Study on the controlled synthesis and photocatalytic performance of rare earth Nd deposited on mesoporous TiO2 photocatalysts

Facile Synthesis of a Crystalline Zinc Sulfide/Chitosan Biopolymer Nanocomposite: Characterization and Application for Photocatalytic Degradation of Textile Dyes and Anticancer Activity

In the present study, we have synthesized a zinc sulfide/chitosan (ZS/CS) nanocomposite by utilizing simple, economical, and environmentally friendly methods. The synthesized nanomaterials were characterized by different analytical techniques such as XRD, FE-SEM, EDS, and FTIR to determine the phase structure, morphology, and elemental composition. FTIR spectroscopy was used to confirm the functional groups of the synthesized zinc sulfide (ZS) nanoparticles and ZS/CS composite. Besides, the optical properties of the as-synthesized nanocomposite was analyzed by a UV-visible spectrophotometer, and the estimated band gap energy is ∼3.03 eV. The photocatalytic efficiency of the synthesized ZS/CS nanocomposite was investigated against two textile dyes, Crystal Violet (CV) and Acid Red-I (AR-I), under UV-visible light irradiation. The nanocomposite showed excellent photocatalytic activity against the dyes, and photodegradation was estimated to be about 93.44 and 90.67% for CV and AR-I, respectively. The nanocomposite was reused for three consecutive cycles. The results revealed that the photocatalyst displayed good reusability during the photocatalytic decomposition and thus is considered a cost-effective and promising photocatalyst in degrading dye pollutants. The kinetic study proved that the pseudo-first-order reaction kinetics was followed by the degradation process. We also examined the anticancer activity of ZS and ZS/CS against human breast and myelogenous leukemia cancer cell lines, namely, MCF-7 and K-562, and the half minimal inhibitory concentrations were found to be less than 50 μg/mL.

Synthesis, Characterization, and Solar Photo-Activation of Chitosan-Modified Nickel Magnetite Bio-Composite for Degradation of Recalcitrant Organic Pollutants in Water

Photocatalysis is a promising process for decomposing harmful organic pollutants in water. In this study, solar/photocatalytic degradation of two model azo dyes, i.e., methylene blue (MB) and methyl red (MR), in water usinga nanostructured chitosan-modified nickel magnetite (CS-NM) bio-composite was investigated. The CS-NM bio-composite was synthesized through a co-precipitation method and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry (TGA), and UV-Vis spectroscopy. FTIR analysis showed the uniform incorporation and conjugation of nickel magnetite (NM) into the chitosan (CS) polymer matrix. SEM showed that the average particle size was 0.5 μm. The TGA results revealed the good thermal stability of the prepared bio-composite at 300 °C. The point of zero charge was calculated as 7.5. The effect of water quality and process parameters, such as concentration of dyes, catalyst dose, solution pH, and temperatures, was investigated, for application purposes. The solar/CS-NM photocatalysis resulted in 99 and 96% degradation of individual MB and MR (C0 = 50 ppm), respectively, in 90 min. The degradation of MB and MR by solar/CS-NM photocatalysis followed pseudo-first-order kinetics, with observed rate constants (k) of 0.077 and 0.072 min−1, respectively. The CS-NM photocatalyst showed high recyclability, represented by only a 4–6% loss in the photocatalytic efficiency, after four cycles. The results showed that solar/CS-NM photocatalysis is an efficient technique for degrading recalcitrant organic pollutants, such as azo dyes, in water environments.

Synthesis, modification and application of titanium dioxide nanoparticles: a review

Titanium dioxide (TiO₂) has been heavily investigated owing to its low cost, benign nature and strong photocatalytic ability. Thus, TiO₂ has broad applications including photocatalysts, Li-ion batteries, solar cells, medical research and so on. However, the performance of TiO₂ is not satisfactory due to many factors such as the broad band gap (3.01 to 3.2 eV) and fast recombination of electron-hole pairs (10^-12 to 10^-11 s). Plenty of work has been undertaken to improve the properties, such as structural and dopant modifications, which broaden the applications of TiO₂. This review mainly discusses the aspects of TiO₂-modified nanoparticles including synthetic methods, modifications and applications.

The effect of hydrothermal temperature on the properties of SBA-15 materials

In present work, ordered mesoporous material SBA-15 was synthesized by using poly (alkylene oxide) block copolymer (Pluronic P123) as template and ethylsilicate as silica source in weak acid environment in a wide range of temperature. The focus of synthesis research was high hydrothermal temperature. The obtained products were characterized by various techniques, including XRD, N₂ sorption isotherms, FTIR spectroscopy and thermogravimetric. The effect of hydrothermal temperature on the specific surface area, pore volume and pore size of SBA-15 products was investigated systematically. As the hydrothermal temperature increases from the 100–120 °C, the specific surface area and the pore volume of the mesoporous molecular sieve increase greatly. When the hydrothermal temperature increase further, the pore volume of the mesoporous molecular sieve increase continually. But the specific surface area decrease significantly. When the hydrothermal temperature is too high (over 140 °C), the order degree begins to decrease, So the specific surface area and pore volume decrease significantly because the pores structure have significant destruction and collapse. Mechanism and structural characteristics of P123 block copolymer could explain in detail the effect of hydrothermal temperature on the property and structure of mesoporous molecular sieve SBA-15.

