Zinc Reduction Research Articles

Enhancing zinc uptake and grain yield of Ciherang and Inpari IR Nutri Zinc rice varieties using Zn-solubilizing bacteria

In elevated atmospheric CO2 conditions, a prominent greenhouse gas contributing to climate change, there is a notable reduction in zinc (Zn) concentration within lowland rice crops. Zn deficiency diminishes rice productivity and lowers Zn content in grains, impacting human health, particularly stunting. This study aims to assess the effects of applying isolated Zn-solubilizing bacteria (ZnSB) strains and ZnSO4 on Zn uptake and yield in two rice varieties: Inpari IR Nutri Zinc (high Zn content) in the first trial and Ciherang (medium Zn content) in the second trial, conducted in an Inceptisol soil. The treatments were organized in a Randomized Block Design with three replications. The first factor involved ZnSO4 fertilizer (Z0 = without ZnSO4; and Z1 = with ZnSO4). The second factor was ZnSB strains (B0 = without ZnSB; B1 = Klebsiella pneumoniae Zn2; B2 = Enterobacter cloacae CmA12; B3 = E. bugandensis CmD2; B4 = S. marcescens CmT13; and B5 = B. thuringiensis PuT1). The results indicated that applying ZnSB strains without ZnSO4 significantly increased grain yields for both Ciherang and Inpari IR Nutri Zinc varieties (7.67% and 4.12%, respectively) and enhanced Zn uptake (28.05% and 13.58%, respectively). Moreover, combined ZnSB and ZnSO4 application also significantly increased yields for both varieties (12.14% and 25.03%, respectively) and Zn uptake (33.29% and 13.99%, respectively), demonstrating the potential of ZnSB for enhancing Zn uptake and rice yield. These findings suggest promising strategies for addressing Zn deficiency in rice cultivation under elevated CO2 conditions.

НЕЙТРАЛ ОРТАДА (NA2SO4) АЙНЫМАЛЫ ТОКПЕН ПОЛЯРИЗАЦИЯЛАНҒАН МЫРЫШ ЭЛЕКТРОДЫНЫҢ ЭЛЕКТРОХИМИЯЛЫҚ ЕРУІ

Мақалада потенциинамикалық поляризация қисықтары арқылы натрий сульфатының ерітіндісінде мырыштың электрохимиялық еруі қарастырылады. Мырыш ерітіндіде екі валентті иондар түрінде анодты еріген кезде және одан әрі сумен әрекеттескенде электрод бетінде пассивті қабат түрінде мырыш гидроксиді түзілетіні анықталды. РН 2-ден 5-ке дейін жоғарылаған сайын мырыштың еру жылдамдығы төмендейді. РН 10-да мырыштың тотығуы үлкен артық потенциалмен жүреді, бірақ гидроксо формасына байланысты электрод бетінде бірдей жылдамдықпен ериді. Электролит температурасының мырыштың анодты еріту процесіне әсері. Температураның жоғарылауымен анодтық токтың максимумдары артады. Температуралық-кинетикалық әдіс бойынша 300, 500 және 700 мВ асқын кернеуді белсендірудің тиімді энергиясы есептелген, оның мәні сәйкесінше 17,8, 15,5 және 15,4 кДж / моль болды, бұл проценттің диффузиялық режимінің басталуын көрсетеді.

ELECTROCHEMICAL DISSOLUTION OF A ZINC ELECTRODE POLARIZED BY ALTERNATING CURRENT IN A NEUTRAL MEDIUM (NA2SO4)

This article discusses the electrochemical dissolution of zinc sulfate solution, sodium registration method potendinamicheskih polarization curves. It has been found that when the anodic dissolution of zinc into the solution as divalent ions, and further by reacting with water formed by hydrolysis of zinc hydroxide , postponing which generates on the electrode surface passivation layer . With increasing pH from 2 to 5 occurs the dissolution rate of zinc reduction. At pH 10, zinc oxidation proceeds with a large over potential, however due form hydroxo metal electrode dissolves at the same rate. The influence of electrolyte temperature on the process of anodic dissolution of zinc. With increasing temperature the increase of anodic current maxima. By temperature- kinetic method to calculate the effective activation energy, overvoltage 300, 500 and 700 mV, its value was 17.8 15.5 15.4 kJ / mol, respectively, which indicates the occurrence of a diffusion process mode.

