A kinetic model for halogenation of the zinc content in franklinite

Mohammednoor Altarawneh, Oday H. Ahmed, Mohammad Al-Harahsheh, Zhong Tao Jiang, Bogdan Z. Dlugogorski

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Electric arc furnace dust (EAFD) signifies a major source of recyclable zinc. Most of the zinc load in EAFD exists as zincite (ZnO) and franklinite (ZnFe2O4). The heterogenous mixture of EAFD renders it technologically challenging to extract the valuable zinc content in EAFD via commonly utilized hydrometallurgical and pyrometallurgical operations. Co-pyrolysis of EAFD with halogen-containing polymers (most notably polyvinyl chloride, PVC, and brominated flame retardants, BFRs) is currently deployed as a potent approach in the selective extraction of zinc from EAFD. A robust optimization of this process necessitates acquiring accurate and representative kinetic parameters of involved chemical reactions. Herein, we construct a microkinetic model that accounts the surface halogenation of zinc ions in franklinite into zinc halides (ZnCl2/ZnBr2). Governing reaction and activation energies for the dissociative adsorption of hydrogen halides and alkyl halides with a franklinite surface were computed with the DFT + U formalism. Products profiles from the constructed kinetic model are discussed in the context of literature available experimental measurements pertinent to transformation of zinc into zinc halides. The predicted temperature window for the synthesis of surface ZnCl2/ZnBr2 moieties coincides with analogous results inferred from pyrolysis experiments. Uptake of HCl and HBr by franklinite commences at 600 K and 500 K, respectively. The model satisfactorily illustrates chemical phenomena that dictate the mass loss curves in EAFD-PVC/BFRs formulations, most notably dehalogenation of halogenated alkanes, evaporation of zinc halides evaporation, and water evolution.

    Original languageEnglish
    Article number150105
    JournalApplied Surface Science
    Volume562
    Early online date18 May 2021
    DOIs
    Publication statusE-pub ahead of print - 18 May 2021

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