Composition and enrichment of sulphide copper ore
For successful flotation of copper ore sulphides, their surface is hydrophobized by sulphydryl collectors (xanthates, aeroflots).
On the sulfide surface, sulfur oxidation processes must be maintained to ensure chemical fixation of xanthate anions. The anions thus enter the mineral's crystal lattice, bonding with metal ions. This fixation is mosaic in nature and manifests itself to a greater extent in the most active areas of the energetically heterogeneous surface of minerals.
After such treatment, compounds of the following type are formed on the surface of sulfides:
MeSO 4 + 2C 2 H 5 OCSSNa = (C 2 H 5 OCSS) Me + 2Na + + SO 4 2-
The most important copper sulphide minerals are: chalcopyrite, chalcocite, covellite, bornite. Chalcopyrite is the main and most common mineral. The remaining minerals are secondary, having undergone oxidation (reduction) in the deposit.
Chalcopyrite (CuFeS2) is one of the most important copper minerals. It is associated with gold and silver. Chalcopyrite is prone to overgrinding. Some hydrophobicity is inherent in the newly formed surface of chalcopyrite. Chalcopyrite is able to adsorb oxygen, which increases its flotation activity. However, with prolonged oxidation, the surface of chalcopyrite is covered with iron hydroxide, which then manifests itself in the deterioration of flotation properties. In neutral and slightly alkaline environments, it remains hydrophobic for a long time.
- At pH > 10 it begins to oxidize with the formation of ions SO 42- , S 2 O 32- , S 4 O 62– .
- In a slightly acidic environment at pH = 6, it oxidizes, and Cu 2+ , Fe 2+ , SO 42- ions pass into the solution .
Chalcopyrite is floated by xanthates, aeroflots, and mercaptans.
Depressed:
- In Cu – Pb flotation with cyanides
- When separating Cu-Mo concentrates with excess sodium sulfide.
To separate Cu-Pb concentrates, chromates, sulfite (Na2SO3), and hyposulfite (Na2S2O3) are used, which do not affect chalcopyrite.
Chalcocite (Cu2S) is prone to overgrinding. Associated elements are silver, gold, cobalt, nickel, iron, arsenic. Good flotation is provided by xanthates.
Depressants: cyanides, sodium sulfide (Na2S), hyposulfite, sodium sulfite (Na2SO3), lime at high consumption. This mineral is easily oxidized, with copper ions passing into the pulp, which activate sphalerite and pyrite. Its presence complicates the separation of copper minerals from zinc ones.
Covellite (CuS) occurs as thin coatings of bright blue color, easily slimed. Characterized by the presence of Cu+ and Cu2+, S2- and S22- ions. In flotation properties, it is close to chalcocite.
Bornite (Cu5FeS4) is between chalcocite and chalcopyrite in flotation properties. It is depressed by cyanides.
Pyrite (FeS2) is the most common sulfide mineral. Associated elements: copper, gold, silver, etc. Oxidizes fairly quickly. Active absorption of oxygen during grinding entails the formation of highly soluble compounds with ions SO42 -, S2O32 -, SO32 - on its surface.
During oxidation, a film of iron hydroxide Fe(OH)3 is formed on the surface of pyrite. As a result, sharp hydrophilization and depression occur. In an alkaline environment, this reaction proceeds very actively. The reaction of pyrite depression proceeds as follows. First of all, pyrite interacts with oxygen, as a result of which compounds are formed that are highly soluble in water. When interacting with lime, an exchange reaction occurs, as a result of which a poorly soluble compound of iron oxide hydrate is formed on the surface of pyrite.
Pyrite is easily floated by xanthates and aeroflots at pH = 6–7. In an alkaline environment, flotation deteriorates. Aeroflots (R 2 O 2 PSSMe) are worse adsorbed on pyrite than on copper minerals, which is used in the selective flotation of copper-pyrite ores.
Pyrite depressants are alkalis and cyanides. Lime has found wide application as a pyrite depressant. Potassium permanganate (KMnO4), chromates (K2CrO4), and dichromates (K2Cr2O7) depress pyrite. Hot starch treated with sulfuric acid selectively depresses pyrite.
Pyrite activation occurs in an acidic environment.
Depending on the type of ore, the phase composition of copper minerals and the size of their inclusions, concentrates containing 12 to 40% copper or more can be obtained. The quality of the concentrate in terms of copper and impurity content is regulated by the relevant standards and specifications.
