Obtaining and production of metals from natural raw materials causes a large amount of liquid, solid, and gaseous wastes of various hazard classes that have a negative impact on the environment. In the production of titanium dioxide from ilmenite concentrate, hydrolytic sulphuric acid is formed, which includes various metal cations, their main part is iron (III) and titanium (IV) cations. Hydrolytic acid waste is sent to acid storage facilities, which have a high environmental load. The article describes the technology of ion exchange wastewater treatment of acid storage facility from iron (III) and titanium (IV) cations, which form compounds with sulphate ions and components of organic waste in acidic environments. These compounds are subjected to dispersion and dust loss during the evaporation of a water technogenic facility, especially in summer season. Sorption of complex iron (III) cations [FeSO 4 ] + and titanyl cations TiO 2+ from sulphuric acid solutions on cation exchange resins KU-2-8, Puromet MTS9580, and Puromet MTS9560 was studied. Sorption isotherms were obtained both for individual [FeSO 4 ] + and TiO 2+ cations and in the joint presence. The values of the equilibrium constants at a temperature of 298 K and the changes in the Gibbs energy are estimated. The capacitive characteristics of the sorbent were determined for individual cations and in the joint presence.
The issues of complex processing of mineral resources are relevant due to the depletion of available raw materials. So, it is necessary to involve technological waste, generated during the processing of raw materials, to obtain valuable components. In the process flow of apatite concentrate treatment using the sulfuric acid method, a large amount of phosphogypsum is produced with an average content of light rare earth metals (REMs) reaching 0.032-0.45 %. When phosphogypsum is treated with sulfuric acid solutions, a part of REMs is transferred to the sulfate solution, from which it can be extracted by means of ion exchange method. The study focuses on sorption recovery of light REMs (praseodymium, neodymium and samarium) in the form of anionic sulfate complexes of the composition [ln(SO 4 ) 2 ] – on polystyrene anion exchanger AN-31. The experiments were performed under static conditions at a liquid-to-solid ratio of 1:1, pH value of 2, temperature of 298 K and initial REM concentration in the solutions ranging from 0.83 to 226.31 mmol/kg. Thermodynamic description of sorption isotherms was carried out by the method based on linearization of the mass action equation, modified for the ion exchange reaction. As a result of performed calculations, the authors obtained the constants of ion exchange equilibrium for Pr, Nd and Sm, as well as the values of the change in the Gibbs energy for the ion exchange of REM sulfate complexes on the AN-31 anion exchanger and the values of total capacity of the anion exchanger. Calculated separation factors indicated low selectivity of AN-31 anionite exchanger for light REMs; however, the anion exchanger is suitable for effective recovery of a sum of light REMs. Based on the average value of ion exchange equilibrium constant for light REMs, parameters of a sorption unit with a fluidized bed of anion exchanger were estimated.
Rare earth elements (REEs) are valuable and strategically important in many high-technology areas, such as laser technology, pharmacy and metallurgy. The main methods of REE recovery are precipitation, extraction and sorption, in particular ion exchange using various sorbents, which allow to perform selective recovery and removal of associated components, as well as to separate rare earth metals with similar chemical properties. The paper examines recovery of ytterbium in the form of coordination compounds with Trilon B on weakly basic anion exchange resin D-403 from nitrate solutions. In order to estimate thermodynamic sorption parameters of ytterbium anionic complexes, ion exchange process was carried out from model solutions under constant ionic strength specified by NaNO 3 , optimal liquid to solid ratio, pH level, temperatures 298 and 343 K by variable concentrations method. Description of thermodynamic equilibrium was made using mass action law formulated for ion exchange equation and mathematically converted to linear form. Values of equilibrium constants, Gibbs free energy, enthalpy and entropy of the sorption process have been calculated. Basing on calculated values of Gibbs energy, a sorption series of complex REE ions with Trilon B was obtained over anion exchange resin D-403 from nitrate solutions at temperature 298 K. Sorption characteristics of anion exchange resin have been estimated: total capacity, limiting sorption of complex ions, total dynamic capacity and breakthrough dynamic capacity.
