Decoupling of sulfation reactions to enhance zinc extraction from electric arc furnace dust: Unveiling the significance of O2 activation and mechanistic insights

• Published in: Separation and purification technology 2025-06, Vol.359, p.130518, Article 130518
• Main Authors: Chen, Yangfan, Li, Jiangling, Gao, Meijie, Meng, Fei, Ding, Chunlian, Yang, Jian, Liu, Qiangcai
• Format: Article
• Language: English
• Subjects: EAFD; Gas–solid sulfation reactions; O2 activation; Solid–solid sulfation reactions; Zinc extraction
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.130518

•The sulfation process for EAFD was decoupled into gas–solid and solid–solid processes.•An impressive zinc extraction rate of 98.76% was achieved, with a low residual iron rate of 0.81%.•The restructuring mechanisms of sulfation during gas–solid and solid–solid roasting were unveiled.•The significant role of O2 activation in the sulfation restructuring process were revealed. Electric arc furnace dust (EAFD) is a hazardous solid waste generated during steelmaking, boasting significant concentrations of zinc and iron. Currently, a large amount of EAFD is disposed of in landfills, causing severe environmental pollution and resource wastage. To address this issue, the sulfation roasting followed by water leaching process was proposed, offering efficient zinc extraction, iron separation, low cost, and environmental friendliness advantages. This study presented a novel experimental design that decoupled the sulfation process for EAFD into gas–solid and solid–solid processes to uncover the sulfation mechanisms. During these processes, Zn-bearing phases were successfully converted into zinc sulfate (ZnSO4), while Fe-bearing phases transformed into iron oxide (Fe2O3). The resulting compounds were then separated using a water leaching process, achieving a high zinc extraction rate of 97.21% and a low iron residue of 0.61%, respectively, for the gas–solid sulfation process, and 98.76% and 0.81% for the solid–solid sulfation process. Comprehensive characterizations, in situ diffusion Fourier transform infrared spectroscopy (DRIFTS) experiments, and density functional theory (DFT) calculations provide a deeper understanding of the sulfation restructuring mechanisms in gas–solid and solid–solid roasting processes, highlighting the significant role of O2 activation. In the solid–solid sulfation process, Fe2(SO4)3, derived from the oxidation of FeSO4 by O2, was identified as the predominant compound responsible for sulfation. In the gas–solid sulfation process, sulfite species (SO32-) played a critical role as intermediates, eventually transforming into sulfate species (SO42-) with the assistance of O2. Moreover, adsorbed SO2 underwent oxidation and activation by adsorbed O2, forming the sulfate functional group. Migration of this functional group to the adjacent Zn atom through a transition state, established a Zn-SO4 bond, disrupting the Zn-O bond on ZnFe2O4 and completing the sulfation of ZnFe2O4. This study provides a fresh perspective on the application of sulfation