Nikitin Institute of Chemistry, Tajik Academy of Sciences, Dushanbe, Republic of Tajikistan:

M. M. Tagoev, Post-Graduate Student
Sh. B. Nazarov, Head of Laboratory, Doctor of Chemical Sciences
U. M. Mirsaidov, Chief Researcher, Academician of the Tajik Academy of Sciences, ulmas2005@mail.ru

The article presents the studies into sulfuric acid-induced decomposition processes in cake after sodium sulfate treatment of raw material from Ak-Arkhar deposit. The influence of different physicochemical factors on recovery of various components from the cake during sulfuric acid-induced decomposition is examined, and the process of acid treatment is optimized. The physicochemical parameters are optimized for different process stages of sodium sulfate treatment of Ak-Arkhar borosilicates, namely:
— raw material and sodium sulfate sintering: temperature 900–950 °C; duration 40 min; ore/sodium sulfate mass ratio 1:2; initial borosilicate ore size 0.16 mm and smaller;
— water treatment of cake: temperature 90–100 °C; duration 60 min; ; liquid/solid mass ratio 8:1; cake size 0.1 mm and smaller;
— sulfuric acid-induced decomposition of solid residue after water treatment of cake: sulfuric acid concentration 15–20 %; temperature 95–100 °C; duration 60 min; liquid/solid mass ratio 6:1;
— separation of marketable products using organic dissolvers: ethyl alcohol mass 0.4 t; acetone mass 0.3 t; temperature 40 °C; duration 20–30 min. H3BO3 0.185 t goes to the organic phase.
The process flow diagram is developed for treatment of Tajik Ak-Arkhar borosilicate ore by the method of sintering with sodium sulfate. Such treatment ensures integrated processing of the material, with production of marketable products such as: boric acid, aluminum and iron sulfates (coagulants); potassium and sodium sulfates (for glass production); construction materials (calcium and magnesium sulfates).

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