A complex heterogeneous process of ion exchange can be defined with an isotherm-isobar equation of the chemical reaction, which describes differential affinity between the process and its effect – the law of mass action. Ion exchange includes processes accompanied by changes in the charge of ions and functional groups caused by the passing of ionic bond into covalent one. Hence isotherm equations of ion exchange for such processes must differ from conventional stoichiometric equations, but they can be obtained by classical study approaches to ion exchange equilibrium. The paper describes a new thermodynamic model, based on linearization of mass action law, modified for the ion exchange equation. The application of this model allows to define stoichiometry of ion exchange and the shape of ions adsorbed by the solid phase of ion-exchange resins, as well as to estimate equilibrium constant and Gibbs free energy of the process. Comparative analysis has been carried out for the thermodynamic model of cerium sorption in the form of anionic complex with Trilon B from a multisalt solution with ionic strength of 1 mol/kg (NaNO 3 ) under рН = 3 and temperature 298 K on a test sample of weak-base anion-exchange resin Cybber EV009. Experimental isotherm of the sorption has been obtained. Calculations of thermodynamic parameters have been performed using Langmuir, Freundlich, Dubinin – Radushkevich, Temkin and Flory – Huggins models, as well as thermodynamic model of linearized mass action law, proposed by the authors. Calculated values of the equilibrium constant and Gibbs energy – K = 9.0±0.5 and ΔrG 0 298 = –5.54±0.27 kJ/mol – characterize the sorption of EDTA cerate ions by ion-exchange resin. The shape of adsorbed ions has been defined in Stern-Helmholtz layer of CeTr, and total capacity of anion resin EV009 for EDTA cerate ions has been estimated as q ∞ = 2.0±0.1 mol/kg.
Modern gas analysis requires an integrated approach to ensure the necessary metrological characteristics and achieve high reliability of detection. A new algorithm for multisensor systems based on synthesized domestic materials possessing semiconductor properties has been developed for the analysis of a wide range of gases of metallurgical industries. The use of gas-sensitive elements made of semiconductor material with n-type conductivity allows solving the main task of modern gas analysis – detection of vapors and gases of a wide range with high stability, necessary selectivity and sensitivity. Due to the developed surface structure formed from polycrystals 3-10 nm in size, semiconductor sensors allow to detect various substances in air in a wide range of concentrations: from trace amounts of 10 -6 -10 -5 mg/m 3 to high 500-800 mg/m 3 . Increase of the selectivity of the sensors is facilitated by the introduction of catalysts into the gas-sensitive layer of doping impurities. The formation of multisensory systems increases degrees of freedom, expanding the range of identification of the analytes. In addition to solving the analytical task of forming gas sensitive elements, digital circuit and aerodynamic solutions have been developed that meet the requirements of gas analysis in a wide range of impurity concentrations and application conditions.
The paper is devoted to solvent extraction of rare earth metals exemplified by Сe, Y from standard test and industrial solutions of wet-process phosphoric acid with di-2-ethylhexyl phosphoric acid used as extractant. The mechanism of rare earth metals extraction with di-2-ethylhexyl phosphoric acid was determined and studied on the basis of calculated thermodynamic characteristics. The paper considers the influence of impurity ions (Fe 3+ , Mg 2+ , ) on extraction of rare earth metals using industrial solutions. It has also been determined that for a stripping process the use of sulfuric acid solutions in concentration of 2 mol/l is the most preferable.
