Study Of RE,P And F Recovery From High-grade Mixed Rare Earths Concentrate

Mixed rare earth ore of Inner Mongolia Baotou is an very important light rare earth resource of the rare earth industry in China,its composition is complex and contains refractory monazite,so it's difficult to dispose.The sulfuric acid roasting method currently used has the problem of polluting the environment and unutilized fluorine and phosphorus.With the increase of mineral extraction depth and the adwance of mineral processing technology,the REO grade of mixed rare earth concentrate has increased from 50%to 55%,and tends to increasing,so the comprehensive recovery of the valuable element in mixed rare earth,especially for China whose fluoride and phosphorus resources is deficient,has a very important significance for China's economic construction.In order to achieve the above objectives,this paper takes high grade mixed concentrate(It referred to rare earth concentrate in the following text)of Baotou Rare Earth Concentrator as the subject,and the recovery process and reaction mechanism of valuable rare earth,phosphorus and fluorine was studied.The research content was divided into the following three parts.In the first part,the decomposition of rare earth concentrates and the recovery of phosphorus from roasted products of mixed rare earth concentrates were studied;In this part,the roasting decomposition mechanism and process conditions of rare earth concentrates were obtained.By the orthogonal regression experiment,the optimum conditions of dephosphorization of hydrochloric acid-citric acid roasting ore were as follows:hydrochloric acid concentration 1.1mol·L-1,The leaching rate of phosphorus was 96.42%,the leaching rate of rare earth was 2.75%,and the leaching rate of fluorine was 2.1%.The leaching rate of phosphorus was 5%,and the ratio of liquid to solid was 9:1,time 35min and stirring speed 200r·min-1.The kinetics of the phosphorus leaching process showed that the phosphorus leaching process was in accordance with the non-reduced nuclear kinetics model,and was controlled by diffusion control and chemical reaction respectively with increasing temperature.When the leaching temperature is from 20? to 30?,the reaction speed is controlled by the solid film diffusion control;when the leaching temperature is 40? to 50??the reaction control step is a chemical reaction;when the leaching temperature is 30? to 40?,Hybrid control step.The pH of the solution was adjusted to 9,and the recovery of phosphorus was 98.13%at room temperature.In the second part,the recovery of rare earth and fluorine from pickling ore were studied.In this part,rare earth and fluorine are recovered from the pickling mine by HCl-H3Cit selective leaching.The quadratic orthogonality regression equation of leaching conditions and leaching rate of rare earth oxides and calcium fluoride were established by quadratic orthogonal regression test.The optimized leaching conditions were obtained as follows:hydrochloric acid concentration 3.6kJ·mol-1,citric acid addition 30%,temperature 40?,liquid to solid ratio of 11:1,leaching time of 25min.Under this condition,the dissolution rate of rare earth is 93.32%,and the dissolution rate of fluorine is 5.19%.The kinetic study shows that the process of acid washing and alkalization match to kinetic equation of 1-(1-?)1/3=Kt,and the reaction rate is controlled by chemical reaction control mode(20?40?),mixed control mode(40?50?)and diffusion control mode(50?60?)respectively.The apparent activation energy of acid washing are E1=46.19kJ·mol-1 for chemical reaction control mode,E2=28.37kJ·mol-1 for mixed control mode,E3=3.42kJ·mol-1 for diffusion control mode respectively.The third part:content main components in the whole processThe results show that the direct recovery of rare earth is 90.85%,the direct recovery of phosphorus is 94.66%,the direct recovery of fluorine was 92.73%,after the process of pickling,alkalizing and leaching of roasted products in Baotou ore.In summary,the paper conceived the new process can not only meet the industrial production,but also in line with the comprehensive utilization of resources and environmental protection requirements.