Sepiolite supported BiVO4 nanocomposites for efficient photocatalytic degradation of organic pollutants: Insight into the interface effect towards separation of photogenerated charges

Although the construction of clay-supported photocatalyst is a promising strategy to develop the low cost and high activity photocatalyst, only few works researched the effect of their interfaces on the photocatalytic performance. Herein, a monoclinic BiVO₄/sepiolite nanocomposite was fabricated as case to study the transport mechanism of photogenerated carries based on the interfaces effect. The obtained BiVO₄/sepiolite nanocomposites exhibited excellent visible light photocatalytic performance. The photocatalytic degradation rates of antibiotic tetracyclines (TCs) and methylene blue (MB) by the nanocomposites are 2 and 5.34 times higher than that by pure BiVO₄ under visible light irradiation. XPS and Raman spectra confirmed the strong interfaces effect existing between BiVO₄ and sepiolite clay. Moreover, PL and transient photocurrent response suggested that the strong interfaces effect effectively promoted the separation of photogenerated electron-hole pairs and further enhanced the photocatalytic performance. In addition, the results of trapping experiments revealed that the photo-induced holes (h⁺) were the dominant active species in the photocatalytic mechanism. This work illuminates the photocatalytic mechanism of monoclinic BiVO₄/sepiolite nanocomposites and provides a novel strategy for designing the clay-supported photocatalyst for degradation of organic pollutants.

Effective Interactions of Ag Nanoparticles on the Surface of SBA-15 in Performing Deep Desulfurization of Real Diesel Fuel

SBA-15 materials as-synthesized and impregnated with Ag nanoparticles were applied to perform adsorptive desulfurization of real diesel fuel. High-angle annular dark-field scanning transmission electron microscopy and field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (HAADF-STEM-EDX and FESEM-EDX) and X-ray photoelectron spectroscopy (XPS) results confirmed that there is uniform distribution of Ag nanodomains on the surface and in the channels of a 2AgSBA-15 (2% Ag) sample. The interaction between sulfur compounds and adsorbent mainly occurred via π-complexation mechanisms, as observed via XPS and equilibrium data. The kinetic results for 2AgSBA-15 were better fitted to the pseudo-second-order model (R2 > 0.9999), indicating that the determining step of the adsorptive process is chemisorption, whereas the equilibrium results were better fitted to the Langmuir model (R2 > 0.9994), thus indicating that the adsorption occurs on the adsorbent surface monolayer with significant adsorption capacity (qm = 20.30 mgS/g), approximately two times greater than that observed for pure SBA-15. The mean desulfurization reached by the adsorbents was up to 86.8% for six recycling steps.

Chitosan‑zinc sulfide nanoparticles, characterization and their photocatalytic degradation efficiency for azo dyes

Herein, chitosan‑zinc sulfide nanoparticles (CS-ZnS-NPs) were developed as an efficient photocatalyst for the degradation of toxic dyes. The as-synthesized CS-ZnS-NPs were analyzed using XRD, FTIR, SEM, and EDS. The functional groups of CS-ZnS-NPs were validated with FTIR spectroscopy. The SEM envisaged the average particle size as 40 nm, whereas EDS interpreted the compositional analysis of the nanocomposite. XRD analysis illustrated the crystallinity and hexagonal crystal structure of the CS-ZnS-NPs. The photocatalytic efficiency of CS-ZnS-NPs was evaluated using two carcinogenic azo dyes, Acid Brown 98 and Acid Black 234. A UV lamp (254 nm) was used as an irradiation source during the photocatalytic degradation of dyes. At the optimum conditions, the synthesized CS-ZnS-NPs showed 96.7% degradation for Acid Black 234 in 100 min and 92.6% for Acid Brown 98 in 165 min. The degradation phenomena followed pseudo-first-order kinetics. The values of rate constant (k) were 0.01464 and 0.04096 min^-1 with correlation coefficient (R²) of 0.98891 and 0.99406 for Acid Brown 98 and Acid Black 234, respectively. The CS-ZnS-NPs were easily recovered and recycled for four successive batches. The results showed that CS-ZnS-NPs are considered as highly productive, cost-effective and promising photocatalyst in degrading pollutants in several consecutive cycles.

Kinetics and mechanism of photocatalytic degradation of methyl orange in water by mesoporous Nd-TiO2-SBA-15 nanocatalyst

High-efficiency nanophotocatalysts with large specific surface areas have a broad range of application prospects in the catalytic oxidation treatment of organic pollutants in wastewater. A chemical method was used to synthesize a TiO₂ nanophotocatalyst with a mesoporous structure upon which a rare earth metal (Nd) was deposited, namely Nd-TiO₂-SBA-15 (NTS). The prepared NTS was characterized using X-ray diffractometry, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectrometry. The photocatalytic mechanism was explored using scavenger experiments with photoinduced carriers combined with total organic carbon and UV-Vis measurements. At the same time, the kinetic properties of the NTS photocatalytic degradation of methyl orange (MO) were evaluated. The results showed that the deposition of TiO₂ nanoparticles on the surface of the SBA-15 molecular sieve did not change the mesoporous structure, and Nd was uniformly distributed on the surface of the nanophotocatalyst. The photogenerated holes of the NTS played an important role in the photocatalysis process. In addition, the synthesized NTS had good adaptability in the range of pH 2-10. At pH 4, the reaction rate constant (k) of the MO photocatalytic degradation by NTS was 0.011825 mg·(L·min)^-1, and the adsorption equilibrium constant (K) was 0.051359 L mg^-1. In addition, the photocatalytic degradation rate of MO by NTS remained above 70%, even when the NTS was recycled four times. The NTS showed a good performance after recycling. This work provides a good foundation for the large-scale application of NTS.