The depressing effect of kaolinite on chalcopyrite and ...
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The depressing effect of kaolinite on chalcopyrite and molybdenite flotation in different aqueous media Andres Ramirez 1, 2 , Dennis Vega-Garcia 1, 2 , Leopoldo Gutierrez 1,2,* 1. Department of Metallurgical Engineering, Universidad de Concepción, Chile 2. Water research Center for Agriculture and Mining (CRHIAM), Universidad de Concepción, Chile
Transcript of The depressing effect of kaolinite on chalcopyrite and ...
The depressing effect of kaolinite on chalcopyrite and molybdenite flotation in different aqueous mediaAndres Ramirez 1, 2, Dennis Vega-Garcia 1, 2, Leopoldo Gutierrez 1,2,*
1. Department of Metallurgical Engineering, Universidad de Concepción, Chile2. Water research Center for Agriculture and Mining (CRHIAM), Universidad de Concepción, Chile
Contents
• Introduction
• Objectives
• Methodologies
• Results
• Conclusions
Introduction
• Low grades ► more tonnage, throughput ► more water is needed, thus waterreuse must be increased.
• High variability of the ores treated which requires online monitoring of processesto optimize water make up.
• Complex minerals: phyllosilicates, clay minerals ► slimes, changes in pulprheology which leads to more water consumption.
• Restrictions on the amount and type of water, new sources of water such asseawater and saline water, reuse of water.
• Water recovery from thickeners is more difficult because of the presence of fineand ultra fine particles.
IntroductionFroth zone
• Coalescence
• Bursting
• Drainage
• Stability
Collection zone
• Collision
• Attachment
• Detachment
• Upwards motion
• Gas dispersion
Bubble
Valuable particles
Gangue particles
Entrainment
Concentrate• How do clay minerals
impact the indicatedsub-processes?
Introduction
Valuable
particle
(e.g.cpy)
Valuable
particle
(e.g.cpy)
Clay mineral particles
Hydrophobic
particle
Less Hydrophobic
particle
The recovery of less hydrophobic particles is low.
Introduction
BubbleBubble
Clean bubble Clay coated bubble
Clay mineral particles
Clay coated bubbles retain fewer valuable particles.
Introduction
Bubble
Valuable
particle
(e.g.cpy)
Adhesion is affected
Introduction
Rheology
Froth zone
• Coalescence
• Bursting
• Drainage
• Stability
Collection zone
• Collision
• Attachment
• Detachment
• Upwards motion
• Gas dispersion
Bubble
Valuable particles
Gangue particles
Entrainment
Concentrate
Objectives
The objective of this work is to study the effect of kaolinite onchalcopyrite and molybdenite flotation in seawater and to evaluate theeffect of sodium hexametaphosphate (SHMP) and sodium silicate (SS)under these conditions.
Methodologies
• Micro-flotation tests, Partridge and Smith cell.
• The chalcopyrite sample (-210+63 μm) was of a high purity and was prepared fromthe mineralized rock specimens obtained from Ward`s Natural ScienceEstablishment. The XRD chalcopyrite content of the sample was 98.9 % with minoramounts of quartz (0.8%) and pyrite (0.3%).
• Molybdenite sample (-88+44 µm): it was obtained from a molybdenumconcentrate and cleaned by three stages of collectorless flotation. The purity of themolybdenite sample was 99.3%.
Methodologies
• Two different samples of kaolinite provided by the Clay Minerals Society were usedin this work, i.e., a well crystalized (kaolinite 1) and a less crystalized sample(kaolinite 2). XRD analyses indicated that both samples had more than 97 % ofkaolinite with minor amounts of anatase, and other impurities.
Results• The Figure shows the effect of kaolinite 1 and kaolinite 2
on flotation of chalcopyrite in seawater (Figure a), and thepositive effect of SHMP and SS (10 ppm in both cases)(Figures a and b).
• In seawater both tested kaolinites depress chalcopyriteflotation in the alkaline pH range over which chalcopyriteis depressed also in the tests without kaolinite.
• Depressing effect of kaolinite 2 is much more pronounced.This depressing effect of kaolinite 2 could, however, berestored by both tested dispersants (Figure c).
• The results in freshwater (not presented) indicated thatover the alkaline pH range kaolinite does not really affectflotation of chalcopyrite, and the depressing effect isclearly visible around pH 7.
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Ch
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85 % cpy+ 15 % kaolinite 2
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85 % cpy+ 15 % kaolinite 1: 10 ppm SS
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85 % cpy+ 15 % kaolinite 2: 10 ppm SHMP
85 % cpy+ 15 % kaolinite 2: 10 ppm SS
(a)
(b)
(c)
Results• The Figure shows the recovery of molybdenite in the absence and
presence of kaolinite (15%) as a function of pH, in fresh andseawater.
• The experimental data indicate that molybdenite recoverydecreases in the presence of kaolinite in both types of water but ata stronger extent in seawater.
• Figure b shows that magnesium and calcium ions have the maindepressing effects on molybdenite flotation in the presence of clays.The results show that neither sodium nor potassium increase thedepressing effect of kaolinite.
Results• The Figure shows the recovery of molybdenite in the presence of
kaolinite, with and without SHMP, and in different aqueoussolutions.
• The results obtained in seawater (a) show that molybdeniterecovery is increased in up to 35 percentage points as SHMP isadded which is more significant at pH>9.
• This effect can be observed from a dose of 20 mg/L SHMP. Figures band c show that SHMP strongly increases molybdenite recovery,effect that is more important in the case of the tests which weredone in magnesium solutions.
ResultsMechanism
Dispersantsremove thehydrophiliccoating
Conclusions
• Chalcopyrite flotation is depressed in freshwater by kaolinite at pH 7. Thisdepressed chalcopyrite flotation at pH 7 could be improved with the use ofboth tested dispersants.
• In seawater chalcopyrite is depressed in the alkaline pH range, in the absenceand presence of kaolinite. In seawater, a very strong depression at pH>9 isobserved.
• The flotation of chalcopyrite depressed by kaolinites 1 and 2 over the pH range7 to 11 could be improved with the use of SHMP and SS. The effect of thesedispersants is stronger in the case of the tests that were performed usingkaolinite 2 which is a poorly-crystallized type of kaolinite.
Conclusions
• Kaolinite depresses molybdenite flotation in fresh and seawater, but thisdepressing effect is more significant in seawater at pH>9.
• The depressing effect of kaolinite on molybdenite flotation in seawater isenhanced by magnesium and calcium hydroxo-complexes at pH>9.
• The attachment of the positively charged hydroxo-complexes of magnesiumand calcium on the molybdenite and kaolinite surfaces is diminished by SHMP.This dispersant renders the molybdenite and hydroxo-complexes ofmagnesium and calcium more negatively charged increasing the repulsiveforces, thus, molybdenite becomes more hydrophobic and recovery increases.
Acknowledgements
CONICYT/FONDAP/15130015
