Applications – Lead/Zinc

Product Overview

The Cu-Pb-Zn separation process is among the most challenging of flotation separations primarily because the first step must entail bulk flotation of the two most readily floatable minerals with these two minerals separated in a differential flotation stage.

As a general rule, because both copper and lead minerals tend to float well, these are usually the target bulk flotation minerals. Therefore, the standard Cu-Pb-Zn flotation practice involves an initial flotation of a Cu-Pb bulk concentrate followed by two parallel circuit stages of copper-lead separation and separate zinc flotation from the bulk flotation tails.

Zinc sulfate and metabisulfide sphalerite and pyrite depressants, respectively, are typically added to grinding. A Cu-Pb bulk concentrate is then recovered with xanthate, dithiophosphate and flotation reagent blends. Collector selection in the bulk flotation step must take into consideration the impact on the subsequent Cu-Pb separation stage where a stronger collector may not be well tolerated. Generally, the lead mineral, typically galena, readily floats.

Selection of flotation reagents and frothers 

Most often the copper minerals are floated after a galena depression. Galena is depressed using sodium dichromate, sodium sulfite, polysaccharide (starch, dextrin) or even Carboxymethyl (CMC). Addition rates of these depressants can be critical if any recirculating load is returned to the bulk rougher circuit. This flotation step is conducted at alkaline pH. In the case where galena is floated and the copper minerals are depressed, copper depression can be achieved by using sodium sulfide, hydrosulfite, lime, cyanide, zinc-cyanide and/or ferricyanide complexes.

Selection of flotation reagents and frothers is a critical consideration. The mineralogy, circuit configuration and process step goals must be accounted for when selecting the flotation reagents.