Comparative evaluation of serum zinc level in head and neck cancer patients before and after radiation therapy.

Head and neck cancers (HNCs) include 5.3% of all cancers and they are the cause of the same 5.3% of cancer deaths. Oxidative stress has a crucial role in cancer progression and cancer therapy. Ionizing radiation causes cell malfunction and death by creating reactive oxygen species. Due to its antioxidant activity, immune system power enhancement and role in apoptosis, zinc is a crucial trace element in oncology including HNCs. We decided to compare serum zinc level of HNC patients before and after RT, to assess the potential effects of ionizing radiation therapy on serum zinc. Fifty-seven HNC patients, who were candidates for curative radiation therapy (RT), were enrolled and their serum zinc level just before and 2 months after completion of RT were checked in a single laboratory. RT was prescribed by linear accelerator with 60 to 70 Gy by conventional method. Data were analyzed by SPSS 20. Mean serum zinc prior to RT and following RT were 77.64±13.45 mg/dl and 68.28±11.93 mg/dl, respectively, which was lower following RT (p<0.001). Patients' sex, age and duration from diagnosis to treatment and site of disease didn't have any impact on serum zinc difference. This study showed that RT of HNCs leads to serum zinc reduction, which is greater in nodal disease because of either larger field or higher dose of radiation. Taking zinc supplements while being treated by RT, may be necessary.

Possible protective effect of zinc administration on renal and cognitive changes occurring in uninephrectomized adult male Wistar rats.

What is the central question of this study? Are renal changes occurring post-nephrectomy accompanied by cognitive changes, and does early administration of zinc supplements such as ZnSO4 to uninephrectomized rats ameliorate the renal and cognitive changes if present? What is the main finding and its importance? Uninephrectomy-induced renal changes were accompanied by species-atypical behaviour in rats in both Morris water maze and T maze tests, together with hypozincaemia and hippocampal inflammatory and oxidative changes. Early zinc administration to uninephrectomized rats ameliorated the renal, behavioural, hippocampal and serum zinc changes. Cognitive impairment is increasingly recognized as an important consequence of kidney disease in humans. Kidney donation is a safe procedure but is known to increase the long-term risk of cardiovascular and kidney disease. Whether kidney donation impairs cognitive function is not known. In the present study, we examined whether the renal changes occurring post-nephrectomy were accompanied by cognitive changes as well, and whether early administration of zinc supplements such as ZnSO4 to uninephrectomized (UNX) rats could ameliorate the renal and cognitive changes if present. The present study included 30 adult male Wistar rats that were randomly assigned to three groups (n=10 per group): sham-operated rats, UNX and UNX treated with ZnSO4 for 20weeks. Before termination, rats were subjected to 24-h urine collection and behavioural testing with the Morris water maze and T maze tests. UNX induced significant proteinuria, renal functional, fibrotic and oxidative changes, as well as increased renal desmin expression. UNX rats also showed significant behavioural changes indicating spatial learning and memory affection, together with decreased hippocampal brain derived neurotrophic factor (BDNF) and antioxidant capacity, and increased glial fibrillary acidic protein (GFAP), nitric oxide and malondialdehyde. In addition, UNX induced significant hyperglycaemia and dyslipidaemia, as well as significant reduction in serum zinc, copper and selenium. Early administration of ZnSO4 starting 1week post-nephrectomy significantly ameliorated renal and behaviouralchanges, as well as hippocampal oxidative, BDNF and GFAP changes. Additionally, Zn recovered serum changes of triglycerides, cholesterol, zinc and copper. Therefore, early administration of zinc to humans undergoing nephrectomy may be of benefit and should be considered in human trials.

