METHOD OF PRODUCING RED IRON OXIDE PIGMENT Russian patent published in 2022 - IPC C09C1/24 C01G49/06 

FIELD: chemistry.

SUBSTANCE: invention can be used in making primers and paints. To obtain red iron oxide pigment, metallic iron of St3 grade is loaded into the reactor, then iron (II) sulphate solution is poured and heated to 40–70 °C. Further, air is fed into the reactor, spraying it at rate of 10 l/min, and the oxidation process is carried out for 10 hours. At the same time, the level of acidity of the reaction medium is constantly regulated, every hour adding water as an additive stabilizing the growth of crystals and an agent regulating the acidity of the medium to the initial volume of the reaction medium until the colour of the solution changes from slightly green to yellow-orange. Obtained suspension is filtered and divided into two equal parts, one of which is dried. Both parts are combined and repulped in a weakly alkaline solution. After that, the suspension is loaded into an autoclave and held at 220–250 °C for 7–10 hours. Suspension is filtered and washed with process water. Obtained paste is dried in a drying oven at 110–160 °C to constant weight and milled.

EFFECT: invention increases the rate of synthesis of the red pigment based on iron (III) oxide while reducing the amount of difficult-to-recycle waste water.

1 cl, 1 tbl, 1 ex