A Stepwise Solvent Extraction Process for Recovering Yttrium from Sulphate Leach Solutions of Deep-sea Mud

Abstract

A novel approach for recovering yttrium from high ferric and strong acidic sulphate leach solutions of deep-sea mud by stepwise extraction and stripping has been developed. The results show that the first step extraction by N235+TBP system can extract H₂SO₄ well and adjust the raffinates to a desirable pH, while only the iron was selectively co-extracted with negligible loss of yttrium ions. The organic solution can be easily regenerated by using a 50 g/L H₂SO₄ solution to strip extracted iron followed by using deionized water to strip H₂SO_4. The raffinate could be directly used for the second step of yttrium extraction by P204+TBP system, while iron was co-extracted. The co-extracted yttrium and iron could be separated well through a sequentially stepwise stripping process using a 50 g/L H₂SO₄ solution and a 0.6 mol/L H₂C₂O₄ solution. Over the whole process, yttrium was separated well from the sulphate leach solutions and enriched into the strip liquor of yttrium sulfate. The organic extractants could be returned for recycling.