The Leaching Technology of Rare Earth Polishing Powder Waste in Thiourea-Hydrochloric Acid System and Recovery of Rare Earth Oxides from the Lixivium Through Oxalic Acid Precipitation

ZHAI Jingyu; LIU Guangyi

doi:10.13779/j.cnki.issn1001-0076.2022.01.023

2022 Vol. 42, No. 1

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ZHAI Jingyu, LIU Guangyi. The Leaching Technology of Rare Earth Polishing Powder Waste in Thiourea-Hydrochloric Acid System and Recovery of Rare Earth Oxides from the Lixivium Through Oxalic Acid Precipitation[J]. Conservation and Utilization of Mineral Resources, 2022, 42(1): 158-164. doi: 10.13779/j.cnki.issn1001-0076.2022.01.023

Citation:

ZHAI Jingyu, LIU Guangyi. The Leaching Technology of Rare Earth Polishing Powder Waste in Thiourea-Hydrochloric Acid System and Recovery of Rare Earth Oxides from the Lixivium Through Oxalic Acid Precipitation[J]. Conservation and Utilization of Mineral Resources, 2022, 42(1): 158-164. doi: 10.13779/j.cnki.issn1001-0076.2022.01.023

The Leaching Technology of Rare Earth Polishing Powder Waste in Thiourea-Hydrochloric Acid System and Recovery of Rare Earth Oxides from the Lixivium Through Oxalic Acid Precipitation

ZHAI Jingyu,
LIU Guangyi^,

College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan, China

More Information

Corresponding author: LIU Guangyi, guangyiliu@csu.edu.cn

Received Date: 15 November 2021

Publish Date: 25 February 2022

Abstract

Abstract

The solubility of Ce(Ⅲ) is far greater than that of Ce(Ⅳ). Thus, the thiourea was used to reduce Ce(Ⅳ) into Ce(Ⅲ) in dilute hydrochloric acid solutions to promote the recovery of rare earth oxides from a rare earth polishing powder waste. The effects of leaching temperature, leaching time, liquid-to-solid ratio (L/S), hydrochloric acid concentration and thiourea dosage on the leaching ratio of cerium from the rare earth polishing powder waste were investigated. The results showed that under the optimal technologies, hydrochloric acid concentration of 4 mol/L, L/S of 4.2, leaching temperature of 90 ℃, leaching time of 60 min, and thiourea dosage of 0.04 g/g, the cerium leaching ratio reached 99.37%. Then, the rare earth ions in leaching solutions were separated and recovered by oxalic acid precipitation approach. After adjusting pH to 1.8-2.0 by ammonia water, oxalic acid was added to deliver rare earth oxalate precipitates which were subsequently roasted under air to obtain the rare earth oxide (REO) product. The total REO content in the REO product was about 97% with 78.00% CeO₂ and 18.93% La₂O₃, and their recovery ratio was 91.66% and 68.44%, respectively. In addition, the findings of laser particle size analysis, XRD and SEM showed that the rare earth oxide products were mainly composed by CeO₂ square particles, and exhibited a narrow particle size distribution with a flat and angular surface.
- rare earth polishing powder waste /
- reduction leaching /
- cerium /
- lanthanum /
- oxalic acid

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References

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