Ammonium Hydroxide Solution Research Articles

Development of a High-Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS) Method to Determine the Presence of Rivastigmine in Human Plasma in Clinical Studies of Comparative Pharmacokinetics

The basis for conducting bioequivalence studies is the determination of the bioavailability of the active substance of the drug at its place of action by establishing the concentration of the drug in biological fluids using sensitive analytical techniques. The bioanalytical technique used should provide reliable results which would lead to satisfactory level of interpretation. To investigate the bioequivalence of rivastigmine preparations, an 8 times more sensitive method (compared to the data in the available literature) for the quantitative determination of rivastigmine in human blood plasma by HPLC-MS/MS was developed. Rivastigmine is extracted from plasma by precipitation of plasma proteins with acetonitrile. Chromatographic separation of rivastigmine and the internal standard was carried out on a YMC Triart C18. 50×2.0 mm (1.9 µm) column in a gradient elution mode with a flow rate of 0.5 ml/min. A 0.1% solution of ammonium hydroxide and acetonitrile were used as mobile phases. The lower limit of the quantitative determination of the method was 25 pg/ml.

Fluorescent Carbon Dots from Food Industry By-Products for Cell Imaging

Herein, following a circular economy approach, we present the synthesis of luminescent carbon dots via the thermal treatment of chestnut and peanut shells, which are abundant carbon-rich food industry by-products. As-synthesized carbon dots have excellent water dispersibility thanks to their negative surface groups, good luminescence, and photo-stability. The excitation-emission behaviour as well as the surface functionalization of these carbon dots can be tuned by changing the carbon source (chestnuts or peanuts) and the dispersing medium (water or ammonium hydroxide solution). Preliminary in vitro biological data proved that the samples are not cytotoxic to fibroblasts and can act as luminescent probes for cellular imaging. In addition, these carbon dots have a pH-dependent luminescence and may, therefore, serve as cellular pH sensors. This work paves the way towards the development of more sustainable carbon dot production for biomedical applications.

Analyze and Compare the Crystallographic Changes for Zinc Substituted Hydroxyapatite using X-Ray Diffraction

The main motive of the study is to analyze and compare the crystallographic changes using the X-Ray diffraction method for zinc substituted hydroxyapatite. Materials and Methods: Different types of zinc substituted hydroxyapatite are used. Calcium nitrate tetrahydrate, zinc chloride hexahydrate, diammonium hydrogen phosphate and ammonium hydroxide solutions are added and they are mixed with ammonium hydroxide solution. The ultrasonic was used to carry the precipitation method. The zinc substituted data(N=4), the total sample size was calculated as 4 using clinclac.com, alpha error is 0.05, the G power at 80%, the enrollment ratio to 0:1 and the confidence interval to 95% and the total sample size was computed. Result: Using SPSS software and a one sample T-test, 0% 1%, 5% and 10% percent of zinc with hydroxyapatite were calculated. There is a statistical significance, P=0.002, (p<0.05). The wt% of Zinc hydroxyapatite is of no significance with P=0.177, (p<0.05). The result shows that when compared to other percentages, 10% of zinc substituted hydroxyapatite. Conclusion: The analysis of this study shows that Hydroxyapatite with 10% Zinc Doped Hydroxyapatite has Superior qualities to other Substitutes for future medical applications.

High efficiency copper recovery from anode slime with 1-butyl-3-methyl imidazolium chloride by hybrid Taguchi/Box–Behnken optimization method

Anode slime which is produced by electrolytic refining of copper, is a significant source of copper production. However, conventional recovery methods for copper are characterized by complex process, huge amount of strong acid consumption and hazardous acid waste. Therefore, novel, green, and high-performance process for copper separation was developed. In this paper, a hydrometallurgical process for copper recovery from copper anode slime was proposed with ionic liquid leaching – precipitation – calcination routes. 1-butly-3-methyl imidazolium chloride (BmimCl) was used as a leaching agent. According to the hybrid Taguchi/Box-Behnken optimization, the optimum leaching conditions for copper leaching were determined as 80 % of ionic liquid concentration, 95 °C of temperature, 4.5 h of time, and 0.07 of solid/liquid ratio. Validation tests performed under optimum leach conditions confirmed the feasibility of the model and 95 % of copper leaching efficiency was obtained. Precipitation with ammonium hydroxide solution at room temperature and calcination at 600 °C processes resulted in a highly pure copper recovery as CuO. Also, under optimum conditions, highly soluble lead was easily separated after filtration by cooling in the form of PbSO4.This hydrometallurgical process is found to be simple, environmentally friendly, and adequate for the recovery of copper from copper anode slime.

