PHYSICO-CHEMICAL AND TECHNOLOGICAL ASPECTS OF PROCESSING KAOLIN CLAYS OF CHASHMASANG DEPOSIT BY SULFATIZATION METHOD

Abstract

The article presents the results of physical and chemical studies on the sulfatization of kaolin clays of the Chashmasang deposit in order to obtain crude and purified coagulants (aluminum sulfate), aluminum hydroxide and alumina. The deposit of kaolin clay Chashmasang is located on the southern slope of the Gissar Range of Tajikistan on the watershed of the Khonaka-Suffa interfluve and covers an area of 0.2 km2. In the course of the research, the chemical and mineralogical composition of kaolin clays of the Chashmasang deposit was determined, the content of aluminum oxide, which is in the aisles of 19-22%, and is mainly present in the form of the mineral kaolinite. The optimal technological parameters that affect the sulfatization process have been identified: temperatures 220-260 °C, duration 60-90 minutes, sulfuric acid concentration 90-95%, acid dosage up to 110% of stoichiometry. Also, the process of water treatment of sulfated sinter was studied in order to obtain a purified mixed liquid coagulant, the optimal parameters of which are as follows: temperature 85-95 °C, duration 40-45 min, ratio between solid and liquid (S:L) = 1:4. With such optimal parameters, the degree of extraction of aluminum sulfate in terms of alumina is more than 90%. The X-ray diffraction confirmed that after sulfatization of kaolin clays from the Chashmasang deposit, new lines appear that are characteristic of the mineral millosevicite (Al2(SO4)3) and alunogen (Al2(SO4)3•18H2O). The results of water treatment of sulfated sinter in order to obtain purified aluminum sulfate was confirmed by X-ray diffraction. It was revealed that silicon oxide in the form of quartz mineral remains in the composition of the solid residue after filtering the pulp, and the evaporated salt of the liquid part is anhydrous aluminum sulfate (millosevichite mineral).