The Influence of Varying Thermal Treatment Conditions on Reducing Zinc Content from a Steelmaking and Blast Furnace Sludge

The prospects of processing blast furnace and steelmaking sludge using the Waelz process in a laboratory rotary kiln, is shown. The influence of different processing temperatures, furnace atmosphere and the type of reducing agents on the level of zinc reduction from sludges was analyzed. In general, the blast furnace sludge contains a high portion of iron (approx. 48 wt.%) and can be reused as a charge after satisfactory zinc reduction. It was found that N- atmosphere and a high content of the graphite or coke oven reducing agent in combination with high temperature can reduce the content of Zn in the sludge to 0.08 wt.% at 1200 °C for a mixture of steelmaking and blast furnace sludge. A significant reduction in the Zn content to 0.66 wt.% occurs at 1100 °C. The content and type of reducing agent plays an important role; graphite has shown a better reducing ability compared to coke oven dust. When nitrogen is used, zinc is reduced even without an additional reducing agent, since the carbon contained in the sludge is made use of for the reduction. In an air atmosphere, without the use of a reducing agent, there was no reduction in the Zn content.

Understanding H2 Evolution Electrochemistry to Minimize Solvated Water Impact on Zinc‐Anode Performance

H2 evolution is the reason for poor reversibility and limited cycle stability with Zn-metal anodes, and impedes practical application in aqueous zinc-ion batteries (AZIBs). Here, using a combined gas chromatography experiment and computation, it is demonstrated that H2 evolution primarily originates from solvated water, rather than free water without interaction with Zn2+ . Using linear sweep voltammetry (LSV) in salt electrolytes, H2 evolution is evidenced to occur at a more negative potential than zinc reduction because of the high overpotential against H2 evolution on Zn metal. The hypothesis is tested and, using a glycine additive to reduce solvated water, it is confirmed that H2 evolution and "parasitic" side reactions are suppressed on the Zn anode. This electrolyte additive is evidenced to suppress H2 evolution, reduce corrosion, and give a uniform Zn deposition in Zn|Zn and Zn|Cu cells. It is demonstrated that Zn|PANI (highly conductive polyaniline) full cells exhibit boosted electrochemical performance in 1M ZnSO4 -3M glycine electrolyte. It is concluded that this new understanding of electrochemistry of H2 evolution can be used for design of relatively low-cost and safe AZIBs for practical large-scale energy storage.

Thermodynamic modeling of metal reduction in copper-smelting slags and experimental verification of its results

Over 110 million tons of slag were accumulated in the dumps of the Russian copper-smelting enterprises, and their number is increasing. Environmental taxes and dumps maintenance costs are burdensome, which makes it necessary to make the most complete disposal of these production wastes. At the same time, these slags contain valuable elements, in particular, iron, copper, zinc, selenium, arsenic and some others, the extraction of which can make recycling profitable. The paper presents the results of a thermodynamic calculation of the behavior of copper-smelting slag elements in the mixture with carbon during heating. Modeling was performed using the TERRA software package. The influence of the process temperature in the range of 600 – 1750 °C on reduction of iron, zinc and silicon was analyzed at the amount of carbon in the system corresponding to the stoichiometry of iron reduction reactions and exceeding the stoichiometric one. It was established that when heated above 650 °C, metallic iron appears in the system, and its full reduction is completed at 1250 °C. The appearance of metallic zinc is observed in two temperature ranges: in the first, appearance of zinc is observed with a simultaneous decrease in concentration of zinc oxide; in the second, an increase in concentration of metallic zinc with a simultaneous decrease in concentration of zinc sulfide. At temperatures above 1650 °C, silicon appears in the system. Under laboratory conditions, the processes of solid-phase reduction of iron with the capture of zinc oxide and separation of the reduction products were tested. It was established that as a result of pyrometallurgical separation by melting reduction products, iron-carbon alloys (steel and cast iron) and alloys with high silicon content can be obtained. The results of the work can be used in development of theoretical and technological foundations for the processing of copper smelting slags, which are not processed by existing technologies.

