Efficient incorporation of highly migratory thallium into struvite structure: Unraveling the stabilization mechanisms from a mineralogical perspective

The remediation of high-concentration thallium (Tl + ) contaminated wastewater is a critical environmental concern. Current research emphasizes the effectiveness of adsorption and oxidation methods for Tl + treatment, yet challenges persist in enhancing their performance. This study explores the feasibility of emergency Tl + wastewater treatment and elucidates the mechanisms of Tl + incorporation into mineral structures, with a focus on the struvite mineral as a framework for Tl + integration via NH 4 + ion exchange. To assess the efficacy and mechanisms of Tl + immobilization, we utilized comprehensive analytical techniques, including X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TG), and Density Functional Theory (DFT) calculations. The findings reveal that struvite adsorbs Tl + onto its surface, followed by an ion exchange process between monovalent cations (NH 4 + /K + ) within the structure and Tl + . Ultimately, Tl + is incorporated in the form of a (NH 4 ,Tl)MgPO 4 solid solution within the structure, achieving a remarkable maximum incorporation capacity of 320.56 mg/g, which significantly surpasses the capacity of typical adsorbents. The findings demonstrate significant Tl + incorporation, validating the approach for emergency wastewater treatment and suggesting the potential of mineralogy in environmental remediation. This research contributes to advancing heavy metal wastewater treatment strategies, offering a foundation for further investigation.