METHOD OF PROCESSING PHOSPHOGYPSUM Russian patent published in 2014 - IPC C22B59/00 C22B3/08 C22B3/44 

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of processing phosphogypsum - wastes of enterprises, producing phosphoric fertilisers. The method includes opening phosphogypsum with sulphuric acid, further extraction of rare-earth elements (REE) and processing purified phosphogypsum with calcium oxide. In the course of opening with one solution of sulphuric acid successively processed are 1-3 lots of phosphogypsum with heating, the water phase is separated by filtration, the sediment is washed with water, apatite is added to the filtrate in a ratio of S:L=1:10-20, with the second heating at a temperature of 50-70°C and mixing for 1-2 hours with neutralisation with sulphuric acid to a concentration not lower than 0.1 mol/l. After that the sediment of the secondary phosphogypsum is separated by filtration and supplied to the beginning of the process. Calcium oxide or hydroxide and then ammonium hydroxide or carbonate are successively introduced into the filtrate until pH=2-3.5, the REE sediment is separated by filtration, and calcium hydroxide or oxide is introduced into the filtrate until pH=7-8, the sediment of feed tricalcium phosphate is separated by filtration, washed with water and discharged from the process.

EFFECT: technical result consists in the reduction of expenditures due to the creation of economically efficient technology.

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