METHOD OF PROCESSING TUNGSTEN-CONTAINING MATERIAL Russian patent published in 2008 - IPC C01G41/00 C01G21/00 

FIELD: hydrometallurgy; processing wastes of production of monocrystal compounds of refractory metals, lead tungstate in particular for obtaining high-purity tungsten and lead compounds used for repeated growing of monocrystals.

SUBSTANCE: proposed method includes two-stage treatment of finely ground waste of lead tungstate PbWO₄ monocrystal process at temperature of 95-105 C by means of nitric acid solution reducing the acid concentration at second stage. At first stage, use is made of 40-45-% nitric acid; treatment of waste is carried out at solid-to-liquid ratio = 1: 0.65-0.7; the procedure is continued for 1.0-1.25 h; at second stage, concentration of acid is reduced to 7-10% due to addition of hot water at temperature of 90-100 C at solid-to-liquid ratio = 1: 0.55-0.65, after which treatment is continued for 0.25-0.5 h. As a result, tungstic acid residue and acid solution of lead nitrate with foreign components in form of Fe, Ca, Mg and Al are formed. Tungstic acid residue is washed with 2-3-% nitric solution and is calcined at temperature of 500-550 C, thus obtaining tungsten oxide. Acid solution of lead nitrate is evaporated by 75-80% of initial volume, cooled to 5-15 C and lead nitrate residue is separated from mother liquor containing foreign components. Residue is washed with 10-12-% nitric acid, dissolved in distilled water and 20-25-% ammonium solution is added for obtaining pH= 8.5-9.0 forming lead oxyhydroxide residue which is filtered and calcined at temperature of 450-500 C, thus obtaining lead oxide. Proposed method ensures decomposition of waste to 99.8-99.9% at reduction of treatment time to 1.25-1.75 h.

EFFECT: enhanced efficiency; reduced duration of treatment of waste.

9 cl, 3 ex