ABSTRACT
In this study, simplex centroid mixture design was employed to determine the effect of urea on ZnO-CeO. The heterojunction materials were synthesized using a solid-state combustion method, and the physicochemical properties were evaluated using X-ray diffraction, nitrogen adsorption/desorption, and UV-Vis spectroscopy. Photocatalytic activity was determined by a triclosan degradation reaction under UV irradiation. According to the results, the crystal size of zinc oxide decreases in the presence of urea, whereas a reverse effect was observed for cerium oxide. A similar trend was observed for ternary samples, i.e., the higher the proportion of urea, the larger the crystallite cerium size. In brief, urea facilitated the co-existence of crystallites of CeO and ZnO. On the other hand, UV spectra indicate that urea shifts the absorption edge to a longer wavelength. Studies of the photocatalytic activity of TCS degradation show that the increase in the proportion of urea favorably influenced the percentage of mineralization.
ABSTRACT
γ-Valerolactone (GVL) has been considered an alternative as biofuel in the production of carbon-based chemicals; however, the use of noble metals and corrosive solvents has been a problem. In this work, Ni supported nanocatalysts were prepared to produce γ-Valerolactone from levulinic acid using methanol as solvent at a temperature of 170 °C utilizing 4 MPa of H2. Supports were modified at pH 3 using acetic acid (CH3COOH) and pH 9 using ammonium hydroxide (NH4OH) with different tungsten (W) loadings (1%, 3%, and 5%) by the Sol-gel method. Ni was deposited by the suspension impregnation method. The catalysts were characterized by various techniques including XRD, N2 physisorption, UV-Vis, SEM, TEM, XPS, H2-TPR, and Pyridine FTIR. Based on the study of acidity and activity relation, Ni dispersion due to the Lewis acid sites contributed by W at pH 9, producing nanoparticles smaller than 10 nm of Ni, and could be responsible for the high esterification activity of levulinic acid (LA) to Methyl levulinate being more selective to catalytic hydrogenation. Products and by-products were analyzed by 1H NMR. Optimum catalytic activity was obtained with 5% W at pH 9, with 80% yield after 24 h of reaction. The higher catalytic activity was attributed to the particle size and the amount of Lewis acid sites generated by modifying the pH of synthesis and the amount of W in the support due to the spillover effect.
ABSTRACT
The pseudocapacitive properties of CeO2 are largely dependent on its surface Faradaic redox reaction kinetics; however, its electrochemical performance is still limited by the low utilization due to the inefficient diffusionfreeways and the limited active sites. Herein, we prepare a 0D/3D composite composed of oxygen-deficient CeO2 quantum dots (0D) anchored on a 3D hollow porous N-doped carbon framework (CeO2-x QD@PHC) via a facile template-confined strategy followed by a chemical co-precipitation. The refined QDs and hollow structure greatly shorten the ion diffusion paths and lower the internal strain during cycling. The integration of CeO2-x QDs with PHC structure endows enriched accessible active sites and enhances the electrical properties. As a result, the optimized CeO2-x QD@PHC exhibits an improved specific capacitance and good rate performance in comparison to those of the CeO2-x-free PHC. Moreover, a symmetric supercapacitor with CeO2-x QD@PHC as an electrode is constructed, delivering a high energy density of 3.874 Wh kg-1 at a power density of 149.98 W kg-1.
ABSTRACT
Heavy metals are one of the most common types of pollutants in ground water due to their wide sources, non-degradability and high toxicity. Many traditional wastewater treatments were not capable of removing enough such contaminants in order to meet quality standards. Nanosized zerovalent transition metals have emerged as a great candidate for ground water remediation, due to their simplicity and low fabrication cost, furthermore they can comply with simple chemical synthesis. Here, we present the synthesis of nano zerovalent nickel (nZVN) by a simple grinding reduction method. The obtained nZVN was characterized with XRD, SEM, EDS and BET surface area. The results confirms the formation of nZVN and the active particle cluster size ranges from 100 to 200 nm. N2 adsorption isotherms revealed that the formation mesoporous cluster of nZVN with good surface area. The adsorption of Cr(VI) using nZVN showed 96% removal efficiency for 10 ppm concentration, and even up to 98% when the temperature is slightly raised to 36 °C (309 K). The removal efficiencies of Cr by zerovalent nickel was well fitted by the Langmuir-Hinshelwood first order reaction kinetic model with deceptive rate constant values of 0.6699, 0.7956 and 1.0251 min-1 at temperature 200, 303 and 309 K, respectively. In total, our studies suggest that nanoscale zerovalent iron is a capable material for Cr(VI) remediation from groundwater.
