Study On The Effect Of Roasting Activation On The Occurrence And Leaching Of Rare Earth Elements In Coal Refuse

With the development and utilization of rare earth deposits,the rare earth resources in China are facing by the dilemma of being exhausted soon.It is of profound significance to seek alternatives for rare earth deposits to improve China's national strategic security.In this paper,the evolution of occurrence state of rare earth elements in coal refuse during roasting and activation and its influence on leaching were explored by means of stepwise chemical extraction and other methods,taking the coal refuse from Jungar,Inner Mongolia,China as the research object,so as to provide theoric basic and technical support for the development and utilization of rare earth resources in coal refuse.Occurrence state of rare earth elements in coal refuse.The stepwise chemical extraction experiments showed that nearly 64% of the rare earth elements in the samples were in the form of silicate and aluminosilicate,about 25% of the rare earth elements were in the form of metal oxidation,and about 10% of the rare earth elements were in the form of organic bond,while the three forms of water soluble,acid soluble and sulfide were very few.Scanning electron microscopy-energy spectrum analysis(SEM-EDS)and correlation analysis showed that the REE was positively correlated with Al,Si and Fe,while the REE was weakly negative linear correlated with S.Evolution of occurrence state of rare earth elements during roasting activation.The stepwise chemical extraction experiments show that the roasting activation can promote the transformation of rare earth from silicate and aluminosilicate state to metal oxide state,but with the continuous increase of temperature,the metal oxidation state is transformed into silicate and aluminosilicate state again.As the roasting temperature increased from 400? to 600? to 900?,the proportion of oxidized rare earth elements increased from 25% to 76% at 600? and then decreased to 36%.The proportion of rare earth elements in organic bound states increases from 10% to 15%,which is basically stable.The proportion of rare earth elements in silicate and aluminum silicate states reduced from 64% to 8% and then increased to 46%.Thermogravimetric analysis,X-ray diffraction analysis(XRD),scanning electron microscopy-energy spectrum analysis(SEM-EDS),fourier transform infrared spectroscopy(FTIR)analysis shows that the roasting temperature of 400 ?,the sample began to intense decarboxylation reaction occurs,kaolinite start into kaolinite,600 ? when transfer reaction was basically completed,the mineral crystal lattice of rare earth elements from the basic release,and as the roasting temperature continues to rise to 900 ?,partial minerals kaolinite form not finalize the corundum.The transition from kaolinite to methacholine is the main reason for the change of rare earth element occurrence state.Leaching of rare earth elements from coal refuse products activated by roasting.Under the optimal leaching conditions(3M HCl,S/V ratio of solid to liquid 1:10,leaching temperature 90?,leaching time 3h,leaching stirring rate 300rpm),and the optimal roasting activation temperature 600?,the leaching rate of each rare earth element reached the optimal.In the roasting temperature increasing to 600?,the leaching rate of rare earth elements increases from 48% to nearly 100%,and the leaching rate nearly doubles.Roasting activation can significantly improve the leaching and extraction effect of rare earth elements in coal refuse.The paper has 34 figure,9 tables,and 118 references.