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ArticleName By-products obtaining from nitric acid technology wastes of apatite concentrate processing
DOI 10.17580/tsm.2017.07.10
ArticleAuthor Sadykova M. M., Tsygankova M. V., Zimina G. V., Spiridonov F. M.

Moscow Technological University, Institute of Fine Chemical Technologies, Moscow, Russia:

M. M. Sadykova, Post-Graduate Student, e-mail:
M. V. Tsygankova, Senior Researcher
G. V. Zimina, Leading Researсher


Lomonosov Moscow State University, Moscow, Russia:
F. M. Spiridonov, Assistant Professor


We investigated the range of chemical reactions, allowing the decomposition of anion [SiF6]2– with obtaining of single fluoric salts and silicates. Na2CO3, K2CO3, NH4OH and H2SO4 were used as decomposition agents. We also investigated the interaction of Na2SiF6 with Na2CO3 in solution: NaF, SiO2·nH2O and CO2 are its products. Usage of K2CO3 in similar conditions leads to formation of NaF and K2SiF6 as intermediate products. Re-processing of the obtained sediment with K2CO3 solution leads to formation of KF and SiO2·nH2O, removed by alkali washing. Usage of K2CO3 as an agent for Na2SiF6 decomposition requires its excess. Mixture of NaF and KF is the product of this interaction. Interaction of NH4OH with Na2SiF6 leads to sedimentation of sodium fluoride and SiO2·nH2O. Only sodium fluoride reflexes stay on radiogram after washing the reaction product with alkali. Water phase contains the products of silicon fluoride interaction with water solution of ammonia: ammonium fluoride and silicon acid. Evaporation of water phase and processing of obtained sediment by sodium hydroxide solution leads to release of NH4F and its purification from SiO2·nH2O. Usage of concentrated sulfuric acid as decomposition agent leads to sedimentation of Na3H(SO4)2 and release of HF and SiF4 mixture in gaseous phase. We offered the possibility of the synthesis of fluorides of rare-earth metals and yttrium using ammonia fluoride (product of sodium hexafluorsilicate processing). Fluoride synthesis used the method, concluded in the interaction of solutions of neodymium and yttrium nitrates with ammonium fluoride solution. NdF3 and NH4F are formed as a result of vacuum thermal treatment (200 oC) of sediment, obtained from neodymium nitrate solution. The complex of NH4Y2F7 was obtained using the yttrium nitrate as a result of vacuum thermal treatment of sediment (200 oC). We offered the principal flowsheet of sodium hexafluorsilicate processing with obtaining of marketable products NaF and LnF3 (Ln — La – Sm) and intermediate products Na2SiO3 and NH4NO3, which may be used in chemical industry and fertilizer production.

keywords Apatite, processing, sodium hexafluorsilicate, sodium fluoride, potassium fluoride, ammonium fluoride, neodymium fluoride, fluor-ammonium yttrium complex

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