scholarly journals The investigation of the kinetics of hydrochemical oxidation of metal sulphides with the aim of determination of the optimal conditions for the selective extraction of molybdenum from ores

2005 ◽  
Vol 41 (1) ◽  
pp. 33-45 ◽  
Author(s):  
V. Lutsik ◽  
A. Sobolev
Keyword(s):  
Rotation Frequency ◽  
Rotating Disk ◽  
Selective Extraction ◽  
Solution Temperature ◽  
Specific Rate ◽  
Disk Rotation ◽  
Diffusion Controlled ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

The kinetics of the oxidation of molybdenyte, pyrite and sphalerite in solutions of nitric acid, hydrogen peroxide, and sodium hypochlorite was studied by the rotating disk method. The influence of the molar concentration of reagent, pH of solution, temperature, disk rotation frequency, and duration of measurements on the specific rate of hydrochemical oxidation of sulpfides was determined. The kinetic models allowing to calculate the dissolution rate of sulphides when these parameters change simultaneously were obtained. The conditions of kinetically and diffusion-controlled processes were detected. The details of mechanism of the studied processes were revealed. The nature of intermediate solid products, the reasons and the conditions of their formation as well as the character of their influence on the kinetics of dissolution processes were determined. The probable schemes of interactions corresponding to the observable kinetic dependences were offered. The conditions of the effective and selective molybdenum leaching directly from ore without its concentration were found.

To the Problem of Reducing the Amount of Harmful Emissions when Refining Silver

2018 ◽  
Vol 284 ◽  
pp. 877-881
Author(s):  
Sergey E. Polygalov ◽  
S.A. Mastugin ◽  
E.A. Shadrina
Keyword(s):  
Nitric Acid ◽  
Nitrogen Oxides ◽  
Dissolution Rate ◽  
Rotating Disk ◽  
Oxidation Potential ◽  
Solution Temperature ◽  
Harmful Emissions ◽  
Environmentally Friendly Process ◽  
Silver Dissolution ◽  
Kinetics Of

The work is devoted to the study of the possibilities of minimizing the release of nitrogen oxides during the dissolution of silver in nitric acid solutions during refining of the gold and silver alloy. Using a rotating disk, the maximum concentration of nitric acid is determined, at which the oxidation potential of the system is insufficient for the oxidation of silver. It has been established that at a temperature of 363 K and a concentration of HNO3 = 50 g/l, the dissolution rate of silver does not exceed 0.00022∙10-5 mol/(cm2∙s), and such conditions can be considered as background for an environmentally friendly process. To initiate dissolution, hydrogen peroxide was used as an alternative oxidizing agent. As a criterion for the rational use of the oxidant and the ecological purity of the process, the excess pressure over the solution was evaluated. The influence of the initial and current composition of the solution, temperature, and conditions of oxidant supply to the reactor on the kinetics of the target process was studied. It is shown that at a silver dissolution rate of 2.7∙10-6 mol/(cm2∙s), no release of nitrogen oxides was observed.

Study of the kinetics of dissolution of copper ferritic by the rotating disk method

2018 ◽  
pp. 29-32
Author(s):  
D. S. Reutov ◽  
◽  
B. D. Khalezov ◽  
L. A. Ovchinnikova ◽  
A. S. Gavrilov ◽  
...  
Keyword(s):  
Rotating Disk ◽  
Kinetics Of Dissolution ◽  
Kinetics Of ◽  
Disk Method

Determination of the kinetics of dissolution of materials in liquid metals

1968 ◽  
Vol 2 (5) ◽  
pp. 411-413 ◽  
Author(s):  
V. N. Eremenko ◽  
Ya. V. Natanzon
Keyword(s):  
Liquid Metals ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

scholarly journals INFLUENCE OF FORMATION OF THE COMPLEXES WITH DIFFERENT KIND OF LIGANDS ON KINETICS OF OXIDATIVE DISSOLUTION OF METALS

2018 ◽  
Vol 61 (8) ◽  
pp. 22
Author(s):  
Vladimir I. Lutsik ◽  
Yury V. Chursanov ◽  
Anatoly V. Starovoytov
Keyword(s):  
Dissolution Rate ◽  
Solid Phase ◽  
Film Formation ◽  
Rotation Frequency ◽  
Rotating Disk ◽  
Gold Surface ◽  
Reaction Products ◽  
Gold Dissolution ◽  
Strong Absorption Band ◽  
Disk Rotation

