A facile synthesis of TiO2/BiOCl and TiO2/BiOCl/La2O3 heterostructure photocatalyst for enhanced charge separation efficiency with improved UV-light catalytic activity towards Rhodamine B and Reactive Yellow 86

Remediation of recalcitrant pollutants in water solution using visible light responsive cerium-doped tungsten trioxide nanoparticles

In order to attain a solar energy-driven photocatalyst for wastewater remediation, cerium-doped WO₃ (W_1-xCe_xO₃ with x = 0, 0.02, 0.04, 0.06, and 0.08) nanoparticles have been synthesized via a chemical co-precipitation technique. X-ray diffraction (XRD) analysis confirmed that W_1-xCe_xO₃ nanoparticles retained their monoclinic structure even after doping. The presence of the vast number of defects produced in the WO₃ lattice was corroborated by Raman spectroscopy. Scanning electron microscopy confirmed the spherical shape of the nanoparticles with particle size range 50-76 nm. The optical band gap of W_1-xCe_xO₃ nanoparticles decreases from 3.07 to 2.36 eV with an increase in x, as confirmed by UV-Vis spectroscopy. Photoluminescence (PL) spectroscopy confirmed that the minimum rate of recombination was observed for W_1-xCe_xO₃ with x = 0.04. Degradation efficiency was explored for methyl violet (MV) and rhodamine-B (Rh-B) with 0.01 g of photocatalyst in a photoreactor chamber having a 200-W xenon lamp as a visible source of light. The results showed that the maximum photo-decolorization towards MV (94%) and rhodamine-B (79.4%) was observed in x = 0.04 sample in just 90 min because of its least recombination rate, highest adsorption capacity, and optimum band edge positions. Intriguingly, it has been observed that the modification with cerium in WO₃ nanoparticles enhances the photocatalytic activity by narrowing the band gap and by efficaciously lowering the recombination rate due to electron entrapment by defects produced in the lattice.

Effect of Doping TiO2 NPs with Lanthanides (La, Ce and Eu) on the Adsorption and Photodegradation of Cyanide-A Comparative Study

Free cyanide is a highly dangerous compound for health and the environment, so treatment of cyanide-contaminated water is extremely important. In the present study, TiO₂, La/TiO₂, Ce/TiO₂, and Eu/TiO₂ nanoparticles were synthesized to assess their ability to remove free cyanide from aqueous solutions. Nanoparticles synthesized through the sol-gel method were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), and specific surface area (SSA). Langmuir and Freundlich isotherm models were utilized to fit the adsorption equilibrium experimental data, and pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit the adsorption kinetics experimental data. Cyanide photodegradation and the effect of reactive oxygen species (ROS) on the photocatalytic process were investigated under simulated solar light. Finally, reuse of the nanoparticles in five consecutive treatment cycles was determined. The results showed that La/TiO₂ has the highest percentage of cyanide removal (98%), followed by Ce/TiO₂ (92%), Eu/TiO₂ (90%), and TiO₂ (88%). From these results, it is suggested that La, Ce, and Eu dopants can improve the properties of TiO₂ as well as its ability to remove cyanide species from aqueous solutions.

Fabrication of fullerene-supported La2O3-C60 nanocomposites: dual-functional materials for photocatalysis and supercapacitor electrodes

