Concentration Of Precipitating Agent Research Articles

Design and Preparation at Scale of Ternary NiFe-M-Ox (M=Co, Mo) Catalysts for OER in Alkaline Media

Due to scarcity of Platinum Group Metals (PGMs) widely used in low temperature water electrolysis as cathodes (Hydrogen Evolution Reaction; HER) and anodes (Oxygen Evolution Reaction; OER) a boosting interest to their substitution to Earth abundant elements is observed. It was successfully demonstrated that elements like iron, nickel, cobalt and other (in their oxide and hydroxide forms) can be effective OER catalysts when operate at high pH ranges from 12 to 14 [1-3].This work is devoted to systematic investigation of influence of third element addition to NiFeOx system on a performance and stability of catalysts in alkaline OER. As a co-catalytic elements Mo and Co were selected, based on our previous experience [4,5]. A systematic study on an effect of NiFe-to-M ratio, concentration of precipitation agent and post-treatment temperature were evaluated in a wide range of parameters. Taking into account that mass loading of PGM-free OER catalysts is substantially higher than iridium/ruthenium once and can be up to several milligrams per cm2 all experiments were designed to be scalable. In a laboratory scale reactor, a fascinating batch size of 25g was achieved, using minimal amount of water-based solvents in order to minimize a waste stream generated. Presentation will discuss characterization of obtained materials by SEM, TEM, XPS, XRD and other methods as well as their performance, stability and durability in alkaline conditions, studying Oxygen Evolution Reaction. Acknowledgements and Statements. The authors acknowledge financial support from H2NEW and ElectroCat consortia. References. [1] X. Lyu, J. Li, J. Yang, A. Serov "Significance of Slight Ambient Temperature Variation on the Electrocatalyst Performance toward Oxygen Evolution Reaction" Journal of Environmental Chemical Engineering (2023).[2] X. lyu, A. Serov “Cutting-edge methods for amplifying the oxygen evolution reaction during seawater electrolysis: a brief synopsis” Ind. Chem. Mater., (2023).[3] X. Lyu, Y. Bai, J. Li, R. Tao, J. Yang, A. Serov "Investigation of oxygen evolution reaction with 316 and 304 stainless-steel mesh electrodes in natural seawater electrolysis" J. of Environmental Chemical Engineering 11 (2023) 109667.[4] A. Serov,N. I. Andersen, A. J. Roy, I. Matanovic, K. Artyushkova, P. Atanassov “CuCo2O4 ORR/OER Bi-Functional Catalyst: Influence of Synthetic Approach on Performance”, J. of The Electrochem. Soc. 162 (4) (2015) F449-F454.[5] N. I. Andersen, A. Serov, P. Atanassov “Metal Oxides/CNT Nano-Composite Catalysts for Oxygen Reduction/Oxygen Evolution in Alkaline Media”, Appl. Catal. B: Environmental 163 (2015) 623-627.

Nanofiber membranes immobilized with in-situ grown nanoparticles for enhanced wetting resistance in direct contact membrane distillation

Immobilizing nanoparticles (NPs) onto the hydrophobic nanofiber membrane surface is an effective method to enhance its resistance to pore wetting in membrane distillation (MD) due to construction of a hierarchical structure. However, loading NPs onto the fabricated membrane through post-treatment techniques (e.g., electrospray, physical vapor deposition etc.) results in agglomeration of NPs and their weak attachment with membrane surface. To address this issue, we utilize precipitation and crystallization methods to achieve in-situ growth of zinc oxide (ZnO) NPs onto nanofiber surface for intensifying their interaction. Morphological characterization demonstrated that the size and amount of in-situ grown ZnO NPs could be controlled by varying reaction time and concentration of precipitation agent. Furthermore, the resultant nanofiber membrane with higher contact angles (163°) showed stable water flux and effective salt rejection in presence of surfactant and oil. Finally, the kinetics of wetting progression monitored by ultrasonic time-domain reflectometry (UTDR) further confirmed that the early partial wetting induced by surfactants was significantly restrained owing to the hierarchical structure generated by the in-situ grown ZnO NPs. This study suggested the modified nanofiber membrane presented outstanding wetting resistance to low-surface-tension foulants and promise for desalination in MD.