At the present time, the unique physical and chemical properties of rare earth metals (REM) mean they can find wide application in the metallurgy, mechanical engineering, avionics, petrochemical, laser and glass industries. In metallurgy, rare earth metals using for production of special grades of steel and cast iron. Adding REM can improve their mechanical properties: hardness, toughness, resistance to corrosion. REM are also used for the deoxidation of metals and alloys. The REM production technology from loparite concentrate that already exists in Russia is not enough for the metal-lurgical, oil, glass, ceramic, nuclear and military industries (just 2 % of the world’s REM are produced in Russia). REM for these industrial proposes is purchased in China, which is recog-nized as having a monopoly on the production of rare metals (96% of REM produced world-wide). If we want to supply these needs in future, we will have to produce 10 tons per year of REM, which requires processing all available resources: mono- and polymineral raw materials. One of the most acceptable source of rare earth metals and some rare metals (zirconium, niobium, hafnium) is eudialyte. The world’s biggest deposits of eudialyte are found on the Kola Peninsula in northwest Russia, near the Lovozero mining and processing plant. Eudialyte concentrate is easily decomposed by acids, which explains its layered structure and weak chemical bonds between its constituent groups. The easy leaching process is the main reason that it is processed. In our work the technological possibility of extraction and separation of lanthanides has been shown, using solutions of naphthenic and oleic acid in an inert diluent with a stoichiometric reagent consumption, without the preoxidation step of the cerium to the tetravalent state. The technological parameters and stages of the process have been established.
Sorption isotherms was obtained in the form sulfate complex of cerium on the anion exchanger D-403 at a temperature of 298 K and pH = 2÷4 in the presence of various concentrations of magnesium sulfate. Thermodynamic description of the sorption isotherm sulfate complexes of cerium by the method, which based on linearization of the equations of the law of mass action modifed for the reaction of ion exchange. The values of the apparent constants of ion exchange and differential Gibbs energy calculated for the ions of Ce(SO 4 ) - 2 .
The modern technical and technological condition of the industrial enterprises color and the ferrous metallurgy, connected with necessity of sewage treatment and their return to the basic manufacture, demands working out of universal technological schemes of sewage treatment. In article it is presented sorption a way of sewage treatment from various forms of iron and variety of nonferrous metals with use new sorption a material on a basis iron magnesia concretions.
Technical and technological state of the modern industrial enterprises, ecological situation, danger of terroristic acts, require developing of modern means of the environment parameters monitoring. The article presents the system of indication and monitoring of atmospheric air, meeting the requirements of speed, selectivity, portability and autonomy, resistance to influence of external factors of various nature, intended to solve of the specified problem.
The kinetics parameters of phenol oxidation by MnO2 on the surface of iron-manganese nodules at pH = 5,5±0,5 at temperature region from 293 till 353 K was described in this paper. The oxidation reaction runs by second order on phenol. At temperature region from 293 till 353 K the limited stage is chemical reaction. The activation energy of oxidation on the surface of iron-manganese nodules is equal 6,65 kJ/mol, and it is less than it’s one for oxidation on MnO2 surface (42,0 kJ/mol). The oxidation products are hydrohinon and less than 10 pier. % p-benzohinon.
Kinetic characteristics of the process of nickel cations sorption by ferromanganese nodules were determined: reaction rate constants at different temperatures, apparent activation energy of the process.
The thermodynamic calculation of oxygen solubility and ionic standing in solutions of cerium(III) phosphate acids allowed us to estimate the ionic composition of solutions and describe the course of crystallization and dilution processes of SePO 4 -0.5H 2 O, as well as to determine the dependence of oxygen solubility on temperature and concentration of solutions.
The thermodynamic calculation of solubility and ionic equilibria in phosphoric acid solutions of cerium(III) allowed us to estimate the ionic composition of solutions, describe the mechanism of crystallization and dissolution processes СеРО 4 ·0.5H 2 O, determine the dependence of solubility on temperature and concentration of solutions.
Kinetic characteristics of the process of iron(II) sorption by ferromanganese nodules have been found: reaction rate constants at different temperatures, apparent activation energy of the process. The limiting stage of the process, which is a redox reaction of the first order, was determined.
