| Ion-type rare earth ore is a unique resource in China,ammonium sulfate is used as a common method to extract rare earth elements(REEs)from ionic rare earth ore.In order to deeply understand the effect of initial p H value of leaching agent on the microstructure of ionic rare earth ores,the technological mineralogy of ionic rare earth ores before and after leaching was studied,the interfacial reactions of ionic rare earth ores during leaching under different initial p H leaching agents were analyzed,and the reaction mechanism during leaching was discussed.Based on the results of the leaching experiment,the model of zeta potential in the leaching process of ionic rare earth ore was established.First of all,in order to study the process mineralogy of ionic rare earth ore,the surface composition and structure of ionic rare earth ore before and after leaching was investigated using column leaching and different experimental techniques,such as X-ray diffraction(XRD),mineral liberation analyser(MLA),infrared spectroscopy(FT-IR),and X-ray photoelectron spectroscopy(XPS).The results show that the ionic rare earth ore is mainly composed by kaolinite,orthoclase,quartz,limonite and some other minerals,the content of REEs is about 0.12%.The relative content of Al,RE,Fe and O decrease after leaching,while some elements such as K and Si had a increase in their relative content.The main reason of the decrease of Al was due to the dissolution reaction between minerals such as kaolinite,limonite and leaching agent,and thus the structure of the ore body is partially destroyed after the leaching.While the reason why Fe decrease is because part of the iron oxide colloid was dissolved and the hydrated iron ions in the ionic rare earth ore were leached into the solution after the leaching.Minerals such as orthoclase and quartz did not participate in the reaction during the leaching process.Elemental N exists mainly in the form of organic matter in the rare earth ores.After leaching,ion exchange reaction took place in the rare earth ores.A large amount of N was present in the tailings with-NH2 bonds,and the amount of organic N was greatly reduced.The partially dissolve of the ore made Al,Fe and other element into the solution,which made the leachate contains impurities.Second,the effects of different initial p H leaching agents on the interfacial reactions of ionic rare earth ore were analyzed.The current theory is used to explain the reason for the decrease in rare earth leaching rate under high acidity.The results indicated that the leaching of rare earth elements(REEs)had a maximum at a p H value of 4.5,extracting 96.7% REEsfrom the ore.The rare earth migration experiment also indicated that the retardation of REEs reached the lowest level when p H=4.5.This phenomenon could be explained by the zeta potential experiments,which showed that the zeta potential of rare earth ore increased from negative to positive with the decrease in p H value.The increasing zeta potential weakened the adsorption of ammonium ions,and impeded the exchange of ammonium ions and rare earth ions,which decreased the REEs extraction.Third,a zeta potential model for the surface of ionic rare earth ores has been established.The calculated value of zeta potential using this model was compared with the experimental value of zeta potential measured by electrophoresis.The results show that the maximum deviation of the simulated value of zeta potential of ion-type rare earth ore at different p H values was 2.077 m V,and the maximum deviation of the simulated value of the zeta potential at different NH4+ concentration was only 2.068 m V.Therefore,thismodel can simulate the zeta potential of the ion-type rare earth ore leaching agents.In summary,this article further perfected the theory of rare earth leaching,and provided theoretical basis for rare earth leaching theory. |
PDF Full Text Request