Structural and opto-electrical properties of Y2O3 nanopowders synthesized by co-precipitation method

The synthesis-dependent structural-optical characteristics of nanomaterials have induced the critical optimization of parameters for nanoparticle synthesis. Considering the potential applications of yttria (Y2O3) in high-temperature IR windows and electro-optic devices, the present study describes the preparation of yttria nanopowders (YNPs) through co-precipitation method. Some special morphological and opto-electrical properties have been observed with a change in the precipitating agent concentration (R = NH5CO3/Y3+ = 1.5–5.5) without using any surfactant. Rietveld refinement confirmed the body-centered cubic (Ia-3 space group) structure of YNPs. Surface functionalities have been determined by Fourier transform infrared (FTIR) spectroscopy. Electron microscopy results confirmed the formation of agglomerated YNPs with R-dependent morphological modifications from flake-like shape to pseudo-spherical and rod-like particles. UV–visible and fluorescence (FL) spectroscopy confirmed the R-dependent optical absorption and emission (indigo, blue and green) characteristics. The dielectric measurement also confirmed the R-dependent variation in the dielectric constant values in the lower frequency range.

High specific surface area γ-Al2O3 nanoparticles synthesized by facile and low-cost co-precipitation method

Alumina (Al2O3) nanoparticles (NPs) are particularly adsorbent NPs with a high specific surface area (SSA) that may well be utilized to clean water. In this study, pure γ-alumina NPs are successfully synthesized by the co-precipitation method, and the effect of ammonium bicarbonate concentration on the synthesized NPs is studied to find the optimum concentration to provide the highest capacity of copper ions removal from water. The results declare that spherical alumina NPs with average diameters in the range of 19–23 nm are formed with different concentrations of precipitation agent, and the concentration has no significant effect on the morphology of NPs. Furthermore, the precipitating agent concentration influences the optical characteristics of the produced alumina NPs, and the bandgap energies of the samples vary between 4.24 and 5.05 eV. The most important impact of precipitating agent concentrations reflects in their SSA and capacity for copper ion removal Ultra-high SSA = 317 m2/g, and the highest copper removal at the adsorbate concentration of 184 mg/L is achieved in an alkalis solution followed by a neutral solution. However, admirable copper removal of 98.2% is even achieved in acidic solutions with 0.9 g/L of the alumina NPs synthesized at a given concentration of ammonium bicarbonate, so this sample can be a good candidate for Cu ions removal from acidic wastewater.

ROS-Mediated Anti-Angiogenic Activity of Cerium Oxide Nanoparticles in Melanoma Cells.

Angiogenesis plays a key role in cancer progression, including transition to the metastatic phase via reactive oxygen species (ROS)-dependent pathways, among others. Antivascular endothelial growth factor (VEGF) antibodies have been trialed as an anti-angiogenic therapy for cancer but are associated with high cost, limited efficacy, and side effects. Cerium oxide nanoparticles (nanoceria) are promising nanomaterials for biomedical applications due to their ability to modulate intracellular ROS. Nanoceria can be produced by a range of synthesis methods, with chemical precipitation as the most widely explored. It has been reported that chemical precipitation can fine-tune primary particle size where a limited number of synthesis parameters were varied. Here, we explore the effect of temperature, precipitating agent concentration and rate of addition, stirring rate, and surfactant concentration on nanoceria primary particle size using a fractional factorial experimental design approach. We establish a robust synthesis method for faceted nanoceria with primary particle diameters of 5-6 nm. The nanoceria are not cytotoxic to a human melanoma cell line (Mel1007) at doses up to 400 μg/mL and are dose-dependently internalized by the cells. The intracellular ROS level for some cells that internalized the nanoceria is reduced, which correlates with a dose-dependent reduction in angiogenic gene expression including VEGF. These findings contribute to our knowledge of the anti-angiogenic effects of nanoceria and help to develop our understanding of potentially new anti-angiogenic agents for combination cancer therapies.

Influence of Precipitating Agent Concentration on Nanoparticles Size and Magnetic Properties of Zinc Ferrites

A series of Zn ferrite nanoparticles was prepared by varying the concentration of precipitating agent (NaOH) in the range of 1 � 5 M. Carboxymethylcellulose (CMC) was used as capping agent for stabilizing the particles and to prevent agglomeration. The synthesis done at low temperature was followed by a thermal treatment at 500ºC for 6 h in air. The crystallite size determined using Scherer formula ranged between 8 - 10 nm while the nanoparticles average size observed by Transmission Electron Microscopy varied in between 7-10 nm showing that the increase of coprecipitation agent concentration influences the particles growth. Vibrating sample magnetometry confirmed the strong influence that nanoparticles morphology and size play on superparamagnetic properties of Zn ferrite.

