Variable Valence Metals Research Articles

Incorporating Ni-Polyoxometalate into the S-Scheme Heterojunction to Accelerate Charge Separation and Resist Photocorrosion for Promoting Photocatalytic Activity and Stability.

The emerging polyoxometalate (POM) nanomaterials are transition metal oxygen anion clusters with d0 electronic configurations, which could be attractive and potential photocatalysts. Hence, a nickel (Ni)-substituted polyoxometalate K6Na4[Ni4(H2O)2(PW9O34)2]·32H2O (Ni4POM)-incorporating step (S)-scheme heterojunction was developed to promote photocatalytic activity and stability in H2 and H2O2 production. The multielectron transfer through variable valence metal centers in Ni4POM would facilitate the recombination of invalid charges through the S-scheme pathway. Moreover, incorporating Ni4POM into the S-scheme heterojunction can broaden the light absorption range and meanwhile lead to resistance to photocorrosion to promote the optical and chemical stability of Cd0.5Zn0.5S (CZS). The optimized CZSNi-70 exhibited a H2 evolution rate of 42.32 mmol g-1 h-1 under visible-light irradiation with an apparent quantum yield of 32.27% at 420 nm and a H2O2 production rate of 295.4 μmol L-1 h-1 under 420 nm light-emitting diode irradiation. This work can provide a new view for the development of transition metal-substituted POM-based stable and efficient S-scheme photocatalysts.

ВИКОРИСТАННЯ ХРОМОКСАНУ В ПРОЦЕСІ ОКИСНЕННЯ ЦИКЛОГЕКСАНУ

Ways of using chromoxane in the process of cyclohexane oxidation are considered. Various technological parameters of chromoxane use in the process of cyclohexane oxidation and their influence on the main indicators of this process have been studied. The combined effect of chromoxane in binary systems with different salts of metals of variable valence on their catalytic activity in the oxidation of cyclohexane was determined.

Binary catalytic systems for the industrial cyclohexane oxidation process

This paper proposes the possibility of creating an efficient binary catalytic system for the industrial oxidation process of cyclohexane based on a compound of a metal of variable valence and a salt of perfluorinated sulfonic acid. Two-component binary mixtures of the main component and additive were used for the study. In addition to industrial cobalt naphthenate, other salts of metals of variable valences, such as manganese naphthenate, as well as stearates of copper, nickel, and cerium, were used as the main component of the binary mixture. A number of salts of perfluorinated sulfonic acids were used as an additive to the binary mixture. Chromoxane is shown to be the most efficient additive to cobalt naphthenate. In the presence of this binary system at the 50th minute of the process, the conversion of raw materials increased to 10.4 mol.%, which is 22% more than the oxidation of pure cobalt naphthenate, while the selectivity with respect to the target products remains high (79.5 mol.%). It is shown that of a number of compounds of metals of variable valence, the most effective main components of binary systems are cobalt naphthenate and cobalt-cerium catalyst. Carrying out the oxidation of cyclohexane in the presence of such systems allows increasing the conversion of the initial cyclohexane by 1.13 to 1.5 times and thus increasing the rate of oxidation of the hydrocarbon in comparison with the industrial process. It is also important that the use of such catalysts allows conducting the oxidation of cyclohexane to high conversions without losing the yield of the target products.

Ligand-variable metal clusters charge transfer in Ce-Por-MOF/AgNWs and their application in photoelectrochemical sensing of ronidazole.

A photoelectrochemical sensing platform based on ligand-variable metal clusters charge transfer was established for the quantitative assay of ronidazole (RNZ) using Ce-porphyrin-metal-organic frameworks/silver nanowires (Ce-Por-MOFs/AgNWs). Rod-like Ce-Por-MOFs and well-dispersed sub-50nm AgNWs were prepared using a hydrothermal method and polyol strategy, and then through simple drop coating to yield Ce-Por-MOFs/AgNWs nanocomposites. We investigated the intrinsic semiconducting properties of the composites. More importantly, it was found that the variable-valence metal node can provide electronic defect states similar to those caused by multi-metal doping, synergizing with the surface plasmon effect of AgNWs, which significantly improved the photoelectric conversion efficiency, thereby resulting in excellent optoelectronic properties. In combination with molecular imprinting, a competitive type trace photoelectrochemical sensor for RNZ was constructed using Fe2+ as the electron donor and probe. Under optimal conditions, the sensor response is proportional to the logarithm of RNZ concentration in the range 0.1-104nM with a detected limit of 0.038nM. The recoveries ranged from 87.2 to 116% with relative standard deviations (RSDs) < 6.5% (n = 3) in milk sample. This work reveals the charge-transfer process of variable-valence metal nodes in MOFs during photoelectrochemical processes, which will provide new insights for the sensing application of variable-valence metal MOFs.