Reductive elimination of alkoxy group in anthraquinone derivatives

Anthraquinone derivatives are constantly in a focus of synthetic chemists due to a diversity of valuable biological, photochemical and redox properties. However, quinone core limits applicability of chemical transformations making a search for new methods of modification of anthraquinones highly demanded. A convenient approach of regioselective reductive α-alkoxy group cleavage of anthraquinone derivatives was developed and evaluated. Most effectively transformation goes via a zinc reduction of quinone moiety and prototropic rearrangement in acidic media followed by the alkoxy group elimination. Strong donors in β-position of anthraquinone core are crucial for transformation and provide the elimination exclusively from α-position. The method simplifies an access to some bioactive 1,3-substituted anthraquinones and was applied for synthesis of natural products, e.g., rubiadin 1-methyl ether, anthragallol 1,2-dimethyl ether, and damnacanthol.

Improvements in Performance and Cost Reduction of Large-Scale Rechargeable Zinc|Manganese Dioxide Batteries and a Future Roadmap Driven through Real World Applications

Zinc|Manganese Dioxide (Zn|MnO2) are widely available as primary batteries for use in small-scale consumer electronics because of its low cost and high energy density. The last decade has seen a resurgence in research to make this chemistry rechargeable by materials engineering, additives and experimenting with various electrolytes. These important contributions have showed that Zn|MnO2 has all the prerequisites to be a post-lithium solution for grid-scale storage.At Urban Electric Power, we have been commercializing proton-insertion Zn|MnO2 batteries in cylindrical and prismatic form factors between 70 to 140Ah nameplate capacity. These batteries contain improved materials and electrode designs with improved utilizations of the cathode and anode theoretical capacity. Both the cathode and anode can achieve 40 to 60% of their theoretical capacity, which is currently the best in alkaline electrolytes and scaled-up cells. These improvements not only reflect the performance but also the manufacturability of cells on a large scale. In this talk, we will present the methodological approach we pursued to achieve these performance metrics and reduce the cost to <$80/kWh. We also cycled these cells according to various protocols that represent real world applications. For example, we found that the newly improved Zn|MnO2 cells can achieve >6 years of performance for solar microgrid applications, which is better than lead acid batteries, the current battery of choice. We have also manufactured gelled Zn|MnO2 batteries that can be considered as “non-spillable” and thus, “non-hazardous” according to transportation regulations. These non-spillable cells manufacturing process and performance will also be presented in the talk. The talk will also expand on the future generations of Zn|MnO2 that are currently under development at Urban Electric Power like the conversion battery which access the complete 2nd electron capacity of the electrodes and the high voltage (>2.5V) battery. These batteries expand the application space of Zn|MnO2 batteries which make it a viable contender for post lithium-ion batteries.

Biogenic plant mediated synthesis of monometallic zinc and bimetallic Copper/Zinc nanoparticles and their dye adsorption and antioxidant studies

