St. Petersburg Mining University (St. Petersburg, Russia):
Dubovikov O. A., Professor, Doctor of Engineering Sciences, dubovikov_OA@pers.spmi.ru
Sundurov A. V., Postgraduate Student, s185092@stud.spmi.ru

REC «Mekhanobr-Tekhnika» (St. Petersburg, Russia):
Ustinov I. D., Head of the Scientific and Educational Center, Doctor of Chemical Sciences, ustinov_id@mtspb.com

Thermochemical processing of low-grade bauxites allows obtaining suitable bauxite concentrates for the Bayer process, which in turn leads to reduced sintering volumes. The article presents the results of an experimental study of the influence of various calcining temperatures on the subsequent output of bauxite concentrate from bauxites of the North Onega region. The influence of the dosage of calcium oxide in the range of 0 to 30 % at the leaching stage on the aluminum oxide recovery and the alkali content in the red mud is shown. Results are presented for the hydro-garnet red mud processing using alkaline solutions for the purpose of additional recovery of alumina. It has been identified that calcining at 1000 °C allows activating the initial bauxite and achieving streamlined desiliconization times with subsequent filtration of the liquid and solid phases. As compared with lower (975 °C) and higher (1100 °C) temperatures, the time required for the maximum recovery of silicon dioxide into the alkaline solution increases, extending the time interval for the separation of liquid and solid phases and minimizing the secondary processes. It has been shown that addition of calcium oxide at the leaching stage causes a sharp decrease in the alkali content in the red mud at the dosage of 13.13 %, while the recovery of alumina from the concentrate decreases only slightly. Red mud treatment with alkaline solutions ensures additional recovery of aluminum oxide, with the recovery values reaching 30% for the sludge and 6.5 % for the concentrate.
The work was carried out with the financial support of the Russian Science Foundation, project No. 18-17-00169.

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