Integrated treatment of tailing material for the selective recovery of uranium, rare earth elements and heavy metals

Processed ores may contain substantial amounts of residual valuable metals. In the case of the mining wastes issued from the exploitation of gibbsite bearing shale ore in the Southwestern Sinai, the characterization of the residue shows the presence of uranium, rare-earth elements (REEs), aluminum and zinc that can be valorized. Pug leaching at 120 degrees C with an acid consumption of about 200 kg H2S4 per ton of ore succeeded in leaching more than 94% of U(VI) and REEs (in addition to substantial amounts of Al(III) and Zn(II)). A series of selective precipitation steps allowed successively recovering (almost quantitatively) Zn(II), Fe(III) and Al(III). In a second step, a magnetic resin has been used for enriching the pregnant leaching solution (by a factor close to 19) through sorption/desorption steps. In the last stage of the process, REEs were recovered by selective precipitation using 25% (w/w) oxalate solution at pH 1.5, while uranium was fully recovered by precipitation with NaOH at pH 9. Energy dispersive X-ray analysis performed on the different precipitates showed purity grades systematically superior to 93%.