The effective separation of yttrium and other heavy rare earth elements with salicylic acid derivatives

In order to develop stable and efficient extractant to meet the needs of ion adsorbed rare earth ores for Y separation, two novel salicylic acid derivatives, i.e., o-octyloxybenzoic acid (OOBA) and o-ethylhexyloxybenzoic acid (EHOBA), are synthesized. OOBA is an oily liquid with single component at room temperature, which is suitable for solvent extraction and has the consistent properties. The extraction behavior of Y by OOBA is resembled to light rare earth elements (LREEs) than heavy rare earth elements (HREEs). Thus, OOBA has better selectivities for Y and other HREEs than common carboxylic acids, such as NA and sec-octyl phenoxyacetic acid (CA-12). By FT-IR and slope analysis, it can be inferred that the extraction mechanism of OOBA is cation exchange, and the extracted complex can be expressed as REL3. The effects of pH value, saponification degree, loading concentration, RE concentration and OOBA concentration on the extraction and separation of HREEs by OOBA are also discussed. OOBA has been provided with low stripping acid concentration, good cycle stability and less loss in the extraction process. The concentration of OOBA in the raffinate is only about 28 ppm. Finally, a process for separating Y from the industrial Y-enriched HREEs feed liquid is developed. Through the simulated fractional extraction including 9-stage extraction and 6-stage scrubbing, Y product with the purity of 99.4% and the yield of 96.4% is obtained.

Automated summary

Two novel salicylic acid derivatives, OOBA and EHOBA, were synthesized for the extraction and separation of Y from ion adsorbed rare earth ores. The study found that OOBA exhibits similar extraction behavior to LREEs and has better selectivities for Y and other HREEs compared to common carboxylic acids. The extraction mechanism of OOBA was determined to be cation exchange. Furthermore, OOBA demonstrated advantages such as low stripping acid concentration, good cycle stability, and minimal loss in the extraction process. A simulated fractional extraction process was developed to separate Y from the Y-enriched HREEs feed liquid, resulting in a Y product with high purity and yield.