The mechanism of rare earth metal (REM) extraction with the organic solvent called di-2ethylhexyl phosphoric acid (DEHPA) has been studied in this paper. Using the physicochemical method for the investigation of the composition of organic REM complexes with the extractant, the solvation numbers of the lanthanides were determined. The growth of solvation numbers from neodymium (2) to ytterbium ( 5) is explained by an increase in the effective charge of the REM atom and, as a result, an increase in the relative stability of the chelating REM complexes with the extractant. The composition of the organic complexes of REM with DEHPA was confirmed by infrared and Raman spectroscopy. The values of the effective thermodynamic constants and standard Gibbs energies of the extraction process are calculated. The increase in the relative stability of lanthanide complexes with DEHPA correlates with a decrease in the ionic radius of the REM.

The methods of decontamination of radionuclides from soils are considered. The literature focuses on fixing radionuclides in soils and creating geochemical barriers that it is prevent the spread of pollution. The main disadvantage of these methods is excluding the possibility of building a territory. It is needed to clean up the area to the sanitary and hygienic requirements for further use and then it is desirable to fix the residual activity. The conducted analysis of forms of radionuclides fixation in soils and mechanics of this fixation, therewith revealed that Cs-137 fixed more strongly on mineral components of soil, than Sr-90, which is mainly in the acid-soluble and exchangeable form, and, as a consequence, passes into the liquid phase during soil deactivation more easily. Contaminated soil deactivation in the urbanized territory is possible by washing it by ferric chloride solution at a concentration 0.02-0.05 M and with an equimolar addition of an ammonium chloride. Therewith, most efficient methods, which use in-situ conditions, are heap and convection leaching technologies with treatment degree, which is not less than 80%. At the same time, the most efficient methods which use in-situ conditions are heap and the convection leaching. The hardware-technological scheme of a convection leaching is presented. It is worth to note that ammonium salts additions slightly rise coefficient of treatment from Sr-90. Because ammonium salts are inexpensive, their additions allow to obtain significant economic benefits due to decreasing ferric chloride consumption, which is more valuable, and waste water volume reduction.

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Равновесные и неравновесные состояния систем Na 2 O-Al 2 O 3 -H 2 O и K 2 O-Al 2 O 3 -H 2 O имеют определяющее значение для установления ключевых технологических показателей глиноземного производства и их оптимизации. Обоснована необходимость систематизации и статистической обработки данных о равновесии в указанных системах для создания достоверной базы их физико-химического состояния, анализа и математического моделирования фазовых равновесий вследствие заметного расхождения экспериментальных результатов и термодинамических расчетов по материалам отдельных исследователей. Выявлена тенденция к уменьшению степени гидратации твердых алюминатов натрия с ростом температуры и переходом систем из области устойчивого состояния гиббсита к равновесию с бемитом. Приведены аппроксимирующие функции, позволяющие с высокими показателями достоверности описать изотермы равновесия в технологически значимой области концентраций систем Na 2 O-Al 2 O 3 -H 2 O и K 2 O-Al 2 O 3 -H 2 O. Упрощение аппроксимирующей функции возможно путем деления изотерм равновесия на два участка с интервалами содержания щелочного реагента 0-0,25 и 0,25-0,4 моль/100 г раствора. Выявлены закономерности в ходе изотерм растворимости для систем Na 2 O-Al 2 O 3 -H 2 O и K 2 O-Al 2 O 3 -H 2 O, которые имеют удовлетворительное объяснение с позиций изменения ионного состава алюминатных растворов в зависимости от их концентрации и температуры, а также вследствие различий, связанных с гидратацией катиона щелочного металла, что имеет принципиальное значение для термодинамического моделирования рассмотренных равновесий.Ключевые слова: системы глиноземного производства; алюминатные растворы; гиббсит; бемит; ионный состав; изотермы равновесия; анализ; математическое моделирование Благодарность. Работа проведена при финансовой поддержке Российского научного фонда по Соглашению № 18-19-00577 от 26.04.2018 о предоставлении гранта на проведение фундаментальных научных исследований и поисковых научных исследований. Как цитировать эту статью: Сизяков В.М. Современное физико-химическое описание равновесий в системе Na 2 O-Al 2 O 3 -H 2 O и ее аналогах / В.М.

Intermediate processing products of apatite raw materials, such as the process solutions of phosphoric acid (PA) containing the in-demand rare-earth elements (REE) of heavy and medium-light groups, are a promising source of rare-earth metals. Apatite concentrate typically has low rare-earth metals grades (up to 1 %); therefore, sufficient economic value may only be achieved with those technologies that yield individual rare-earth metals without modifications in the underlying apatite raw materials process. Extraction methods have significant technological advantages, mainly due to the simplicity of implementation and the possibility of accelerated industrial-scale adaptation. Rare-earth metals recovery from PA process solutions into the organic phase based on di-2-ethylhexylphosphoric acid (D2EHPA) is associated with the simultaneous extraction of titanium (IV). Additional separation processes are, therefore, required in view of the presence of titanium in the REE extract. It has been found that effective titanium recovery from the organic phase is achieved by using oxalic acid with the concentration of 0.25 mol/l at the phase ratio of 0.5 and the mixing rate of 400 min–1. The content of impurity elements in the concentrates of individual REM compounds obtained of does not exceed 10–4 %. The complex processing operations performed for obtaining individual rare-earth metals represent a complete technology for the integrated processing of apatite raw materials. The work was carried out with the financial support of the Russian Science Foundation (project No. 19-19-00377).