what pH are you running at?

David,

pH 8-9 adjusted by soda ash.
Thank you,

Cheers,

Darrel

OK
I would not try to depress this small amount of copper. You will depress gold doing it.
I would up my pH to 10 and go.
Gold floats like copper - 10 pH is optimum.
You may need a small cleaner cell for the rougher concentrate before leaching.

What are the assays of your rougher concentrate now?

"intensive leach prior to EW process" direct or carbon/strip in between?

David,
The copper became problem since Cu content in EW cake about 25-35% and refinery regulation for Cu content max 5% in dore.
Current teratment are using sulfuric acid wash of EW cake prior to smelting.

Rougher concentrate assay about Au 50g/t, Ag 1500 g/t Cu 1200g/t. 

Direct leaching and leach rate up to 95% gold.
The problem in leach due to many froth not breaks and cyanide consumption is too high. May be because of xhantate consume the cyanide.

Could you please help me what kind of chemical to break the froth prior to leaching.

Currently I have purchase some NaHS to trial in flotation.

Thank you,

Regards,

Darrel

After reading your information, I would like to make some comments,

If the sample or samples tested in the met lab are not representative, the metallurgical performance will be different in the industrial flotation circuit.

The gold and silver mineralogy should be similar, otherwise, the precious metals recovery will be different. The mineralogy has an impact on the degree of liberation of gold and silver bearing minerals.

If the flotation feed size in the testing program and the plant are not similar, the recovery of precious metals is affected.

Other parameter to evaluate is the retention in the lab and rougher flotation circuit. The flotation time in the lab is multiplied by a factor (e.g. 2.8, 3.0) to estimate the rougher flotation in an industrial flotation circuir. Try to evaluate it.

The copper content is low for flotation, but it could be a problem in the leaching circuit. It is importnat to know the copper mineralogy. For example, if there is malachite or crysocolla, they have a low recovery by flotation, but they can contaminate the concentrate in small quantities, which could consume NaCN. The presense of secondary sulphide copper mineras such as chalcocite or covellita is a problem because they can be reported easily in the concentrate and can be leached partially by NaCN. You should know your mineralogy to know the effect of NaCN.

As with a cyanide process, copper can be a problem when looking for gold recovery.  Almost any reagent that works well with gold, we also float copper to varying degrees.  The opposite is often true also, any reagent that floats copper will also float gold and silver.  The case is also true for depressants.

The answer is then generally to make this work for you by going for a high copper recovery, which will usually allow for a good gold and silver recovery.  Then during the EW step set is up for best copper plating, whihc will often leave the gold and silver in the sludge.  The sludge can then be leached for gold recovery.

Based on your new comments, the lab performed the tests using a sample from the flotation circuit. That's good. If the lab operator did not make any mistake, you can consider the result. I don't know if the test was repeated to confirm the first result. Sometimes, it is a good practice to repeat the test to evaluate the variability.

Apparently, there is a problem in the rougher flotation circuit, I think, you should review the addition of flotation reagents. I mean, addition points, dosificaction (ml/min), reagents feeder (clarkson, pump, solenoid valve, clamp). Also, the collector preparation system (equipment and strength)

Other point to evaluate is related to the flotation cells. Maybe, there is a mechanical problem in any of them. The Maintenance Department  should provide information on the replacement of rotors and stators.

The metallurgical performance cell by cell can provide information on the recovery of precious metals cell by cell. You need to collect samples of feed, concentrator and tails. In this way, you can build a recovery curve cell by cell. It is important to collect samples 8 or 12 hours. Also, you can evaluate and confirm the retention time.