NON-THERMAL DRAINLESS METHOD FOR NEUTRALISING MERCURY-CONTAINING WASTE Russian patent published in 2022 - IPC C22B43/00 B09B3/00 C22B7/00 

FIELD: treatment of waste.

SUBSTANCE: invention relates to environmental protection, namely, to a method for neutralising mercury-containing waste (temperature controllers, thermometers, luminescent lamps, pressure gauges and barometers) containing metallic mercury. The method includes joint grinding of mercury-containing waste with elemental sulphur powder and water in a sealed reactor in the form of a drum- or vibration-type mill. The ratio of the mass of elemental sulphur to the mass of metallic mercury is 3:1. Grinding is executed until 95 to 96% of the mass of metallic mercury is bound to mercury sulphide. At the final stage of grinding, iron (III) chloride and iron (II) sulphide in the form of pyrite are added to the reactor to fully bind the metallic and oxidised mercury into mercury sulphide and produce a suspension. Bentonite in the amount of 1:8 to the solid phase of said waste and water are then introduced into the reactor to bring the S:L ratio to 1:4 forming a stable mobile non-separating suspension subsequently drained from the reactor and held while stirring for 24 to 48 hours. The suspension is then directed for drying into a dryer with a fluidised bed or a spray dryer, producing a dried product with a content of metallic mercury and compounds thereof as calculated for mercury, excluding mercury sulphide, less than MAC = 2.1 mg / kg.

EFFECT: invention provides a possibility of transferring mercury from mercury-containing waste into water-insoluble and diluted acid-insoluble environmentally stable mercury sulphide without pretreatment, increase in the temperature of the process and use of additional reagents.

1 cl, 1 ex