Effect of Cationic Surfactant in the Synthesis Process of Nano γ-Alumina for Petroleum Industry Application

Nanotechnology is widely used in industries, including catalyst synthesis for oil and gas industries to enhance and perform new Characteristics of materials. Cetyl tri methyl ammonium bromide (CTAB) cationic surfactant was used in the synthesis of spherical nanostructured γ-alumina to enhance the morphology of the prepared nano gamma alumina which is used as a catalyst support in the naphtha reforming process. The preparation was carried out by co-precipitation method by adding drop wise of ammonium hydroxide solution and aluminum nitrate nonahydrate solution simultaneously to a solution of surfactant medium, PH and temperature of reaction were kept at 8 and 30 cᵒ respectively. The gamma alumina obtained were characterized by X- Ray Diffraction (XRD), nitrogen adsorption-desorption analysis (ASAP 2020, Micromeretics) and atomic force microscope (AFM). The sample of synthesized gamma alumina with the CTAB cationic surfactant showed that surface are (314 m2/g), pore volume (0.37 cm3/g), and pore size (3.6 nm).

Separation of platinum group metals using deep eutectic solvents based on quaternary ammonium salts

A new technique for selective separation and enrichment of platinum group metals (platinum, palladium, rhodium, iridium, ruthenium) from model hydrochloric and chloride media into hydrophobic deep eutectic solvents without the use of chelating agents is presented for the first time. The process consists in extraction of precious metals into an eutectic solvent based on tetraoctylammonium bromide and a carboxylic acid with further re-extraction of metals with ammonium hydroxide and nitric acid solutions. The extraction efficiency of metals from 0.1 M HCl was > 99.7 % for Pt and Pd; 87.3 % for Ru; 45.1 % for Ir; 28.5 % for Rh using the tetraoctylammonium bromide/hexanoic acid eutectic solvent. The developed technique was applied for the separation of platinum and palladium from refinery wastewater to obtain individual fractions with purity of > 99.9 %. The procedure does not involve the use of toxic, volatile or flammable solvents and can be an environmentally benign alternative to traditionally used approaches.

Selective Etching of Si versus Si1-xGex in Tetramethyl Ammonium Hydroxide Solutions with Surfactant.

We investigated the selective etching of Si versus Si1−xGex with various Ge concentrations (x = 0.13, 0.21, 0.30, 0.44) in tetramethyl ammonium hydroxide (TMAH) solution. Our results show that the Si1−xGex with a higher Ge concentration was etched slower due to the reduction in the Si(Ge)–OH bond. Owing to the difference in the etching rate, Si was selectively etched in the Si0.7Ge0.3/Si/Si0.7Ge0.3 multi-layer. The etching rate of Si depends on the Si surface orientation, as TMAH is an anisotropic etchant. The (111) and (010) facets were formed in TMAH, when Si was laterally etched in the <110> and <100> directions in the multi-layer, respectively. We also investigated the effect of the addition of Triton X-100 in TMAH on the wet etching process. Our results confirmed that the presence of 0.1 vol% Triton reduced the roughness of the etched Si and Si1−xGex surfaces. Moreover, the addition of Triton to TMAH could change the facet formation from (010) to (011) during Si etching in the <100>-direction. The facet change could reduce the lateral etching rate of Si and consequently reduce selectivity. The decrease in the layer thickness also reduced the lateral Si etching rate in the multi-layer.

Implementation of Magnetic Nanostructured Adsorbents for Heavy Metals Separation from Textile Wastewater

In the framework of sustainability, water shortages and water pollution are two important aspects to be considered. Proposing efficient and low-impact technologies is of paramount importance to promote circular economies associated with the use of water in the industrial context, especially in the textile industry. In this work, the application of a set of magnetic nanostructured adsorbents (MNAs) to cleanse metal ions from textile wastewaters was studied and analyzed. MNAs were generated with a low-cost process, involving iron (II/III) salts (e.g., chlorides), sodium or ammonium hydroxide solutions, and graphene oxide, obtained from graphite by a modified Hummers’ method at room temperature. The shape and the size were studied with transmission electron microscopy. Adsorbents were tested with different metal ions (e.g., copper, chromium (III), and nickel). Metal ion concentrations were analyzed by means of inductively coupled plasma optical emission spectroscopy (ICP-OES), and adsorption isotherms were characterized. From the results, the MNAs exhibited the capability of removing metal ions up to a yield of 99% for Cr3+, 94.7% for Cu2+, and 91.4% for Ni2+, along with adsorption loads up to 4.56 mg/g of MNAs.

