Effect of preliminary alkali desilication on ammonia pressure leaching of low-grade copper–silver concentrate

Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 0836-2020-0020Funding: This work was financially supported by the Russian Science Foundation Project No. The SEM-EDX analyses were funded by State Assignment, grant number 0836-2020-0020

Leaching kinetics of arsenic sulfide-containing materials by copper sulfate solution

The overall decrease in the quality of mineral raw materials, combined with the use of arsenic-containing ores, results in large amounts of various intermediate products containing this highly toxic element. The use of hydrometallurgical technologies for these materials is complicated by the formation of multicomponent solutions and the difficulty of separating copper from arsenic. Previously, for the selective separation of As from copper–arsenic intermediates a leaching method in the presence of Cu(II) ions was proposed. This paper describes the investigation of the kinetics of arsenic sulfide-containing materials leaching by copper sulfate solution. The cakes after leaching of arsenic trisulfide with a solution of copper sulfate were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analysis (EDS). The effect of temperature (70–90 °C), the initial concentration of CuSO4 (0.23–0.28 M) and the time on the As recovery into the solution was studied. The process temperature has the greatest effect on the kinetics, while an increase in copper concentration from 0.23 to 0.28 M effects an increase in As transfer into solution from 93.2% to 97.8% for 120 min of leaching. However, the shrinking core model that best fits the kinetic data suggests that the process occurs by the intra-diffusion mode with the average activation energy of 44.9 kJ/mol. Using the time-to-a-given-fraction kinetics analysis, it was determined that the leaching mechanism does not change during the reaction. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 − X) + [(1 − X) − 1/3 − 1] = 4,560,000Cu3.61e−44900/RT t. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.10.7347.2017/8.9Russian Science Foundation, RSF: 18-19-00186Funding: The research was funded by the Russian Science Foundation, grant number 18-19-00186. The SEM/EDS analyses were funded by State Assignment, grant number 10.7347.2017/8.9

Leaching kinetics of sulfides from refractory gold concentrates by nitric acid

The processing of refractory gold-containing concentrates by hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in the ores. This paper describes the investigation of the kinetics of HNO3 leaching of sulfide gold-containing concentrates of the Yenisei ridge (Yakutia, Russia). The effect of temperature (70–85 °C), the initial concentration of HNO3 (10–40%) and the content of sulfur in the concentrate (8.22–22.44%) on the iron recovery into the solution was studied. It has been shown that increasing the content of S in the concentrate from 8.22 to 22.44% leads to an average of 45% increase in the iron recovery across the entire range temperatures and concentrations of HNO3 per one hour of leaching. The leaching kinetics of the studied types of concentrates correlates well with the new shrinking core model, which indicates that the reaction is regulated by interfacial diffusion and diffusion through the product layer. Elemental S is found on the surface of the solid leach residue, as confirmed by XRD and SEM/EDS analysis. The apparent activation energy is 60.276 kJ/mol. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 - X) + [(1 - X)-1/3 - 1] = 87.811(HNO3)0.837(S)2.948e-60276/RT·t. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The research was funded by the Russian Science Foundation, grant number 18-19-00186. The SEM/EDS and microprobe analysis were funded by State Assignment, grant number 11.4797.2017/8.9

Assessing the role of natural fracturing by multiscale geophysical investigation

The article presents an estimation of tectonic fracturing role in terrigenous and carbonate blocks containing hydrocarbon deposits. Geological and geophysical datasets of different scale were used to characterize the fracturing of rocks. The good convergence is found between the orientation of natural fracturing by formation microimagers in wells, three-dimensional surface seismic survey, microseismic monitoring of hydraulic fracturing propagation and regional lineament analysis by satellite imagery. The article contains examples of comparison between the direction of maximum horizontal stress axis and stress state and the direction of horizontal wells and fluid flow. New factors of unsuccessful multistage hydraulic fracturing operations in carbonate rocks are considered in the context of natural fracturing systems' kinematics. Complex data analysis of the fracturing at different scales allowed to divide fracturing systems basing on the kinematics. It is shown that the method of structural and geomorphic lineament analysis detected on the satellite images allows to determine the orientation of regional stress field axes for the platform areas with small number of geological outcrops. It is found that during the hydraulic fracturing the main fracture is developed following the system of tectonic fractures and the propagation of the fracture tip is not linear - the fracturing follows both the shear and tensile cracks. It is suggested that the reorientation of the principal stress axes within one field is associated with gently sloping low-amplitude tectonic deformation. The main fundamental conclusion obtained as a result of studies is a justification of the leading role of modern tectonic stress field in the fracturing kinematics. The practical conclusion is a necessity of a selective stimulation of fractured rock blocks to achieve the maximum production for the redeveloped of oil fields

