Presented paper

IMWA2019 Students work

To Recycle or Not? A Bench Scale Simulation of Water Recirculation in Sulfidic Cu-Ni Ore Flotation

Manono, Malibongwe Shadrach; Corin, Kirsten Claire; Wiese, Jenny Gael
Centre for Minerals Research, South Africa

The mining industry recycles and re-uses its process water as a way of responding to the global scarcity of water. This allows the mining industry to reduce its reliance on fresh water. The recycling of water may increase the salinity of process water; this may in turn affect mineral flotation. Residual reagents may also be present in the recirculated water. A cost benefit may exist, considering that recirculated water contains residual reagents, thus lowering fresh reagent dosages.

It is thus important to mimic water recycling by performing bench scale flotation tests under various CMC dosages. The flotation tails were investigated for how long the solids took to settle before a supernatant of a recyclable quality appeared in order to mimic and assess the recyclability of water from tailings ponds and thickener overflows. The clear supernatant or filtrate from the tails was also analysed for its electrical conductivity and pH as proxies for the inorganic content of the recycled water. The du Bois method was used to determine the amount of residual CMC in the liquid supernatant that is to be recycled.

The findings of this work showed increases in the electrical conductivity of recirculated water suggesting an accumulation of ions in the recirculated water. This in turn resulted in an increase in the amount of water and solid particles reporting to the concentrate. Cu and Ni recoveries remained unchanged showing that the increase in solids recoveries was due to increases in gangue recovery and therefore a decrease in the concentrate grades. Furthermore, there was an increase in residual xanthate and CMC with each recirculation.

It is anticipated that work of this nature will give an idea of whether reductions in reagent dosages can be implemented in recirculated process water. Moreover this work seeks to determine those limits within which fresh reagent dosing would be necessary as well as limits that would prompt to the need to treat the process water before further recirculation.