Constant Stirring Research Articles

МОЛОЧНАЯ СЫВОРОТКА – ЦЕННОЕ СЫРЬЕ В ТЕХНОЛОГИИ КИСЛОМОЛОЧНЫХ ПРОДУКТОВ

The integrated use of raw materials, including the processing of secondary resources, whey, can increase the efficiency of the dairy industry. The purpose of the study is to offer a fermented milk product obtained from cow’s milk and dry demineralised whey. Raw cow’s milk meets the Russian national standard GOST 31449-2013; demineralised dry whey with a 50 % demineralisation level meets GOST R 56833-2015. To obtain a fermented milk product, the necessary amount of demineralised whey was introduced into warm cow’s milk (40 °C2 °C) with constant stirring, then pasteurized (85 °С2 °С). After cooling to 40 °C2 °C, yogurt starter culture was added to the milk mixture, then the mixture was kept up to the titrated acidity of 75– 80 °T. The study established organoleptic parameters (GOST R ISO 22935-2-2011), titrated acidity (GOST R 54669-2011), viscosity of fermented milk product (GOST 9070-75), microbiological parameters (GOST 1044411-2013, GOST 32901-2014, GOST 33566-2015, GOST 33566-2015) for products with different demineralised whey content (0–6 %). As a result, yogurt containing 2 % of whey had the highest score. This product was milk-white in color, had a sour-milk taste and thick homogeneous consistency. The product energy value was calculated. The study found that 2 % demineralised whey powder increased proteins by 4 %, carbohydrates by 34.2 %, and the energy value of the product by 7.33 %. Whey is rich in biologically active substances, it boasts of antioxidant, immunomodulatory, and antitumor properties. Therefore, using whey for obtaining new food products is promising: it allows you to use health-saving technologies, solve environmental issues related to the disposal of production waste, resource conservation, secondary use of dairy raw materials.

Acute Toxicity of Aqueous Extract from Bredemeyera floribunda Root Bark in an Animal Model

The medicinal plant Bredemeyera floribunda Willd. is used to treat cardiovascular disease, chronic fatigue, low libido, as well as increased diuresis. However, studies considering the toxicity of this plant are scarce. Develop an aqueous extract of B. floribunda considering traditional use and determine the average lethality (LD50), signs, and symptoms of toxicity. The B. floribunda extract was obtained by immersing the root bark in ultrapure water for 18 hours at 4°C, under constant stirring. The test extract was administered in a single dose of 2.000 mg/kg by gavage to rats. Signs and symptoms of toxicity were determined according to the Hippocratic screening test and compared with the control group. In addition, a necropsy was performed for macroscopic evaluation of the organs in the abdominal cavity. A powder was obtained from aqueous extracts that showed the same organoleptic characteristics and emulsification capacity as those presented by the fresh root when prepared according to popular tradition. The LD50 was greater than the test dose with three animals surviving. On the other hand, necropsy of dead rats showed necrosis and reduction in lung mass, in addition to the presence of foam and excessive distension of the stomach and intestines. The main symptoms of toxicity were anesthesia, ataxia, sedation, loss of muscle strength, and excessive drowsiness in the first 24 hours. There was no difference between the control and extract groups with regard to body mass, food, and water intake, as well as in macroscopy of the heart, liver, lungs, intestines, spleen, pancreas, and kidneys. The aqueous extract of the B. floribunda was considered nontoxic or of very low toxicity. However, it is capable of altering the activity of the central nervous system and causing disorders in the respiratory and digestive systems.

SYNTHESIS, CHARACTERIZATION OF ORGANO CHEMO SENSORS AND THEIR APPLICATION FOR ANION DETECTION IN WATER SAMPLES

Organo chemo sensors were used to detect fluoride ions in water samples and were synthesized by mixing two compounds in a 1:1 ratio with constant stirring for two hours using a stirrer with the addition of acetic acid and ethanol. The products were checked for a single spot using TLC paper. The experiment was taken further for the detection of fluoride ions by making a solution of chemo sensor and water sample at a 1:2 ratio and checked using a spectrophotometer and colorimeter. The values of absorbance were then compared with the standard solution containing fluoride ions. The formation of H - F bonding between the chemo sensors and fluoride ions in the water samples was confirmed. The results indicate the presence of fluoride ions in terms of ppm in the different water samples taken.

