STATISTICAL MODELING OF O-2-CACL2-HCL LEACHING OF A COMPLEX U/RA/NI/AS ORE

The statistical modelling of the O2-CaCl2-HCl leaching of a high-grade arseniferrous uranium ore (Key Lake, North Saskatchewan) was studied with the objective of optimizing the co-extraction of uranium and radium. To this end, tests designed using statistical methods were carried out. These involved leaching of samples of the Key Lake ore. The optimization of U/Ra co-extraction was attempted using computer-aided response surface methodology. An incomplete three-level, four variable factorial design (Box-Behnken) was applied in the region: 0.33 kg/l less-than-or-equal-to D(s) (pulp density) less-than-or-equal-to 1.0 kg/l; 0.5 M less-than-or-equal-to [HCl]0 less-than-or-equal-to 1.5 M; 1.5 M less-than-or-equal-to [CaCl2]0 less-than-or-equal-to 3.5 M; and 2 h less-than-or-equal-to time less-than-or-equal-to 6 h. Temperature and oxygen pressure were kept constant at 68-degrees-C and 510 kPa (75 psi), respectively. Uranium and radium were found to dissolve simultaneously and rapidly (99% co-extraction in 2 h). Effective reduction of radioactivity levels from 10,000 pCi/g Ra-226 down to 160 pCi/g was achieved in a single-stage batch process.