Leaching Behavior of Valuable Elements in the Low-Temperature Concentrated Sulfuric Acid Roasting-Water Leaching Process of Mixed Rare Earth Concentrates AITranslate

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Chinese Library Classification Number:TF845[冶金工程—有色金属冶金]

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Aiming at the problems of high acid consumption,acidic gas escape and difficult treatment of radioactive slag in the treatment of mixed rare earth concentrates by high-temperature concentrated sulfuric acid roasting process,a low-temperature concentrated sulfuric acid roasting-water leaching process was developed.The effects of roasting time,roasting temperature,acid-mineral mass ratio and iron-phosphorus mass ratio on the leaching of various elements in the mixed rare earth concentrates were systematically studied.The results show that under the conditions of roasting time of 60 min,roasting temperature of 300℃,acid-mineral mass ratio of 2.0 and without adjusting iron-phosphorus mass ratio,the leaching rates of RE and Th reach 94.34%and 95.05%,respectively,and the formation of radioactive waste residue is significantly reduced.However,white precipitate is generated after the leaching solution stands,resulting in a decrease in the content of RE and Th in the leaching solution.By adding Fe₂O₃ to regulate iron-phospho-rus mass ratio in the roasting raw material to 3.0,the leaching rates of RE and Th are 94.80%and 71.20%,respectively,and the precipitation of rare earth pyrophosphate in the leaching solution is effectively inhibited.According to thermodynamic analysis,under low temperature conditions(≤300℃),the reactions between sulfuric acid and rare earth minerals proceed more readily,and the emission of SO₂ and SO₃ acidic gases can be suppressed.Compared with the high-temperature concentrated sulfuric acid roasting method,the low-temperature concentrated sulfuric acid roasting process combines environmental friendliness and resource efficiency,providing a way for the green extraction of mixed rare earth concentrates.