The Pyrite Depression in a Copper Only Flotation circuit is simple enough.  If your froth flotation system only tries to recover chalcopyrite-copper, you need to bring the plant’s pH up to the other side (right side) of the PYRITE curve.  The more flotation collector you have on, the higher you will need to increase that pH for effective pyrite depression.  You also need to insure your pyrite and copper minerals are well liberated for good chemical separation by pH.  In froth flotation, depressing pyrite or any metal is impossible if minerals are locked.

Effective grinds-liberation and good pH targeting will let you effectively depress pyrite.

Generally, the higher you raise the pH, the less floatable sulphides become.

pH control and pyrite depression/rejection in a poly-metallic environment is different.