Investigation of the adsorption performance and mechanism of multi-source mineral composite calcination materials on heavy metal ions

To address the challenges of plume generation and the release of heavy metal ions caused by deep-sea mining operations, this study utilized multi-source minerals, including steel slag (SS), oceanic manganese nodules (OMN), attapulgite (AT), and sawdust (SD), to fabricate a multi-source mineral composite calcination material (MMCCM) through a sintering process, and then the preliminary heavy metal ion adsorption experiment was carried out. The results indicated that both Langmuir and Freundlich models can describe the adsorption behavior of Cu2+ in a single system, while the Freundlich model was more applicable in competitive systems. The adsorption of Co2+ and Ni2+ consistently aligned with the Langmuir model across all systems. The adsorptive behavior conformed to pseudo-second-order kinetics, indicating that chemisorption played a leading role. The intraparticle diffusion was the principal rate-limiting step, and the adsorption process was spontaneous. BET, TGDTG, SEM-EDS, XRD, FT-IR and XPS elucidated that surface physical adsorption, ion exchange, complexation with functional groups, electrostatic attraction, and co-precipitation, which were the predominant adsorption mechanisms for MMCCM. Evaluations of regenerability, economy, security, and suitability demonstrated that MMCCM is an eco-friendly adsorbent, which provides materials and data support for future heavy metal marine sewage treatment, especially for immobilizing heavy metal in deep-sea sediments.