| 简介 |
FIELD : chemistry.SUBSTANCE : invention can be used in chemical industry to extract rare-earth elements from phosphogypsum. The method involves carbonising phosphogypsum to obtain phosphochalk, dissolving said phosphochalk in nitric acid to obtain a product suspension and then separating the insoluble residue - a black concentrate of rare-earth elements - by filtering. The product suspension is divided into two parts, one of which is fed for filtration to separate the insoluble residue - black concentrate, and the second is fed for premixing with nitric acid. The mixing process is carried out for 3-5 minutes with the ratio CaO/HNOequal to 0.75-2.25. When dissolving, pH is kept at 2.2-4.EFFECT : invention enables to extract rare-earth elements from phosphogypsum in form of a back concentrate with high content of rare-earth elements and stabilise the process in industrial conditions.4 tbl, 5 ex |
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