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Sodium Cyanide in Flotation of Copper (11 replies)

Tarun Karakoti
9 months ago
Tarun Karakoti 9 months ago

I’m looking for copper concentrate plants that use sodium cyanide as a depressant for pyrite in the flotation of copper. Does anyone have experience in this case?

Rahil Khan
9 months ago
Rahil Khan 9 months ago

My experience in the case of pyrite depression is the flotation of mixed sulphide-oxide Lead & Zinc ore types like "IGhalaCi" Lead & Zinc ores. Further more the amount of much more cyanide didn't influence as much as the mixture of lime and iron sulfate. So As I saw in such these ore types, it’s better to depress pyrite by this mixture with a specific ratio of mixture. I don't know whether it will have a positive influence in your ore or not but it did work in that ore types well enough.

Marshal Meru
9 months ago
Marshal Meru 9 months ago

Yes, cyanide is used as a depressant for pyrite in copper flotation. There are however a number of alternatives such as sodium meta-bisulphite (SMBS) or a combination of lime & NaCN or lime & SMBS, soda ash and NaOH (all pH modifiers together with NaCN or SMBS). The NaCN is usually your most economic option; however you may not be able to use NaCN due to environmental constraints or legislation. Ferrous/ferric sulphate, aluminum and ferric chlorides have also been used, but I'm not aware of any commercial application.

9 months ago
Oberfuhrer 9 months ago

I have worked on two mines with copper and pyrite I do have a training manual for the floats circuit which include the use of cyanide.

David Kano
9 months ago
David Kano 9 months ago

There is a small operation in Southern Chile that uses Ferrocyanide for exactly that purpose.

9 months ago
Unterstarm 9 months ago

My experience confirmed NaCN to be a good depressant for pyrite in upgrading the copper concentrate. However if precious metals (Au and Ag) are present then sodium cyanide will leach them and decrease their recoveries within the copper concentrate. In this case it would be safer and economical to depress pyrite with lime and consider lowering the copper grade of concentrate. Obviously you need to evaluate the increase of transportation and smelting cost with the lower grade copper concentrate option.

Victor Bergman
9 months ago
Victor Bergman 9 months ago

Ok so one of the important questions that needs to be asked, is what your specific mineralogy is. There is no point trying to glean information from other projects if yours is not that same or similar. Have you done any lab tests on representative samples?

Typically CN is going to be used when there is a significantly high Py:CuS ratio that lime alone cannot deal with. Where are you on this? Also water types, liberation, presence of secondary minerals are going to play a part here. MBS is an alternative but don’t think it is environmentally any better than CN!

Bill Rico
9 months ago
Bill Rico 9 months ago

You are so logical. One needs to do the mineralogy of the ore first. Cyanide is beneficial when the pyrite is rimmed with copper. This factor is not influenced by lime. Kennecott Ely and Chino mines had this mineralogy. The Cerro Casale project in Chile has this in the outer zones of the ore body.

Sachin Prakash
9 months ago
Sachin Prakash 9 months ago

My experience for the past 25 years in Pb-Zn processing! We use Sodium cyanide at pH greater than 7. (You need to add lime to increase pH if it is less). We are operating 16000 tph plant producing Pb and Zn concentrate using Na Cn to depress Pyrite.

9 months ago
Standartenfurer 9 months ago

In Peru most of the polymetallic concentrators are using CNNa for depressing Py as well as Zn, for copper flotation most of the plants are using selective collectors to control py flotation. I think that you must know your orebody mineralogy in order to set -up your reagents.

Sugar Watkins
9 months ago
Sugar Watkins 9 months ago

I used to add cyanide to depress pyrite in the cleaner circuit. The dosage must be very small; otherwise chalcopyrite will be reported in the first cleaner-scavenger tailings. The addition should be considered when the lime is not enough to depress pyrite. For example, if the iron content changes from 8% to 24% (pyrite is the main iron mineral) you will realize that the addition of lime is not enough to depress pyrite and obtain a good copper concentrate grade. A very important aspect is to check the pH and pulp potential values. Also, it is important to determine the degree of liberation; otherwise non-liberated chalcopyrite particles would be depressed if they were associated with pyrite. The presence of high levels of secondary copper sulphides is a special case.

Bill Fraser
9 months ago
Bill Fraser 9 months ago

As Copper (chalcopyrite) is usually floated at higher pH 10.5-11. It is convenient to depress pyrite with calcium (Ca(OH)2) than sodium (CN-) because absorption of calcium ions on pyrite surface increases with the increase of pH which can cause a marked depression of it.

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