Abstract: Aiming at the ammonia-nitrogen pollution problem existing in the current ammonium bicarbonate precipitation
process for rare earth ions,this study took yttrium chloride solution as the research object and systematically compared the precipitation
effects of four precipitants,namely ammonium bicarbonate,ammonium carbonate,sodium bicarbonate,and sodium
carbonate. The optimal precipitant was screened through indicators such as precipitation rate and precipitate volume,and in-situ
pH monitoring and Fourier Transform Infrared Spectroscopy (FTIR) were comprehensively used to analyze its precipitation
mechanism. The results showed that sodium carbonate was the optimal ammonia-free precipitant. When the molar ratio of sodium
carbonate to yttrium ions was 1. 6,the yttrium precipitation rate could reach 99. 17%,and no irritating gas or ammonia-nitrogen
wastewater was generated. Mechanism studies indicated that under this condition,the product was well-crystallized hydrated
yttrium carbonate (Y2(CO3)3·xH2O). An excessively low molar ratio tended to form chlorine-containing double salts,
while an excessively high molar ratio easily led to the formation of colloidal impurities. This study demonstrates that sodium carbonate
can be used as an efficient and environmentally friendly precipitant to replace traditional ammonium salts,providing a
theoretical basis and technical scheme for the green extraction of ionic rare earths.

Key words: ion-adsorption rare earth,rare earth carbonate,ammonia-free precipitant,precipitation enrichment,sodium
carbonate