Cu layered double hydroxides as catalysts for N-methylation of p-anisidine: Influence of synthesis conditions

Cu-containing layered double hydroxides were synthesized by co-precipitation method using base solution (NaOH and Na2CO3) with different concentration of carbonate ions. The influence of the precipitating agent concentration on formation of hydrotalcite phase was investigated. Characterization of the surface of the obtained samples calcined at 450 °C and 650 °C was performed by x-ray photoelectron spectroscopy. Catalysts based on Cu-layered double hydroxides were investigated in N-methylation of p-anisidine by methanol obtaining N-methyl-p-anisidine using autoclave reactor. Effect of precipitating agent concentration during synthesis of the Cu-layered double hydroxide on the catalyst performance was studied.

Stabilization of dispersive soils by means of biological calcite precipitation

Stabilization of dispersive soils is of great importance and has been looked into in various studies across the globe. In this study, the biological soil stabilization as a novel method has been investigated. In order to improve the erodibility resistance of dispersive soil samples, the bacteria Bacillus sphaericus has been employed. In this research, we focus on the improvements induced in dispersive soils as a result of microbial calcite precipitation and furthermore, the controlling factors are looked into. Pinhole experiments are used to investigate dispersivity of laboratory-made dispersive soil samples. Soil samples before and after biological stabilization have been carefully tested to determine their level of dispersivity. Factors such as curing time, as well as bacterial cell density, precipitating agent concentration, and temperature have been examined. The test results demonstrated that microbial calcite precipitation is a promising technique for stabilizing dispersive soils. The pH-decrease during microbial activity, and subsequently the decrease in the double layer thickness, as well as stabilization of exchangeable sodium ions were proposed to be major mechanisms contributing to the observed reduction in erosion potential of the soil samples. Furthermore, microbially-induced calcite precipitation results in further bonding which reduces erodibility potential of the soil samples.

Nanostructured ZnS with random close-packed structure: Synthesis, formation rate, and crystal structure study

The chemical precipitation of nanocrystalline ZnS from aqueous alkaline solutions containing zinc ethylenediamine complex salt Zn(En)2+ and thiocarbonic acid diamide N2H4CS was studied in the course of time in terms of formal chemical kinetics. The ZnS formation rate was found to depend on the concentration of precipitation agent (N2H4CS) and to decrease with increasing the ligand (ethylenediamine) concentration, whereas the pH dependence is less pronounced. The size of resulting ZnS nanoparticles does not exceed 5 nm, and their crystal structure was identified as a random close packed structure.

Recovery of zinc from industrial waste pickling liquor

The constantly increasing global demand of zinc metal along with the decreasing zinc ore reserves has led to an upward trend of zinc production from secondary sources. Galvanizing industry generates byproducts and wastes containing zinc in the form of intermetallic compounds or oxides (zinc dust). One such byproduct, waste pickling liquor (WPL) is generated in galvanizing industry during the pickling of defective galvanized material. WPL contains Zn and Fe in ionic form and is discarded after neutralization. In the present work, chemical precipitation method is used to recover zinc from WPL; with an objective to retain maximum possible iron within the WPL solution. The effect of precipitating agent concentration, number of reactions steps, temperature and stirring speed were considered to determine process parameters for maximum zinc recovery. The iron rich WPL solution with negligible quantities of zinc is a valuable ingredient for production of red oxide pigment. Thereby, two products are obtained by adopting this technique: (i) Zinc rich precipitates and (ii) iron rich pickling liquor. X-ray diffraction (XRD) analysis of precipitates (heated at elevated temperature), shows that zinc oxide and zinc ferrite phases were formed from the zinc rich precipitates.

Attempts to rationalize protein crystallization using relative crystallizability

Protein crystal growth (PCG) remains the bottleneck of crystallography despite many decades of study. The nucleation zone in the two-dimensional-phase diagram has been used to evaluate the relative crystallizability of proteins, which is expressed as a percentage over the phase area delineated by experimental protein and precipitating agent concentration ranges. For protein-salts which are subject to a direct temperature effect on solubility, as represented by Egg Lysozyme, a decrease in temperature augments the nucleation zone percentage whereas for those with retrograde solubility as a function of temperature, for example fructose-1,6-bisphosphatase in the presence and absence of AMP, an increase in temperature can significantly enhance the relative crystallizability. These results have been confirmed by the number of “hits” using PEGs as precipitating agents in Sparse Matrix Screen experiments for different proteins and are in excellent agreement with the relative crystallizability. The relationship between solubility dependence, relative crystallizability and crystallization success, has been evidenced. Such crystallizability can become a guide to identify efficient crystallization regions, providing a rational approach to PCG and structural biology.