Rotating disk method has been used to study the dissolution of gold in the presence of an oxidizer and a mixture of dissimilar ligandforming reagents. Kinetic regularities of gold dissolution were investigated in aqueous systems thiourea-thiocyanate with Fe (III) and Cu (II) ions as the oxidizer; thiosulfate-thiocyanatewithFe(III)EDTA oxidizing complex and thiosulfate-thiocyanate with ammonia complex [Cu(NH3)4]2+ asoxidizing agent. Peculiarities of these mixed systems is a possibility to form the monoligandas as well as geteroligand complexes of gold. The influence of gold complexes formation with different sorts of ligands on the metal dissolution rate have been considered. The dependence of the dissolution rate on the ratio of ligands concentrations and on the oxidizing agent nature was investigated.  Interrelation was established: the use of dissimilar ligandforming reagents - the higher thermodynamic stability of the geteroligand complexes of gold (relative to the homoligand ones) - synergistic increase of the gold dissolution rate. It was found that the heterophase reaction makromechanism for the thiourea-thiocyanate-Fe(III) system is determined by the proximity of the rates of chemical and diffusion stages (experimental activation energy - 21.6 kJ/mol; the reaction order in respect to the disk rotation frequency – 0.23). Diffusive limitation is due to the slow withdrawal of the reaction products -Au (I) compounds - from the solid phase surface. The formation of stronger heteroligand complexes and the corresponding increase in the reaction products concentration at the surface increases a rate of the metal diffusion into the solution. For the thiourea-thiosulfate-Fe(III)EDTA system a film formation of the reaction solid products on the gold surface was observed. To identify it the infrared reflection spectra of the polished gold surface after the etching were obtained. There is a strong absorption band on the spectra at 804 cm-1. Absorption in this area has been associated with the stretching vibrations of C=S bond of the thiourea molecules joined to the surface and the products of their oxidation.

scholarly journals DISSOLUTION KINETICS OF GOLD IN SYSTEM THIOUREA–THIOSULFATE WITH OXIDANT OF Fe(III)EDTA

2018 ◽  
Vol 61 (12) ◽  
pp. 94-100
Author(s):  
Yury V. Chursanov ◽  
Vladimir I. Lutsik ◽  
Anatoly V. Starovoytov
Keyword(s):  
Activation Energy ◽  
Dissolution Rate ◽  
Rotation Frequency ◽  
Reaction Products ◽  
Rotating Disc ◽  
Heteroligand Complexes ◽  
Disk Rotation ◽  
Mixed Regime ◽  
Experimental Activation Energy ◽  
Kinetics Of

Cyanidation remains the predominant technology for the dissolution of gold from mineral raw materials. Environmental and technological disadvantages in the use of cyanides are the cause of the development of alternative systems, which include reagent-oxidant and reagent-complexant. A special place is occupied by the solvents, in which the formation of heteroligand complexes of gold is possible. Thus due to the formation of more durable compounds the rate of dissolution of the metal increases. In this work, as the ligands the thiourea and the ions of thiosulfate in the form of sodium salt were used, as the oxidant – complex of the iron (III) and EDTA. The influence of the mixed solvent composition on the kinetic characteristics and the reaction mechanism was studied by the rotating disc method. To confirm the role of different ligand complexes, the dependence of the dissolution rate of gold by the mixed system – thiosulphate and thiourea in the isomolar series, was determined. With a constant total ligands concentration, the molar ratio of reagents was changing. On the basis of the data obtained, a mathematical model of the process of oxidative dissolution of gold is proposed. A characteristic feature of the calculated results is a substantial increase in the reaction constants for the formation of heteroligand complexes, which confirms their role in the process of gold oxidation. The influence of pH and concentration of oxidant and ligand-forming substances on the kinetics of gold dissolution is established. To elucidate the mechanism of the limiting stage of the heterophase process, the experimental activation energy is calculated and the effect of the disk rotation frequency on the dissolution rate is studied. The experimental activation energy is 28.1 kJ/mol. The order by the disk rotation frequency is 0.35. Evaluation of the contribution of the diffusion and kinetic components of rate is estimated on the basis of the modified Levich equation for the mixed regime. Diffusion component of rate is almost an order of magnitude smaller than the kinetic one. Calculation of the diffusion flux of the supplied reagents showed that the only process that inhibits mass transfer is the diffusion of the reaction products from the surface of the rotating disc. The formation of more durable heteroligand complexes and a greater equilibrium constant of the oxidation reaction lead to an increase in the concentration of products at the surface and, consequently, to an increase in the rate of diffusion of the metal into the solution. An important factor affecting the oxidation of gold in the system studied is the formation of intermediate solid reaction products on the metal surface. To identify solid products, IR spectra of reflection of polished gold surface after etching in the system studied were obtained. A strong absorption band in the 808-762 cm-1 region is observed on the spectra. Absorption in this region is associated with valence symmetrical vibrations of the bond of the –C = S group adsorbed or chemically bound to the surface of the molecules of thiourea and its oxidation products. Depending on the composition of the solution and the temperature, the maximum of the peak shifts, and its intensity also changes. This can be explained by a change in the composition of the adsorbed compounds. The efficiency of regeneration of the oxidant Fe(III)EDTA by oxygen in thiourea-thiosulfate solution has been showed.  

scholarly journals Influence of the textural and structural functions of the Urals carnallite rocks on the kinetics of dissolution processes

2021 ◽  
pp. 62-67
Author(s):  
Т.Р. Шакиров ◽  
М.С. Вафина
Keyword(s):  
Chemical Composition ◽  
Structural Features ◽  
Dissolution Process ◽  
Insoluble Residue ◽  
The Urals ◽  
Slowing Down ◽  
Rate Of Dissolution ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

