Development of a Potentiometric Sensor Sensitive to Polysorbate 20

Polyoxyethylated sorbitans (polysorbates) are widely used in the chemical, pharmaceutical, and cosmetic industries, but only quantitative determination is used mainly for chromatographic methods. In this paper, the results of the development and testing of a potentiometric sensor sensitive to nonionic surfactant polyoxyethylene sorbitan monolaurate (polysorbate-20) are presented. An anion of the heterogeneous acid of the Keggin structure (12-molybdophosphate heteropolyacid) was used as a counterion to obtain the electrode-active substance for the potentiometric sensor membrane. Polysorbate-20 does not form cations when dissociating in water and cannot directly interact with heteropolyanion; therefore, a cationic complex of polysorbate-20 with barium ions was previously prepared (similar to the interaction of metals with crown ethers). The resulting ion associate meets the basic requirement for the electrode-active substance of plasticized film polyvinyl chloride membranes of potentiometric sensors (poor water solubility and good solubility in organic solvents). Phthalic acid derivatives (dibutyl phthalate and dioctyl phthalate) were used as solvent-plasticizers for a polyvinyl chloride membrane. To determine the optimum conditions for the functioning of a potentiometric sensor sensitive to polysorbate-20, the influence of various factors on the electrode characteristics was studied. Quantitative content of the ionic associate in the polyvinyl chloride membrane, the nature of the membrane solvent-plasticizer, pH of a series of standard polysorbate-20 solutions) on the electrode characteristics of the plasticized membrane of the potentiometric sensor (sensitivity or slope of the electrode function, lower limit of linearity and minimum detectable concentration of polysorbate-20, which can be determined with the help of the developed potentiometric sensor) was studied. The optimal conditions for using the developed potentiometric sensor were found. The developed sensor allows for a short period of time (5–10 min) determining the quantitative content of polysorbate-20 in industrial products at the level 10–5–10‑6 mol/l. The potentiometric sensor sensitive to polysorbate-20 can be used for the development of a potentiometric method for determining the clinical reception of polysorbate-20 in various types of industrial products

Electrochemical Reducing of Terbium and Holmium Ions in the Sodium and Potassium Chlorides Melt with Equimolar Composition

Interest to rare-earth metals (REM) and their alloys is due to the possibility of using them for the creation of new materials need for modern technology. For instance, REM as alloying components allows for preparation of material with special magnetic properties. A promising method for forming such coating is the surface treatment of metals. This process has an electrochemical character as such for the organization of technology the knowledge of kinetics and mechanism of these processes is important. Despite significant interest in rare-earth metals, these issues are not well described in the literature. In order to choose an adequate mathematical model for calculation of kinetic primers, preliminary experiments that allow evaluating the reversibility of the electrode process have been conducted. Based on that, it was concluded that cathodic reduction of terbium and holmium ions in equimolar NaCl-KCl melt is irreversible. By means of voltammetric analysis, kinetic parameters (transfer coefficients, heterogeneous constants of charge transfer rate) of terbium and holmium electroreduction in equimolar NaCl-KCl melt were determined. The experiment was conducted in a three-electrode cell under a purified argon atmosphere. A dependency of kinetic parameters on the concentration of terbium and holmium chlorides wt (%): 1, 3, 5, 7, 10, was determined. The experiment was conducted in 1073–1173K temperature range. Values of kinetic parameters increase with temperature but decrease with the increase of REM chloride. Based on obtained data, it was found that electroreduction of chloride complexes LnCl63– (Ln–Tb, Ho) in equimolar NaCl-KCl melt is irreversible in the studied range of temperatures and REM concentrations. In summary of experimental data, in range of temperature and rare-earth chloride concentration, and assumption was made that reduction of terbium and holmium ions occurs in two stages. The process includes the preceding stage of complex dissociation. A mechanism of LnCl63– complex reduction in the mentioned melt is proposed. The obtained results are in agreement with literate data for analogues systems

Determination Of Formation Regimes For Bilayer Cobalt Dysprosium Intermetalic Surface Alloy

High tech industrial fields on modern development stage are in need of construction materials with an optimal ratio of volume and surface properties, along with low cost of material itself. As evidenced by studies, in order to give a set complex of properties to a workpiece that operates under specific conditions, it is often sufficient to only modify its surface area. Over the course of studies, by means of gravimetric, influence of technological parameters (temperature and time samples are kept in the melt) on specific mass change of cobalt samples, that act as substrate, during electroless diffusive saturation with dysprosium in eutectic melt of lithium and potassium chlorides have been studied. A mathematical dependency was established for specific mass change of cobalt samples on time spent in melt for temperature range of 873–973 K. Composition of intermetallic coats obtained on surface of cobalt samples was studied means of EDX and SEM analyses. It was discovered, that for chosen temperature range, diffusion layers formed on surface of cobalt samples consists of two structural zones that correspond to Co-Dy and Cp2Dy phases

“Smart” Anti­corrosion Pigment Based on Layered Double Hydroxide: Construction and Characterization

