Flotation Separation And Mechanism Of Rare Earth And Calcium Bearing Minerals In Bayan Obo Mine

Bayan Obo iron-rare earth-niobium polymetallic co-（accompanied）ore is the world’s largest mixed light rare earth ore,whose industrial production under the guidance by"circle ore by iron,comprehensive utilization".The ore body is huge.H205 special collector and“weak magnetic-strong magnetic-continuous flotation”process realize the comprehensive utilization of iron and rare earth resources.As an important non-metallic associated mineral resource in Bayan Obo mine,fluorite has a resource reserve of 130 million tons and a grade of about 22%（CaF₂）.At present,it has not been comprehensively recycled.Bayan Obo Mine has an important strategic position in China.Green development and comprehensive and efficient utilization of its valuable minerals are not only the requirements to realize the mine value,but also are the requirements of national industrial policy,moreover,it is also the requirements of environmentally friendly development.The grade of rare earth concentrate in Baogang Group is relatively low at present,with about 30%of the impurities.These impurities are mainly associated with fluorite,niobium,scandium,thorium,sulfur,phosphorus,barite and so on,which are not recycled effectively for a long time,but these impurities exist in the form of"three wastes"emissions in the process of sulfuric acid roasting rare earth metallurgy.2015 main project of Baogang Group Steel,the grade of fluorite rough concentrate is only 86%at present,which would not meet the fluorite concentrate grade quality standards.And,increasing the rare earth concentrate grade from 50%to 56%could not realize its corresponding economic value,however,in the rare earth smelting process,a large amount of iron is needed to balance the raw materials,nor can it achieve environmental benefits.In this paper,systematic basic mineralogical research and analysis are carried out on the minerals produced in Bayan Obo mine and various stages of mineral processing to find out the mineral characteristics and reveal the mineral processing mechanism.The specific research contents are as follows:Aiming at a series of problems in metallurgy process of 56%rare earth concentrate produced by Baoshan Mining due to low Fe/P ratio,mineralogical analysis（BPMA）was carried out on the beneficiated raw ore to find out the mineral composition,particle size distribution,co-generation relationship and dissociation degree.Based on single factor flotation test,it was revealed that the main reason of high phosphorus in rare earth concentrate was the presence of polyacrylamide（PAM）in the mineral processing water.The adsorption capacity of polyacrylamide（PAM）on the surface of rare earth minerals and apatite was measured by UV-1800PC UV-visible spectrophotometer according to Lambert-Beer law.According to kinetic and thermodynamic fitting,the results show that the adsorption kinetics conforms to the model of second-order kinetics,and the isothermal adsorption process accords with the model of Freundlic.The adsorption constant K_F of apatite on PAM was 0.0654 and the adsorption strength 1/n was 0.3959.The adsorption constant K_F of rare earth on PAM was 0.02265 and its adsorption strength 1/n was 0.61302,which indicated this multilayer adsorption was not firm or physical adsorption is the main adsorption.The adsorption constant K_F of apatite on polyacrylamide（PAM）was greater than that of rare earth on polyacrylamide（PAM）.The adsorption strength 1/n of apatite on PAM was less than that of rare earth on PAM,indicating that the adsorption capacity of PAM on apatite was obviously greater than that on rare earth,and 506E has stronger selectivity to rare earth.Using 10mg/L polyacrylamide（PAM）to treat apatite,the Zeta potential of apatite surface shifted negatively,and the absorption peaks showed obvious strain or tension at 957-1122 cm^-1,1083 cm^-1,571 cm^-1 and 663 cm^-1.XPS analysis showed that the absorption peaks were amide（-C（=O）N-）and carboxyl（-C=O）up to 20.11%on the apatite surface.The advanced oxidation process（AOPs）using Fe³⁺,H₂O₂ or Fe³⁺/H₂O₂ in combination can effectively degrade the total organic carbon（TOC）content in the backwater.The single flotation experiment shows that the reflotation of 56%rare earth concentrate with slurry water treated by advanced oxidation process（AOPs）for more than 24 hours can greatly improve the grade of rare earth concentrate and significantly reduce the content of phosphorus,among which FeCl₃/H₂O₂ combination is the best project.Degradation rate experiments show that the degradation rate of total organic matter in pulp water can reach more than 75%by the advanced oxidation method（AOPs）using FeCl₃,H₂O₂ or FeCl₃/H₂O₂combined for 24h.FT-IR test also confirmed that the rare earth minerals in the presence of Polyacrylamide（PAM）at 727 cm^-1 and 569 cm^-1 have obvious stretching,but after Fe³⁺/H₂O₂ oxidation treatment,the stretching is obviously weakened or even disappeared,indicating that polyacrylamide（PAM）in pulp water has been effectively degraded.More than 65%of high grade rare earth concentrate can be obtained by open circuit flotation test in simulated flotation production site,and the phosphorus content in the concentrate can be greatly reduced.The closed-circuit test under the same conditions did not deteriorate the flotation test index,and confirm that the ree dissociation degree and particle size distribution in 56%rare earth concentrate could meet the requirements of reflotation.The closed-circuit test obtained a high grade,high recovery and low phosphorus concentrate with 66.08%REO,86.02%recovery and 1.47%P content.Phthalic acid（PA）under the condition of weak acid can realize efficient fluorescent and rare earth separation.Flotation experiments show that under the same conditions,the use of phthalic acid（PA）as a collector in flotation separation to treat fluorite rough concentrate（whose grade is 86%）,and rare earth and fluorite recovery ratio is 1∶3.9,shows that the better selective collecting are needed in flotation performance of similar minerals flotation separation.At the same time,it is necessary to control the ph of pulp reasonably and increase the floatability of minerals to achieve efficient separation of rare earth and fluorite.Zeta potential changed from p H=3.8 to p H=1.9 after fluorite minerals reacted with phthalic acid（PA）.The characteristic peaks measured by FT-IR at 1090 cm^-1,1050 cm^-1 and881cm^-1 merged,weakened or even disappeared.Energy spectrum（XPS）test can detect the fitting peak of benzene ring C peak at 291.58 e V,whose the content is up to 2%.Titration analysis of stability constants of Ca²⁺,Ce³⁺ions and collector phthalic acid（PA）complexes showed that the stability constants of the complex formed by fluorite dominated by surface Ca²⁺and phthalic acid（PA）were larger than those formed by rare earth ions and phthalic acid（PA）complexes,namely,showing that total log K_（Ca）>total log K_（RE）and indicating that phthalic acid（PA）had a strong adsorption effect on Ca²⁺under weak acid conditions.Under the condition of weak acid,Ca²⁺on the surface of fluorite was more likely to form complex with phthalic acid（PA）to float up due to the complex of hydrophobicity and lipophilicity,and p H=5 was the best condition to realize the separation of fluorite and rare earth.While under the condition of weak base,RE（OH）_x^（3-x）+（x=1,2）formed on the surface of rare earth was more likely to form complex with phthalic acid（PA）.Phthalic acid（PA）has strong collection ability for fluorite under weak acid condition,which can realize efficient separation of fluorite and rare earth.The 86%fluorite coarse concentrate produced by Baoshan mining industry can meet the industrial requirements of FC-95 through the closed-circuit test of one roughing,three refining,two sweeping and medium ore step-by-step return.The grade and recovery are95.23%and 83.34%respectively,which greatly improves the industrial value of fluorite resources.Tailings can be directly returned to the rare earth beneficiation section for rare earth flotation to reduce the loss of rare earth resources.The rare earth reverse flotation has got rare earth concentrate of 63.56%grade and the 65.33%recovery.