Nature of influence exerted by Na2SiF6 on REE recovery from orthophosphoric acid solution in the course of CaSO4×0.5H2O crystallizationстатья
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Аннотация:Chemical and X-ray phase analyses were used to study the influence exerted by Na2SiF6 on the isomorphic inclusion of cerium into the structure of CaSO4∙0.5H2O precipitates formed from solutions of phosphoric acid hemihydrate (38 wt % P2O5). The poorly soluble suspensions of CaSO4∙0.5H2O precipitates can serve as adsorbents for cerium compounds, with CaSO4∙0.5H2O–NaCe(SO4)2∙H2O and CaSO4∙0.5H2O–CePO4∙0.5H2O solid solutions formed. The introduction of Na2SiF6 makes the sorption properties CaSO4∙0.5H2O several times better because the Na2SiF6 phase is a source of sodium cations and creates the necessary Na: Ce ratio of 1: 1 for extracting cerium from the liquid phase into a precipitate in the form of a CaSO4∙0.5H2O–[NaCe(SO4)2∙H2O + CePO4∙0.5H2O] solid solution. Under the industrial conditions in which extraction phosphoric acid is manufactured, a similar isomorphous capture of rare-earth elements of the cerium group (La–Sm) may occur in joint precipitation of CaSO4∙0.5H2O and Na2SiF6.