(Digital Presentation) Green Synthesis of Calcium Ferrite Particles and Preliminary Study of Their Application for Electrochemical Detection

This work presents results of the synthesis of mixed metal oxides such as calcium ferrite by dissolving Ca(NO3)2.4H2O, Fe(NO3)3.9H2O and NH4OH with constant stirring, and assisted with conventional heating or microwave (MAE) combustion. using natural aloe vera extract as fuel at 900°C for 3 hours. The resulting material was characterized by instrumental methods for powders. Calcium ferrite powders were used for the modification of the surface of a glassy carbon electrode. The modified electrodes were used for the electrochemical investigation of acetaminophen (ACe) and acyclovir (ACy), at controlled pH. The preliminary results demonstrated the potential application of calcium ferrite powders in the electrochemical detection of molecules of pharmaceutical interest.

Kinetic Study of the Removal of Reafix Yellow B8G Dye by Boiler Ash

The textile sector has great relevance in the Brazilian socioeconomic context, generating large volumes of effluents of varied composition, with dyes being one of the most worrying contaminants due to their characteristics of high solubility, harmfulness and low degradability. Among them the Reafix Yellow B8G (ARB8G) dye has an azo nature, harmful to organisms in the aquatic environment. According to Brazilian laws, it is recommended to dispose of waste through incineration or landfill, due to its resistance to biodegradation. One of the methods for treating effluents is the adsorption of contaminants using materials with adsorption capacity, such as residue from the burning of biomass in boilers (ash). The general objective of this work was to evaluate the adsorption kinetics by contact time of the ARB8G dye by boiler ash. The test was based on mixing the adsorbent material with a dye solution at 75 mg.L-1, at constant temperature and stirring at different time intervals. To quantify the amount of adsorbed dye, the UV-Vis spectrometry method was used. The kinetic test indicated an equilibrium time of 30 minutes, with 100% removal under the tested conditions. From this result and considering that boiler residue is an underutilized and low-cost material, it is concluded that this substance has significant potential to be applied as an alternative material for the treatment of effluents containing dyes.

ANALYSIS OF EXISTING METHODS FOR IMPROVING THE PHYSICAL AND CHEMICAL CONDITIONS OF THE ION EXCHANGE PROCESS IN WATER TREATMENT

The article deals with the issues of existing processes for improving the physical and chemical conditions of the ion exchange process in water treatment. Patents and publications on the use of the ion exchange method in water treatment have been analysed. The expediency and scientific significance are determined by the possibility of further improving the efficiency of the ion exchange process in water treatment on the basis of the obtained results. Existing methods, such as thermal and cryogenic treatment, membrane plants, distillation and reverse osmosis, have a number of disadvantages, such as high energy consumption of the process and the inability to be used on an industrial scale. A promising method to improve the efficiency of modified ion exchange resins is to use the effect of a magnetic field on the feed water with constant stirring. The article analyses ion exchange resins and their problems, existing research aimed at modernising the ion exchange process, considers ways to optimise the selectivity of ion exchange resins, their modification with dendritic aggregates, and the use of mixed cationic and anionic ion exchange resins. Regeneration of ion-exchange resins using ammonium bicarbonate technology, reagent-free regeneration methods, such as electrodialysis, electrodionization systems, in order to reduce process waste, possible schemes of using ion-exchange plants in combination with other methods of water treatment. The analysis shows the relevance of using the ion exchange process in water treatment and the prospect of further research on ways to intensify the process to reduce energy and economic resources. The obtained results demonstrate the most advanced ways to improve the method of ion exchange for water treatment, such as reagentless regeneration of ionites using electrodialysis, modification of resins by introducing the necessary functional groups.

