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Effect of excess ZnSO4 on zinc recovery? (5 replies and 3 comments)
In your comments there is not information about the additions of NaCN. The typical depressants are NaCN and ZnSO4. If you eliminate one of them, you should think it very well. SBMS works well with NaCN and ZnSO4. When there is an excessive addition of ZnSO4, it possible get a heavy layer of zinc hydroxyl species and/or zinc hydroxide on the sphalerite (zinc sulphide) surface.
The addition of copper sulphate required to get maximum recovery in the rougher stage is influenced by some factors such as the activation environment, ore type, and the type of zinc sulphide. For example, when the addition of collector is not appropriate, the floatability of zinc sulphide is affected. The pH is other point to consider. When there is not a balance between CuSO4 and Collector, the floatability of sphalerite is affected. In some cases, all the zinc rougher cells could not overflow any froth.
The type of zinc sulphide is a key factor, especially the presence of iron in the crystalline structure because the reaction between the sphalerite surface and the copper ions could be very slow.
You should a testing program to understand better your polymetallic ore. The first step is to perform kinetics tests in the lead rougher circuit to identify the appropriate dosage of depressants and collector. The addition of lime and soda ash is important to evaluate. In this way, you will know the best conditions to get a good selectivity between galena and sphalerite. When you have an acceptable performance in the lead circuit (rougher and cleaner), you should start kinetics tests in the zinc rougher circuit to evaluate the effect of pH, activator and collector.
Hi Jorge, thanks for the reply. We have a CIP circuit for the flotation tailings, so our grinding process water actually contains approx 50ppm CN-.
Without dosing ZnS04, we are actually getting good recoveries on both Pb and Zn circuit, with good selectivity. For example, we are producing a Pb con with 60% Pb/ 7% Zn, and a Zinc con with 48% Zn/ 6%Pb.
Based on this, we came to the conclusion that the only variant was the ZnS04. I would like to decrease the Zn in the Pb con to below 5%, so not sure if adding more SMBS will do the trick, or if we need to add some ZnS04, obviously without adding too much that the Zn circuit suffers.
At the moment, what is the dosage of ZnSO4? Also, it is important to know the head grade (Ag, Pb, Zn). Do you know if the pyrite content is high?
Based on the information you provided, the Pb grade reported in the zinc concentrate is relatively high, apparently, it is necessary to review any part of the lead flotation circuit. SMBS can be useful, but the mineralogy is other factor to analyze.
Can you provide some data of the lead rougher concentrate?
Hi Jorge, we are not adding any ZnSO4 currently. The head grade is approx 7%Pb / 6%Zn. Don't have access to any work files but the pyrite is not overly high.
The Pb in the Zn is definitely high, and we are working on optimising the Pb circuit by increasing Pb recovery into the Pb circuit and the Pb in the Zn con is gradually reducing. Previous mineralogy does not indicate high amounts of Pb-Zn binaries, with good liberation for both galena and sphalerite.
You can add ZnSO4 in the cleaner circuit. It is common to add NaCN too. Usually, the depressants are added in the first cell of the first or second cleaner. You can try to add a higher dosage of SMBS in the primary grind circuit. It is important to take samples every three hours to know the effect of the changes. If you add an excessive dosage of SMBS, the floatability of galena could be affected. The addition of Soda Ash to regulate the pH in the lead circuit is useful.
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Hi all, is it possible dosing excess ZnS04 to the grinding circuit to depress Zn in the Pb circuit would affect Zn recovery in the Zn circuit? On several occasions we had very poor Zn recoveries when using the reagent, and adding more than the usual amount of CuS04 doesn't seem to help. We are currently only using SMBS to depress the Zn, but does not seem to be as efficient though the Zn recoveries are good. How can one determine optimal dosages without adversely affecting downstream?