Recovery of rare earths from wet-process phosphoric acid

Phosphorite ores are a potential resource of rare earths (RE) as well as phosphate so the recovery of rare earths during the wet processing of phosphoric acid is important. This study investigates the influence of operating conditions and crystal modifiers on the leaching of RE and the solvent extraction of RE with organo-phosphorus reagents. The results indicate that lower temperature. higher concentration of phosphoric acid and larger liquid/solid ratio are beneficial to RE enrichment in the phosphoric acid. Surfactant additives which enhance the crystal growth of gypsum also enhanced RE leach recovery about 75% under optimized conditions. Studies on the solvent extraction of RE found that D2EHPA mixtures with neutral organo-phosphorus reagents were antagonistic and that Fe3+ competed strongly over RE. Higher D2EHPA concentration, larger phase ratio, lower temperature and lower phosphoric acid concentration increased the RE extraction efficiency. A negative enthalpy change was found indicating an exothermic extraction reaction. (C) 2009 Elsevier B.V. All rights reserved.