The purpose of this research is to develop a new method of extraction and separation of rare earth metals, which will be effective in hydrometallurgical processes, i.e. in the processing of eudialyte concentrate. The task of the research is the experimental determination of distribution and separation coefficients in solvent extraction of rare earth metals from aqueous solutions with organic extractants, as well as the calculation of the extraction mechanism and thermodynamic constants on the basis of experimental data.
Extraction of cerium (3+) with tributyl phosphate was studied. The extraction constants were calculated from the dependences of the distribution coefficient on the concentration of salvent and extractant. According to their values, cerium salts are arranged in the series chloride < sulfate < nitrate corresponding to the Pearson reduction of the "hardness" of anions.
In order to calculate parameters of purification of soils from 90 Sr the exchange isotherm of Sr 2+ Ha cations of iron (III) between Cambrian clay and aqueous solution with pH = 3 was studied. Isotherms of joint cation adsorption in joint presence are described by the Langmuir equation. Using the values of the Langmuir constants, the Gibbs constant and energy of ion exchange equal to 15 and -6.7 kJ/mol, respectively, were calculated. These values coincide with those calculated from the individual adsorption isotherms of Sr 2+ and Fe (III) cations on clay. According to the obtained constants it is possible to deactivate soils from 90 Sr contamination by means of ion-exchange washing with solutions of iron (III) salts, which is confirmed by field studies in the 5th quarter of Vasilievsky Island. The performed technical-economic assessment of the decontamination of the 5th quarter shows that the washing cleaning will give an economic effect of about 150 million rubles compared to soil removal and burial.
It is experimentally proved that adsorption of Fe(3+) and Sr(2+) cations on Cambrian clay is described by the Langmuir isotherm. The adsorption limit is 0.026 and 0.034 mol/kg, respectively, and the capacity of the clay is 73±5 mEq/kg. The landing sites of cations are 38.0 and 28.6 Å 2 , respectively, and the radii of hydrated cations are 348 and 302 pm. The latter value agrees with the Stokes radius of 309 pm. The Langmuir constants are 731 and 294, respectively, and the distribution coefficients between the solid and liquid phases at rn = 3.0+3.5 are 27±4 and 10±1.8. The ion exchange constant for the reaction ½ Sr 2+ (s) + 1/3 Fe 3+ (aq) ↔ ½ Sr 2+ (aq) + 1/3 Fe 3+ (s) is 0.95. Based on the data obtained, it is feasible to clean the pounds from strontium-90 contamination by washing with a Fe(3+) salt solution. Field tests in the 5th quarter of Vasilievsky Island of St. Petersburg confirmed the conclusion. The initial specific radioactivity of the pound reached up to 1.07 10 -4 Ci/kg. At heap leaching the purification degree of 60% was obtained, in conditions of convective leaching 90%. A formula for calculating the conditions for obtaining a given degree of purification is proposed.
The content of rare-earth metals (REM) in Kola apatite is about 1%. In the production of concentrates over 8 million tons per year, more than 80 thousand tons of REM are dumped into waste dumps annually, polluting the environment. The main bulk of apatite is processed according to the sulfuric acid scheme to produce extractive phosphoric acids. To extract rare-earth metals from phosphoric acid streams with a capacity of 45 t/h, it is necessary to develop a process lasting several minutes, which does not affect the basic technology and does not require expensive costs of reagents. Crystallization of lanthanide combinations on inoculum directly from production solutions of extractive phosphoric acids meets the requirements. Another pressing problem is the purification of soils contaminated with heavy metals and radionuclides. In laboratory and natural conditions, the purification of soils from 90Sr contamination of the 5th quarter of Vasilievsky Island and Novozybkovsky district of the Bryansk region from 137Cs contamination has been studied. Among different methods of soil decontamination, the most cost-effective and suitable for large soil masses and large territories is soil washing with diluted solutions of mixtures of ammonium and iron (3+) salts. This method can also be used to clean soils from heavy metal contamination in mining regions.