Correlation of Surface Adsorption and Oxidation with a Floatability Difference of Galena and Pyrite in High-Alkaline Lime Systems

Abstract

When it comes to Pb-Zn ores with high amounts of pyrite, the major problem encountered is the low separation efficiency between galena and pyrite. By virtue of high dosage of lime and collector sodium diethyl dithiocarbamate (DDTC), pyrite and zinc minerals are depressed, allowing the galena to be floated. However, there have been significant conflicting reports on the flotation behavior of galena at high pH. In this context, correlation of the surface adsorption and oxidation with the floatability difference of galena and pyrite in high-alkaline lime systems would be a key issue for process optimization. Captive bubble contact angle measurements were performed on freshly polished mineral surfaces in situ exposed to lime solutions of varying pH as a function of immersion time. Furthermore, single mineral microflotation tests were conducted. Both tests indicated that the degree of hydrophobicity on the surfaces of galena and pyrite increased in the presence of DDTC at natural or mild pulp pH. While in a saturated lime solution, at pH 12.5, DDTC only worked for galena, but not for pyrite. Surface chemistry analysis by time-of-flight secondary ion mass spectrometry (Tof-SIMS) confirmed the preference of DDTC on the galena surface at pH 12.5, which contributed to a merit recovery. Further important evidence through measurements of Tof-SIMS, ion chromatography, and high-performance liquid chromatography indicated that in high-alkaline lime systems, the merit floatability of galena could exclude the insignificant contribution of elemental sulfur (S) and was dominantly attributed by the strong adsorption of DDTC. In contrast, the poor flotation response of pyrite at high pH was due to the prevailing adsorption of CaOH species. This study provides an important surface chemistry evidence for a better understanding of the mechanism on the better selectivity in the galena-pyrite separation adopting high-alkaline lime systems.

Insight on Exogenous Calcium/Magnesium in Weakening Pyrite Floatability with Prolonged Pre-Oxidation: Localized and Concomitant Secondary Minerals and Their Depression Characteristics

“…The EDS elements mapping and point analysis were proved available to schematically distinguish the distribution characteristics of secondary minerals on the pyrite surface, as they are the main source of surface oxygen element [41]. Moreover, the localized distribution of hydrophilic species means a weaker hydrophilic modification than their uniform coverage on the pyrite surface when involved in the prolonged surface precipitation of secondary hydrophilic minerals herein [12,18]. When pyrite oxidized in Ca/Mg-free solution for 360 min (Figure 4a), unoxidized areas appeared to dominate the bulk of the pyrite particle surface with sparse and patched iron oxides/oxyhydroxides.…”

“…They suggested that the Ca-bearing minerals precipitated more stably on the surface ferrous/ferric sulfates substrate via a "cementation effect" and showed a synergistic relationship with the reprecipitation of Fe-bearing species. Recent investigations of pre-oxidation treatments of pyrite considered important factors such as prolonged oxidation treatment with various oxidizing agents, and pulp chemistry including dissolved oxygen (DO), redox potential (Eh), and pH [16][17][18]. In view of the fact that the contact time of sulfide minerals with coexisting Ca 2+ and Mg 2+ will be amplified with multiple stage flotation, closed water circuits, and tailings recycling in flotation plants, the time-related interaction among Ca/Mg species and sulfide minerals should also be systematically examined [8,19,20].…”

Selective Flotation of Pyrite from Galena Using Chitosan with Different Molecular Weights

“…The contact angle test is a common method to detect the hydrophobic changes of mineral surfaces in the presence or absence of flotation reagents [40]. The wettability of the prepared pyrite and galena samples in the presence or absence of chitosan with different molecular weights at a dosage of 400 g/t was measured at pH 8.…”

Interfacial Adsorption Mechanism of Diethyldithiocarbamate in High-Sulfur Residue Flotation

“…Diethyldithiocarbamate(DDTC) 10 is a robust collector used in the sulfide ore flotation, with a strong collection ability 11 . Niu et al 12 found that DDTC could significantly improve the separation efficiency of pyrite and galena in the high-alkaline lime system. Zhang et al 13 found that adding DDTC caused desirable flotation performance in the jamesonite despite of a wide range of pH 2~13.…”