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Prophecy Platinum Corporation – Wellgreen Property – Project 50149-001
Due to the lack of any positive effect of talc pre-float and CMC addition, the base case (Test F3) was
shown to be the preferred one. Thus, further cleaner flotation tests were followed based on the rougher
flotation conditions of the base case.
4.1.2. Cleaner Flotation Tests
To further assess grades and recoveries of minerals into a final saleable concentrate a series of 15 batch
cleaner flotation tests was conducted, allowing grade-recovery relationships to be developed. Grade-
recovery relationships assist in understanding the extent of cleaning stages required to reach target
concentrate grade and identify stage recovery losses within the circuit. In each test, mineral assays were
estimated using the metal and sulphur assays of the products and the nominal contents of the preceding
elements in each mineral, i.e. chalcopyrite, pentlandite and pyrrhotite. As MgO is critical to concentrate
quality, tracking its deportment through particularly the cleaners, is crucial. The target is less than 5%
MgO. The ratio of Fe:MgO greater than 4.5:1 in the final concentrate would be another critical parameter.
The key flotation circuit conditions and the main results are summarized in Table 9 and Table 10 for the
batch cleaner tests and details are provided in Appendix E.
A bulk rougher concentrate was floated under conditions similar to those utilized in the rougher kinetics
testwork. The bulk rougher concentrate was then subjected to a bulk cleaner flotation, with further
additions of collector and/or depressants as required.
Tests F9-F25 attempted to establish a grade-recovery relationship for the master composite in a three
stage cleaner test. A typical flowsheet for a conventional cleaner circuit is displayed in Figure 21. The
rougher flotation scheme and reagent suite used followed that of F3. While maximum copper recovery of
88.6% was achieved in test F14, the Ni recovery was 64%. A low quality concentrate with Cu+Ni grade of
8% and 17.5% MgO was achieved in this test. Test F10 recovered the maximum Ni recovery of 65.5%,
again the grade was low and MgO high. The results are shown in Table 10.
Many of the PGM ores have a floatable silicate gangue component which is rich in MgO. The MgO is a
deleterious component in the smelting of concentrates and must be removed in the mineral processing
stage. Not all silicates that float into the concentrate are naturally floatable. Non-floatable silicates are
also recovered when they are still locked with sulphides. The distinction between the floatable silicates
and the middling-silicates is an important one and is an important issue during flotation.
The main focus of the cleaner tests was on silicates depressant effects in the cleaner circuit. Both CMC
depressant and guar gum were examined. The effect of Calgon, which has been a proven effective
dispersant on low-grade Cu/Ni ores, was also investigated. The purpose of using dispersant is to
eliminate the heterocoagulation between two different mineral particles via increasing the repulsive
interactions between them. The most commonly used dispersants are sodium hexametaphosphate
(Calgon), carboxymethyl cellulose (CMC), and gums. When added to the slurry, the dispersant adsorbs
onto the particles surfaces and leads to a very high repulsive potential energy barrier to prevent the
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