The Application of Magnetic Adsorbents in Gold Recovery

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Xia, Jinsong
adsorption , magnetic adsorbents , gold recovery
Gold is a highly valuable precious metal that plays a crucial role in both economic and technological domains. Hydrometallurgy is a widely adopted process for extracting gold from both primary ores and secondary sources. Adsorption is a popular solution purification technology used in hydrometallurgical process for gold solution concentration and recovery due to its low cost, high efficiency, and eco-friendliness. However, current gold adsorption techniques suffer from limitations such as low efficiency, poor selectivity, and solid-liquid separation problems. Magnetic adsorbents have emerged as a promising solution to overcome these challenges. This thesis presents three magnetic adsorbents that could potentially advance the gold adsorption process. In order to address the challenges of slow kinetics and solid-liquid separation associated with conventional activated carbon adsorbents, a one-pot solvothermal method was employed to synthesize magnetic activated carbon. The magnetic activated carbon synthesized through this approach displays excellent magnetism and a high specific surface area. Moreover, the magnetic activated carbon exhibited a remarkable gold recovery rate, which was considerably faster than the rate for the commercial granular activated carbon. A novel approach using magnetic iron sulfide (Fe3S4/Fe7S8) materials has been developed for the recovery of Au(III) through magnetic adsorption. Four different magnetic iron sulfide materials were synthesized using either hydrothermal or solvothermal methods, and their gold adsorption abilities were analyzed and compared. One of the materials demonstrated an exceptional adsorption capacity of 2020.7 mg/g, further tests confirmed its remarkable properties, including selectivity, magnetism, and recyclability. The adsorption-reduction mechanism was analyzed in detail using XRD and XPS analyses. A core-shell structured Fe3O4@CuS was further developed for gold recovery from chloride solution through in-situ reduction. The resulting gold-loaded adsorbent can be easily separated using an external magnet, offering advantages such as high efficiency, ease of operation, low cost, low materials consumption, and low waste generation. Results show that this adsorbent has an outstanding gold recovery efficiency and selectivity. This research shows the feasibility of using Fe3O4@CuS for efficient gold recovery, and provides insights into its adsorption behavior and mechanism.
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