247 In Vitro Characterization of Equine Fore- and Midgut Digestion

Abstract Considerable advancements can be made in the field of equine nutrition and diet formulation, by improved feed characterization and the development of nutritional models, including in vitro models, to describe nutrient degradation. Methodologically, literature values for in vitro small intestine incubation times are widely variable ranging from 2 to 18 h. While some incubation times are selected to represent approximate mean retention times, conversely, insufficient in vitro incubation times and sampling time points could prohibit or result in inaccuracies characterizing nutrient degradability characteristics, ultimately affecting both degradability and digestion values and their use. The objective of this trial was to assess whether macronutrient degradability plateaus when digested for 2 h in a simulated gastric environment plus 8, 12, or 16 h in a simulated small intestinal environment. To replicate in vivo digestion, a pepsin-pancreatin approach was selected. The first step of this method replicates the gastric environment. Ten g of each test ingredient are weighed into beakers containing 60 mL hydrochloric acid (HCl; 0.1 M) and 0.4 g pepsin (~2,500 U/g) solution. Beakers are then covered and incubated for 2 h at 39 ℃ under constant stirring. One mL aliquots of the digestion liquid are sampled at 0, 5, 10, 20, 30 60, 90 and 120 min after the start of the gastric simulation. Before replicating intestinal digestion, samples are neutralized with sodium hydroxide and the pH is increased to 7. The second step of this method replicates the small intestinal environment. Fifty mL of pancreatin-phosphate buffer (350 U/g protease, 6,000 FIP U/g lipase, 7,500 U/g amylase) is added to the beakers, which are then covered and incubated for either 8, 12, or 16 h at 39 ℃ under constant stirring. One mL aliquots of the digestion liquid are sampled at 0, 5, 10, 20, 30 60, 90, 120, 150, 180 min and thereafter hourly up until the end of digestion (480, 720, or 960 min). Aliquot samples are analyzed for starch via a glucose assay, protein via o-phthalaldehyde assay, and lipids via gas chromatography. A model will is fit to the time point data to determine degradation rates and degradable fractions of the digested samples. Results from these analyses go beyond estimating gross nutrient and digestible nutrient values and inform on the rate of degradation of nutrients of equine feedstuffs and the impact of in vitro methodology. The resulting degradability values will be used in a mechanistic model of equine digestion which will inform precision feeding. Ultimately this will improve how we feed horses to reduce nutrient excretion into the environment and reduce the risk of metabolic conditions such as laminitis.

Production of surfactant-modified banana peel biosorbents applied to treatment and decolorization of effluents

In this study, banana peels (BP) were pretreated under different conditions and modified with surfactants cetyltrimethylammonium bromide (CTAB), dodecyl trimethylammonium bromide (DTAB), or sodium dodecyl sulfate (SDS). The biosorbents were used for the removal of the anionic Direct Blue 86 (DB86) from synthetic solutions as well as for the treatment of a textile effluent. The biosorbents were characterized by Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and point of zero charge (pHPZC). The results showed that the pretreatment using natural oxidation of BP showed better adsorbent performance than other pretreatments at pH 2. Treatment with SDS did not improve the sorption efficiency of the material. The biosorbents modified with DTAB (B-DTAB) and CTAB (B-CTAB) showed good performance with a maximum dye removal of 96.2% (at pH 2) and 91.7% (at pH 6), respectively, using 1.00 g L−1 of the biosorbents, constant stirring of 150 rpm for 60 min at 25 °C, and DB86 concentration of 10.0 mg L−1. The kinetics of B-DTAB and B-CTAB showed the best fit to the pseudo-first and pseudo-second-order models, respectively. The intraparticle diffusion model suggested that adsorption on B-CTAB may be guided by pore and film diffusion. Sips isotherm was found to be the best fit with theoretical maximum adsorption capacities from non-linear fit of 25.2 and 147 mg g−1, respectively, for B-DTAB and B-CTAB (1.00 g L−1 of the biosorbents, constant stirring of 150 rpm, 25 °C, and initial pH 6). Results suggest that mainly precipitation, hydrophobic interactions, and electrostatic attraction drives the sorption process. The treatment of the textile effluent using B-CTAB resulted in a reduction of 60.6% in color and 53.2% in effluent turbidity, demonstrating the potential of modified banana peels as promising biosorbents for environmental applications.