Nowadays, water pollution and energy crises worldwide force researchers to develop multi-functional and highly efficient nanomaterials. In this scenario, the present work reports a dual-functional La₂O₃-C₆₀ nanocomposite fabricated by a simple solution method. The grown nanomaterial worked as an efficient photocatalyst and proficient electrode material for supercapacitors. The physical and electrochemical properties were studied by state-of-the-art techniques. XRD, Raman spectroscopy, and FTIR spectroscopy confirmed the formation of the La₂O₃-C₆₀ nanocomposite with TEM nano-graphs, and EDX mapping exhibits the loading of C₆₀ on La₂O₃ particles. XPS confirmed the presence of varying oxidation states of La³⁺/La²⁺. The electrochemical capacitive properties were tested by CV, EIS, GCD, ECSA, and LSV, which indicated that the La₂O₃-C₆₀ nanocomposite can be effectively used as an electrode material for durable and efficient supercapacitors. The photocatalytic test using methylene blue (MB) dye revealed the complete photodegradation of the MB dye under UV light irradiation after 30 min by a La₂O₃-C₆₀ catalyst with a reusability up to 7 cycles. The lower energy bandgap, presence of deep-level emissions, and lower recombination rate of photoinduced charge carriers in the La₂O₃-C₆₀ nanocomposite than those of bare La₂O₃ are responsible for enhanced photocatalytic activity with low-power UV irradiation. The fabrication of multi-functional and highly efficient electrode materials and photocatalysts such as La₂O₃-C₆₀ nanocomposites is beneficial for the energy industry and environmental remediation applications.

Comparative Study of the Effect of Doping ZnTiO3 with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO₃ (ZTO), La/ZnTiO₃ (La/ZTO), and Ce/ZnTiO₃ (Ce/ZTO). The nanoparticles were synthesized by the sol-gel method and characterized by X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), and Specific surface area (SSA). The adsorption equilibrium data were fitted to the Langmuir and Freundlich isotherm models. Adsorption kinetics were also evaluated using the pseudo-first-order and pseudo-second-order models and the intraparticle diffusion model. Likewise, the photodegradation of cyanide under simulated sunlight was investigated and the reusability of the synthesized nanoparticles for cyanide removal in aqueous systems was determined. The results demonstrated the effectiveness of doping with lanthanum (La) and cerium (Ce) to improve the adsorbent and photocatalytic properties of ZTO. In general, La/ZTO showed the maximum percentage of total cyanide removal (99.0%) followed by Ce/ZTO (97.0%) and ZTO (93.6%). Finally, based on the evidence of this study, a mechanism for the removal of total cyanide from aqueous solutions using the synthesized nanoparticles was proposed.

Facile Synthesis, Characterization, and Photocatalytic Evaluation of In2O3/SnO2 Microsphere Photocatalyst for Efficient Degradation of Rhodamine B

The tin dioxide (SnO₂) photocatalyst has a broad application prospect in the degradation of toxic organic pollutants. In this study, micron-sized spherical SnO₂ and flower indium oxide (In₂O₃) structures were prepared by a simple hydrothermal method, and the In₂O₃/SnO₂ composite samples were prepared by a "two-step method". Using Rhodamine B (RhB) as a model organic pollutant, the photocatalytic performance of the In₂O₃/SnO₂ composites was studied. The photocurrent density of 1.0 wt.% In₂O₃/SnO₂ was twice that of pure SnO₂ or In₂O₃, and the degradation rate was as high as 97% after 240 min irradiation (87% after 120 min irradiation). The reaction rate was five times that of SnO₂ and nine times that of In₂O₃. Combined with the trapping experiment, the transient photocurrent response, and the corresponding characterization of active substances, the possible degradation mechanism was that the addition of In₂O₃ inhibited the efficiency of electron-hole pair recombination, accelerated the electron transfer and enhanced the photocatalytic activity.

Template-Free Synthesis of g-C3N4 Nanoball/BiOCl Nanotube Heterojunction with Enhanced Photocatalytic Activity

There are many reports on g-C3N4 nanosheet and BiOCl nanosheet, but few studies on other morphologies of g-C3N4 and BiOCl. Herein, a g-C3N4 nanoball/BiOCl nanotube heterojunction prepared by a simple one-step acetonitrile solvothermal method is reported. The XRD results prove that the g-C3N4/BiOCl composites can be prepared in one step. SEM results revealed that the g-C3N4 was spherical and the BiOCl was tubular. The HRTEM results indicate that g-C3N4 has an amorphous structure and that the (100) crystal plane of BiOCl borders the g-C3N4. Spherical g-C3N4 has a narrow band gap (approximately 1.94 eV), and the band gap of g-C3N4/BiOCl after modification was also narrow. When the BiOCl accounted for 30% of the g-C3N4/BiOCl by mass, the quasi-primary reaction rate constant of RhB degradation was 45 times that of g-C3N4. This successful preparation method for optimizing g-C3N4 involving simple one-step template-free synthesis may be adopted for the preparation of diverse-shapes and high-performance nanomaterials in the future.

