What do you know about the liberation characteristics of the copper minerals vs. pyrite? Is the pyrite liberated at the grind size you are using?

Do you have any water chemistry data to share?Do you have more information of the ore? If the copper is being depressed at the same time than pyrite maybe is not well liberated. Can you share more information?

I have not really looked at the liberation characteristics; I just used the plant grind size which i think the pyrite might still be locked with the copper mineral. Maybe i should take the sample of each fraction size for mineralogy analysis? No i don't have any water chemistry data; i have not looked at that.

pH: It plays a major role in process. Before changing parameters confirm from lab tests different pH Vs Recovery and grade and then fix the parameters. In plant practice actual pH will be very nearer to it. Even high pH depresses copper. Keep minimum pH and try NaCN. Even at low pH NaCN depress pyrite. You try 1st in lab and then try in plant.

Flotation of copper at different alkaline pH from 7upto 10 and using different Xanthates as collector vs. recovery of copper may give some clue. Minimum Pyrite obtained in copper concentrate is the starting point for further flotation test work. Depressing Pyrite is always a tricky matter. The non- float is naturally your Pyrite Concentrate after cleaning.

Lacking liberation you will lose copper recovery when increasing pyrite recovery. Of course that may happen to some extent in any case. Additional details would help - What are operating conditions (reagents, pH, etc.). How high was the pH, what was aeration process, etc.Is this a porphyry ore or massive sulfide, etc?

I would check your liberation as suggested previously. If you're dealing with massive (I assume chalcopyrite or other Fe bearing minerals) you'll need to ensure you're getting as much liberation as economically feasible. The same could be said for disseminated ores too. Oxidising the iron sulphide will probably reduce your recovery as it would be hard to not oxidise any of the CuS minerals. Trying to recover copper sulphides (possibly with a dash of Fe mixed in) and reject FeS2 is not a battle I would enjoy.

If your Cu minerals are reasonably free of Fe (e.g. chalcocite, covellite, cuprite which I doubt as your recovery seems to be linked to the pyrite recovery) have you considered magnetic separation?

And one for you experts as I'm not familiar with or worked with them, would spirals be able to separate the liberated Iron and the Copper minerals in the ore by the weight of the minerals? Maybe spiralling cyclone under flows! There's a little more than 1 g/cm^3 difference in their densities.

Practically followed normal trends! Sodium cyanide is the only chemical which can depress pyrite. Used in all industries for the past history. Go to Google search and type pyrite depression you get the solution.

In the work I conduct I have seen that altering the pulp chemistry can play huge roll in better selectivity against Pyrite. Typically changing media type from Forged steel to High chrome media can alter pulp chemistry to more oxidizing (or less reducing) conditions. You find your copper species have improved kinetics and the amount of iron sulfides to the concentrate is lower. Pyrite has a stronger affinity to float in reducing condition.

Using reagents, I have seen the great success with MX5149 I think from Cytec. Conducting a few tests the improvement in selectivity against Pyrite was impressive. Some mines in Zambia now only use this reagent.

AERO MX 5149 (Сytec) is a promoter. It is not a depressant for pyrite.

Read few books on net or buy them on flotation By Taggart, or buy hand book of mineral engineering or talk to Chemical suppliers Cytec, CIBA.

You are correct, that’s why I mentioned improved selectivity against Pyrite. The word promoter slipped my mind.

Aeration with Metabisulfite is another way to depress pyrite effectively. Use of NaCN is not the preferred way these days mainly due to environmental regulations and health concerns. Most concentrators would prefer a non-cyanide route to avoid permitting and various contamination issues etc. MBS is used in North and South America to depress pyrite in Cu flotation.

Cyanide suppresses pyrite. Also cyanide is depressant for chalcopyrite (and other copper sulfides). Na2S, Metabisulfite (Na2S2O5) suppresses all sulfides. CaO. At low concentrations in the solution suppresses pyrite. When the concentration in the solution suppresses chalcopyrite!

Of course, there are other depressants for pyrite (more selective). The world of the flotation reagents has changed. Now there are a lot of good new reagents on a commercial scale. 

Aeration - The surface of the pyrite oxidizes rapidly and it floated worse. At the same time at a short aeration of the pulp extraction of copper increases. With further increase in the duration of aeration copper recovery can be reduced by 10-45%.

It is hard to depress pyrite but not to depress copper minerals. I resolve my pyrite problem with changing collector type (xanthate with thionocarbamate ), more stages of cleaning and more lime. But problem with pyrite in copper ore is very, very tricky to be described in few words.

It depends on your ore type, liberation by size, operating conditions, i.e. pH, Eh, conditioning time, etc. I worked on a porphyry copper ore from Philippines before where I found that dithiophosphate worked better in depressing pyrite in the rougher stage. I experienced a copper-gold massive ore type where thionocarbamate seemed to work better. Also, SMBS is a common pyrite depressant. Dithionocarbamates are very selective in copper flotation. It will not float pyrite. Can be used at a slightly elevated pH (9). It is a common approach in copper flotation.

If promoter floats pyrite badly, it floats badly other sulfides too. For example, if you replace the butyl xanthate to thionocarbamate, recovery of pyrite will decrease by 10%, and the recovery of chalcopyrite will decrease by 5%. It is possible to choose a mixture of other promoters (or mixture of promoter with other reagents), then recovery of pyrite will decrease and recovery of chalcopyrite will increase. Of course, there are selective depressors for pyrite. Reagents are selected individually in each case. More details: http://is.gd/iWcEmO

The question posed was bound to see a number of diverse responses covering territory from change in collector, pH, Eh (i.e. pulp chemistry changes from change in media), etc. because the issue of rejecting (depressing) pyrite is complex and very ore specific. So you're best going to basics and conducting laboratory tests under different conditions with materials that work well as supposed pyrite depressants as documented in the literature. Bulatovic's "Handbook of Flotation Reagents" is an excellent start. For instance, Cytec's S-7261A depressant, napthalene sulfonates, lignosulfonates, dextrin, quebracho, etc or synergistic blend combinations of the above (and some suppliers do sell them) are a good starting point, because unlike SMBS or lime which have high dosage requirements or cyanide which has a dangerous EHS profile, these can be tested at lower dosage. Running such reagents on cleaner or regrind circuit streams also has the added advantage of using less. Needless to say the problem is tricky to get the reagent scheme and pulp chemistry optimized.

Are you sure that the problem is only pyrite? Maybe you need a Mineralogy study, because can be another type of iron sulfides, pyrrotite for example. So when you know what the mineralogy is, you can do the entire test: Grinding to liberation, improve pH to depress pyrite, improve reagents (Aero 5100 and Aero 3894 of Cytec are very selective in copper flotation) select a depressor, and all the parameters to improve your flotation.

Try Chrome balls you can run lower PH and still maintain copper recovery. Though i am just a out of work process worker.

I have been following very well and i did reply to the questions posed whether i know the mineralogy of the ore very well and if it was fully liberated at the grind size am operating at, most of all am carry out more research on the reagents that have been suggested. am so grateful and i have learned a lot from you people, my 1st step will be to check the grind size then go on to using the suggested reagents.

Good to see your reply. Thank you. Come back after knowing liberation size. It should be 80% liberated, not 100%. Or else all particles will go in to submicron size which is very tough to float.

Or Liberate in primary grinding 50 to 60%. Then liberate further in Regrind ball mill. RGBM this is more conventional method. In RGBM we have done R&D and found that open circuit gives more grade and recovery. After RGBM slurry is fed to Cyclone. Cyclone over flow will be fed to Scavenger circuit, and underflow to rougher. This process is sent for patenting in INDIA.