Metal-organic frameworks-derived bimetallic oxide composite nanozyme fiber membrane and the application to colorimetric detection of phenol

MOF-derived nanozyme has attracted much attention due to its abundant active sites, great pore structure and diversity of composition. In this work, variable-valence metal Co/Mn bimetallic MOF-74 is used as precursor to prepare bimetallic oxide composite nanozyme with peroxidase-like activity. Compared to monometallic MOFs-derived nanozyme, the coupling of Co and Mn species produces the synergistic effect owing to binary-valence property of Co and Mn, which can promote the catalytic activity. The nanozyme and cellulose are combined to form nanozyme fiber membrane (NFM) through suction filtration. The prepared NFM exhibits stable pore structure and excellent peroxidase-like activity, which can be used to prepare test strip for rapid and in situ detection of phenol. The detection method with the test strip has wide linear range from 0.5 to 500 μM with a low detection limit of 0.2 μM, which is superior to previously reported phenol detection methods. And is successfully applied to in situ and naked-eye detection of phenol in seawater. In our perception, the rational design of bimetallic MOF-derived NFM with special surface physicochemical properties, porous nanostructures and efficient catalytic activity may pave a new path to the development of high-performance in situ detection platforms.

Ecological and Process Aspects of Oxidative Biodegradable Films Production Based on Low Density Polyethylene

Modifying additives impact – pro-oxidants – on low-density polyethylene oxidative degradation under short-term aging conditions in a thermostat with forced convection at 70 °C and ultraviolet irradiation with different exposures (48, 96, 144 h) was studied. It is concluded that for polyethylene films modified with stearates of metals of variable valence, under short-term aging conditions, the formation of aldehydes (1733–1740 cm-1) and carboxyl (1700 cm-1) was observed and accompanied by a sharp decrease in the intensity of absorption bands at 1465–1470 cm-1, which is specific to stretching and bending deformations of CH2 of the polyethylene polymer matrix and indicating the destruction of polymer chains. It is shown that the short-term aging of oxidatively biodegradable polyethylene affects environmental and technological problems associated with the pollutants release, including in particular, formaldehyde and other pollutants.

Plant Antioxidants in the Oxidative Mayonnaise Spoilage Study

The article presents the data systematization results on the plant antioxidants use in mayonnaise, that is a popular seasoning at home and in the food industry. The objective disadvantage of fat-containing products is the process of self-oxidation under the influence of a number of factors changing the organoleptic properties of mayonnaise, reducing nutritional value, safety and shelf life. Manufacturers solve the lipid oxidation problem of fat-containing products and the fat phase of mayonnaise by using officially registered antioxidants / oxidation inhibitors mainly of synthetic origin. Due to the increased demand for natural antioxidants caused by the growing market of food products with natural food additives, one of the promising approaches to the mayonnaise oxidation prevention is the use of isolated individual substances and plant extracts with the high antioxidant activity. The paper systematizes the examples of the plant antioxidants use in the mayonnaise composition described in modern scientific literature, reveals the features of their influence on the oxidative spoilage process and organoleptic indicators. A man indicated that plant extracts containing polyphenolic substances, vitamins, carotenoids, α-tocopherol and terpenes inhibit the mayonnaise oxidative spoilage process, acting as primary antioxidants slowing down the lipid oxidation onset, and secondary – reducing the oxidation rate. The research proved the plant antioxidants ability to suppress targets of oxidant activity – hydroxyl radical, superoxide, singlet oxygen lipid radical, lipid peroxides and metals of variable valence.

