The article analyzes the information on modern developments in the utilization of phosphogypsum. Only a few directions give the prospect of large-scale use of both freshly formed phosphogypsum and phosphogypsum accumulated in dumps. Under the conditions of the Russian Federation, it is promising to use phosphogypsum for the production of building materials, as well as for agriculture, for reclamation of soil and the creation of mounds of a certain type. The possibility of using phosphogypsum as a raw material for obtaining rare-earth elements is shown.

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To increase the efficiency of hydrometallurgical processing of lean rare-earth raw material, the effect of salt anion and metal cation on the characteristics of Ce(III) and Y(III) recovery from dilute aqueous solutions with tri-n-butyl phosphate was studied on the basis of the thermodynamic theory of extraction.Modern hydrometallurgy of rare-earth metals (REM) is based on the extraction of their nitrates with tri-n-butyl phosphate (TBP). However, as lean rareearth raw materials, for instance, eudialyte ores of the Kola peninsula, are involved in the process the efficiency of extraction recovery and separation of lanthanide salts should be increased. It becomes urgent to search for new, more efficient extractants and study the effect of the salt anion on the extractability. It is advisable to characterize the extraction by Gibbs constants and energies of extraction. Previously, we studied the thermodynamics of extraction of zirconium salts with TBP and solutions of trialkylbenzylammonium salts (TABA, alkyl: C 4 H 9 3C 10 H 21 ) in o-xylene [1, 2] and extraction of cerium and yttrium sulfates with TABA sulfate in o-xylene [3,4]. In this work, we compare the characteristics of extraction of Ce(III) and Y(III) salts with TBP and TABA.The features of Ce(III) and Y(III) extraction with TBP were studied using model systems REM nitrate3 Mg(NO 3 ) 2 . The REM content was approximately preset by the weight of the metal nitrate taken and was then refined photometrically. All the reagents were of chemically pure grade. The metal ion concentration was similar to the REM content in solutions from leaching of eudialyte concentrates and was about 0.01 mol kg 31 .The extraction and phase separation were performed in separating funnels. The stirring rate was 2000 rpm and was preset with an automatic stirrer. The duration of phase contact required for equilibration was determined experimentally and amounted to 30 min. The phases fully separated within 15 min.The content of cerium(III) and yttrium(III) in the aqueous phase (initial and equilibrium) was determined photometrically (l 670 nm) with Arsenazo III in the acetate buffer solution at pH 3 [5]. The chemicals used in the analysis were of analytically pure grade. The REM content in the organic phase was determined as the difference of the concentrations in the initial and equilibrium aqueous phases with regard to the difference in the phase volumes (weights):where c org is the equilibrium metal concentration in the organic phase (mol kg 31 ); c aq , REM concentration in the equilibrium aqueous phase (mol kg 31 ); c 0 , initial content of cerium or yttrium in the aqueous phase (mol kg 31 ); and m aq /m org , ratio of weights of the aqueous and organic phases, respectively.The experimental values of the metal distribution coefficients were determined as follows:where D is the metal ion distribution coefficient; c aq , c org , equilibrium concentrations of the metal ion in the aqueous and organic phases, respectively (mol kg 31 ).The experimental data were obtained at pH 3. pH was ...