Исследование системы KLa(SO 4 ) 2 · H 2 O–SrSO 4 · 0.5H 2 O

A method has been developed for the synthesis of the metastable trigonal modification SrSO4⋅0.5H2O, isostructural to the well-known CaSO4⋅0.5H2O modification (space group P3121). Frozen solutions of NaCl in water have been proposed as a precursor in the crystallization of SrSO4⋅0.5H2O. The SrSO4⋅0.5H2O structure can be stabilized by isovalent substitution of calcium ions for strontium ions or by aliovalent substitution of potassium and lanthanum ions for strontium ions. The compound of composition K0.25La0.25Sr0.5(SO4)⋅0.5H2O has been synthesized as an example of the stabilized SrSO4⋅0.5H2O modification. The unit cell parameters have been determined and refined. A model of the structure of SrSO4⋅0.5H2O with a statistical distribution of potassium, lanthanum, and strontium atoms over the positions of Ca atoms in the well-known СаSO4⋅0.5H2O structure has been proposed.

Synthesis and Stabilization of Crystal Hydrate Modification SrSO4⋅0.5H2O

Bushuev,

Sysoev,

Velikodny

2023

Investigation of the KNd(SO4)2·H2O–SrSO4·0.5H2O System

Bushuev,

Tatosyan

2023

The cocrystallization of potassium, neodymium, and strontium sulfates from aqueous solutions has been studied using X-ray powder diffraction, thermogravimetry, energy-dispersive X-ray spectral analysis, and electron microscopy. Extensive solid solutions based on trigonal KNd(SO4)2⋅H2O have been found to exist in the concentration range 100–20 mol % of the KNd(SO4)2⋅H2O–SrSO4⋅0.5H2O system. The unit cell parameters of the solid solutions have been determined. Two phases have been discovered: trigonal KNd(SO4)2⋅H2O (space group P3121) and monoclinic KNd(SO4)2⋅H2O (space group P21/c1). The heterovalent substitution scheme 2Sr2+ → K+ + Nd3+ stabilizes the structure of solid solutions based on the isostructural KNd(SO4)2⋅H2O and SrSO4⋅0.5H2O trigonal phases.

Solubility of Scandium Cesium Double Sulfate CsSc(SO4)2 in Sulfuric Acid Solutions

Pasechnik,

Medyankina,

Tyutyunnik

et al. 2023

Cesium sulfatoscandate CsSc(SO4)2 (space group P, a = b = 5.0971(1) Å, c = 8.6924(5) Å, V = 195.580(2) Å3, Z = 1) has been crystallized from aqueous solutions in layered hexagonal prisms sized up to 50 µm and up to 2–5 µm thick. Its water solubility is 0.0104 mol/L at 25 ± 1°С. A way to reduce the solubility of scandium as CsSc(SO4)2 is to increase acidity to 3.5–5.5 М H2SO4 and add Cs2SO4. Experimental evidence is supported by calculations that took into account changes in the ionic strength of the solution and the influence of the simultaneous presence of Cs+ andions. The results will be useful for those who will study the behavior of rare-metal compounds having similar properties and their separation.