• The eco-friendly Zn NPs and Cu/Zn NPs were synthesized by using an aqueous extract of Mirabilis Jalapa. • Synthesized Zn NPs and Cu/Zn NPs were assessed for their antioxidant potential. • The Cu/Zn NPs possessed greater antioxidant and dye removal efficacy as compared to their monometallic counterpart. • Antioxidant potential of nanoparticles, determined by DPPH radical scavenging method 72% and 89.5%. In the present research zinc (monometallic) and copper/zinc (bimetallic) nanoparticles were synthesized using the green approach. Aqueous extract of Mirabilis Jalapa was used for the reduction of zinc and copper salts to generate zinc (monometallic) and copper/zinc nanoparticles (bimetallic). The morphology, crystal structure and elemental composition of the constructed nanoparticles were evaluated by SEM, Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and energy dispersive X-ray (EDX) studies. The constructed nanoparticles were evaluated for their antioxidant ability. Antioxidant potential of nanoparticles, as determined by DPPH radical scavenging method was found to be 72% for Zn monometallic NPs while 89.5% scavenging potential was recorded for copper/zinc bimetallic nanoparticles at the concentration of 1500 μg/ml. Percentage scavenging potential was found to be increased with an increase in concentration. Zinc nanoparticles had total antioxidant activity and total phenolic content of 1.263 and 296 (mg/g GAE), whereas copper/zinc had 2.06 and 287 (mg/g GAE). The percentage removal of Congo red and methylene blue dyes was chosen by varying different parameters such as time, temperature, pH, adsorbent dose, and concentration of adsorbate. Results showed better removal efficacy of dyes with Cu/Zn nanoparticles as compared to the Zn nanoparticles.

Isolation of Echimidine and Its C-7 Isomers from Echium plantagineum L. and Their Hepatotoxic Effect on Rat Hepatocytes.

Echimidine is the main pyrrolizidine alkaloid of Echium plantagineum L., a plant domesticated in many countries. Because of echimidine’s toxicity, this alkaloid has become a target of the European Food Safety Authority regulations, especially in regard to honey contamination. In this study, we determined by NMR spectroscopy that the main HPLC peak purified from zinc reduced plant extract with an MS [M + H]+ signal at m/z 398 corresponding to echimidine (1), and in fact also represents an isomeric echihumiline (2). A third isomer present in the smallest amount and barely resolved by HPLC from co-eluting (1) and (2) was identified as hydroxymyoscorpine (3). Before the zinc reduction, alkaloids (1) and (2) were present mostly (90%) in the form of an N-oxide, which formed a single peak in HPLC. This is the first report of finding echihumiline and hydroxymyoscorpine in E. plantagineum. Retroanalysis of our samples of E. plantagineum collected in New Zealand, Argentina and the USA confirmed similar co-occurrence of the three isomeric alkaloids. In rat hepatocyte primary culture cells, the alkaloids at 3 to 300 µg/mL caused concentration-dependent inhibition of hepatocyte viability with mean IC50 values ranging from 9.26 to 14.14 µg/mL. Our discovery revealed that under standard HPLC acidic conditions, echimidine co-elutes with its isomers, echihumiline and to a lesser degree with hydroxymyoscorpine, obscuring real alkaloidal composition, which may have implications for human toxicity.

Absolute Quantitation of N-Nitrosamines by Coulometric Mass Spectrometry without Using Standards.

Carcinogenic N-nitrosamines were recently found in the sartan family of drugs and caused many drug recalls. Both of their detection and quantification are therefore important. Methods reported for N-nitrosamine quantitation rely on the use of standards and are just applicable to simple N-nitrosamines. There is an urgent need to quantify N-nitrosamines derived from drugs with a complicated structure that lack standards. To tackle the issue, this study describes a novel absolute quantitation strategy for N-nitrosamines using coulometric mass spectrometry (CMS) without standards. In our approach, N-nitrosamine is first converted into electrochemically active hydrazine via zinc reduction under acidic condition and the resulting hydrazine can then be easily quantified using CMS. To validate our method, six simple N-nitrosamines, N-nitrosodiethylamine (NDEA), N-nitroso-4-phenylpiperidine (NPhPIP), N-nitrosodiphenylamine (NDPhA), N-nitrosodibutylamine (NDBA), N-nitrosodipropylamine (NDPA), and N-nitrosopiperidine (NPIP), were chosen as test samples, and they all were quantified with excellent measurement accuracy (quantitation error ≤1.1%). Taking this one step further, as a demonstration of the method utility, a drug-like N-nitrosamine, (R)-N-(2-(6-chloro-5-methyl-1'-nitroso-2,3-dihydrospiro[indene-1,4'-piperidin]-3-yl)propan-2-yl)acetamide (VII), was also synthesized and successfully quantified using our method at 15 ppb level in a complex formulation matrix, following solvent extraction, N-nitrosamine isolation, and reductive conversion. Because of the feature of requiring no standards, CMS provides a simple and powerful approach for N-nitrosamine absolute quantitation and has great potential for analysis of other drug impurities or metabolites.

