Leaching of lanthanides from various weathered elution deposited ores

Lanthanides adsorbed on clay minerals were easily recovered by ion exchange leaching with inorganic monovalent salt solutions under ambient conditions. The leaching efficiency (as per cent extraction) of various salts at 0.5M and 25 degrees C was investigated as a function of cation type and salt system (sulphates versus chlorides). The selected lixiviant concentration was based on a 3 : 1 stoichiometric ratio between total lanthanide content and the exchange cation. Leaching efficiency decreased in the order Cs+>NH4+>Na+>Li+, from 90% to similar to 60% respectively, with sulphates exhibiting similar to 10% higher extraction than chlorides; differences in lanthanide desorption were explained in terms of differences in cation hydration energies. (NH4)(2)SO4 was identified as the optimum lixiviant and a procedure was established to investigate the influence of temperature, pH and agitation on desorption kinetics and lanthanide extraction levels. It was determined that maximum extraction required pH below 5 and moderate temperatures (<50 degrees C).