METHOD OF BLEACHING KAOLIN Russian patent published in 2016 - IPC C04B33/04 

FIELD: technological processes.

SUBSTANCE: invention relates to ceramic industry, particularly to methods of bleaching kaolin containing iron impurities, giving it colour used in production of ceramic articles. Technical result is achieved by bleaching clay-containing ceramic material by iron removal, which involves preparation of kaolin suspension, introduction into it nutrient medium, activating the natural microflora and suspension curing in time at constant temperature, followed by magnetic separation and chemical treatment of the obtained residue by washing with ammonium oxalate solution. In compliance with this invention, it is required intensify bioreduction of Fe(III) by adding together with a nutrient medium inoculum in the form of adapted to nature kaolin of active cenosis of aerobic and anaerobic bacteria with their waste products and Fe(II) compounds, obtained in a given amount of kaolin suspension. Volume ratio of the introduced inoculum and kaolin suspension is 1:4÷8 respectively with content of the nutrient medium in amount of 1.0÷2.5 wt% of dry weight of kaolin, temperature mode maintained suspension in time is 20÷30°C with maintenance of its until values of redox potential pe from -0.5 to -2.0 at pH 7.0±1.0, and further chemical treatment of suspension is carried out at leaching mode prior to magnetic separation.

EFFECT: improved whiteness and reduced kaolin yellowing due to intensification of Fe(III) reduction with formation of new Fe(II)-compounds and more complete removal thereof during further processing of kaolin.

4 cl, 1 tbl