Study On Leaching Mechanism Of Weathered Crust Elution-deposited Rare Earth Ore With Ammonium Carboxylate System

The Weathered Elution deposited Rare Earth Ore is an important source of medium and heavy rare earth in China.In recent years,it has attracted the attention of experts and scholars,and its mining has high commercial value.At present,relevant experts at home and abroad have carried out a large number of research on its mechanism and industrial production,and achieved fruitful scientific research results.In view of the problems existing in the existing in-situ leaching mining methods,on the basis of reducing the amount of ammonium salt and maintaining environmental friendliness,the system of carboxylate leaching the Weathered Elution deposited Rare Earth Ore is explored,and the leaching law and mechanism of rare earth and impurity aluminum are comprehensively analyzed.Through the indoor column leaching test,the simulated in-situ leaching process was carried out.On the basis of using ammonium acetate,ammonium formate and ammonium citrate as leaching agent under the compound conditions,the effects of different leaching agent ratio,concentration,leaching temperature and initial p H on the leaching effect of weathered crust Leaching Rare Earth and the mass transfer effect of rare earth and aluminum in the leaching process were investigated,The leaching process is analyzed through leaching kinetics,which not only provides a new way for in-situ leaching of weathered crust Leaching Rare Earth Ore with high efficiency,low consumption and environmental protection,but also provides a theoretical basis for the promotion and industrial application of new leaching agents at this stage.The main research contents and results are as follows:(1)The effects of leaching agent ratio,reaction temperature,initial concentration of leaching agent and p H on the leaching effect of rare earth ions and impurity aluminum in Leaching Rare Earth in weathered crust under different carboxylate systems were investigated.The results show that the leaching rate of rare earth and aluminum can be improved by increasing ammonium concentration or leaching ambient temperature to a certain extent.Leaching under strong acid conditions can only improve the leaching rate of aluminum.The optimum process of column leaching with ammonium acetate and ammonium citrate under the compound condition is as follows: under the condition that the liquid-solid ratio is 2:1 in the column leaching simulation,adjust the molar ratio of the two carboxylates to 7:3,the ammonium concentration to 0.15mol/l,set the leaching ambient temperature to 40 ℃,and adjust the initial p H of the leaching agent to about 4.At this time,the leaching rate of rare earth can reach more than 95%.The optimum process of ammonium acetate compounding ammonium formate is as follows: molar ratio3:7,ammonium concentration 0.2mol/l,leaching temperature 50 ℃ and p H 4-6.Under these conditions,the leaching rate of rare earth can reach 90%.With the increase of the apparent leaching rate,the leaching speed also increases.It was found that the apparent leaching rate of ammonium acetate combined with ammonium formate was higher than that of ammonium citrate.(2)The leaching kinetics of rare earth and aluminum in carboxylate leaching system was studied.The leaching of rare earth and aluminum was controlled by internal diffusion kinetics.The activation energies of leaching reaction were 14.9 and 19.1kj/mol respectively,and the reaction orders of rare earth and aluminum were 0.98 and 0.79 respectively.The internal diffusion kinetic equation of temperature and concentration is established.The leaching kinetics of Leaching Rare Earth from weathered crust is studied by column leaching process,which opens a new way for leaching rare earth minerals with high efficiency,low consumption and environmental protection,which has certain guiding significance for the popularization and industrial application of new leaching agents.(3)The chromatographic tray theory is used to analyze the leaching process of ammonium acetate mixed with ammonium citrate system under different conditions.It is concluded that different carboxylate molar ratios have great differences in the leaching of rare earth and aluminum.The group with higher ammonium citrate concentration has higher rare earth concentration in the initial leaching stage.When the ratio is 1:9,HETP is the smallest and the leaching efficiency is the highest,indicating the important role of ammonium citrate in the mixed leaching agent.When the ratio is 7:3,HETP is also small,and the rare earth leaching rate is the highest.In a certain range,increasing the concentration of leaching agent and temperature will reduce HETP,so as to improve the mass transfer efficiency of rare earth and aluminum.When the p H of leaching agent is 4,the leaching speed of rare earth is fast and the final leaching rate is high.