Paint coatings are widely used for decorative purposes and to prevent corrosion of metal surfaces. However, regular paint coating only provides passive protection of the metal. To create an active type of corrosion protection, various anti-corrosion additives are added to paint formulations. As a result of analyzing available data, a bi-functional (colored and anti-corrosion) pigment was theoretically constructed as monophase Zn-Al-tripolyphosphate LDH with the generalized formula Zn0.8Al0.2(P3O10)0.04. In this LDH, Zn2+ as “host” cation and Al3+ as “guest” cation govern white color of the pigment, and intercalated tripolyphosphate-anions – corrosion inhibitor. A continuous constant pH synthesis at a temperature of 70°С was selected as a preparation method. This method was used to prepare theoretically constructed pigment. The crystal structure of the pigment sample was studied by means of X-ray diffraction, morphology and particle size were determined by means of scanning electron microscopy, thermal properties were evaluated by means of thermogravimetry. Color characteristics were recorded using the color comparator, anti-corrosion properties were evaluated by recording anodic polarization curves of 08KP steel in 5 % (wt.) Na2SO4 solution with and without the pigment extract. By means of X-ray diffraction analysis, it was found that bi-phase precipitate, containing the constructed LDH (with Zn(OH)2 structure) and Zn-Al LDO (ZnO structure) was formed. This indicated partial decomposition of LDH during synthesis, but the reason for it is unknown. By means of SEM, the formation of agglomerates of the same particles with high surface area was found. The study of color characteristics revealed that the prepared pigment has high whiteness value (diffuse reflection coefficient above 90 %, color purity below 1 %, lightness above 96 %). This is due to the color of both LDH and LDO phases. By recording anodic polarization curves, it was found that corrosion rate in the presence of water extract of the pigment is lower by 5.36 times (corrosion current density decreased from 5.63 mA/cm2 to 1.03 mA/cm2. All of this shows that a bi-functional pigment was prepared, which has great pigment properties, high whiteness, and high anti-corrosion properties

“the Popcorn Effect”: Obtaining of the Highly Active Ultrafine Nickel Hydroxide by Microwave Treatment of Wet Precipitate

Nickel hydroxide is widely used as an active material of supercapacitors. The most active are samples of Ni(OH)2 with (α+β) layered structure synthesized in a slit diaphragm electrolyzer. However, the processes that occur during filtering and drying, negatively impact electrochemical activity. The influence of microwave treatment of different times (from 0.5 to 5 min) on the structure, surface morphology and porous structure, and also on the electrochemical properties of nickel hydroxide samples prepared in a slit diaphragm electrolyzer, has been studied. A hypothesis was proposed on the existence of the “popcorn effect”: short-term high-power microwave irradiation of the wet sample would result in water boiling and internal explosion of the sample. Treated and untreated samples were studied by means of X-ray diffraction analysis, scanning electron microscopy and BET nitrogen adsorption-desorption. Electrochemical characteristics were studied by means of galvanostatic charge-discharge cycling in the supercapacitor regime. The existence of the “popcorn effect” has been confirmed by increased sample thickness after microwave treatment by 1.94 times, specific surface area 2.13 times, pore volume by 2.66 times, and average pore diameter by 1.46 times, It was discovered, that increasing treatment duration to 2–5 min leads to microwave drying. XRD results revealed the occurrence of ageing (crystallization) processes of nickel hydroxide during thermal drying and their absence upon realization of the “popcorn effect”. This results in the formation of X-ray amorphous samples. Comparative analysis of electrochemical characteristics of treated and untreated Ni(OH)2 samples was performed. An increase of specific capacity at high current densities (80 and 120 mA/cm2) for treated samples was observed: by 10.9 % upon microwave drying, 24–42 % upon realization of the “popcorn effect”. The maximum capacity of 231.1 F/g has been observed for the sample, in which the “popcorn effect” was realized the most. However, microwave treatment resulted in lower capacities at low cycling current density. This is related to the thermal treatment of the particle surface, caused by rapid boiling of water. A magnetron of a higher power is required for avoiding this negative effec

