As for zinc, Figure 10 shows that, at 50 g/ton of chitosan, the recovery of zinc in the froth increased by 40% compared to NaCN at its optimum dosage which is undesirable in the differential flotation
of sulfide minerals where lead and copper sulfides are floated in the first flotation stages while sphalerite is depressed.
Zinc and copper concentrates are produced by differential flotation
and are sold to Zincor and O'Okiep respectively.
Complex mineralogy dictated differential flotation
. Last year was its first full year of production and output was some 50,000 t of zinc.
Start-up: 1992 Mining methods: mechanised cut and fill and longhole stoping Ore treatment: differential flotation
Production: 750,000-930,000 t/y of ore, yielding 130,000 t of zinc, 32,000 t of lead and 12,000 t of copper concentrates
Similarly seasonal variations in water quality, because of periods of drought, can also cause adverse effects on plant production and results, especially where selective or differential flotation
Until 1988 differential flotation
of the galena was carried out in this plant using ZnS[O.sub.4] and NaCN as depressors.