Uraninite and masuyite are the major uranium minerals, essentially fine grained, in the ores studied. Over 40% of the uranium is distributed in the -8µm fractions compared with copper, which is concentrated mainly in the +8-20µm range. Uranium is concentrated mainly in the copper ore zones, with only marginal levels in the gold-only ores. Poor liberation (due to association with copper sulphides) and entrainment are the major factors identified, which should contribute to uranium recovery in the concentrate. In this study, approximately 60% of the total uranium was recovered due to association with copper sulphides whilst 40% was via entrainment. Minimizing entrainment of liberated fine uranium particles is crucial to reduce concentrate uranium grade. Strategies such as effective froth washing and careful consideration of flotation cell hydrodynamics would be required to optimize fine U rejection.
Petrographic examinations of the ore had indicated the impracticability of attempting to concentrate the uranium by floating individual grains of uraninite. Liberation of the uraninite required grinding to sizes below those suitable for flotation. However, there was preferential association of the uraninite with some minerals while others were free of uraninite attachment. The approach to the development of a flotation process was, therefore, based upon an attempt to concentrate the uraninite by floating carrier minerals. The following paragraphs discuss the various stages of the process with regard to the factors tested and the conditions under which best results were obtained.Laboratory Flotation Characterisation of a Uranium bearing Copper ore