Fast photo-Fenton-like oxidation in bismuth catalysis: A novel Fe(III) self-doped sodium bismuthate nanosheet

Sodium bismuthate dihydrate (NaBiO3.2 H2O, NBH) nanosheets were successfully prepared in this study using the persulfate oil bath oxidation method. Benefited from the unique layered structure of NBH, the Fe(III) as a variable valence metal ion was explored for enhancing NBH activation of peroxymonosulfate (PMS) to degrade levofloxacin (LVF) in the visible-light catalytic system. Based on results of the reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis, singlet oxygen (1O2) and superoxide radical (O2·-) were identified as the main ROS. The morphology, chemical structure, and optical properties of NBH were analyzed using various characterization methods. It was confirmed that Fe(III) embedded in the NBH via the ion exchange with Na, resulting in lattice oxygen vacancies on the surface of the NBH, after the formation of oxygen defect sites, reacts with PMS in the solution to produce active oxygen species with oxidizing efficiency. This study expands the technological application of NBH in the catalytic oxidation of variable valence metals, which are essential for the removal of fluoroquinolone antibiotics.

B-site regulated bimetallic perovskite fluoride NaCo1−xNixF3/reduced graphene oxide as the enhanced performance electrode material for supercapacitors

Perovskite fluoride is a potential electrode material for supercapacitors because its high theoretical specific capacitance. However, the relatively poor cyclic stability and rate performance limit its practical application. In this paper, we successfully synthesized the bimetallic perovskite fluorides/reduced graphene oxide (NaCo0.2Ni0.8F3/rGO) composite materials through a simple solvothermal method. The effects of the Co/Ni ratio regulation and the addition of rGO on the electrochemical properties of the perovskite composite materials have been investigated in detail. The variable valence metal ions by Co/Ni ratio regulation can lead to multiple redox reactions, which are helpful to improve the specific capacity of the materials. Meanwhile, the addition of rGO could improve the cycle stability and rate performance by virtue of the great conductivity of the rGO and the uniform dispersion of perovskite nanoparticles on it. The NaCo0.2Ni0.8F3/rGO composite electrode displays the high specific capacity of 805.7 C g−1, excellent rate performance (82% capacity retention from 0.5 to 16 A g−1) and superior cycle stability (92% retention over 5000 cycles). Furthermore, the active carbon//NaCo0.2Ni0.8F3/rGO asymmetric supercapacitor exhibits a high energy density of 52.19 Wh kg−1 under a power density of 750 W kg−1. It is believed that the above findings supply an efficient electrode design for the future practical application of perovskite fluorides in high-performance supercapacitor.

Dehydrochlorination study of plasticized poly(vinyl chloride) contianing modified titanium dioxide, cerium stearate, organotin and β-diketone complex after long-term storage

Understanding the influence of additives on the dehydrochlorination of plasticized poly(vinyl chloride) (PVC) from the source and long-term storage is an attractive topic. In this work, the effects of folic acid modified nano titanium dioxide (FANT), cerium stearate, organotin and β -diketone compound additives on the dehydrochlorination of plasticized PVC and long-term storage were investigated using conductivity measurements. The results showed that the induction time of hydrogen chloride removal of plasticized PVC (C-1) containing composite stabilizer at 200 °C were 243% higher than those of the control (S1). After storage, the heat stability of the control decreased significantly. Instead, the induction time and stability time of plasticized PVC containing FANT, cerium stearate, organotin and β- diketone composites were significantly enhanced at 200 °C. The thermal stability sequence from difficult to easy for removal of hydrogen chloride was : 3.0 phr (1.90% wt) (C2) >1.0 phr (0.64% wt) (C1) > 5.0 phr (3.17% wt) (C3) with FANT. It is inferred that this is due to the FANT’s hydrogen bonding van der Waals force and the complexation reaction of variable valence metal Ce+3/Ce+4 with C-Cl bond in PVC polymer molecule. The induction time (min) of hydrogen chloride removal at 200 °C before and after storage is as follows: C-20 (71.9) > C-10 (70.6) > C-1 (60.7) > C-3 (57.2) > C-30 (52.7) > C-2 (49.9) > S1 (25.3) > S10 (19.7). The critical temperature for hydrogen chloride removal by the composite film is around 210 °C. If the content of FANT increased to 3.17%, the intermolecular force and repulsive force in PVC system offset each other, indicating that the increase of FANT content will lead to the increase of repulsive force with PVC. A certain amount of FANT, cerium stearate, organotin and β- diketone composites has a significant synergistic effect on the thermal stability of PVC.

