ИСТИНА

Recovery of heavy elements from industrial wastes (e.g., spent lithium ion batteries or nickel alloys) becomes crucial both from environmental and economic points of view. Such processes often include leaching with an acid, e.g. methanesulfonic acid, which is regarded as a greenchemistry reagent [1]. Using thermodynamic modeling, one can optimize recycling processes. The base for a thermodynamic model are binary parameters, as well as stability parameters of phases which exist in binary systems, as well as in multicomponent systems. The aim of the work is to continue research started with Me(CH3SO3)2-H2O (Me=Cu, Zn)[2, 3] concerning vapor-liquid (VLE) and solid-liquid equilibria (SLE) in 3d-metal methanesulfonate - water systems. SLE in the Me(CH3SO3)2-H2O (Me=Co, Ni, Mn) systems were studied by isothermal solubility and DSC. TG and XRD were used to reveal solid phases in equilibria with the solution. Water vapor pressure was determined by static method at 288.15 К, 298.15 and 308.15 K in the Me(CH3SO3)2-H2O (Me=Co, Ni, Mn) systems. Although in two systems (Me=Ni, Mn) there were low-temperature stable hydrates which are isostructural to Zn(CH3SO3)2∙12H2O [2] , in the third the low-temperature hydrate was quite different, Co(CH3SO3)2∙9H2O. Following hydrates were revealed as well during the study: Co(CH3SO3)2∙6H2O, Co(CH3SO3)2∙4H2O, Ni(CH3SO3)2∙6H2O, and Mn(CH3SO3)2∙2H2O. Based on VLE and SLE (ice melting curve), parameters of the Pitzer-Simonson-Clegg (PSC) model were obtained. Due to rather low solubility, a suitable description was obtained using only α 0 , α 1 , β 0 , β 1 , whereas U, V, W were fixed as 0. Similar results were reported earlier for Cu(CH3SO3)2-H2O [3]. Stability parameters of all the hydrates were estimated from binary solubilities using only 2 parameters. Binary phase diagram fragments were calculated with the resulted parameters using the PSC model. Acknowledgements The financial support of RSCF 21-73-00039