Efficient isolation of keratin from protein-rich waste biomass: a practical approach to minimize environmental impact and valorize waste biomass

Among various protein-containing biomass wastes, waste animal wool, poultry feather, and human hair are considered one of the most important renewable sources of keratin. Animal wool and human hair are utilized for the production of several products. However, the substantial quantity of short fibers that are inappropriate for spinning and being unusable is thrown away as waste resulting in significant environmental issues in terms of their accumulation in water bodies resulting in obstruction of waterways and other related problems. Similarly, poultry wastes, especially waste chicken feathers (WCF) are dumped or burnt or used as low-value fertilizer in certain applications. The purpose of this research is to develop an efficient method that can extract the recoverable keratin from various wastes and effectively utilize the spent solvent in the extraction process. Herein suitability of an aqueous solution of quaternary ammonium hydroxide known as tetramethyl ammonium hydroxide (TMAOH, 25% w/w in water) to solubilize these protein wastes and extract keratin from them was investigated. The solvent could solubilize ca. 39–44% w/w of waste animal wool (WAW), 19–25% of waste human hair (WHH), and 55–60% of WCF. Crude keratin with ca. 19–20%, 35–37%, and 69–74% were isolated from WAW, WHH, and WCF, respectively. The chemical and structural stability of keratin thus isolated was established. The recovered TMAOH, insoluble WAW, and WCF were found to be nontoxic to soil microbes. The recovered TMAOH thus generated after isolation of keratin was used for green gram (Vigna radiata) seed treatment, and a substantial increase in the height (4–12%) and weight (9–58%) of the plants was observed. Treating biomass waste as a source of high-value compounds may minimize environmental impact by reducing the waste load.

ИЗМЕНЕНИЕ ХАРАКТЕРИСТИК МОТОРНЫХ МАСЕЛ В ДВИГАТЕЛЯХ ЗЕРНОУБОРОЧНЫХ КОМБАЙНОВ

As a result of changes in the physical and chemical characteristics of motor oil in the engines of combine harvesters, it was found that during the period of harvesting, the base number of the oil changes to a greater extent. In particular, in Don-1500 combines, the alkaline number decreased from 8 mg KOH/g to 5-6 mg KOH/g. At the same time, the viscosity of the oil and the flash point changed minimally over the period of operation of 180 hours. It was determined that during the period of storage and downtime of the combine for 10 months, the alkaline number decreased by no more than 5%, while the acid number increased, which indicates oxidative processes occurring in the oil during the downtime of combines in an open area. In terms of considering the possibility of cleaning the engine oil from resins and oxidation products, laboratory studies were carried out to remove insoluble sediment. It has been established that the addition of a 2% ammonium hydroxide solution with dissolved carbamide to the oil in a ratio of 50:50, followed by heating and centrifugation, makes it possible to reduce the content of insoluble contaminants by 10 times, the value of the acid number decreases by 2 times. In the process of conducting laboratory studies, the effect of downtime of combine harvesters on the protective properties of the oil was considered. It was determined that traces of corrosion were formed on plates made of St3 steel, not exceeding 7 ... 10% of the area of the surface treated with oil. The obtained results of the research are one of the stages in the development of technology for extending the service life of engine oil and protecting engine parts from corrosion during their post-harvest storage. The obtained results of the research are one of the stages in the development of technology for extending the service life of engine oil and protecting engine parts from corrosion during their post-harvest storage.

Toward Controllable Wet Etching of Monocrystalline Silicon: Roles of Mechanically Driven Defects.

Wet chemical etching is essential not only for processing silicon (Si) wafers but also for forming diverse structures, significantly promoting the development of the semiconductor industry. However, tight control of etched topography at the nanoscale and even atom-scale in a controllable and reproducible fashion can be hardly achieved in either laboratory research or industrial production, seriously hindering further enhancement of high-performance Si-based electronic devices. Herein, the roles of mechanically driven defects in wet etching were systematically investigated toward promoting controllable wet etching of monocrystalline Si. The role of antietching of mechanically driven amorphous Si (a-Si) and the role of promoting etching of distorted Si (including dislocations and stacking faults) were revealed in anisotropic or isotropic etchants. It was also found that the nucleation of nanocrystals in the a-Si area with increasing contact pressure can lead to deactivation of the antietching mask, and the required contact pressure for deactivation in KOH and tetramethyl ammonium hydroxide solutions was much higher than that in HF/HNO3 mixtures. The selective etching mechanisms for every defect including a-Si, distorted Si, and nanocrystals were further addressed down to the atom-scale based on the proposed dissolution model. This study provides insights into deeply understanding the role of defects in wet etching and pushes forward the idea of controllable wet chemical etching in the Si-based semiconductor industry.