Electromembrane extraction – capillary zone electrophoresis for the quantitative determination of β-lactam antibiotics in milk samples

Three penicillin-based β-lactam antibiotics (benzylpenicillin, amoxicillin, and ampicillin) were extracted by electromembrane extraction (EME) and determined in the resulting extracts by capillary zone electrophoresis (CZE) with UV–Vis detection. The EME was optimized for the simultaneous clean-up of complex samples and preconcentration of the three antibiotics and employed 1-octanol as the organic phase interface (impregnated in the pores of a hollow fiber), acidified donor solution (pH 3), and phosphate buffer (pH 5.6) as the acceptor solution. The EMEs were carried out for 20 min at 300 V and constant stirring (750 rpm) of the donor solution. At the optimized EME-CZE conditions, the sensitivity of the analytical method was sufficient for the determination of the three β-lactam antibiotics in undiluted cow's milk at concentrations below the EU maximum residue limits (4 μg/L) in foodstuffs. The method was simple, rapid, and convenient and offered extraction recoveries of 13.5 – 87.3 %, enrichment factors of 23.6 – 152.8, repeatability (RSD values) better than 7.6 %, linear analytical response in the 1 – 100 μg/L (3 – 100 μg/L for benzylpenicillin) concentration range with correlation coefficients ≥ 0.9997, and limits of detection from 0.2 to 1.2 μg/L. The proposed analytical concept was used for the rapid control of milk quality (i.e. assessment of excessive use of antibiotics in dairy animals), moreover, it was further extended to the trace determination of β-lactam antibiotics in other complex samples, such as in wastewater.

Empirically developed model of the stirring-controlled Belousov–Zhabotinsky reaction

The Belousov–Zhabotinsky chemical reaction is famous for its oscillatory behavior occurring due to inherent physicochemical processes. Oscillations of the Belousov–Zhabotinsky reaction may be periodic or chaotic, depending on parameters, and these dynamics can be controlled by external impacts such as stirring. The complex behavior, the variability of the oscillatory modes, and controllability make the Belousov–Zhabotinsky reaction an important research subject in many fields of science, including various applications such as chemical computing or smart materials. One of the key limitations for the practical application of this oscillatory reaction is the absence of its exact mathematical model which can reproduce dynamics close to the real chemical process. This work aims to fill this gap by designing a novel model of the Belousov–Zhabotinsky reaction based on experimental data. To solve this task, we designed a complex experimental setup based on a photometric station with controllable stirring mechanisms. We performed two experiments in batch reactors (cuvettes). In the first experiment, we investigated how constant stirring with different rates affects the reaction behavior, and in the second experiment, we periodically stirred the reaction and observed its response. As a result, we found that chemical oscillations in the Belousov–Zhabotinsky reaction are in both cases chaotic, their amplitude depends on stirring more than their period does, and they are highly non-stationary: in the course of the reaction, their sensitivity to stirring decreases, so the oscillations remain controllable only during the first hour. Using a novel two-stage differential equation reconstruction approach, we managed to develop a complex of local dynamical models for the stirring-controlled BZ reaction with good correspondence to the empirical data. The presented models are more consistent with experimentally observed Belousov–Zhabotinsky dynamics than earlier models. The developed model can be used in various applications and extended to a wide class of controlled oscillatory reactions.

Enhancing the Longevity and Functionality of Ti-Ag Dry Electrodes for Remote Biomedical Applications: A Comprehensive Study.

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode's surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.

Characteristics of mucous-forming polysaccharides extracted from flax seeds

The research used the seeds of long flax of the "Vruchy" variety and oil-curly flax of the "Original" variety. To extract mucus, whole flax seeds were hydrated for 3 hours. in tap water, at a ratio of 1:20 and a temperature of 18 – 20 °C with constant stirring with a magnetic stirrer. This study aimed to evaluate the effect of temperature and duration of extraction on the yield of mucilaginous polysaccharides in aqueous solution from flaxseed. Change range: the temperature is selected in the range from 0 °С to 100 °С with a step of 20 °С; with a duration, ranging from 10 min to 140 min in 10 min increments. The yield of polysaccharides from flax seeds was determined for each combination of controlled factors. It was established that in the first 10 – 20 min. there is an increase in the yield of polysaccharides and the rate slows over time. For 90 min. equilibrium occurs at a temperature of 80 °C. This period of the process is optimal for the extraction of mucilage-forming polysaccharides from flaxseed. The mass of the extracted polysaccharides, from the mass of the seeds after a time of 95 min was 5.74%, and 6.00% at a temperature of 80 °С. A package of applied statistical programs was employed during the research to process the experimental data. A mathematical model of the process of extracting mucus-forming polysaccharides in an aqueous solution of flax seeds was built using regression analysis methods. The obtained regression equations determined the optimal regimes of the sought values in terms of temperature (80 – 85 °C), time (85 – 90 min) and conducted in compliance with the prescribed amount of water of 200 cm3. Within 10 – 20 min the formation of a transparent gel capsule around the flax with a phase separation boundary under seed contact with water, which does not change further. This indicates the completion of the hydration process.

