Synthesis of lanthanum oxide nanosheets by a green carbonation process

Synthesis of Yttrium Oxide Nanoneedles with Carbon Dioxide Carbonization

In this study, a CO₂ carbonization method is introduced for the preparation of 1D yttrium oxide powders. Using YCl₃ as the raw material, sodium hydroxide was initially used to completely precipitate Y³⁺ into yttrium hydroxide, and then CO₂ was introduced into the yttrium hydroxide slurry for homogenization-like carbonization to obtain yttrium carbonate precipitation. Then, by studying the effects of carbonization conditions, such as the temperature, CO₂ flow rate, and stirring speed, on the morphology and phases of yttrium carbonate, the temperature was observed to exert a greater effect than the other experimental parameters on the morphology and structure of the carbonized products. Finally, Y₂(CO₃)₃·2H₂O nanoneedles were obtained at optimal conditions. The carbonized crystals of the acicular yttrium carbonate precipitate because of the solution supersaturation and then quickly complete their crystal growth process through the oriented attachment (OA) and Ostwald ripening (OR) mechanisms. After heat treatment, yttrium carbonate retained a good crystal morphology and produced Y₂O₃ nanoneedles with a length of 1-2 μm and a width of 20-30 nm.

Lanthanum-Zinc Binary Oxide Nanocomposite with Promising Heterogeneous Catalysis Performance for the Active Conversion of 4-Nitrophenol into 4-Aminophenol

This work intended to enhance the unique and outstanding properties of lanthanum by synthesizing its nanocomposite. A lanthanum-based nanocomposite was prepared by a simple and cost-effective “co-precipitation” method. Lanthanum nitrate (La (NO3)3) and zinc nitrate (Zn (NO3)2) were used as precursors. The lanthanum/zinc oxide nano composite formed was then calcined at 450 °C for 4 h in order to obtain a fine powder with size in the nano range of 1–100 nm. Characterization of the prepared catalyst was done by ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence. Crystallinity and morphology were found by X-ray diffraction and scanning electron microscopy. The synthesized nanocomposite material was also tested for heterogeneous catalytic applications of 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP). It was found to be successful in complete reduction of 4-NP with enhanced catalytic performance.

Gold Nanoparticles on Nanosheets Derived from Layered Rare-Earth Hydroxides for Catalytic Glycerol-to-Lactic Acid Conversion

Layered rare-earth hydroxides (LREHs), as a series of special lamellar compounds having a similar structure to layered double hydroxides (LDHs), are becoming a new type of catalyst materials. In this study, we have prepared a series of uniform LREH (RE = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm) nanosheets through a reverse-microemulsion method. After deposition-precipitation of HAuCl₄ and calcination, supported Au catalysts (denoted as Au/LREO) were subsequently obtained. The catalytic properties of all the derived Au/LREO catalysts were evaluated by aerobic conversion of glycerol to lactic acid under mild conditions (90 °C, 1 atm). Among these catalysts, Au/LPrO displays the best performances, including the highest glycerol conversion, lactic acid, and C₃ product selectivity. Both the catalytic activities and the characterizations of the structure of Au/LREO indicate that the kind of rare-earth ions plays a key role in determining the Au particle size and its valence state and reducibility, which are the important factors correlated with the catalytic activities in glycerol conversion. In fact, the three features of gold particles, the extra-small size (∼3 nm), high content of Au⁰ species, and high reducibility, are the essential prerequisites for achieving the superior catalytic performance of Au/LPrO.

Facile Synthesis, Characterization, and Adsorption Insights of Lanthanum Oxide Nanorods

This study synthesized lanthanum oxide (La2O3) nanorods to develop a practical approach for the removal of arsenic from groundwater. La2O3 nanorods were synthesized by a simple hydrothermal process followed by calcination at 500 °C and were characterized by spectroscopic and microscopic techniques. To evaluate the adsorption mechanism of La2O3 nanorods, adsorption parameters including solution pH, temperature, equilibrium isotherms, and kinetics for arsenic were studied. The results suggested that the arsenic uptake was a rate-limiting, monolayer adsorption interaction on the La2O3 nanorods homogeneous surface. In addition, it was found that the adsorptive removal behavior of La2O3 for As(V) was sensitive to the initial pH and temperature, and the maximum uptake amount of as prepared La2O3 was found to be 260.56 mg/g of As(V) at pH 6.0 and 25 °C. Furthermore, the uptake capacity of La2O3 nanorods for As(V) increased with temperature. The resultant thermodynamic parameters (ΔG0, ΔH0, and ΔS0) suggested an endothermic adsorption of As(V) on La2O3. The adsorption capacity of La2O3 was higher than that of several reported nanocomposites, suggesting its practical applicability and novelty for As-contaminated wastewater treatment.