Hello Lorelie,

this is a classic. Galena flotation always precedes sphalerite flotation.  The separation is done via pH control while zinc sphalerite is still inactive. Once the Pb is removed, the addition of copper sulphate will activate the zinc and allow you to float it (at a higher pH).  Your situation may vary a little but here is an example. Also see this older concept.

And this here was one the the most complex Pb/Zn separation story that ever took place (successfully).

Mill man is correct as I used this same procedure for years. Zn SO4 and cyanide in the ball mill to depress the sphalerite and pyrite, soda ash to kick the pH up a little, I used 8 to 8.5, SIPX for the rougher lead flotation, a little PAX in the scavenger circuit. After the lead flotation, Into a conditioner add lime to kick up the Ph to 10.5 - 11.0, CuSO4 to activate the sphalerite, SIPX in the rougher circuit again a little PAX in the scavenger circuit. Xanthates where also stage added as needed. I did 350 tpd day for 10 years using this differential flotation. Most of the copper and silver in the ore went with the lead concentrate. This ore was very high in pyrite, making a good zinc concentrate difficult.

Most Pb/Zn circuits will have at least a Pb regrind and often a Zn regrind. You need to test for that.

Is it okay if I put a conditioning tank in the lead circuit? Then add the reagents only in the conditioning tank?

Hi Lorelie,

the above answers are both excellent and in answer to your latest question, yes.  I have worked on two Pb/Zn plants and both utilized conditioning tanks before both the Pb and the Zn circuits.  Just ensure residence time is sufficient for the reagents to work.  Further staged addition along the floats is also usually used.

One of the plants I was on did start the pH modification in the ball milling stage and the other started pyrite depression in the ball mill.

On the grind size I would have your primary grind around the Zn liberation number, then regrind the Pb rougher product to achieve Pb liberation prior to cleaning.

If the Zn does not need additional liberation I would skip the regrind on the Zn circuit.  Cost saving step.