S‐Scheme Heterojunction and Defect Site Engineering on CuxIn5S8−Cu2‐ySe for Highly Efficient Photoreduction of CO2 to methanol

AbstractThe conversion and utilization of CO2 is imminent. Herein, the CuxIn5S8−CuySe S‐scheme heterojunction catalyst was successfully synthesized by the MOF‐derived method and the strategy of surface hydrogenation. In a photocatalytic performance test, Cu1.5In4.5S7.5−Cu1.45Se has excellent catalytic activity, and the production rate of methanol is 5.250 umol g−1 h−1, and the methanol selectivity is about 100 %. In addition, through DFT calculation and in situ FT‐IR, a new mechanism for the catalytic reduction of CO2 to methanol by bimetallic sites or variable valence metal sites is revealed, which opens up a new strategy to conversion of CO2 into energy fuel. This research couples charge accumulation centers, active sites and adsorption sites on the exposed active interface to enhance the visible light‐driven photocatalytic performance of the catalyst through defect engineering, morphology engineering and heterojunction engineering, which provides a promising approach to facilitate the selective photocatalytic reduction of CO2 to methanol.

Modern chemical disinfectants and antiseptics. Part II

Aim. To generalize and systematize information on the properties of modern chemical disinfectants and antiseptic agents (DA and AA) – peroxide compounds, surfactants, salts of heavy metals and metals of variable valence in the highest oxidation state, alcohols, phenols and quaternary ammonium salts.Results and discussion. The classification of DA and AA by the chemical structure was performed. The spectrum of their activity, directions and forms of DA and AA were given. Toxicity and the impact on the environment were described.Conclusions. The results of the study conducted allow us to state that modern DA and AA of a wide spectrum of action are peracetic acid and, to a certain extent, hydrogen peroxide. However, they are unstable in dilute solutions. Other reagents are chemically stable, but they are characterized by a weak or average action against spores and viruses. The most effective DA and AA are mixtures (combinations) of compounds belonging to different classes. The examples of these combinations are “surfactants + biguanidine derivatives”; “quaternary ammonium salts + phenol derivatives”; “surfactants + aldehydes”; “quaternary ammonium salts + hydrogen peroxide”. These mixtures combine the advantages and compensate for the disadvantages of individual DA and AA.

Metal-Organic Frameworks With Variable Valence Metal-Photoactive Components: Emerging Platform for Volatile Organic Compounds Photocatalytic Degradation

With their outstanding diversities in both structures and performances, newly emerging metal-organic frameworks (MOFs) materials are considered to be the most promising artificial catalysts to meet multiple challenges in the fields of energy and environment. Especially in absorption and conversion of solar energy, a variety of MOFs can be readily designed to cover and harvest the sun irradiation of ultraviolet (UV), visible and near-infrared region through tuning both organic linkers and metal nodes to create optimal photocatalytic efficiency. Nowadays, a variety of MOFs were successfully synthesized as powerful photocatalysts for important redox reactions such as water-splitting, CO2 reduction and aqueous environmental pollutants detoxification. MOFs applications in indoor-air VOCs pollutants cleaning, however, are less concerned partially because of limited diffusion of both gaseous pollutant molecules and photo-induced active species in very porous MOFs structures. In this mini-review, we focus on the major breakthroughs of MOFs as photocatalysts for the effective removal of indoor-air VOCs such as aldehydes, aromatics and short-chain alcohols. According to their nature of photoactive centers, herein MOFs photocatalysts are divided into two categories to comment, that is, MOFs with variable valence metal nodes as direct photoactive centers and MOFs with non-variable valence metal nodes but after combining other photoactive variable valence metal centers as excellent concentrated and concerted electron-transfer materials. The mechanisms and current challenges of the photocatalytic degradation of indoor-air VOC pollutants by these MOFs will be discussed as deeply as possible.

