Optimisation of mass transfer in column elution of rare earths from low grade weathered crust elution-deposited rare earth ore

An investigation was carried out to optimize the leaching and mass transfer of rare earth metals with ammonium sulfate solution during the column elution of a low grade weathered crust elution-deposited rare earth ore. The effects of flow rate, concentration of leach reagent and ore grade on the leaching performance were examined. The experimental data was analyzed using chromatographic non-equilibrium plate theory in order to elucidate the mass transfer phenomena. It was found that the relationship between the height equivalent to a theoretical plate (HETP) and the leaching flow rate can be described by the Van Deemter equation and there is an optimum flow rate in the leaching process. Compared with similar higher grade ores which have a sharp peak followed by a short tail, the leach curve of low grade ores has a long tail following a broader peak.