Biodiesel Production from Seed Oil Obtained from Pongamia pinnata L.

At the present time biodiesel are the most promising source of energy as it is renewable and can accomplished the rising energy demand. Pongamia pinnata L. (commonly known as Karanj) is an evergreen tree of family Fabaceae sub family Papilioneaceae, has been recognized as a potential source of biodiesel prepared from the oil obtained from its seeds. In the present work, biodiesel fuel was prepared by alkaline-catalyzed esterification of high free fatty acids present in Karanj oil. The transestrification reaction was performed by varying practical parameters such as NaOH percentage (0.50%, 0.75%, 1%), methanol to oil ratio ( 3:1, 6:1, 9:1), and reaction temperature and time (40°C for 2h, 60°C for 2h, room temperature for 24h) at constant stirring at 150 rpm. Optimum alkaline-catalyzed transesterification was achieved using 1% NaOH as a solid alkaline catalyst with a methanol-to-oil ratio of 1:6, temperature at 600C. The yield of methyl esters from Karanja oil under the optimal condition was 92%. The biodiesel and oil contents were analysed using Gas Chromatography and Mass Spectroscopy (GC-MS) analyser. Fuel properties of the biodiesel obtained by transesterification were tested and found to meet the ASTM (American Society for Testing and Material) specifications.

Catalytic oxidative desulfurization of thio-compounds by employing χ-Anderson-type polyoxometalates-porphyrin covalent organic framework (COF)

Severe environmental sulfur contents due to the consumption of fuels in automobiles and industries resulted in serious health hazards and pollution because of it, desulfurization of diesel become inevitable. Targeting the profound desulfurization of diesel, we performed experiments to deeply desulphurized the thio-compounds by catalytic-oxidative desulfurization technique. We synthesized new metalloporphyrin (C52H36N4O8Sn)4MeO-SnPor which after conversion into (C64H64N8O16Sn)4Tris-SnTP leading towards the synthesis of covalent organic framework [(N(C4H9)4]12[HNC(CH2O)3]4[(CO)4C44H24N4Sn] [NiMo6O18]4(SnTP@NiAdCOF). SnTP@NiAd COF showed the outstanding catalytic property for deep desulfurization of thio-compounds above than 96% of thiobenzoic acid (TB) and 99% of 2-aminothiophenol (2-ATP) sulfur contents were oxides after 100 min of reaction using H2O2 as an oxidant at room temperature with constant stirring. During desulfurization percentage desulfurization efficiency was checked for different time intervals by TLC and further confirmed by reverse phase high-performance liquid chromatography (RP-HPLC). Reverse-phase high-performance liquid chromatograms indicated that the peak area and peak height of thio-compounds decrease gradually with the passage of reaction time which confirmed the removal of thio-compounds from the reaction mixture. Sulfur contents removed up to 5 ppmw showed excellent catalytic characteristics of synthesized SnTP@NiAdCOF. The exceptional catalytic efficiency of prepared catalyst SnTP@NiAdCOF was because of the existence of active oxidizing centers of χ-NiAd and metalloporphyrin that are MoO and [(Por)SnII], respectively. The potential mechanism appeared to be the formation of Mo(O2) and [(Por)SnII–OOH] from MoO and [(Por)SnII], respectively that act as active oxidizing centers and efficiently converted the thio-group into oxides and sulfones. Effective removal of sulfur grants the desulfurization of fuels by using SnTP@NiAdCOF catalyst to lessen the energy expenditure and also to enhance the production of environmentally-safe fuels.

Facile Preparation of SrZr1-xTixO3 and SrTi1-xZrxO3 Fine Particles Assisted by Dehydration of Zr4+ and Ti4+ Gels under Hydrothermal Conditions.

