Physicochemical aspects of acetic-acid decomposition of borosilicate ores

The purpose of work is to elaborate the physicochemical aspects for production of boron compounds from boron-bearing ores of Tajikistan deposits by acid methods. As an object of research the initial borosilicate ores of the Ak-Arkhar Deposit of Tajikistan and its concentrates have been used. X-ray diffraction, differential thermal and chemical analysis were used to determine the mineralogical and chemical composition of borosilicates ores of the Ak-Arkhar Deposit. It was revealed that the main ore-forming minerals of the ore are danburite, datolite, garnet, calcite and pyroxenes. The mass fraction of boron oxide in the initial ore is 10.4% and in the concentrate it is 17.1%. The acetic acid decomposition of the initial ore and concentrate was studied. It was defined that the extraction ratio of B₂O₃ is not more than 20%. Therefore, the ore was subjected to preliminary calcination at 900-1050 deg C during 50-60 minutes. The components extraction is significantly increased and amounts to 78.2% for the initial calcined borosilicate ore, 90.3% for the calcined concentrate at the following optimal conditions: acid concentration - 20%, temperature - 90-95 deg C, process duration - 45-60 min, quantity acids 140-150%. The kinetics of acetic acid decomposition of calcined borosilicate ore has been studied. It has been established that the rate of the decomposition reaction corresponds to a first-order kinetic equation. The calculated activation energies of the process were 19 kJ/mol and 18.6 kJ/mol respectively for the initial ore and for the concentrate, which indicates that the process runs in the diffusion area. Based on conducted studies the basic technological scheme for obtaining boron products from borosilicate ores of Ak-Arkhar Deposit by acetic acid method has been elaborated, which consists from the following stages: calcination at 950 deg C, ore crushing, acetic acid leaching, pulp filtration, product crystallization, separation and drying. (author)