Study On Crystallization Enrichment Of Rare Earth From Slag With Low Rare Earth Content

The Bayan Obo symbiosis ore is a world-renowned iron-rare earth-niobium symbiosis deposit rich in rare earth resources.Rare earth resources form the processing,decomposition and extraction process for rare earth separation,but the utilization rate of rare earth is low,and a large number of rare earth is placed in the tailings dam along with the tailings heap.The iron concentrate produced in Bayan Obo also contains small amounts of rare earths,which enter the slag with the blast furnace and are lost when the slag is watered for cement and other construction purposes.Therefore,it is of great significance to enrich and extract rare earth from the slag with low rare earth content.The rare earth can be enriched in slag with low rare earth content by pyrometallurgy.The enrichment and separation of rare earth in slag is the key technology for the efficient utilization of rare earth resources.In this paper,pure reagents were used to simulate the low rare earth content slag system of CaO-SiO₂-Al₂O₃-15wt%La₂O₃-?CaF₂?-?P₂O₅?.To explore the influence of basicity,CaF₂ and P₂O₅ on slag viscosity and slow cooling crystallization.First using ND-?slag comprehensive tester using the rotating cylinder method,1480?temperature viscosity and the cooling curve of different samples were determined,found that P₂O₅ join can improve the slag is 1480?isothermal viscosity and melting temperature,and the effect of CaF₂ instead.The increase of basicity will decrease the constant temperature viscosity at 1480?and increase the melting temperature.Subsequently,the samples with different components were heated to 1550?in a high-temperature tubular furnace and removed after 4h to 1100?.After cooling at room temperature,the samples were analyzed by SEM-EDS and XRD.By studying the morphology,chemical composition and structure of the rare earth crystalline compounds in the slag,it is proved that in the slag system of CaO-SiO₂-Al₂O₃-?15wt%?La₂O₃-?P₂O₅?-?CaF₂?,the slow cooling precipitation of the rare earth phase is cerium calcium silica?CaLa₄?SiO₄?₃O?,and the other phase is Ca₂Al₄SiO₇.The addition of P₂O₅ and CaF₂ separately promotes the precipitation of rare earth rich phase in the basic slag system,and P₂O₅ has a stronger promoting effect than CaF₂.The joint addition of P₂O₅ and CaF₂ has a certain promoting effect on the precipitation of rare earth rich phase,but also reduces the content of rare earth in the rare earth phase.The increase of basicity will promote the precipitation of rare earth-rich phase.The main significance of this study is to make the rare earth better enriched in the slag with low rare earth content to provide scientific basis for the subsequent separation and extraction of rare earth elements.