In zinc hydrometallurgical plant, neutralizing precipitation and the subsequent dissolution are implemented to enrich scattering metals, Gallium (Ga) and Indium (In), and Cu from zinc leaching solution, facilitating further extraction and separation of Ga/In and others. The formation of jarosite presents both challenges and opportunities for Ga/In extraction, as Ga/In can substitute Fe within the jarosite structure. In this work, the evolution of the Ga/In occurrence state, especially its relationship with jarosite was investigated and the role of Fe/K/Pb was emphasized. Results show that jarosite formation is inevitable at pH 1–2, with K-jarosite forming kinetically faster than Pb-jarosite. By supplying sufficient K, precipitation rates reached 95.7 % for Ga and 98.1 % for In at pH 2 with little Cu/Ge loss. Eventually, a more appropriate and efficient flowsheet for recovery of scattering metals and Cu from zinc leaching solution is recommended, providing a practical framework comprehensive utilization in zinc hydrometallurgy.
Germanium is one of the strategic scattering metals, and recovering a minor concentration of scattering metals from zinc concentrate’s leaching solution is an essential resource worldwide. Practically, neutralizing precipitation and the subsequent dissolution are implemented to enrich scattering metals from zinc leaching solution, facilitating further extraction of Ge and others. Silicon poses significant challenges to the efficient extraction of Ge due to their similar chemical property and the inert nature of silica. However, the evolution of the Ge occurrence state, especially its relationship with Si, during the precipitation and dissolution process in zinc hydrometallurgy is unclear, and there is a lack of an effective method to separate Si/Ge. This paper started with a detailed characterization and leaching behavior of Ge-enriched residue obtained from the plant, followed by a systematic investigation of Ge behavior in synthetic Si/Ge binary and Fe/Si/Ge ternary systems. Eventually, options for Ge enrichment from zinc leaching solution and Si/Ge separation are recommended, providing a practical framework for mitigating the negative influence of Si on the extraction of Ge in zinc hydrometallurgy. The significant findings are that Ge/Si are both presumably co-adsorbed by Fe(OH) 3 colloids upon neutralization to pH 5 of zinc leaching solution, which could be acid redissolved at the unrealistically high liquid-to-solid ratio of 200/1 at the practically meaningful liquid-to-solid ratio of 5/1, Si concentration is high enough to quickly condense and polymerize, resulting the formation of silica precipitate and permanent encapsulating of Ge into silica; interestingly, the Si-O-Ge bonding becomes weakened with pH increasing up to alkaline region and Ge leaching rate exceeding 80% at pH 10, effectively separating Ge from SiO 2 .
Electric arc furnace (EAF) dust is a hazardous waste material containing valuable elements, such as zinc (Zn) and iron (Fe), as well as other environmentally harmful elements. In the conventional process, the existence of zinc ferrite (ZnFe 2 O 4 ) in EAF dust results in a low recovery ratio of zinc and can induce high energy consumption or difficulties utilizing iron resources. In this article, a hydrothermal reduction method in a NaOH system is proposed to recover Zn selectively from EAF dust. First, when pure ZnFe 2 O 4 was used as the input material to test the feasibility of the new method, 70% Zn leaching efficiencies and the isolation of Fe in the residue through the formation of ferroferric oxide (Fe 3 O 4 ) were achieved at the optimal conditions of 260 °C, 6 M [NaOH], 10 g/L [C 6 H 12 O 6 ] n and 50 mL/g of L/S. Second, a leaching process of EAF dust was proposed using the following two procedures: (i) first leaching under normal pressure to dissolve zinc oxide (ZnO); and (ii) second leaching of the first leach residue under hydrothermal reduction conditions to dissolve ZnFe 2 O 4 . The leach liquor from the second step was recycled to the first step. Under optimum conditions, the leaching efficiencies of Zn during the first and second leaching were 66.4% and 69.3%, respectively. The total Zn leaching efficiency was calculated to be 89.7%, producing Zn-impregnated leach solution and a leach residue rich in Fe (up to 39.4 wt%) that are suitable as resources for a steel-making plant. However, this process also has its shortcomings owning to larger liquid-solid ratio in the leaching process. Overall, the study technically provides an alternative approach to improve the recycling of zinc and iron and effectively reduce environmental risks from EAF dust.
危险品化学品经营许可证（带存储）