Treatment of apatite raw materials is associated with the formation of large-tonnage waste – phosphogypsum. The content of rare earth metals in such waste reaches 1 %, which makes it possible to consider it a technogenic source for obtaining rare earth metals and their compounds. Up to the present moment, there are neither processing plants, nor an efficient process flow to handle phosphogypsum dumps. It is rational to use a way that involves extraction of valuable components and overall reduction of phosphogypsum dumps. Such process flow is available with carbonate conversion of phosphogypsum to alkali metal or ammonium sulfate and calcium carbonate upon the condition of associated extraction of rare earth metal (REM) compounds. Associated extraction of REM compounds becomes possible since they form strong and stable complexes with hard bases according to Pearson, which among other things include carbonate, phosphate and sulfate anions. Formation of lanthanide complexes with inorganic oxygen-containing anions is facilitated by the formation of high-energy Ln-O bonds. The study focuses on the dissolution of lanthanide phosphates in carbonate media. It was established that formation of REM carbonate complexes from their phosphates is a spontaneous endothermic process and that formation of lanthanide carbonates and hydroxides serves as thermodynamic limitation of dissolution. A shift in equilibrium towards the formation of carbonate complexes is achieved by increasing the temperature to 90-100 °C and providing an excess of carbonate. The limiting stage of REM phosphate dissolution in carbonate media is external diffusion. This is indicated by increasing rate of the process with an intensification of stirring, first order of the reaction and the value of activation energy for phosphate dissolution from 27 to 60 kJ/mol. A combination of physical and chemical parameters of the process allowed to develop an engineering solution for associated REM extraction during carbonate conversion of phosphogypsum, which included a 4-5 h conversion of phosphogypsum at temperature of 90-110 °C by an alkali metal or ammonium carbonate solution with a concentration of 2-3 mol/l. As a result, a solution with alkali metal (ammonium) sulfate is obtained, which contains REMs in the form of carbonate complexes and calcium carbonate. The rate of REM extraction into the solution reaches no less than 93 %. Rare earth metals are separated from the mother liquor by precipitation or sorption on anion exchange resins, while the excess of alkali metal or ammonium carbonate is returned to the start of the process.
Population balance model is crucial for improving the method of aluminum hydroxide massive crystallization and enhancing the quality of control over industrial precipitation trains. This paper presents the updated population balance model, which can be used for simulation of industrial-scale precipitation. Processes of birth-and-spread and particle breakage are considered integral parts of the precipitation process along with secondary nucleation, growth and agglomeration of particles. The conceptual difference of the proposed system of equations is its ability to reproduce the oscillatory process that occurs in precipitation circuits as a result of cyclic changes in the quality of the seed surface. It is demonstrated that self-oscillations can occur in the system without any external influence. The updated model is adjusted and verified using historical industrial data. The simulation of seed-recycle precipitation circuit showed an exact correspondence between the calculated dynamic pattern of changes in particle size distribution of aluminum hydroxide and the actual data.
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.
The information about life time of famous chemist and metallurgist N.S.Kurnakov and the capsule review of his scientific achievementsis represented in this paper. The formation of chemical and metallurgical scientific school in Saint Petersburg Mining Institute is shown.
Experimental data on solvent extraction of lanthanum (III) and samarium (III) by solutions of naphthenic acid from nitrate medium was obtained. Dependences of distribution coefficient of pH, concentration of organic and aqueous phase was obtained. thermodynamic characteristics of extraction equilibrium was calculated.
Experimental data on solvent extraction of lanthanum (III) and samarium (III) by solutions of naphthenic acid from nitrate medium was obtained. Dependences of distribution coefficient of pH, concentration of organic and aqueous phase was obtained. thermodynamic characteristics of extraction equilibrium was calculated.
Technology of solvent extraction and separation of cerium lanthanides by solutions of naphthenic acid in o-dimethylbenzene was obtained. The sequence of extraction Eu > Sm > Ce > La from nitrate media was calculated.
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.
Experimental data on solvent extraction of cerium (III), yttrium (III), lanthanum (III) by solutions of oleinic acid in o-dimethylbenzene was obtained. The possibility of extraction sepa- ration of cerium(III), yttrium(III), lanthanum (III) from nitrate media was shown.
