Non-ammonia enrichment of rare earth by magnesium oxide from rare earth leaching liquor in magnesium salt system

In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ion-adsorption type rare earth ore, the technology of non-ammonia precipitation with magnesium oxide precipitant was carried out. It is determined that the rare earth precipitation efficiency is 99.6% and the purity of rare earth concentrates is only 85.89 wt% under the optimum precipitation conditions. And the contents of MgO, SO₃ and Al₂O₃ in the rare earth concentrates are 5.12 wt%, 6.77 wt% and 1.78 wt%, respectively. Furthermore, the thermo-decomposition process of precipitates was investigated by TG-DSC, XRD and FI-IR. The thermal decomposition process consists of two stages: the dehydration of rare earth hydroxide and alkaline rare earth sulfate within 900 °C and the thermal decomposition of RE₂O₂SO₄ at 900–1300 °C. Therefore, a high-temperature calcinations method for removing SO₃ from precipitates is proposed. When the precipitates are calcined at 1300 °C for 2 h, the rare earth concentrates with a purity of 92.03 wt% can be acquired. Moreover, the content of SO₃ in the concentrate is only 0.46 wt%. In the MgO precipitation and high-temperature calcinations process, the raw material cost is low and the quality of rare earth concentrates is acceptable. It could have great significance for non-ammonia enrichment of rare earth from the rare earth leaching liquor, and finally solve the problem of ammonia nitrogen in the extraction process of the ion-adsorption type rare earth ore within magnesium salt system.