The dissolution of the rare-earth phosphates in carbonate-alkaline media

The article is dedicated to the dissolution process of some rare-earth phosphates in carbonate-alkaline media. The object of the study are model sediments of rare-earth phosphates. Different groups of the rare earth elements (REE) have been researched according to their masses: heavy-weight - holmium and ytterbium; medium-weight - samarium and gadolinium; light-weight - neodymium and yttrium though it does not belong to lanthanoids. REE-phosphates are impurity and taken place into technogenic waste phosphogypsum (PG). It is considered to be the PG has being be produced from 10 to 15 million tons per year. Because of the PG goes to disposal site, it causes ecological issues. For the rational use of natural raw materials, it is necessary to develop a solution that allows the phosphogypsum process into commercially valuable products. Concentrate of rare earth metals may be one of these. REE are widely used in various industries: defense, energy, electronics, metallurgy, catalysis and others. However, there are low-level production and incomplete production cycle in the several REE industry, this it is in need of import. Therefore, the study is aimed at achieving economic stability and technological sovereignty of the Russian Federation. The article demonstrates an illustration of the influence of temperature, concentration of carbonate solution, liquid to solid ratio and intensity of mixing on the REE-phosphates solubility. In the concentration range under consideration at a temperature of 90 °C, the maximum equilibrium degrees of extraction into solution were: E(Ho) = 75.6 %; E(Yb) = 85.5 %; E(Nd) = 62.5 %; E(Gd) = 71.6 %; E(Y) = 73.1 %; E(Sm) = 46.1 %. The results of this research are part of the thermodynamic analysis of the REEPO4 - K2CO3 system, which can subsequently be used to model the process of associated REE extraction from industrial waste (phosphogypsum, for example) by liquid carbonating conversion method.