Synthesis and Characterizations of Novel Spinel Ferrites Nanocomposites Al0.5Cr0.5Zn0Fe2O4 and Zn0.5Cr0.5Al0Fe2O4

In this study, novel spinel ferrites nanocomposites containing aluminum chromium zinc nanoferrites, Al0.5Cr0.5Zn0Fe2O4 and Zn0.5Cr0.5Al0Fe2O4 have been fabricated and characterized to determine the properties of highly stable conduction materials. The nanocomposites have been synthesized through the sol–gel method. Zinc and aluminum-doped chromium ferrites were prepared with the stoichiometric composition ZnxAlx-0.5Cr0.5Fe2O4 with ammonium hydroxide solution (NH4OH) and polyethylene glycol (PEG) at different temperatures with consecutive steps. After sintering the final nanoferrites, characterizations for morphological, spectral properties, and crystallinity have been determined through scanning electron microscope (SEM), Fourier transformation infrared spectroscopy, and X-ray diffraction spectrometer, respectively. SEM micrographs presented that higher sample density and agglomeration of the nanocomposite outer surface with temperature increase. The investigation of the dielectric and conduction properties presented with varying sintering temperature and Al–Zn doping greatly influenced the dielectric properties of spinel nanoferrites dielectric properties: dielectric loss tangent and dielectric constant. The effects of various sintering temperatures provide synergistic effects on the morphology and dielectric conductivity features. The characterizations presented that the dopants (Al, Zn) enhanced the magnetic and electrical properties of both chromium nanoferrites which can be implemented in high frequency single-layered electromagnetic waves absorbing devices in electrical and medical appliances in future.

Sustainable TLC-densitometric method for pharmacokinetic study of the concurrently used ibuprofen and metronidazole: Green metric assessment

Combination therapy with metronidazole has been demonstrated to be superior in surgical site infections and pain treatment protocols. Ibuprofen, on the other hand, is an effective and safe medication with long duration of action for patients with post-operative pain.In this investigation, in vivo estimation of metronidazole and ibuprofen was performed, followed by a pharmacokinetic study using an ecological TLC-densitometric approach. Separation of drugs and the internal standard, furosemide from plasma matrix was performed using ethyl acetate: ethanol: ammonium hydroxide solution 33% (5:5:0.1, by volume) on TLC silica gel 60 F254 plates and scanning at 220.0 nm and 310 nm. The method was sensitive for metronidazole and ibuprofen in the ranges of 0.1–2.5 and 0.1–3.0 µg/band, respectively.Furthermore, the devised method’s performance was evaluated by analyzing various samples obtained from volunteers at different time intervals who received either a single medication or a combination of drugs. The information gathered was utilized to investigate the pharmacokinetic properties of both medicines. According to the findings of the pharmacokinetic study, co-administration of metronidazole and ibuprofen increased their maximum plasma concentrations and time required to reach this concentration. It was also discovered that ibuprofen greatly influenced the bioavailability and distribution of metronidazole. Accordingly, care should be taken when both medications are used simultaneously, especially for metronidazole, which requires dose regulation. Furthermore, different novel Green analytical chemistry metrics were applied to assess the suggested method, including GABI, RGB colored tool, AGREE, and hexagon. The results revealed that the developed analytical approach had a negligible environmental impact.

Selective Recognition of Caffeine by (3-aminopropyl) Triethoxysilane Based Polymers

