Experimental Study On Separation And Enrichment Of Valuable Metal Elements In Niobium-rich Slag

Bayan Obo deposit is the largest rare-earth-niobium deposit in China,and the reserves of rare earth and niobium are also in the forefront of the world.At present,iron can be recovered by carbothermal reduction and melting separation.However,a large number of valuable elements such as rare earth,niobium and titanium are enriched in niobium rich slag.Because the physical and chemical properties of titanium and niobium are very similar,the separation and extraction of niobium are difficult,which seriously hinders the recovery and utilization of valuable metal resources in niobium rich slag.Taking the niobium rich slag of Bayan Obo niobium tailings after carbothermal reduction and iron removal as the research object,the occurrence state transformation of niobium,titanium,rare earth and other valuable metal elements and the migration behavior of elements in slag-Metal system in the process of siliconthermal reduction reaction of niobium rich slag are studied by thermodynamic calculation and high temperature simulation experiment.Combined with the temperature control cooling experiment of siliconthermal reduction tailings,the cooling behavior is investigated The effects of system and slag composition on the mineral phase composition of siliconthermal reduction tailings are discussed.The feasibility of enrichment of lanthanum and titanium in specific ore phase is discussed.The results are as follows:(1)Thermodynamic analysis shows that the reduction of niobium in niobium rich slag is prior to that of titanium,and rare earth is not reduced.The selective reduction of niobium oxide can be realized by adding appropriate amount of silicon(6%)into niobium rich slag,thus realizing the separation of niobium and titanium.(2)The high temperature simulation results show that during the slag gold reaction between Nb rich slag and ferrosilicon alloy,niobium is selectively reduced into the alloy phase to form Fe-Nb-Si alloy,and Ti and Re are retained in the slag.When the w(CaO)/w(SiO2)of niobium rich slag is 1.0,the recovery rate of niobium in the alloy phase can reach more than 80%after the siliconthermal reduction reaction for 60 min.The Fe-Nb(2.77wt%)-Si(1.03wt%)alloy is obtained.(3)During the cooling process of siliconthermal reduction CaxTiyLazOn phase,which is similar to perovskite crystal structure,is precipitated.Lanthanum and titanium in the tailings are selectively precipitated in this ore phase,and the content of other ore phases is very low.(4)The cooling system and the w(CaO)/w(SiO2)of tailings have significant effects on the precipitation and growth of mineral phase in siliconthermal reduction tailings.The results show that the siliconthermal reduction tailings with w(CaO)/w(SiO2)of 1.2～1.9 are kept at 1100℃ for 4h,the main precipitated mineral phases were CaxTiyLazOn,CaMgSiO4 and MgO.The area fraction of CaxTiyLazOn phase was more than 37%,and lanthanum and titanium were enriched in the ore phase.In this paper,the separation of niobium and titanium from niobium rich slag was realized by silicothermic selective reduction,and then the enrichment of lanthanum and titanium in siliconthermal reduction tailings was realized by mineral phase reconstruction.The research results can provide reference for the separation and enrichment of valuable elements in Baiyun Obo tailings.