Nitric Acid Dissolution of Tennantite, Chalcopyrite and Sphalerite in the Presence of Fe (III) Ions and FeS2

This paper describes the nitric acid dissolution process of natural minerals such as ten-nantite, chalcopyrite and sphalerite, with the addition of Fe (III) ions and FeS2. These minerals are typical for the ores of the Ural deposits. The effect of temperature, nitric acid concentration, time, additions of Fe (III) ions and FeS2 was studied. The highest dissolution degree of sulfide minerals (more than 90%) was observed at a nitric acid concentration of 6 mol/dm3, an experiment time of 60 min, a temperature of 80 °C, a concentration of Fe (III) ions of 16.5 g/dm3, and an addition of FeS2 to the total mass minerals at 1.2:1 ratio. The most significant factors in the break-down of minerals were the nitric acid concentration, the concentration of Fe (III) ions and the amount of FeS2. Simultaneous addition of Fe (III) ions and FeS2 had the greatest effect on the leaching process. It was also estab-lished that FeS2 can be an alternative catalytic surface for copper sulfide minerals during nitric acid leaching. This helps to reduce the influence of the passivation layer of elemental sulfur due to the galvanic linkage formed between the minerals, which was confirmed by SEM-EDX. © 2022 by the author. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 075-03-2021-051/5, 20-79-00317, FEUZ-2021-0017Funding: This work was funded by the Russian Science Foundation Project No. 20-79-00317. The SEM-EDX, XRF, XRD analysis were funded by State Assignment, grant No. 075-03-2021-051/5 (FEUZ-2021-0017)

Исследование реакционной способности производных коричной кислоты – предшественников лигнина