Thermodynamic Modeling of Iron and Zinc Reduction from B2O3–CaO–Fe2O3–ZnO Melt by СО–СО2 and Н2–Н2О Mixtures

Thermodynamic Modeling of Iron and Zinc Reduction from B2O3–CaO–Fe2O3–ZnO Melt by СО–СО2 and Н2–Н2О Mixtures

The impact of the transport and road complex on heavy metal pollution of soils and plants

This work aims to analyze heavy metals (HM) in soils and plants of the Balashikha, Moscow region. The authors studied HM content in soil and plant organs of Caragana arborescens and Taraxacum officinale depending on the distance of a motorway. The article shows the relationship between the concentration of HM in the soil and its content in plants. The authors also revealed the peculiarities of accumulation of some heavy metals - cadmium, lead, zinc and copper - in vegetative and generative organs of the studied plants. The authors noted the highest concentration of all heavy metals in dandelion growing near a motorway. According to the share in the total content of the determining elements, the metals can be arranged in the following order: Zn&gt; Pb&gt; Cu&gt; Cd. The authors also observe a different pattern: Zn&gt; Cu&gt; Pb&gt; Cd in soils with less pollution, i.e. in plants located at a 3000 m from the motorway. It has been observed that with a length of 3000 m from the highway compared to the 5 m zone of the road. There is a 1.13 times reduction in lead, 1.74 times reduction in cadmium, 1.89 times reduction in zinc and 1.66 times reduction in copper content in the soil and plants. The analysis shows that the studied plants can be used as bio-indicators of pollution of the biota of large cities. The most hazardous elements are cadmium and lead, which belong to the first hazard class, found in the atmosphere and ecosystems of cities, which is connected with intensive vehicular traffic. On working days, the traffic intensity in the morning hours (08.00-09.00) was 2500 cars and in the evening hours (18.00-19.00) 3000 cars (federal road M7 “Volga”).

Process Development for Integrated Use of Metallurgical Production Wastes

A physicochemical mechanism was studied for carbon thermal reduction of zinc and iron oxides from blast furnace slurries as well as from gas cleaning unit dusts of steelmaking furnaces. With the use of the kinetic analysis the optimal conditions were defined for the carbon thermal reduction as well as the initial data for the development of the joint carbon thermal reduction processes of zinc and iron oxides. An appropriate and clean process was developed; it allows pellet production from zinc containing dusts and their processing in a rotating furnace with an almost complete zinc rundown and trapping in the hose filters; while the metallic iron remaining in the pellets may be used for conversion. The data obtained through the industrial testing confirms the appropriateness of the process implementation and allows the cost effectiveness analysis of the zinc containing dust reclaiming.

Influence of Different Carbon Content on Reduction of Zinc Oxide via Metal Bath

Electric arc furnace dust (EAFD) is an important secondary resource for the zinc industry. The most common process for its recycling is the pyro-metallurgical treatment in the Waelz process. However, this process focuses on the recycling of the zinc, whereas the recovery of other metals from the EAFD—such as iron and other alloying elements—is neglected. An up-to-date version of reprocessing can involve multi-metal recycling by means of a metal bath containing carbon. The use of a liquid iron alloy requires a higher processing temperature, which enables the reduction and melting of iron oxides as well as other compounds occurring in the dust. Furthermore, the Zn yield is higher and the reduction kinetics are faster than in the Waelz process. This paper is only focused on the zinc reduction in such a metal bath. In order to determine the influence of the carbon content in the molten metal on the reduction rate, experiments were carried out on the reduction behavior of zinc oxide using a synthetic slag. This slag, with a basicity B2 = 1, was applied to an iron bath with varying carbon contents. (0.85%, 2.16%, 2.89%, and 4.15%) The decrease in the zinc oxide concentration was monitored, along with the reaction rates calculated from these data. It was found that the reaction rate increases with rising carbon content in the melt.