Влияние металлов переменной валентности на окислительную модификацию аминокислотных остатков альбумина

BACKGROUND: The constancy of the protein composition of the body is one of the most important conditions for normal vital activity. Deviations in the content of the main bioelements, in particular, mixed valence metals, caused by environmental factors, improper nutrition and other factors, lead to various disorders. One of the properties of metals of mixed valence is the abil-ity to cause metal-catalyzed oxidation of proteins in joint action with active forms of oxygen. It seems interesting to study the oxidative modification of the amino acid residues of albumin and the change in its properties. AIM: To study the effect of reactive oxygen intermediates generated by the Fenton reaction in the presence of Fe2+ and Cu2+ on the oxidative modification of amino acid residues of bovine serum albumin. MATERIALS AND METHODS: The study was carried out on bovine serum albumin (BSA), which was incubated for 2 hours in a mixture of Fenton's reagents – FeSO4 + H2O2 and in a mixture of СuSO4 + H2O2. The quantitative protein content in the samples was determined with the bromcresol green reagent (Albumin-Olvex). The content of carbonyl derivatives of proteins was estimated by the method of R.L. Levine modified by E.E. Dubinina. The content of thiol groups in albumin samples from the control and experimental groups was determined by the Ellman method with DTNB (under non-denaturing conditions. RESULTS: The presented results demonstrate that under the action of Cu2+ ions, the formation of carbonyl derivatives of aliphatic amino acids of albumin is less than in the presence of Fe2+, which can be explained by the different degrees of albumin affinity to metals of variable valence. The rate of mobility of oxidatively modified albumin in polyacrylamide gel decreases, which is explained by protein aggregation due to bityrosine cross-links. CONCLUSION: Variable valence metals affect the modification of albumin. The change in the functional properties of the protein is of physiological significance, including the case of extracellular mobilization of iron and copper.

Activity of Manganese Carboxylates in the Process of Liquid-Phase Oxidation of Ethylbenzene with Atmospheric Oxygen

The process of oxidation of hydrocarbon with oxygen proceeds with formation of the corresponding hydroperoxide as the primary product [1,2]. A catalyst is the most important factor that influences on the direction of flow of the oxidation reaction. Catalysts based on metals of variable valency, and their derivatives are the most active in reactions of oxidation of hydrocarbon [3].

Respiratory RNA Viruses: How to Be Prepared for an Encounter with New Pandemic Virus Strains

The characteristics of the biology of influenza viruses and coronavirus that determine the implementation of the infectious process are presented. With provision for pathogenesis of infection possible effects of serine proteinase inhibitors, heparin, and inhibitors of heparan sulfate receptors in the prevention of cell contamination by viruses are examined. It has been determined that chelators of metals of variable valency and antioxidants should be used for the reduction of replicative activity of viruses and anti-inflammatory therapy. The possibility of a pH-dependent impairment of glycosylation of cellular and viral proteins was traced for chloroquine and its derivatives. The use of low-toxicity drugs as part of adjunct therapy increases the effectiveness of synthetic antiviral drugs and interferons and ensures the safety of baseline therapy.

Катализаторы для процесса конверсии метана

Бұл мақалада табиғи газды каталитикалық өңдеудің метанның жартылай, толық, су буымен, көмірқышқылды тотығуы және ыдырау секілді заманауи бағыттары көрсетілген. Үлкен энергетикалық ресурстарымен бай Қазақстан үшін газ ресурстарын құнды химиялық өнімдерді алуға мүмкіндік беретін жаңа газхимиялық технологияларды құру маңызды болып табылады. Қазіргі уақытта осы реакцияларға негізделген процестер өндірісте Қазақстанда жүзеге асырылған жоқ. Реакциялардың әрқайсысы үшін жақсы өнімділікке жететін каталитикалық жүйелер көрсетілген. Барлық процестерде ауыспалы валентті металдар негізіндегі оксидті катализаторлар белсенді де тиімді болып табылады. Болашақта осы катализаторлардың белсенділігін арттыру бағытында жұмыс жасалуы қажет. Катализаторлар тасымалдағыштың ылғал сыйымдылығы бойынша капиллярлы сіңіру әдісімен дайындалып, 2000С 2 сағат бойы кептіріліп, 5000С-та 3 сағат қақталды.&#x0D; Мақала бойынша синтез-газ алу үшін метанның жартылай тотығу реакциясында никель-цирконий (3%NiО-2%ZrО2) негіздегі катализатор белсенділік көрсетті. Аталған катализатор бойынша реакция өнімдері - Н2 - 60.5 көл.%, СО - 30.5 көл.% құрады. Метанның көмірқышқылды конверсиясы реакциясындағы никель-кобальт-церий (3%NiО-7%Со2О3-0,5%Сe2O3) катализаторында метанның конверсиясы 95,6%-ды құрады және сутегі мен көміртегі монооксидінің шығымы 47,0 және 45,9 көл %-ға тең. Церий оксидімен модифирленген 3%NiО-2%СеО2/γ-Al2O3 катализаторы метанның толықтай тотығу реакциясында төменгі температураның өзінде (350 оС) метанның 29,6% конверсияға ұшырайды. Метанның сутегі газына ыдырау реакциясы үшін темір негізіндегі катализаторлар тиімді болып табылады. 5 мас.% Fe/ɣ-Al2O3 катализаторында 700оС кезінде метанның конверсиясы 2% құрап, 850оС-та оның мөлшері 13 % -ға және сутегі газының шығымы 5,8 көл.% - ға дейін артатынын көруге болады.

