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Effect of flotation reagents on carbon during leaching (2 replies)

Bob Mathias
2 months ago
Bob Mathias 2 months ago

What effect do flotation reagents have on activated carbon during gold adsorption?
Do they have an effect or not? What effect do they have?

Do these flotation reagents get adsorbed onto the pore of activated carbon or form a superficial layer on the external surface of activated carbon?

2 months ago
Colette 2 months ago
2 likes by Wayne and David

Hi there Bob

I was always taught that a significant amount of organic fouling on carbon came from flotation reagents (or leaking gearboxes), and in some cases, especially with frothers and high molecular weight collectors, can severely affect kinetics.

The following papers discuss this in some detail:

La Brooy, S.R. and Bax, A.R., 1985. “The Fouling of Activated Carbon by Organic
Solvents”, Chemica 85, Paper B4C, Australian Chemical Engineering Conference,
Perth, Western Australia.

La Brooy, S.R., Bax, A.R., Muir, D.M., Hosking, J.W., Hughes, H.C. and Parentich,
A., 1986. “Fouling of Activated Carbon by Circuit Organics”, in Gold 100 (Proc. Int.
Conf. on Gold, Fivaz, C.E. and King, R.P. (eds)) Vol. 2 Extractive Metallurgy of Gold
(S. Afr. Inst. Min. Metall., Johannesburg), pp. 123-132.

La Brooy, S.R., Hosking, J.W., Muir, D.M., Ruane, M., Smith, I. and Hinchliffe, W.,
1985. “Studies on the Fouling and Regeneration of CIP Carbon”, in Proceedings of
the AusIMM Regional Conference, Gold Mining, Metallurgy and Geology, Kalgoorlie,
Western Australia, pp. 257-269.

La Brooy, S.R., 1991. “Activated Carbon Properties” in CIP and Gold Processing
Technology Workshops Course Notes, Australian Mineral Foundation Workshop
Course No. 722a, Cairns, Australia, April 1991.

My opinion regarding the location of the reagents is that it may be a combination of the two, depending on the size of the molecule in question - opinion only, I don't have back-up for this.

Paul Morrow
2 months ago
Paul Morrow 2 months ago
1 like by Wayne

Hi Bob,

It depends on the reagent. Carbon, being naturally hydrophobic, will float easily, with a frother and that could cause unwanted foam and floating of the carbon. Fuel oil based collectors will coat the carbon and this may inhibit gold collection. My experience says "Yes". Reduced carbon activity over time results, which may result in non-optimum gold-on-carbon profile through the adsorption circuit. Thus, the rate of moving carbon through the desorption/regeneration process is driven by need to keep carbon activity high, rather than gold production.
A further issue is that the off-gases from reactivation can contain some nasty organics, requiring a high temp after-burner in the flue system.
Flotation reagents are most times organic substances and they acts as organic foulants when they come in contacts with carbons. The process of flotation may however ensure that all these organic substances are washed off to ensure further recovery processes so it will be difficult for these substances to even enter the adsorption circuit.
Most flotation reagents are oil-based or organic based and may often have affinity for carbon just like gold and silver, however, depending on their polymeric chains such as frother short chains tend to break up easily. However, if a Metallurgical plant has a wash thickener where most flotation concentrates and tails get thickened up to 65% to 75%, having separated most water with the organics prior to pumping underflow solids to concentrate leaching or carbon-in-leach leaching circuits.

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