Farklı Flotasyon Davranımına Sahip Sfalerit Minerallerinin İncelenmesi
Özet
In flotation of Copper-Zinc complex sulfide ores, variations in Cu-Zn flotation performance are usually observed in different deposit and even in different parts of the same ore body. The reasons for these differences are generally considered as; the differences in the crystal structures and surface chemistry of the sphalerite, the chemical and mineralogical structure of the ores and activation of sphalerite in the flotation circuit, degree of oxidation of the ores (during formation and/or in the stockpile). In this thesis, the differences in surface chemistry of sphalerite mineral from Cu-Zn sulfide ores with different flotation performance were investigated. Sphalerite samples were obtained from Gediktepe Cu-Zn and Balya Pb-Zn ores for the experimental studies.
SEM-EDS and surface characterization by XPS, contact angle measurements, cyclic voltammetry tests (CV) and electrical impedance spectrometry studies (EIS) were conducted in the experimental section. Flotation tests were performed using different depressant types and mixtures. A rougher copper flotation concentrate was produced under optimum conditions (0.5 kg/t Na2S, 3 kg/t MBS, 1 kg/t ZnSO4), assaying %13,86 Cu and %5,34 Zn at recoveries of %60 and % 8, respectively.
SEM-EDS studies show that Balya sphalerite and Gediktepe sphalerite samples had different chemical structures and surface features. Cu-S like species were observed at the surface of Gediktepe sphalerite particles. The differences between the two sphalerite samples were also determined by Contact Angle and EIS tests.
A contact angle of 65° was measured with Gediktepe sphalerite in the presence of SIPX and no contact angle (0°) with Balya sphalerite. EIS test results showed that the coating resistance (Rc) of Gediktepe sphalerite increased in the presence of SIPX, on the other hand the coating resistance (Rc) of Balya sphalerite did not change significantly. Both contact angle and EIS measurements confirmed that the collector adsorbed on Gediktepe sphalerite without an activator. This was attributed to the Cu-S like species observed with Gediktepe sphalerite.
Surface characteristics of Gediktepe sphalerite were modified by using the depressants (Na2S, MBS and ZnSO4) and the activation due to the presence of Cu-S like formation was inhibited. As a result of that, the contact angle value decreased down to 40° in the presence of SIPX, a strong collector, and to 0° in the presence of a selective dithiophosphate collector, Na-AF. These results show that the dosage and the type of collectors are as important as the dosage and the type of depressants in Cu-Zn selective flotation.
XPS analysis of Gediktepe sphalerite was performed in the absence and presence of depressants. A sulphate (SO4-2) peak was observed at 168 eV when the sphalerite was treated with MBS, ZnSO4 and a mixture of Na2S+ ZnSO4+MBS. This result shows clearly that the use of depressants forms a hydrophilic and stable metal-sulphate compounds on the surface of the sphalerite, and hence the sphalerite flotation could be depressed.
Depressant molecules react with the Cu atoms in the Cu-S layers and also with the Zn atoms on the sphalerite surface. As a result of these reactions, copper and zinc sulphate compounds form on the surface of the mineral, and the sphalerite particles are depressed in the copper flotation stage.
A similar impact could be observed on the surface of the copper minerals. Therefore, the dosage of the depressants should be carefully optimized to avoid depression of the copper minerals at high dosages.