Objectives. Cinnamic acid derivatives belong to a large class of phenolic compounds, which are widely distributed in plants and have high potential for use in the medical and industrial fields. They have various useful practical properties, e.g., antioxidant, anti-inflammatory, antiplatelet, and anti-melanogenic properties. Hydroxycinnamic acids are of particular interest as phenylpropanoids, which are the starting compounds of lignin. The aim of this work was to study the electronic structure and analyze the reactivity of the simplest representatives of phenylpropanoids formed during the biosynthesis of the coumaric (p-hydroxycinnamic), caffeic (3,4-dihydroxycinnamic), ferulic (3-methoxy-4-hydroxycinnamic), sinapic (3,5-dimethoxy-4- hydroxycinnamic), and 3,4-dimethoxycinnamic acids. These acids are the biogenetic precursors of most other phenolic compounds (coumarins, melanins, lignins, and flavonoids) and are found in almost all higher plants.Methods. Calculations with full optimization of the geometric parameters were performed using the original Hartree–Fock theory and hybrid density functional method. All calculations were performed using the Firefly program. Results. A comparative quantum chemical calculation of the geometric parameters of hydroxycinnamic acid molecules was conducted via two methods, and the values of the charges on atoms according to Mulliken were determined. It was found that with the addition of hydroxyl and methoxy substituents at the meta and para positions relative to the carboxyl fragment, the electron density shifts toward the benzene ring, and the symmetry of the molecule decreases. Additionally, in these structures, there is π,π-conjugation of the carboxyl fragment of the –СН=СНСООН molecule with the aromatic ring, which significantly affects the geometric configuration of the molecule. The maximum positive charge is concentrated on the C9 atom, while the maximum negative charge is on the oxygen atoms belonging to the methoxy substituents and the hydroxyl group, which confirms the role of oxygen atoms in the chemical transformations of acids. Conclusions. Two different methods were used to calculate the geometric, electronic, and energy parameters and electrophilicity indices of the studied hydroxycinnamic acids in the gas phase. The obtained values were consistent (within the limits of error) with the experimental data as well as the results described in earlier works’ calculations by other methods.Цели. Производные коричной кислоты относятся к большому классу фенольных соединений, которые широко распространены в растительности и обладают высоким потенциалом для применения в медицине и промышленности. Они обладают различными практически полезными свойствами, например, антиоксидантными, противовоспалительными, антиагрегантными и антимеланогенными свойствами. Отдельный интерес представляют оксикоричные кислоты как фенилпропаноиды, являющиеся исходными соединениями лигнина. Целью данной работы является исследование электронной структуры и анализ реакционной способности простейших представителей фенилпропаноидов, образующихся в процессе биосинтеза: кумаровой (п-оксикоричной), кофейной (3,4-дигидроксикоричной), феруловой (3-метокси-4-гидроксикоричной), синаповой (3,5-диметокси-4-гидроксикоричной) и 3,4-диметоксикоричной кислот. Эти кислоты являются биогенетическими предшественниками большинства других фенольных соединений (кумаринов, меланинов, лигнина и флавоноидов) и встречаются практически во всех высших растениях. Методы. В рамках ограниченного метода Хартри Фока и метода гибридного функционала плотности оптимизированы исследуемые молекулы. Все расчеты проводились с использованием программы Firefly. Результаты. Проведен сравнительный квантово-химический расчет геометрических параметров молекул оксикоричных кислот двумя методами, приведены значения зарядов на атомах по Малликену. При введении гидроксильных и метоксильных заместителей в м- и п-положения относительно карбоксильного фрагмента происходит смещение электронной плотности в сторону бензольного кольца и, как следствие, понижение симметрии молекулы. Также в исследуемых структурах имеется π,π-сопряжение карбоксильного фрагмента молекулы –СН=СНСООН с ароматическим кольцом, что существенно сказывается на геометрической конфигурации молекул. Максимальный положительный заряд сосредоточен на атоме С9, а максимальный отрицательный – на атомах кислорода, относящихся к метоксильным заместителям и гидроксильной группе, что подтверждает роль кислородных атомов в химических превращениях кислот. Выводы. В работе двумя различными методами были рассчитаны геометрические, электронные и энергетические параметры, а также индексы электрофильности исследуемых оксикоричных кислот в газовой фазе. Полученные величины согласуются в пределах погрешностей с экспериментальными данными, а также описываемыми в ранних работах при расчетах другими методами

Deposition of arsenic from nitric acid leaching solutions of gold—arsenic sulphide concentrates

At present, the processing of refractory gold–arsenic sulphide concentrates is becoming more relevant due to the depletion of rich crude ore reserves. In the process of the nitric acid leaching of arsenic sulphide minerals, solutions are formed containing 20–30 g/L of arsenic (III). Since market demand for arsenic compounds is limited, such solutions are traditionally converted into poorly soluble compounds. This paper describes the investigation of precipitating arsenic sulphide from nitric acid leaching solutions of refractory sulphide raw materials of nonferrous metals containing iron (III) ions using sodium hydrosulphide with a molar ratio of NaHS/As = 2.4–2.6, which is typical for pure model solutions without oxidants. The work studied the effect of temperature, the pH of the solution and the consumption of NaHS and seed crystal on this process. The highest degree of precipitation of arsenic (III) sulphide (95–99%) from nitric acid leaching solutions containing iron (III) ions without seed occurs with a pH from 1.8 to 2.0 and a NaHS/As molar ratio of 2.8. The introduction of seed crystal significantly improves the precipitation of arsenic (III) sulphide. An increase in seed crystal consumption from 0 to 34 g/L in solution promotes an increase in the degree of transition of arsenic to sediment from 36.2 to 98.1% at pH = 1. According to SEM/EDS and XRF sediment data, from the results of experiments on the effect of As2S3 seed crystal consumption, acidity and molar ratio of NaHS/As on the precipitation of arsenic (III) sulphide and the Fetotal/Fe2+ ratio in the final solution, it can be concluded that the addition of a seed accelerates the crystallisation of arsenic (III) sulphide by increasing the number of crystallisation centres; as a result, the deposition rate of As2S3 becomes higher. Since the oxidation rate of sulphide ions to elemental sulphur by iron (III) ions does not change significantly, the molar ratio of NaHS/As can be reduced to 2.25 to obtain a precipitate having a lower amount of elemental sulphur and a high arsenic content similar to that precipitated from pure model solutions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was financially supported by the Russian Science Foundation Project No. 20-79-00321. The SEM–EDS analyses were funded by State Assignment, Grant No. 0836-2020-0020