Background: The metal alkoxides undergo the sol-gel process leads to highly dense polymer networks in nano range size particles. Template-mediated nanomaterial fabrication involves functional monomers, cross binders, catalysis, and other favorable thermal conditions optimized to prepare thermal, mechanical, and chemo-stable tailor-made complimentary recognition sites ceramic materials. Methods: The present study is focused on imprinting of caffeine by sol-gel method, wherein functional monomer as (3-aminopropyl) triethoxysilane (APTES), crosslinker as tetraethyl orthosilicate (TEOS), and ammonium hydroxide solution as catalyst were considered to prepare materials, and those materials characterized. The catalyzed hydrolysis and condensation were carried with a wide range of composition mixtures in acetonitrile optimized at 60 oC. The imprinted polymers (MIPs) and Non-Imprinted Polymers (NIPs) characterized by FTIR, GC-MS, SEM, and EDS techniques. Further post-polymerization studies were carried to investigate recognizing capacity specificity and the binding capacity of the caffeine and its structurally similar analogs with imprinted / non-imprinted polymers. Results: The studies revealed that efficiency in the template removal was high in the imprinted polymers in which low concentration of crosslinker and whereas the selectivity of the template was observed to be high compared with polymers with higher concentrations. Conclusion: In conclusion, high binding affinity was observed in imprinted polymers to that of non- Imprinted polymers.

Constructing a heparin-modified penile decellularized scaffold to improve re-endothelialization in organizational reconstruction.

BackgroundDue to the unique anatomy and complex function of the penis, the reconstruction of penile defect is fraught with great challenges. The current standard methods are limited by numerous complications and insufficient donor sites. While functional vascularized penile tissue engineering offers a novel way to address this problem, revascularization remains the primary concern.MethodsIn this study, a penile scaffold with associated modifications was constructed. The performance of decellularized penile scaffolds (DPSs) was improved by conjugation with heparin (HEP) and reseeding with human umbilical vein endothelial cells (HUVECs). There were three groups according to the modifications, including native DPSs, HEP-DPSs, HEP-HUVECs-DPSs. After perfusing with 1% Triton X-100/0.1% ammonium hydroxide solution, the cellular components were removed. Subsequently, the covalent binding of heparin in the DPSs was performed with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide, followed by reseeding with HUVECs. Scaffolds were implanted into the backs of rats and the implanted tissues were harvested at 1, 2, 3, and 4 weeks. Then hematoxylin and eosin (H&E) staining and immunofluorescence assays were performed to assess the degree of angiogenesis.ResultsThe native DPSs retained the extracellular matrix and heparinized modification. The H&E results indicated that more HUVECs covered the inner surface of tubular structures in the HEP-DPSs group compared to the native DPSs group. The number of vessels in the HEP-HUVECs-DPSs was significantly increased compared to the control scaffolds at all time points.ConclusionsThese results suggested that, compared to the native DPS, heparin-conjugated scaffolds provided a superior environment for the growth of HUVECs and the modified methods provided a perspective for overcoming the obstacles in tissue engineering of transplantable penile tissues and the establishment of a functional vasculature.

Experimental study of maghemite nanomaterials towards sustainable energy storage device application

In this paper, the facile synthesis and characterization aspects of maghemite nanoparticles has been presented, in the context of energy storage device technology. An experimental study of the structural, magnetic, optical and thermal properties of cobalt and zinc doped maghemite nanoparticles prepared by coprecipitation of ferrous, ferric, and the dopant precursors in water at different temperatures and pH of ammonium hydroxide solution has been done. The structural characterization establishes that all the samples have high surface area and are highly crystalline, 5–10 nm spherical nanoparticles with the cubic spinel structure. The magnetization curve is steeply linear with saturation magnetization in the tune of 60 emu/gm. The magnetic characterization reveals peculiar trends with zinc and cobalt doping, main features being the increase in the saturation magnetization, coercivity with doping, and thermal stability. The high sensitivity evident from magnetization features can be used for state estimation of the energy storage devices. In comparison to 2.2 eV of the bulk maghemite, the optical band gap of the nanoparticles has been calculated as 3.9 eV, which can be modulated up to 4.67 eV with the doping reported herein, thus establishing the conductivity modulation strength of the synthesized samples. The thermal gravimetric analysis establishes the thermal stability of the maghemite. The affordability of the maghemite electrode iron batteries will surely be helpful for scaling up the renewable energy storage technology.

Effect of the Number of Dipping Cycles for a Cadmium Oxide Film Prepared by SILAR Method

The thin films of cadmium oxide (CdO) were deposited using the SILAR (Successive ionic layer absorption and reaction) method at various deposition cycles. CdO thin films were made on glass substrates at a temperature of 95°C, using a cadmium acetate source material and an ammonium hydroxide solution. One of the main criteria that impact the quality of thin films is the number of deposition cycles. The size of the crystals decreases with the increase in the number of cycles from 33.7 nm at the immersion cycle 10 to 22.7 nm at the immersion cycle 20, as shown by the X-ray diffraction results. The optical band gap energy of the films reduces as the number of deposition cycles increases, while the transmittance of the Cadmium oxide film increases as the dipping cycle increases. FTIR analytics of the sample showed that the transmittance increases with the immersion cycles. The thickness of the sample measured by the Michelson method increases with the increase in sedimentation.