Photocatalytic activity of ZrO2/TiO2/Fe3O4 ternary nanocomposite for the degradation of naproxen: characterization and optimization using response surface methodology

In this study, ZrO₂, TiO₂, and Fe₃O₄ components were synthesized by co-precipitation, sol–gel, and co-precipitation methods, respectively. In addition, solid-state dispersion method was used for synthesizing of ZrO₂/TiO₂/Fe₃O₄ ternary nanocomposite. The ZrO₂/TiO₂/Fe₃O₄ nanocomposite was characterized by different techniques including XRD, EDX, SEM, BET, FTIR, XPS, EELS, and Photoluminescence (PL). The FTIR analysis of ZrO₂/TiO₂/Fe₃O₄ photocatalyst showed strong peaks in the range of 450 to 700 cm⁻¹, which represent stretching vibrations of Zr–O, Ti–O, and Fe–O. The results of FTIR and XRD, XPS analyses and PL spectra confirmed that the solid-state dispersion method produced ZrO₂/TiO₂/Fe₃O₄ nanocomposites. The EELS analysis confirmed the pure samples of Fe₃O₄, TiO₂ and ZrO₂. The EDAX analysis showed that the Zr:Ti:Fe atomic ratio was 0.42:2.08:1.00. The specific surface area, pores volume and average pores size of the photocatalyst were obtained 280 m²/g, 0.92 cm³/g, and 42 nm respectively. Furthermore, the performance of ZrO₂/TiO₂/Fe₃O₄ nanocomposite was evaluated for naproxen removal using the response surface method (RSM). The four parameters such as NPX concentration, time, pH and catalyst concentration was investigated. The point of zero charge of the photocatalyst was 6. The maximum and minimum degradation of naproxen using photocatalyst were 100% (under conditions: NPX concentration = 10 mg/L, time = 90 min, pH = 3 and catalyst concentration = 0.5 g/L) and 66.10% respectively. The stability experiment revealed that the ternary nanocatalyst demonstrates a relatively higher photocatalytic activity after 7 recycles.

La-Doped ZnTiO3/TiO2 Nanocomposite Supported on Ecuadorian Diatomaceous Earth as a Highly Efficient Photocatalyst Driven by Solar Light

Currently, there is great interest in the use of TiO2 for photocatalytic remediation of wastewater. Doping, heterojunction, and immobilization on porous materials are effective methods to improve the photocatalytic efficiency of this semiconductor oxide. In this study, ZnTiO3/TiO2 (ZTO) and ZnTiO3/TiO2/La (ZTO/La) nanocomposites were successfully prepared and immobilized on diatomaceous earth (DE). The composition and texture of the composites prepared were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM-EDX), and specific surface area (SSA). The adsorption capacity and photocatalytic activity of the composites were determined via degradation of methylene blue (MB) in batch reactors. The materials evaluated were prepared in the shape of 0.2 cm (diameter) and 1.0 cm (length) cylindrical extrudates. The results indicate that the ZTO/La-DE composite exhibited higher efficiency for the removal of MB under solar irradiation than both ZTO-DE and DE. The pseudo-second-order model and the Langmuir isotherm model were better suited to explain the adsorption process. The highest degradation percentage of MB obtained was 96% after 150 min of irradiation. The results indicate that synthesized composite could be used for the removal of cationic dyes in wastewater.