using a MWCNTs/CoFe2O4 nanocomposite. [ABSTRACT FROM AUTHOR]

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide–tin oxide nanocomposite (NiO-SnO2 NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles' morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV–visible diffuse reflectance spectroscopy (UV–vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO2 NC was evaluated by monitoring the degradation of MO in aqueous solution under irradiation with full light spectrum. The effects of calcination temperature, pH, initial MO concentration, and catalyst dose were all assessed to understand and optimize the physicochemical and photocatalytic properties of NiO-SnO2 NC. Results: NiO-SnO2 NC was successfully synthesized via a biological route using F. elastica leaf extract. XRD showed rhombohedral NiO and tetragonal SnO2 nanostructures and the amorphous nature of NiO-SnO2 NC. Its degree of crystallinity, crystallite size, and stability increased with increased calcination temperature. SEM depicted significant morphological changes with elevating calcination temperatures, which are attributed to the phase conversion from amorphous to crystalline. The elemental analysis and colored mapping show the formation of highly pure NiO-SnO2 NC. FTIR revealed a decrease in OH, and the ratio of oxygen vacancies at the surface of the NC can be explained by a loss of its hydrophilicity at increased temperatures. All the NC samples displayed significant absorption in the visible region, and a blue shift is seen and the energy band gap decreases when increasing the calcination temperatures due to the dehydration and formation of compacted large particles. NiO-SnO2 NC degrades MO, and the photocatalytic performance decreased with increasing calcination temperature due to an increase in the crystallite size of the NC. The optimal conditions for the efficient NC-mediated photocatalysis of MO are 100 °C, 20 mg catalyst, 50 ppm MO, and pH 6. Conclusions: The auspicious performance of the NiO-SnO2 NCs may open a new avenue for the development of semiconducting p–n heterojunction catalysts as promising structures for removing undesirable organic pollutants from the environment. [ABSTRACT FROM AUTHOR]