Anionic Carbonate Activation of Layered (α+β) Nickel Hydroxide

Nickel hydroxide is widely used as the active material in supercapacitors. Samples of Ni(OH)2 with the (α+β) layered structure, synthesized in the slit-diaphragm electrolyzer, are the most active. The possibility of carbonate activation of layered (α+β) Ni(OH)2 was studied by the synthesis of samples in the slit-diaphragm electrolyzer using a mixture of sodium hydroxide and sodium carbonate as the electrolyte. The molar part of sodium carbonate in the NaOH+Na2CO3 mixture was controlled by acid titration in the presence of two indicators. The synthesis of nickel hydroxide samples was conducted at the molar part of carbonate from 0.16 (NaOH without the additional introduction of carbonate) to 0.83. The crystal structure of the samples was studied by means of X-ray diffraction analysis, electrochemical characteristic – by means of cyclic voltammetry and galvanostatic charge-discharge cycling in the accumulator regime. By means of XRD analysis, it was found that upon increasing the molar part of carbonate in the anolyte to 0.49, the crystallinity of the monophase layered (α+β) structure increases. It was found that a further increase of the carbonate part results in a more amorphous structure due to a partial breakdown of the hydroxide lattice with the formation of basic salts and formation of the bi-phase system. This conclusion is supported by cyclic voltammetry and discharge curves. The study of the electrochemical characteristics revealed, that for the molar part of carbonate below 0.39, carbonate activation of hydroxide occurs resulting in an improved specific capacity. Increasing the carbonate part to 0.49 results in a lower specific capacity, and even further increase results in the breakdown of hydroxide into basic salts and a significant drop in electrochemical activity. Thus, it was found, that to achieve the maximum activating effect, the optimal molar part of sodium carbonate (in a mixture with sodium hydroxide) should be about 40 %. The specific capacity of nickel hydroxide under this optimal condition is 234 mA·h/g, and this sample is found to be susceptible to activation with cobalt compounds, which further improved capacity to 254 mA·h/g

Comparison of Oxygen Evolution Parameters on Different Types of Nickel Hydroxide

A simple method for determining the oxygen evolution parameters, that uses step­wise potentiostatic regime was proposed. The proposed method was used to study the oxygen evolution on the nickel hydroxide samples that were prepared using different methods and had different grain size. The samples used in the research were studied using Scanning Electron Microscopy, X­ray diffraction, IR­spectroscopy, and Energy Dispersive X­ray analysis. It was demonstrated that the used Ni(OH)2 samples have different morphology, structure and composition. The industrial β­Ni(OH)2 sample has a shard­like structure, high degree of crystallinity and no intercalated anions. The electrochemically prepared sample has a low degree of crystallinity and has a structure that is composed of α and β­forms that contain carbonate and sulfate ions. It had been demonstrated that polarization of oxygen evolution depends on the methods of nickel (II) hydroxide synthesis and its grain size. The effective constants of the Tafel equation had been determined, which for industrial Ni(OH)2 samples are аeff=0.383 beff=0.055 (0–70 µm grain size) and аeff=0.414, beff=0.067 (0–40 µm grain size), for the electrochemically prepared sample – аeff=0.451, beff=0.089 (0–70 µm grain size). It was also demonstrated that polarization of oxygen evolution is affected differently by high current densities for different powders

Optimization of Nickel Hydroxide Electrode of the Hybrid Supercapacitor

Nickel hydroxide is an active material for a wide range of chemical power sources: various types of alkaline accumulators and hybrid supercapacitors. In order to obtain maximum electrode capacity and charge efficiency, the optimization of the electrode composition i.e. the content of activating and electroconductive additives and the binder is needed. The amount of these compounds is governed by various factors, the influence of which is different and often non-linear.The factors that can affect the specific capacity and are determined by the binder content have been reviewed. The effect of these factors has been demonstrated experimentally. The influence of the binder content has been studied. The study has been carried out using polytetrafluoroethylene suspension as a binder, and components used in the manufacturing of accumulators: industrial sample of nickel hydroxide “Bochemie”, and electroconductive additive GAK-1.The optimal binder content in active mass has been determined to be 2 %. It has been demonstrated that PTFE content of 1 % in active mass is insufficient for good contact of active mass with the electrode, resulting in a maximum capacity of 11 F/g at 40 mA/cm2. The PTFE concentration of 3 % is excessive and under high current densities leads to screening of active material particles, with a maximum capacity of 67 F/g at 20 мА/cm2. The best result for specific capacity has been achieved with PTFE content of 2 % and current density of 40 mA/cm2 – 67 F/g.After analyzing the acquired data, it has been assumed that optimal binder content may depend on the particular type of hydroxide, namely its structure and morphology

A Study of the Increased Temperature Influence on the Electrochromic and Electrochemical Characteristics of Ni(OH)2-PVA Composite Films

Electrochromic devices, as an element of “smart” windows, can be exposed to extreme temperatures due to their purpose and location. Exposure to high temperatures can change the characteristics of electrochromic devices and lead to malfunction. The present study is intended to fill in the gaps related to the stability of electrochemical and electrochromic parameters of one of the known materials – nickel hydroxide (II).The present study highlights changes in some physico-chemical characteristics that occur during prolonged exposure to high temperature in different media. Ni(OH)2-polyvinyl alcohol, prepared using the cathodic template method, was aged at 80 °С under the air atmosphere and in the working electrolyte solution – 0.1 М KOH for 8 hours. The temperature was chosen based on the maximum registered temperature on Earth, possible film heat up and possible rapid degradation of electrochromic films.As a result, it was found that degradation does occur in a basic solution, while on air some improvement was observed instead. The authors propose the mechanism that explains experimental results, which lies in “ageing” of active material Ni(OH)2. The latter occurs in the active mass of alkaline batteries. Possible methods for preventing degradation are also proposed, which can be realized with the use of thickened electrolytes or special films that are deposited onto the electrochrom