Thermal Treatment For Separation Of Rare Earth Phosphate

Rare earth minerals are important strategic resources,and rare earth elements are known as the“industrial vitamins”.Thus,rare earth elements are widely used in many fields for its high degree of utilization.The requirements of rare earths or non-rare-earth impurities are very high,often in the PPM level,so that the separation of rare earth elements puts forward higher requirements.The separation process of rare earth elements includes mineral processing of rare earth minerals,decomposition of rare earth concentrates and purification of rare earth minerals.In order to solve of the problems of environmental pollution and waste of resources in the process of decomposition of rare earth concentrates in China,in this paper,thermal treatment for separation of rare earth phosphate was studied in detail by using concentrated sulfuric acid low-temperature roasting method and caustic soda pressure decomposition to decompose Baotou mine solitary stone slag and pure monazite.Mine monazite slag is from Baotou mixed rare earth concentrate with"oxidation roasting?sulfuric acid leaching"and the rare earth separation treatment,then rare-earth phosphates were converted into soluble rare-earth sulphates using low-temperature roasting of monazite,followed by leaching with sulfuric acid solution.Finally,the objective of separation and enrichment of rare earths in monazite slag from Baotou Mine was achieved.The effects of different experimental conditions,including roasting temperature,roasting time,mixed acid amount,liquid-solid ratio and leaching time on the separation process of solitary stone were studied in detail,and the optimum separation condition was obtained,under which the rare earth leaching rate was 95.01%.Compared with the traditional low-temperature roasting method,the acid consumption of the experiment is less,the emission of sulfide gas is avoided,the corrosion of the equipment is greatly reduced environmentally friendly and the production cost is reduced.The monazite concentrate is a phosphate mineral composed of?Ce,Nd,La,Pr?PO₄ and radioactive thorium and uranium.It is one of the major extraction sources of light rare earth elements.Its exploitation can greatly reduce the mining of single rare earth,which is good for the conservation of rare earth mineral resources.But in the monazite separation process,environmental damage and water consumption and other issues are difficult to solve.In this paper,pure monazite concentrate as raw material is treated by caustic soda.The influence of temperature,liquid-solid ratio,time and phosphorous removal rate on the leaching rate of rare earth elements were discussed.Compared with the traditional method of liquid caustic soda and atmospheric decomposition,this process consumes less alkali and is easy to operate.In the calcinating process,the trivalent cerium in the monazite ore can be oxidized to tetravalent cerium with the oxidation rate above 95%.The rare earth Leaching rate is96%.During water washing process,the water was evaporated and crystallized to form sodium phosphate products.XRD,ICP-OES were used to characterize the phase and composition of the minerals in different period.