St. Petersburg Mining University (St. Petersburg, Russia):
Cheremisina O. V., Head of Chair, Doctor of Engineering Sciences, ovcheremisina@yandex.ru
Sergeev V. V., Assistant Lecturer, Candidate of Engineering Sciences, sergeev.spmi@yandex.ru
Fedorov A. T., Postgraduate
Alferova D. A., Student

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).

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