Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Removing Dissolved Silica in Copper SX (7 replies)

David Kano
2 years ago
David Kano 2 years ago

I need to know more about silica’s impact on copper SX and best practices for dissolved silica for its removal.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

The dissolved Si would create high Aqueous Continuity Phase Disengagement Time (AC PDT) in extraction – the extractors need to run in OC and in stripping the instability of OC continuity due to its precipitation in high acidic medium – it would require more than 3 of O/A ratio to maintain the OC PDT. The solution to this would be the use of coagulant (and flocculent) prior to the PBC to precipitate it out, but this is quite tricky as the coagulant might impact the SX PDTs. The coagulant should be added first at relatively low dosage and then some flocculent to help in settling out the coagulated silica. The coagulant should also be diluted before it addition and the addition point should be in the place where there is a quite vigorous agitation.

John Koenig
2 years ago
John Koenig 2 years ago

If you can't prevent or minimize Si dissolution then call in the pros - flocculent can be as bad as Si for PDT.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

A product called Polysil ® which is being used commercially in the copper belt as well. This product coagulates colloidal silica to allow flocculent to be effective. Colloidal silica particles are extremely small and therefore not amenable to flocculation. Although these particles are small, they are very numerous which can result in major problems with phase separation and entrainment losses. As mentioned it is easy to overdose flocculent/coagulant, and depending on the product used it can cause other problems. However, this product is quite safe to use and cannot be overdosed due to the nature of the coagulant.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

The better solution is to minimize the Si dissolution in avoiding the direct contact of concentrated acid with ore at leaching. The conc. acid should be diluted in the raffinate stream before being pumped to leaching tanks…Otherwise when “dosed correctly” the use of the combination coagulant – flocculent can help.

Ace Levy
2 years ago
Ace Levy 2 years ago

I have had success using a combined treatment of two different coagulation agents on two separate operations going back 14 years ago. It worked by tying up the silica so it did not react in SX. It did not take off as the conferences of the time and "experts" were all too focused on religiously promoting Spintek filters, and were not open to any other suggestions. A paper was presented at Alta in Brisbane on the discovery. I believe the patent on the discovery has expired now, so you are free to use it. Be wary of using just any coagulant/flocculent, as some will react with the organic. You also need good dose control and technical support as overdosing will cause other issues.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

In our SX the PLS feed is 1000 to 2000 gpl SiO2, we have the problem of the PDT in AC but in OC is right 120 seconds, we run all SX stage in OC to solve this problem. The PLS feed prepare every day content 1200 gpl SiO2 and the free acid it's very high 18 gpl, before this solution feed we spray on copper ore heap dolomites after we collect the solution where the SiO2 is removed 50 percent means 600 gpl SiO2 and the free acid is down.

Marshal Meru
2 years ago
Marshal Meru 2 years ago

Dissolved silica is a kind of disease in copper belt in DRC,its impact on SX operation is terrible and mainly when the ore does contain a lot of silica species and processed by agitation leach 

patty is right in saying that no conc. acid should not be added directly in contact with ore and dilute through another stream such raffinate.
Any coagulant to be used need to be prior tested for SX operations compatibility as in some plant trial end up with issue of PDTs
Dissolved silica has also impact on equipment like dual media filter, also in EW it polymerized due to high acid in spent and causes copper quality.

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