Experimental Method for Evaluating the Reactivity of Alkali-Carbonate Reaction Activity.

The main aim of this study was focused on the Method of testing alkali-carbonate reaction activity to avoid alkali-carbonate reaction damage. In this paper, the alkali-carbonate reaction activity and alkali-silica reaction activity of ten kinds of aggregates were determined and analysed by existing standards and methods, by making specimens with aggregates of 2.5–5 mm and 5–10 mm particle size, cured in 1 mol/L tetramethyl ammonium hydroxide solution at 60 °C and 80 °C. Tetramethyl ammonium hydroxide solution was used to exclude the expansion caused by alkali-silica reaction. Effects of aggregate particle size and curing temperature on the expansion of samples were systematically investigated to determine alkali-carbonate reactivity of aggregates. In order to explore the relationship between stress and strain of aggregates, these aggregates were prepared into compacted bodies to test their stress and try to discover the pattern. The results showed that the expansion of the mould specimen prepared by the aggregate of 5–10 mm particle size, cured in 1 mol/L tetramethyl ammonium hydroxide solution at 80 °C was greater than 0.1% after 42 days, which could be used as a reference criterion to determine the alkali-carbonate reaction activity of the aggregate. In addition, the expansion stress test suggest that the alkali-carbonate reaction can generate expansion stress. The expansion stress of aggregates with alkali-carbonate reaction activity were much larger than that of aggregates without alkali-carbonate reaction activity. Through SEM and EDX analysis of the products of the alkali-carbonate reaction, it was shown that the dolomite crystals in the dolomitic aggregates reacted with the TMAH solution and resulted in alkali-carbonate reaction, forming calcite and brucite.

Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts

First-row (3d) transition metal oxyhydroxides have attracted increasing attention due to their various advantages. Although investigating the oxidation mechanism and processing such materials into hierarchical architectures are greatly desired for their further development, it remains unclear how the oxidation state change occurs, and efforts to produce hierarchical oxyhydroxides in compliance with high ecological and economic standards have progressed slowly. Here, we describe a facile one-step coprecipitation route for the preparation of hierarchical CoOOH, NiOOH and MnOOH, which involves the diffusion of NH3 originating from ammonium hydroxide solution into an aqueous solution containing metal ion salts and K2S2O8. Comprehensive characterizations by scanning electron microscope, transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and in situ pH measurement demonstrated that K2S2O8 induces the oxidation state change of metal ion species after the start of hydrolysis. Meanwhile, it was found that, benefiting from the OH– concentration gradient created by the NH3 diffusion method and the suitable growth environment provided by the presence of K2S2O8 (high nucleation rate and secondary nucleation), the formation of hierarchical oxyhydroxide structures can be realized in aqueous solution at ambient temperature without the use of heat energy and additional structure-directing agents. The hierarchical CoOOH structures are performed as the electrocatalysts for the oxygen evolution reaction in alkaline media, which exhibit good activity with an overpotential of 320 mV at 10 mA cm−2 and a low Tafel slope of 59.6 mV dec–1, outperforming many congeneric electrocatalysts. Overall, our study not only provides important insights to understand the formation mechanism of hierarchical oxyhydroxides, but also opens up new opportunities for the preparation of hierarchical oxyhydroxides via a facile, green and low-cost method.

Sorption of Copper Ions from the Nitric Acid Solution of Electrolytic Refining of Silver with Using Chelating Resin Axionit BPA

The article considers a sorption method for extracting copper ions from a model nitric acid solution based on a solution of electrolytic refining of silver with using sorbents with bis-picolylamine functional groups: Dowex M-4195 and AXIONIT BPA. The possibility of extracting copper to residual concentrations in the solution of less than 10 mg/l is shown. The working capacity of both samples under batch conditions, as well as the dynamic exchange capacity and the full dynamic exchange capacity under dynamic сonditions (column test), are determined. The effect of the flow rate of the solution into the column on the kinetics of the sorption of copper ions on AXIONIT BPA is shown. The possibility of desorption of copper with a solution of 3 %, 5 % NH4OH was investigated, and a two-stage scheme of desorption of copper was tested: 5 % and 10 % with a solution of ammonium hydroxide