In recent decades, perovskite-type compounds (ABB'O3) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO3-SrTiO3 was conducted under hydrothermal conditions in a KOH (5 M) solution at 200 °C for 4 h under a constant stirring speed of 130 rpm. The precursors employed were SrSO4 powder (<38 μm size) and coprecipitated hydrous gels of Zr(OH)4•9.64 H2O (Zr-gel) and Ti(OH)4•4.5H2O (Ti-gel), which were mixed according to the stoichiometry of the SrZr1-xTixO3 in the compositional range of 0.0 > x > 100.0 mol% Ti4+. The XRD results revealed the formation of two crystalline phases rich in Zr4+, an orthorhombic structured SrZr0.93Ti0.07O3 and a cubic structured SrZr0.75Ti0.25O3 within the compositional range of 0.1-0.5 mol of Ti4+. A cubic perovskite structured solid solution, SrTi1-xZrxO3, was preferentially formed within the compositional range of 0.5 > x > 0.1 mol% Ti4+. The SrZrO3 and SrZr0.93Ti0.07O3-rich phases had particle sizes averaging 3 μm with a cubic morphology. However, a remarkable reduction in the particle size occurred on solid solutions prepared with hydrous Ti-gel over contents of 15 mol% Ti4+ in the reaction media, resulting in the formation of nanosized particle agglomerates with a cuboidal shape self-assembled via a 3D hierarchical architecture, and the sizes of these particles varied in the range between 141.0 and 175.5 nm. The limited coarsening of the particles is discussed based on the Zr-gel and Ti-gel dehydration capability differences that occurred under hydrothermal processing.

Sorption of Lead, Zinc and Copper from Simulated Wastewater by Amberlite Ir-120 Resin

The presence of heavy metals in the environment is major concern due to their toxicity. In the present study a strong acid cation exchange resin, Amberlite IR 120 was used for the removal of lead, zinc and copper from simulated wastewater. The optimum conditions were determined in a batch system of concentration 100 mg/L, pH range between 1 and 8, contact time between 5 and 120 minutes, and amount of adsorbent was from 0.05 to 0.45 g/100 ml. A constant stirring speed, 180 rpm, was chosen during all of the experiments. The optimum conditions were found to be pH of 4 for copper and lead and pH 6 for zinc, contact time of 60 min and 0.35 g of adsorbent. Three different temperatures (25, 40 and 60°C) were selected to investigate the effect of adsorption temperature on heavy metals adsorption onto Amberlite IR. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms. The thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes were calculated. Moreover, in order to understand the heavy metal extraction kinetics in the presence of Amberlite IR 120, the ion exchange kinetics was also studied. The ion exchange kinetics data were regressed by the pseudo first-order, second-order models. The results obtained show that the Amberlite IR 120 strong acid cation exchange resin performed well for the removal of lead, zinc and copper.

Improving the quality of metallurgical-grade silicon by acid leaching

This work deals with the problem of hydrometallurgical refining of metallurgical-grade silicon. Samples of metallurgical-grade silicon after oxidative refining from JSC Silicon, RUSAL (Shelekhov, Irkutsk Oblast, Russia) were subjected to X-ray fluorescence and electron microprobe analysis. The conducted elemental analysis determined their following composition, wt%: Al – 0.53, Fe – 0.6094, Ti – 0.0491, Ca – 0.0628, V – 0.0066, Cr – 0.002, Mn – 0.014, Cu – 0.003, P – 0.010, Ba – 0.007, Ni – 0.007, and Zn – 0.002. The examined samples were found to comprise the following intermetallic compounds: AlFeSi2 (with an admixture of Ca), FeSi2 (with an admixture of Al), and FeSi2Ti (with an admixture of Zr). In order to purify silicon from impurities, 10% H2SO2, HCl, HNO3, as well as 4% HF in different ratios were used as solvents. The feasibility of interactions between the intermetallic compounds and the selected solvents was assessed by calculating changes in the Gibbs energy, which had negative values. Experiments on impurity leaching were carried out using silicon samples with a particle size of –200 µm under constant stirring with a magnetic stirrer under the temperature of 600С, the liquid-to-solid ratio of 5:1, and the leaching duration of 60 min. The highest degree of silicon purification (86.85%) was achieved under leaching with a mixture of sulfuric and hydrofluoric acids in a ratio of 1:1. The use of a mixture of sulfuric and hydrochloric acids at a ratio of 1:3 resulted in the silicon purification of 41.48%. Thus, optimal solvents allowing the maximum purification of silicon from impurities were determined.

