In order to better understand the leaching process of rare earth （RE） and aluminum （Al） from the weathered crust elutiondepositedRE ore, the mass transfer of RE and Al in column leaching was investigated using the chromatographic plate theory. Theresults show that a higher initial ammonium concentration in a certain range can enhance the mass transfer process. pH of leachingagent in the range of 2 to 8 almost has no effect on the mass transfer efficiency of RE, but plays a positive role in the mass transferefficiency of Al under strong acidic condition （pH〈4）. There is an optimum flow rate that makes the highest mass transfer efficiency.The optimum leaching condition of RE is the leaching agent pH of 4？8, ammonium concentration of 0.4 mol/L and flow rate of0.5 mL/min. The mass transfer efficiencies of RE and Al both follow the order： （NH4）2SO4〈NH4Cl〈NH4NO3, implying thecomplexing ability of anion.
In order to reveal the permeability rule of leaching agent solution and the effects of anions in the leaching process of weathered crust elution-deposited rare earth（RE） ores, the effects of ammonium concentration, temperature, particle size and porosity on the permeability were discussed in detail with（NH4）2SO4, NH4Cl and NH4NO3 as the leaching agent. It was found that the permeation velocity of ammonium salts increased linearly with the increase of hydraulic gradient. The seepage of ammonium salts solution in the RE ores followed Darcy’s law and displayed a laminar flow. The properties of the leaching agent solution and RE ores were the main factors that affect the permeability of RE ores. With the decrease of ammonium concentration and increase of temperature, the viscosity of solution decreased and the permeability coefficients of RE ores increased. And the effects of temperature on the viscosity and permeability were larger than ammonium concentration. The permeability of RE ores became worse with the decrease of particle size and porosity, and the particle size played a more important role compared with porosity. The permeability coefficient of RE ores increased and the viscosity of ammonium salts solution decreased in the order of（NH4）2SO4, NH4Cl and NH4NO3, implying that the penetrating power of anions increased in the order of SO42-, Cl- and NO3-. The results may play a vital role in improving the permeability of weathered crust elution-deposited RE ores.
In order to intensify the leaching process of rare earth（RE） and reduce the impurities in the leachate, ammonium chloride（NH4Cl） and ammonium nitrate（NH4NO3） were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH~＋_4Cl and NH_4NO_3, ammonium（NH_4） concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity aluminium（Al） was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could enhance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equivalent to a theoretical plate（HETP） could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1：1（molar ratio） of NH_4Cl and NH_4NO_3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL /min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant difference value（around 20 mL） of retention volume at the peak concentration between RE and Al provided a possibility for their separation. It suggested the potential application of the novel compound leaching agent（NH_4Cl/NH_4NO_3）. It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.