Epidemiological dynamics of nephropathia epidemica in the Republic of Tatarstan, Russia, during the period of 1997-2013

Copyright © Cambridge University Press 2015.This report summarizes epidemiological data on nephropathia epidemica (NE) in the Republic of Tatarstan, Russia. NE cases identified in the period 1997-2013 were investigated in parallel with the hantavirus antigen prevalence in small rodents in the study area. A total of 13 930 NE cases were documented in all but one district of Tatarstan, with most cases located in the central and southeastern districts. The NE annual incidence rate exhibited a cyclical pattern, with the highest numbers of cases being registered once in every 3-5 years. The numbers of NE cases rose gradually from July to November, with the highest morbidity in adult males. The highest annual disease incidence rate, 64·4 cases/100 000 population, was observed in 1997, with a total of 2431 NE cases registered. NE cases were mostly associated with visiting forests and agricultural activities. The analysis revealed that the bank vole Myodes glareolus not only comprises the majority of the small rodent communities in the region, but also consistently displays the highest hantavirus prevalence compared to other small rodent species

Analysis of patients’ therapy with the superficial venous thrombosis

The results of the analysis of the treatment of patients with superficial subcutaneous venous thrombosis. The medical histories of patients that were treated in 2019 in the cardiovascular departments of two clinical hospitals of Ekaterinburg: MAI "City clinical hospital №40" PHI "Clinical hospital "Railways- Medicine". We analyzed and compared the results of various tactics for the treatment of superficial venous thrombosis (SVT): operative and conservative in 82 patients with an average age of 55.5 years. The obtained data was compared with the national recommendations for the treatment of SVT. Operative tactics were used in 69 patients (84.1% of cases), conservative – in 13 patients (15.9% of cases). 81 (98.7 %) patients were discharged from the hospital with recovery. There is 1 fatal case due to massive PE in 1 day after admission. According to the results of the control examination, complete relief of the inflammatory process was registered in most cases – 76 (93.8%), partial in 5 cases (6.2%). However, a different pattern was observed for the regression of the thrombotic process: complete recanalization was registered only in 7 (8.7%). An addition to the existing treatment strategy for HTP HAS been proposed.Представлены результаты анализа лечения пациентов с поверхностным варикотромбофлебитом. За основу были взяты истории болезни пациентов, лечившихся в 2019 году в сосудистых отделениях двухклинических больниц г. Екатеринбурга: МАУ «Городская клиническая больница №40» и ЧУЗ «Клиническая больница «РЖД-Медицина». Проанализированы и сравнены результаты различных тактик по лечению поверхностного варикотромбофлебита (ВТФ): оперативной и консервативной у 82 пациентов, средний возраст которых составил 55,5 лет Полученные данные были сравнены с национальными рекомендациями по лечению ПВТФ. Оперативная тактика была принята у 69 пациентов (84,1% случаев), консервативная – у 13 пациентов (15,9% случаев). Из стационара с выздоровлением выписан 81 (98,7 %) пациент. Имеется 1 летальный случай вследствие массивной ТЭЛА в 1 сутки после поступления. По результатам контрольного осмотра зарегистрировано полное купирование воспалительного процесса в большинстве случаев – 76 (93,8%), частичное в 5 случаях (6,2%). Однако по регрессу тромботического процесса наблюдалась другая картина: полная реканализация зарегистрирована лишь у 7 (8,7%). Предложено дополнение к существующей тактике лечения ПВТФ