The use of simple analytical techniques to assess surface oxidation of sulphide ores

Abstract

• Simple, low-cost techniques can be used to indicate surface oxidation for varied ore types. • The EDTA and OCF values differed between the different ores. • The OCF and EDTA values increased with finer grinding for both ores A and B. • High reactivity translated to poor flotation recovery. Surface oxidation is known to have a negative impact on the flotation performance of sulphide minerals. This is because severe oxidation makes it more difficult to process low-grade sulphide minerals, which reduces the recovery of valuable minerals during flotation. It may be possible to quantitatively correlate the rate/level of oxidation to oxidized sulphide ores using simple surface analytical techniques. This, if done well, could eliminate the need for numerous mineralogical tests, saving both time and money. This study investigated the EDTA Extraction Technique and Oxygen consumption factor (OCF) Technique as possible techniques to quantitatively describe oxidation levels in different ore types with different mineral compositions and grades. The aim was to determine if the changes in the surface character generated by oxidation are linked to a measurement obtained from the selected techniques. The techniques were validated on fresh ores of varying grades; high grade Cu (HG Cu) and Upper Group 2 (UG2). The two ores were then ground to generate varying particle size distributions and liberation profiles to study the link between oxidation, particle size and liberation. Based on ore type and sulphide liberation, the tests attempted to provide an indicator of feed grade and surface oxidation. Flotation is used as a diagnostic for the parameters mentioned. The results showed that (for Ore A/UG2) as particle size decreased (from grind size 40 %–75 μm), the recovery increased until it hit a maximum (grind size 60 %–75 μm) before monotonically declining (to grind size 80 %–75 μm). The OCF and EDTA values increased as the grind size became finer. The grind size 80 %–75 μm had suffered significantly more oxidation than the other grind sizes and this was indicated by the high OCF and the EDTA value. The liberated base metal sulphides (BMS) for Ore B (HG Cu) was generally consistent throughout the three grind sizes, however, the highest recovery was achieved by the grind size 80 %–75 μm (95.11 %), followed by grind sizes 60 %–75 μm and 40 %–75 μm respectively (92.25 % and 90.86 %). The recovery of this ore increases as the grind size becomes finer. Ore B demonstrated a direct correlation between the OCF and EDTA value for ore B increased as the grind size became finer, and the recovery. It is possible that the particles that were ground to achieve particle size 80 %–75 μm were at their most hydrophobic state, owing to the increased liberation of the BMS, particularly chalcopyrite.