Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
Magnetic MgxCoyZn(1-x-y)Fe2O4 nanoparticles were successfully prepared by the rapid combustion approach, and SEM, XRD, VSM, EDX, and FTIR techniques were applied for their characterization. The influence of the element ratios (Mg2+, Co2+, and Zn2+) in magnetic MgxCoyZn(1-x-y)Fe2O4 nanoparticles on their properties was explored. To acquire a larger specific surface area for better adsorption of methyl blue (MB), magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles calcined at 400°C for 2 h with 25 mL anhydrous ethanol were selected, and their average particle size and the saturation magnetization were about 81.3nm and 13.5 emu·g-1, respectively. Adsorption kinetics models and adsorption isotherm models were applied to research the adsorption characteristics of MB onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles. The pseudo-second-order kinetics model (R2 > 0:99) and Temkin isotherm model (R2 = 0:9887) were the most consistent with the data, indicating that the adsorption was the chemical multilayer adsorption mechanism, and the process was an exothermic reaction. The E of the Dubinin- Radushkevich (D-R) isotherm model was 0.2347 KJ·mol-1, indicating the adsorption involved physical adsorption besides chemical adsorption. The ΔG0 and ΔH0 (ΔH0 = −10:38 KJ·mol-1) of the adsorption process of MB adsorbed onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles measured through the thermodynamic experiment were both less than 0, which proved that the process was a spontaneous exothermic reaction. The adsorption capacity of MB onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles increased with the pH of MB solution increasing from 2 to 4 at room temperature, and it had no significant change when the pH of MB solution was 4-12, while the relative removal rate was 98.75% of the first one after 2 cycles. The electrochemical impedance spectroscopy (EIS) and the cyclic voltammetry (CV) data further demonstrated that MB was adsorbed onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles....
The results of the modification of the atomic structure of the Pt surface after bombardment by accelerated beams of Ar+ ions are presented. Field ion microscopy was used to study the irradiated surface on an atomic scale. From the analysis of the ion contrast of the atomically clean surface of platinum after bombardment with Ar+, a large number of radiation defects of various types were found. Individual vacancies, interstitial atoms, Frenkel pairs, depleted zones, nanoclusters of displaced atoms, etc. have been registered. It has been established that the depth of the near-surface volume of the irradiated metal with defects (except for zero-dimensional defects) is 1 - 1.5 nm for the bombardment regime: F = 1016 ion/cm2 and E = 30 keV....
Ammonia is one of the promising carriers for hydrogen and a critical ingredient in many industries including fertilizers and pharmaceuticals. In the KAAP process, ruthenium- (Ru-) based catalysts showed 10-20 more activity compared with iron- (Fe- ) based catalysts. The modifications that are applied to Ru-based catalysts revolve around changing the material of its support and/or promoters. This study compares the performance of a Ru-based catalyst for ammonia synthesis supported by La2Ce2O7 using barium (Ba), cesium (Cs), potassium (K), and lithium (Li) as promoters. Based on structural, physicochemical, adsorption, and electronic state analysis, the Cs-promoted catalyst is expected to perform best among all the promoted catalysts, while our findings suggest that the K-promoted catalyst performed the best in the actual catalytic reaction. This result will affect the development of Ru/La2Ce2O7-based catalysts, especially in ammonia synthesis at different temperatures and pressures....
This study investigated the effectiveness of immobilizing Saccharomyces cerevisiae invertase (SInv) on magnetite nanoparticles to produce fructooligosaccharides (FOSs). Based on the existing literature and accompanied by parameter estimation, a modified kinetic model was employed to represent the kinetics of sucrose hydrolysis and transfructosylation using SInv immobilized on magnetite nanoparticle surfaces. This model was utilized to simulate the performance of batch reactors for both free and immobilized enzymes. The maximum FOS concentration for the free enzyme was determined to be 123.1 mM, while the immobilized case achieved a slightly higher concentration of 125.4 mM. Furthermore, a continuous stirred-tank reactor (CSTR) model was developed for the immobilized enzyme, resulting in a maximum FOS concentration of 73.96 mM at the reactor’s outlet and a dilution rate of 14.2 h−1. To examine the impact of glucose inhibition on FOS production, a glucose oxidase reaction mechanism was integrated into the fitted immobilized theoretical model. In a batch reactor, the reduction or elimination of glucose in the reactive media led to a 2.1% increase in FOS production. Immobilizing the biocatalyst enhanced the overall performance of SInv. This enzyme immobilization approach also holds the potential for coupling glucose oxidase onto functionalized nanoparticles to minimize glucose inhibition, thereby improving FOS synthesis and facilitating optimal enzyme recovery and reuse....
This paper provides an overview of hydrometallurgical copper extraction studies in which liquid extraction technology has been used with four copper deposits of different compositions. The sulfuric acid consumption rate and copper extraction efficiency, which are dependent on the initial content and forms of calcium compounds and other impurities in ore samples, were calculated, and the results are presented herein. It was established that during the leaching process, silicate compounds of alkaline earth metals, in addition to calcium and magnesium carbonate compounds, would affect the levels of sulfuric acid consumption, thereby actively lowering the acidity of the environment. Moreover, these compounds could partially sorb copper ions from sulfuric acid leaching solutions. Thus, the analysis of waste ore samples showed that residual copper is mainly contained in the form of complex silicate complexes. The presence of divalent iron compounds in the composition from one of the deposits also allowed us to perform a biochemical leaching experiment with preliminary oxidation using an Acidithiobacillus ferrooxidans bacterial culture adapted to the ore composition. The use of this biochemical method in the copper leaching process resulted in a significant reduction in sulfuric acid consumption, by 40%, and a copper recovery rate of 87.2%....
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