Processing of ore from the Nud II deposit by the method of low-temperature roasting with ammonium sulfate

The Murmansk region has a significant amount of sulfide copper-nickel raw materials. Deposits of the Nud massif associated with Monchepluton are promising for processing. The Nud II deposit cut-off grade ore with an initial Ni content of 0.45 % and Cu of 0.39 % has been chosen as the research object. During the research, the ore was mixed with ammonium sulfate, grinded, and the mixture was roasted in a muffle furnace with static air atmosphere. The roasted mixture was leached in heated distilled water with constant stirring. The maximum metals recovery was achieved when crushing to a fraction of –40 µm, the ratio of ore : ammonium sulfate is equal to 1 : 7, roasting temperature 400 °C, roasting duration 300 min. In the mixture roasted at these parameters, reflexes of copper and nickel sulfates were recorded by the x-ray phase analysis (XRD) method. At the stage of water leaching, the maximum recovery was: Ni – 79.1 %, Cu – 75.8 %.

Биотехнология воспроизводства и выращивания рыбопосадочного материала балхашской маринки (Schizothrax argentatus) в индустриальных условиях

Artificial reproduction is one of the most popular ways to preserve rare fish species. Researchers of the Balkhash branch of the Research and Production Center for Fisheries of the Republic of Kazakhstan carried out the reproduction and cultivation of Balkhash marinka at their own fish farm using a recirculating water supply system. There have been considered the technological methods of removing the marinka spawners from the natural environment, their pre-spawning maintenance in fish tanks, hormonal stimulation of spawning, intravital methods for selecting reproductive products, artificial insemination, incubation of eggs, growing viable material for stocking a native reservoir. The catch of the required number of spawners was carried out from the river Tokyraun (Northern Balkhash). After adaptation and quarantine, female species were exposed to 2x and 3x hormonal stimulation with acetonated carp pituitary. Males were injected once. Reproductive products were obtained from a female injected 3 times, after 15 hours; from a female 2x injected – after 21 hours. Duration of insemination for marinka was 2 minutes. The degluing process lasted 40 minutes with constant stirring and partial replacement of the solution. The eggs were incubated in Weiss apparatus, completely protected from light. With a high quality of reproductive products, the fertilization of eggs was 90%. The incubation time at a water temperature of 19.5-20.0 °C continued 3-4 days (60-78 degree days). The yield of prelarvae made 19-20%. Under industrial conditions, keeping the larvae lasted 4-5 days. When feeding marinka larvae, in order to increase their survival, it is advisable to use only decapsulated Artemia eggs. The juvenile period of development of Balkhash marinka began on the 30-35th day. Aller Aqua dry food was gradually introduced into the diet of fry. Under optimal abiotic and biotic conditions, the fry growth rate reached 0.075 and 7.32%/day. At the end of September marinka underyearlings with an average weight of 11.0 g were released into Lake Balkhash. The research results will serve as a theoretical and practical basis for the development of adapted technologies for the artificial reproduction of rare and endemic fish species and their introduction at fish farms.

Polymer co-crystallization from LLE: Crystallization kinetics of POCB hydrate from two-phase mixtures of POCB and water

Polyoxacyclobutane (POCB, –[CH2CH2CH2O−]n) has the rare ability to co-crystallize with water to form a hydrate. Above the melting point of the hydrate (∼37 °C), mixtures exist in liquid-liquid equilibrium (LLE) between a POCB-rich and a water-rich liquid phase over a wide range of POCB:water ratios. Such phase behavior, which combines liquid-liquid equilibrium (LLE) and co-crystallization of a polymer with a small molecule, appears to be unique to POCB-water mixtures. Here, we examine the kinetics of isothermal hydrate co-crystallization when mixtures that are initially in liquid-liquid equilibrium (LLE) are cooled to below the hydrate melting point. Hydrate co-crystallization requires both POCB and water, and hence, it is coupled with transport of species between the liquid phases. Optical microscopy shows that hydrate crystallization occurs within the POCB-rich domains, and hydrate spherulites grow at constant speed. The temperature-dependence of the speed of hydrate growth front is consistent with the Hoffman Lauritzen model for homopolymer crystallization. Dilatometric measurements of bulk co-crystallization kinetics are conducted with constant stirring to avoid gravitational separation of the liquid phases. The temperature-dependence of bulk crystallization kinetics of these stirred mixtures in LLE is found to be far weaker than that of spherulitic growth kinetics, or of the quiescent bulk crystallization kinetics of mixtures starting from homogeneous conditions.