Flow Effects on the Morphology of Silicon Materials Produced in a Gas Phase Reaction of SiCl&lt;sub&gt;4&lt;/sub&gt;

Chemical reaction formula does not provide information on size and morphology of formed solids. In this talk, we introduce our recent results on process-dependent changes in size and morphology of silicon solids produced via zinc reduction of SiCl4. Silicon whiskers, microparticles and nanowires form in the reaction, in which zinc vapor reduces SiCl4 and zinc droplets catalyse crystallization of silicon. Flow of gases in a reactor and temperature of substrate affect solidification processes of silicon. Effects of there factors on the formation of silicon whiskers and nanowires are discussed using both experimental results and numerical analysis.

Thermodynamic modeling of iron and zinc reduction from B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; ‒ CaO ‒ Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; ‒ ZnО melt by СО ‒ CO&lt;sub&gt;2&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt; ‒ Н&lt;sub&gt;2&lt;/sub&gt;О mixtures

The paper presents the thermodynamic modeling results of zinc and iron reduction from B2O3 ‒ CaO ‒ Fe2O3 ‒ ZnО melts by CO ‒ CO2 and H2 ‒ H2O mixtures containing 0 – 60 % CO2 (H2O) at 1273 – 1673 K using a technique describing the reduction of metals from an oxide melt by gas in bubbling processes, under conditions that provide an approximation to real systems. Its originality is equilibrium determination for each individual portion of gas supplied into the working fluid. The reducible metals oxides content in each calculation cycle is taken from the previous data. During the calculations, changes in the content of zinc (СZnO ) and iron (СFe2O3 , СFe3O4 and СFeO ) oxides in the melt and the degree of their reduction were estimated. When using CO or H2 as a reducing agent, this process proceeds in three stages. In the first stage, Fe2O3 is reduced to Fe3O4 and FeO. CFe2O3 values decrease to almost zero, while CFe3O4 and CFeO increase simultaneously. By the end of the stage, СFe3O4 reaches its maximum value. At the second stage, the Fe3O4 → FeO transition occurs, when СFeO values reach its maximum. At these stages, there is a slight increase in the CZnO . At the third stage, the values CFeO and CZnO decrease, and iron and zinc are reduced. An increase in temperature dramatically reduces the gas consumption for zinc reduction by 2 – 3 times, and the replacement of CO with H2 reduces it by less than 20 %. In the presence of oxidizing agents (CO or H2O), only zinc is reduced. The process ends when the final content of zinc oxide in the melt corresponds to the equilibrium with the initial gas composition. The higher the temperature, the less CZnO is. The obtained data are useful for the development of technologies for the selective recovery of metals.

Cobalt-Catalyzed Chemo- and Enantioselective Hydrogenation of Conjugated Enynes.

Asymmetric hydrogenation is one of the most powerful methods for the preparation of single enantiomer compounds. However, the chemo- and enantioselective hydrogenation of the relatively inert unsaturated group in substrates possessing multiple unsaturated bonds remains a challenge. We herein report a protocol for the highly chemo- and enantioselective hydrogenation of conjugated enynes while keeping the alkynyl bond intact. Mechanism studies indicate that the accompanying Zn2+ generated from zinc reduction of the CoII complex plays a critical role to initiate a plausible CoI /CoIII catalytic cycle. This approach allows for the highly efficient generation of chiral propargylamines (up to 99.9 % ee and 2000 S/C) and further useful chemical transformations.