Basic Research On The Application Of Magnesium Bicarbonate Solution In The Extraction And Separation Of Rare Earth

Solvent extraction is the most widely used process for the separation and purification of rare earth.At present,in most solvent extraction separation and purification of rare earth,ammonia,liquid alkali,etc.are used to saponify the extraction agent,so as to avoid the reducing of extraction capacity because of equilibrium acidity being too high in the extraction process.However,this saponification process will lead to the discharge of ammonia nitrogen wastewater or high-salt wastewater,and these wastewaters are difficult to meet the discharge standards.The Beijing Research Institute for Nonferrous Metals has developed a new separation and purification process with magnesium bicarbonate.In this new process,magnesium salt wastewater and CO2 are recycled to prepare magnesium bicarbonate which replaces liquid ammonia and liquid caustic to be used for saponification extraction of rare earth.This new process solves the problem of ammonia nitrogen wastewater and high-salt wastewater discharge and realizes the recycling of resources.This paper mainly studies the mechanism of related reactions in the new process system,the strike of impurity elements in the saponification extraction process,and the related chemical reaction kinetics.This paper studies the two processes of the new rare earth separation and purification process with magnesium bicarbonate.They are the saponification with magnesium bicarbonate solution process and extraction process of rare earth by P507 loaded with magnesium.The kinetics of magnesium carbonate saponing P507 and saponified P507 extracting the rare earth was systematically studied using the constant interfacial area stirred Lewis cell.The main research contents and results are as follows:(1)The kinetics of saponification of P507 by magnesium bicarbonate was studied.The effects of stirring intensity,temperature,interface area,and other factors on the saponification reaction rate were investigated.The results showed that the saponification process was controlled by diffusion and chemical reaction,and the reaction occurred at the interface of the two phases.(2)The distribution of impurity elements in the saponification process was studied systematically.Research shows that:In the process of saponification of P507 by magnesium bicarbonate,calcium and iron ions almost all enter the organic phase,while aluminum ions partially enter the organic phase and silicon hardly enters the organic phase.Of the impurities that enter the organic phase,most of the calcium and almost all aluminum enter the raffinate at the extraction stage of the rare earth,while the iron enters the final stripping solution during the stripping stage.(3)The extraction kinetics of rare earth using P507 saponified by magnesium bicarbonate was studied.The effects of stirring intensity,temperature,interface area and concentration of saponified P507 on the extraction rate were studied.The results show that the extraction process is controlled by diffusion and chemical reaction,and the extraction reaction occurred at the two-phase interface.The apparent activation energy of the reaction is 16.88 kJ/mol,and the extraction reaction is first-order reaction.The kinetic equation of the reaction is R=10-3.54[Mg(HA2)2]1.13[Nd3+].(4)The mechanism of extraction of rare earths by saponified P507 was discussed.The extraction rate equation derived from this mechanism is consistent with the experimental results.