E-nose for the monitoring of plastics catalytic degradation through the released Volatile Organic Compounds (VOCs) detection

The work presents the results of an artificial olfaction E-nose system application for detection of Volatile Organic Compounds (VOCs) – destruction products of OXO-biodegradable polyethylene films when exposed to Ultraviolet (UV) irradiation and heating. The E-nose system was based on eight piezoelectric quartz resonator sensors coated with polymeric sensing materials with various selectivity to analytes. The effect of prooxidants, materials based on variable valence metals, such as D2w, ferric stearate and ferric carboxylate, addition on polyethylene films (PE) photo destruction was studied. The dependence of the composition of VOCs mixtures emitted by PE films on the processing time, the power of the UV irradiation and on the nature of the modifying additive was established. In addition, the main emitted volatile compounds were identified and the dynamics of their formation for different catalysts during the plastics destruction were studied. The proposed E-nose system has proved to be an effective tool for assessing catalyst-prooxidants properties.

Modeling of hydrothermal processes of transformation of super-viscous oil of the Ekaterinovsky deposit in the presence of clay minerals

Using a set of physicochemical methods, the influence of hydrothermal effects on the composition of super-heavy oil of the Ekaterinovsky field in a carbon dioxide medium in the presence of a composition of catalysts - metals of variable valence in model experiments on clay rock-forming minerals was studied. Peculiarities of the transformation of the oil composition associated with the destruction of its high molecular weight components - resins and asphaltenes, and the formation of light saturated and aromatic hydrocarbons are revealed. Changes in the structural-group composition indicate an increase in the aromaticity of the products of the experiments. The greatest changes occur in the composition of resins and asphaltenes, which is reflected in a change in their structural-group composition and their paramagnetic properties. The high sorption ability of the rock to metals included in the composition of the used catalyst composition was revealed.

Influence of mining activities on groundwater hydrochemistry and heavy metal migration using a self-organizing map (SOM)

Tongling is a typical metal ore concentration area in the Yangtze Metallogenic Region. Years of mining activities have resulted in serious regional groundwater problems. Therefore, it is of great significance to systematically study the impact of mining activities on the local groundwater. In this paper, a self-organizing map (SOM) calculation and stable isotopes were used to illustrate groundwater hydrochemistry and heavy metal migration, especially concerning Fe, based on the test results of 92 groundwater samples from the study area. Due to mining activities and acid mine drainage (AMD), SO4–Ca-type groundwater with high total dissolved solids (TDS) and low pH values was mainly distributed in the mining areas. In the runoff area, carbonate neutralization and runoff rates were accelerated, while the groundwater TDS gradually decreased and the pH increased. Due to the influence of evaporation and surface water recharging, the major component and heavy metal contents of groundwater increased in the discharge area. With changes in the redox conditions and the influence of variable-valency metals, such as Fe and Mn, heavy metals are easily coprecipitated from groundwater or absorbed by secondary minerals, such as ferrihydrite and birnessite. Therefore, the contents of heavy metals in the groundwater of the study area were relatively low. The main controlling factors determining the groundwater hydrochemical characteristics and heavy metal precipitation are mining activities, redox conditions and rock-water interactions. This study may be helpful for the sustainable development and protection of groundwater resources in the study area and other mining zones in the Yangtze Metallogenic Region.