Method for recovering rare earth elements from waste red phosphor

[0016] Example 1

[0017] Take 1000g of discarded red phosphors for three primary color fluorescent lamps, total rare earth (TREO): 81.56%, Eu 2 O 3 /TREO: 7.25%, Y 2 O 3 /TREO: 92.73%, other rare earth <0.02%, calcined at 550℃ for 3 hours, then acid-dissolved in 2.45L composite acid system for 6 hours. The composite acid composition is: hydrochloric acid (HCl) (89%)-oxidant (H 2 O 2 )(3%)-glacial acetic acid (CH 3 COOH) (8%), amount of rare earth metal: volume of composite acid = 1:3, acid dissolution conditions are: acidity 0.5N, acid dissolution temperature 90℃, after acid dissolution, filter to remove insolubles to obtain 2.4L concentration of 338.1g/l The rare earth chloride solution, the calculated yield of rare earth dissolution is 99.5%. Dilute the rare earth chloride solution to a concentration of 120±5g/l and adjust the pH to 2.5±0.3, and enter the fractionation extraction system of 22% naphthenic acid + 18% mixed alcohol + 60% sulfonated kerosene in the organic phase saponified with NaOH After extraction and separation, after 75-stage extraction and 15-stage washing, high-purity yttrium chloride (YCl 3 ) Solution, the solution is precipitated and filtered with high-quality oxalic acid to obtain solid yttrium oxalate, and yttrium oxalate is burned to obtain high-purity yttrium oxide products. Eu 3+ Then enter the organic phase, use 4N±0.5N concentration of high-purity hydrochloric acid (HCl) to back extract the organic phase to obtain europium chloride (EuCl 3 ) Is the main component of the solution, dilute the solution to a concentration of 120±5g/l and adjust the pH to 2.5±0.3, add zinc powder to the solution to make Eu 3+ Revert to Eu 2+ , The reduced europium chloride solution enters the P507-sulfonated kerosene-HCl extraction system under the protection of argon, and after 30-stage extraction with three-outlet fractionation extraction method, high-purity Eu is obtained in the water phase 2+ Eu in solution, water phase 2+ It becomes Eu after being oxidized by hydrogen peroxide 3+ After oxalic acid precipitation, filtration, and burning of europium oxalate, high-purity europium oxide products are obtained. The other small amounts of rare earths enter the organic phase, and the organic phase is back-extracted with 4N±0.5N hydrochloric acid (HCl) to obtain the rare earth chloride enrichment solution, which is then precipitated with oxalic acid, filtered and burned to obtain the rare earth oxide enrichment product. The zinc chloride solution is obtained from the third outlet, and the zinc oxide product with higher purity is obtained by ammonium carbonate precipitation, filtration and burning.

[0018] Example 2

[0019] Take 1000g of discarded red phosphors for tri-color fluorescent lamps, total rare earth (TREO): 81.56%, EU 2 O 3 /TREO: 7.25%, Y 2 O 3 /TREO: 92.73%, other rare earth <0.02%, calcined at 850℃ for 0.5 hours, and then acid-dissolved in 2.45L composite acid system for 3 hours. The composite acid composition is: hydrochloric acid (HCl) (92%)-oxidant (H 2 O 2 )(5%)-glacial acetic acid (CH 3 COOH) (3%), amount of rare earth metal: volume of composite acid = 1:3, acid dissolution conditions: acidity 0.5N, acid dissolution temperature 110°C, after acid dissolution, filter to remove insoluble matter to obtain 2.41L with a concentration of 337.0g/l The rare earth chloride solution, the calculated yield of rare earth dissolution is 99.6%. The subsequent process steps are the same as in Example 1.

[0020] Example 3

[0021] Take 1000g of discarded red phosphors for three primary color fluorescent lamps, total rare earth (TREO): 81.56%, Eu 2 O 3 /TREO: 7.25%, Y 2 O 3 /TREO: 92.73%, other rare earth <0.02%, calcined at 550℃ for 3 hours, then acid-dissolved in 2.45L composite acid system for 6 hours. The composite acid composition is: nitric acid (HNO 3 )(89%)-oxidant(H 2 O 2 )(3%)-glacial acetic acid (CH 3 COOH) (8%), amount of rare earth metal: volume of composite acid = 1:3, acid dissolution conditions are: acidity 0.5N, acid dissolution temperature 90℃, after acid dissolution, filter to remove insolubles to obtain 2.41L concentration of 337.0g/l The calculated rare earth nitrate solution yield is 99.6%. Dilute the rare earth nitrate solution to a concentration of 120±5g/l and adjust the pH to 2.5±0.3, and enter it into a fractional extraction system of 22% naphthenic acid + 18% mixed alcohol + 60% sulfonated kerosene in the organic phase saponified with NaOH Extraction and separation, after 75-stage extraction and 15-stage washing, high-purity yttrium nitrate (Y(NO 3 ) 3 ) Solution, the solution is precipitated and filtered with high-quality oxalic acid to obtain solid yttrium oxalate, and yttrium oxalate is burned to obtain high-purity yttrium oxide products. Eu 3+ Then enter the organic phase, use 4N±0.5N concentration of high-purity hydrochloric acid (HCl) to back extract the organic phase to obtain europium chloride (EuCl 3 ) Is the main component of the solution. The subsequent process steps are the same as in Example 1.