Flotation Separation And Mechanism Study Of Bastnaesite And Monazite

The current separation process in Baiyan Obo mainly produces mixed rare earth concentrates of bastnaesite and monazite.Because of the different properties of bastnaesite and monazite,the metallurgical process of mixed rare earth concentrates is quite complicated.The water leaching slag produced by the smelting of mixed rare earth concentrates is radioactive and needs to be stored in a special slag bank.If these two rare earth minerals are separated,not only can the rare earth smelting be simplified,but also can reduce the emission of pollutants in the rare earth smelting process and protect the environment.Rare earth concentrate mainly consists of fluorocarbon cerium ore and monazite,and impurity minerals are fluorite,apatite,pyrite,magnetite and hematite.Bastnaesite and monazite are small in size,mainly in the form of monomers.Some of them are associated with other minerals,and the distribution relationship is complex.In view of the properties of rare earth concentrate,this paper puts forward the technological method of separating fluorocarbon cerium ore from monazite by flotation after upgrading and reducing impurities of rare earth concentrate to improve the grade of rare earth concentrate.Rare earth concentrate was treated with sodium silicate as depressant and P86 as collector.The optimum conditions were as follows:pH 9,sodium silicate 4.0 kg/t,P86 1.25kg/t and pulp concentration 30%.A high grade rare earth concentrate with a grade of 58.66%and a recovery of 81.22%can be obtained by one roughing.Using alum as inhibitor of monazite and phthalic acid as collector of bastnaesite can effectively separate the two minerals.The optimum conditions are:pH 5,alum dosage 4 kg/t,phthalic acid dosage 2 kg/t,2#oil dosage 300 g/t,temperature 30?,pulp concentration 35%.Through the open circuit test of"one roughing,two refining and two sweeping",we can get the concentrate of bastnaesite with grade of 63.45%,recovery rate of 56.34%,purity of92.99%,grade of 52.34%,recovery rate of 42.13%,and purity of monazite of 91.18%.The inhibiting mechanism of alum on monazite and the collecting mechanism of phthalic acid on bastnaesite were analyzed by means of flotation solution chemistry,Zeta potential and infrared spectroscopy.Under the condition of pH 5,the inhibition mechanism of alum is mainly the preferential adsorption of Al³⁺produced by alum hydrolysis by PO₄^3-ionized monazite,which increases the hydrophilicity of the surface of monazite and makes it difficult for monazite to float.The collection mechanism of phthalic acid is mainly the chelating reaction of carboxyl group and rare earth cation in phthalic acid,which makes the surface of bastnaesite hydrophobically float.