Immobilization mechanism of As, Mn, Pb and Zn ions in sulfide tailings by the addition of triethylenetetramine-montmorillonite nanocomposite

The conventional environmental remediation materials, which are applied for the long-term treatment of mine tailings are easy to fail when affected by acid rain. Therefore, dynamic column simulation experiments were conducted to compare the immobilization persistence of As, Mn, Pb and Zn by the addition of triethylenetetramine modified montmorillonite (TTA-Mt) and calcium-based montmorillonite (Ca-Mt) in sulfide tailings during a simulated 5-year study of acid rain leaching. The structural and morphological characteristics of TTA-Mt were analyzed with FTIR, XRD, SEM, TEM and EDS. Results showed that the additions of TTA-Mt could persistently immobilize the heavy metal ions while Ca-Mt additions had little effect. After long-term simulated leaching for 5 years, TTA-Mt still had superior environmental stability for Zn and As with the immobilization rates of 96% and 86%, and the leaching amounts of Mn and Pb were less than 4.23 and 0.66 mg/kg, respectively. Morphology and chemical fraction analyses confirmed that the immobilization was mainly due to the formation of relatively stable phases by complexation and precipitation. Results presented here demonstrated the significant potential of TTA-Mt for long-term immobilization of heavy metals in tailings against acid rain and thus could provide guidance for remediation of tailings.