Cerium removal from mixed rare earth Sulfate solution by oxidative precipitation with hydrogen peroxide: Batch and continuous studies

Cerium(III) removal from mixed rare earth sulfate solutions via oxidation to Ce(IV) with hydrogen peroxide and subsequent precipitation as Ce(OH) 4 was investigated in batch reactors to identify optimum conditions for maximum Ce elimination with minimum rare earth element (REE) losses. Depending on the pH and H 2 O 2 dosage, Ce rejection in a batch setting was below 20% at pH 3, regardless of H 2 O 2 dosage, while at pH 4 and 4.5 and 100% excess of H 2 O 2 , it reached 85% and 90%, respectively. The REE losses were between 10% to 50%. Following slurry ageing for 3 h at 80 °C and pH 3, the REE losses were reduced to between 1% and 7% while up to 50% of the co-precipitated Ce(III) was also redissolved. Approximately 90% of Ce was removed in continuous reactors operating under the optimal conditions of pH 4 and 100% excess H₂O₂. An optimized strategy was proposed to further enhance Ce removal while minimizing REE losses. In this approach, after solid-liquid separation, the Ce-depleted solution from oxidative precipitation is directed to downstream REE processing, while the solids are aged separately in pH 3H₂SO₄. After ageing, the solution containing ~44% of the initial Ce and the recovered REEs are returned to the oxidative precipitation tank. The effects of pulp density, duration and temperature during this separate ageing step were investigated to assess REE sulfate solubility limitations. Optimal conditions were identified as pH 3, 70 °C, ≤ 10% pulp density, and extended ageing (3–4 h). These parameters provided the best balance between maximizing Ce rejection (at ~45%) while maintaining minimal REE losses in the sulfate system (~ 4%). • Cerium separation from REE sulfate solution by oxidative precipitation with H2O2. • Batch and continuous experiments were performed to simulate industrial conditions. • Optimum pH and H2O2 excess conditions for maximum Ce removal were identified. • Ce removal was 90% at pH 4 and 100% H2O2 excess. • REE losses less than 5% were achieved by 3 h solids ageing at 70 °C, pH 3 and 10% solids.