What is the composition of the ore, what the present leach process is and what your leaching yield is? Is there recycling of the raffinate to increase Cu in PLS?

Oxide and sulphide concentrate of copper and cobalt. Sulphide concentrate is roasted and then send to leaching plant. Leaching is under agitated tanks and recycling of raffinate exists also.

What is your current leaching efficiency of Cu? You may consider the following parameters: Residence time: at least 2 hours, final pH 1.8 - 2, Temp. 40 deg C, the particle size should be fine as you are processing the concentrates and I assume that your agitation is OK. Are you close to these values? For Cobalt you need at least 6 hours of leaching time and 350 mV of ORP.

I agree with the residence time should be respected, 2h for copper and more or less 6 hours for cobalt because cobalt laying much of a problem after its form, if your concentrated has lots of Co3 + the residence time should be a bit long because there will be lots of reaction among other reduction etc. and this can be a time residence may even go up at 8am for a good leaching efficiency.

The raffinate also plays the role of dilution leaching; your percent solid is how much?

Please also control all incoming and unwanted waters/flows in your circuit. Be sure of all your feeding grade.

Look particularly oxide and sulphide or soluble and insoluble copper and cobalt proportion in the feed. What is the residual sulphide content of the roaster calcine? Has your plant still have residual sulphide flotation facilities? You need some characterization and microscopic (liberation) tests on the tails to determine the residual soluble metals proportion and the required residence time and reducing agent for cobalt.