Key Takeaways & Executive Findings
- •• Critical conditions for galena transformation to lead jarosite are 130°C, 30 g/L H2SO4, 15 g/L Fe3+, and 0.4 MPa O2 partial pressure. • Higher Fe3+ and O2 pressure do not enhance jarosite formation; lower temperature and higher acidity favor PbSO4 and inhibit jarosite. • Potassium, sodium, and high zinc sulfate all inhibit jarosite formation; potassium sulfate promotes potassium jarosite instead. • High zinc sulfate alters product morphology and coprecipitates with lead jarosite, affecting residue composition.
Abstract
The phase transformation of galena in H2SO4 −Fe2(SO4)3 system under oxygen pressure was investigated. Results indicated that the critical conditions for the phase transformation of galena into lead jarosite (Pb-J) were 130 ℃, 30 g/L H2SO4, 15 g/L Fe3+, and an oxygen partial pressure of 0.4 MPa. Furthermore, increased Fe3+ concentration and oxygen partial pressure did not enhance jarosite formation. Conversely, lowering the temperature and increasing the H2SO4 concentration facilitated PbSO4 formation and inhibited its further conversion to Pb-J. Additionally, the effects of potassium sulfate, sodium sulfate, and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests, XRD, SEM-EDS, and FT-IR analyses. All three sulfates inhibited the conversion of galena to Pb-J. Among these, potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite. However, high concentrations of zinc sulfate facilitated the crystallization of both PbSO4 and Pb-J, which altered the morphology of the product. Zinc ions coprecipitated with Pb-J, thereby integrating into the product.
1. Introduction
Galena (PbS), the primary commercial source of lead (Pb), is frequently associated with minerals such as sphalerite (ZnS), chalcopyrite (CuFeS2), and pyrite (FeS2) [1]. As the metallurgical industry advances rapidly, the consumption of high-quality mineral resources is on the increase, thereby leading to their gradual depletion. Therefore, there is a growing emphasis on the development and utilization of low-grade, complex non-ferrous metal ores. In China, complex sulfide minerals containing Pb, zinc (Zn), and copper (Cu) are prevalent. The primary mineral compositions of polymetallic concentrates include PbS, ZnS, tetrahedrite (Cu12Sb4S13), CuFeS2, and argentite (Ag2S) [2, 3]. China possesses abundant lead-zinc ore resources, primarily in the form of lead-zinc sulfide ore [4]. Furthermore, during grinding, the release of Cu2+, Pb2+, and Ag+ ions from fluid inclusion rupture and mineral dissolution activates sphalerite, thereby enhancing its floatability. However, the similarity in surface properties of lead-zinc minerals presents a significant challenge for their effective separation. The flotation process offers a versatile solution and enables the efficient processing of low-grade ores with finely embedded particles. It also facilitated the comprehensive recovery of co-associated lead-zinc components, thereby yielding improved beneficiation indices. The success of this approach relies heavily on the optimization of the flotation process and the selection of appropriate reagents, which are critical for achieving the effective separation of lead-zinc sulfide ores [5 −7].
Traditional roasting leaching processes for treating high Pb ores are problematic, owing to issues such as sinter and damage to fluidized bed furnaces [8]. However, the oxygen-pressure acid leaching process has emerged as a promising alternative. It offers simpler operation, environmental friendliness, higher efficiency, and lower costs [9 −11]. For instance, XU et al [12] employed oxygen-pressure acid leaching to treat Gacun complex Cu-Pb bulk concentrate (Pb: 36.85 wt%), where Pb was present as tetrahedrite and galena. The results of the pilot scale test indicated that the leaching rates of Cu and Zn were 98.9% and 94.8%, and Pb and silver (Ag) were transformed into sulfate and sulfide precipitations, respectively. CHEN et al [13] found that a layer of lead sulfate (PbSO4) and lead jarosite (Pb-J) was formed on galena, hindering its oxidation during the treatment of mixed Zn-Pb concentrates (Pb: 20.80 wt% ) through pressure leaching. XIE [14] investigated the comprehensive recovery of copper-lead-zinc polymetallic complex sulfide ores (Pb: 31.37 wt% ) through pressure leaching. The results indicated that PbS was converted to PbSO4, which remained in the leaching residue.
In summary, during oxygen-pressure leaching, galena typically precipitates as PbSO4 in the leach residue but often further transforms into Pb-J [15]. The Pb-J formation not only reduces the Pb content in the leach residue, lowering the economic value of Pb production but also produces a significant amount of less stable material [16, 17]. Annually, China
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SUN Pu, BAO Chong-jun, WANG Ji-bo, LI Xing-bin, WEI Chang, DENG Zhi-gan, LI Min-ting (2025). Phase transformation behavior of galena during oxygen pressure leaching in H2SO4-Fe2(SO4)3 system. Journal of Central South University. https://doi.org/10.1007/s11771-025-6043-y
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Frequently Asked Questions
What are the critical conditions for galena transformation to lead jarosite?
The critical conditions are 130°C, 30 g/L H2SO4, 15 g/L Fe3+, and an oxygen partial pressure of 0.4 MPa.
How do increased Fe3+ concentration and oxygen partial pressure affect jarosite formation?
Increased Fe3+ concentration and oxygen partial pressure do not enhance jarosite formation; they have no significant positive effect.
What effect do potassium, sodium, and zinc sulfates have on galena phase transformation?
All three sulfates inhibit the conversion of galena to lead jarosite. Potassium sulfate prevents lead jarosite formation and promotes potassium jarosite, while high zinc sulfate alters product morphology and coprecipitates with lead jarosite.
Why is lead jarosite formation undesirable in oxygen pressure leaching?
Lead jarosite formation reduces the lead content in the leach residue, lowering the economic value of lead production, and produces less stable material.
What analytical techniques were used in this study?
The study used leaching tests, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and Fourier-transform infrared spectroscopy (FT-IR).
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