Distribution and Mass Transfer Behavior of Ammonium and Rare Earth During Column Leaching of Ionic Rare Earth
The distribution behavior of ammonium and rare earth during ammonium sulfate column leaching can provide a theoretical reference for the estimation of ammonium sulfate dosage.Ammonium sulfate column leach-ing of ionic rare earth in a mining area in Dingnan,Jiangxiprovince,was carried out,and the distribution and mass transfer behavior of ammonium and rare earth at each stage were investigated by using indoor column leaching and equiproportional split sampling and analysis methods.The results indicate that the mass transfer be-havior of column leaching finally exhibits as a process of ion exchange between ammonium and rare earth ions in the stagnant water layer and the bilayer on the surface of clay particles,and mass transfer between the stag-nant water layer and the flowing water layer.During the column leaching process,a"rare earth leaching zone"would be formed in the mineral soil,which will gradually complete the leaching of the mineral soil in the col-umn with the downward penetration of the leaching solution.There may exist a vacant sublayer in the diffusion layer of the double electron layer on the surface of ionic rare earth clay particles,which adsorbs ammonium and rare earth ions during column leaching.This is the reason why the clay particles have an antisorption behavior for rare earth ions.Based on the distribution and mass transfer behavior of ammonium and rare earth a simpler method of estimating the minimum dosage of ammonium sulfate was deduced.A high rare earth leaching rate can be obtained by combining the theoretical minimum dosage of leaching agent and electrolyte drenching,and the quality of rare earth products is consistent with that by ammonium sulfate leaching alone,which is hoped to provide theoretical reference for the early resumption of production and green mining of ionic rare earth mines in Gannan area.
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