В статье показана необходимость исследования кинетики процессов растворения карналлитовых пород Приуралья. Описана методика подготовки образцов и лабораторного изучения скорости растворения. Представлены данные о химическом составе образцов 4-х цветовых разностей карналлитовых пород, текстурно-структурных особенностей, результатов по определению скорости растворения и вещественного состава нерастворимого в воде остатка. Цель исследования заключалась в изучении скорости и процессов растворения в воде при температуре 500С в режиме вынужденной конвекции и оценке влияния текстурно-структурных особенностей карналлитовых пород. Задачами исследования являлись: определение солевого и минерального составов, изучениеструктуры и микровключений в шлифах, проведение экспериментов по кинетикерастворения. При решении поставленных задач использовались следующие методы: АЭС-спектрометрия, петрографический анализ, гидростатический метод, РКФА. Проанализирован фактический материал исследования, сделаны соответствующие выводы. Проведенными исследованиями было показано, что важными факторами, влияющими на кинетику процессов растворения, являются вещественный состав и текстурно-структурные свойства. В работе определена суммарная (массовая) скорость растворения образцов. Железооксидная пленка, оконтуривающая зерна карналлитовых пород, экранирует поверхность растворения, замедляя процесс диффузии. Наличие галита и неравномерное его содержание вызывает колебания скорости растворения изамедляет процесс растворения во времени. Микровключения газов положительно влияют на динамику процесса растворения, усиливая конвекцию и массоперенос. С увеличением гидродинамических параметров растворителя (плотности и вязкости) скорость растворения понижается. Установленные закономерности могут оказывать существенное влияние на процессы, происходящие при скважинной добыче (подземное растворение) и галургической переработке карналлитовых руд. The article shows the need to study the kinetics of the dissolution processes of carnallite rocks of the Permian deposits of the Urals. The technique of preparation of samples, laboratory study of the rate of dissolution in water is described. The data on the chemical composition of samples of 4-color differences of carnallite rocks, textural and structural features, the results of determining the rate of dissolution and the material composition of the water-insoluble residue are presented. The purpose of the study was to study the rate and processes of dissolution in water at a temperature of 500C in the forced convection mode and to assess the influence of the textural and structural features of the carnallite rocks of the Urals. The objectives of the study were: determination of salt and mineral compositions, study of textural and structural features and assessment of the effect of microinclusions on the kinetics of the dissolution process. When solving the tasks, the following methods were used: study of the textural and structural features of carnallite rocks - by the petrographic method; determination of the rate of dissolution and density of samples - by the gravimetric method; determination of the density of brines - pycnometric method; the chemical composition of the initial samples and solutions (brines) was analyzed by AES-spectrometry; the mineral composition of the water-insoluble residue - by X-ray quantitative phase analysis. The factual material of the research is analyzed, the corresponding conclusions are drawn. Studies have shown that important factors affecting the kinetics of dissolution processes are the material composition and textural-structural properties. In this work, the total (mass) rate of dissolution of samples was determined, including the vertical and horizontal components. The iron oxide film outlining the grains of carnallite rocks screens the dissolution surface, slowing down the diffusion process. The presence of halite and its uneven content causes fluctuations during dissolution, slowing down the dissolution process over time. Microinclusions of gases have a positive effect on the dynamics of the dissolution process, enhancing convection and mass transfer. With an increase in the hydrodynamic parameters of the solvent (density and viscosity), the dissolution rate decreases. The research results can be suitable for the organization of mining by underground dissolution and for the processing of carnallite rocks of the Permian deposits of the Urals by the halurgical method.

Diffusion Coefficients of Aromatic Hydrocarbons in Their Lowest Triplet State: Anthracene in Hexane, Octane, Hexadecane, Perfluorohexane, and Methylcyclohexane; Pyrene and 9,10-Di-phenylanthracene in Hexane

1980 ◽  
Vol 35 (5) ◽  
pp. 503-520 ◽  
Author(s):  
E. Georg Meyer ◽  
Bernhard Nickel
Keyword(s):  
Triplet State ◽  
Aromatic Hydrocarbons ◽  
Ground State ◽  
Diffusion Coefficients ◽  
Absolute Accuracy ◽  
Perfect Agreement ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Metastable Triplet State

Abstract An experimental method is described which allows the determination of the diffusion coefficient D of an aromatic hydrocarbon in its lowest and metastable triplet state T1 with an absolute accuracy of ±5%. D was determined at 25 °C. With anthracene the temperature-dependence of D was measured from 0°C to 60°C in hexane and from 20°C to 89°C in hexadecane; it was found to be in good but not perfect agreement with the Stokes-Einstein equation. With the investigated systems, D of molecules in T1 is estimated to be at most 10% smaller than D of molecules in the ground state. No evidence for the formation of triplet excimers was found. Some applications of the method are proposed, and in this connection some questions concerning the kinetics of diffusion-controlled reactions of molecules in T1 and the existence of triplet excimers are discussed.

Sign in / Sign up

Export Citation Format

Share Document