Deciphering the transport, retention, and mechanisms of stabilized sulfidated microscale zerovalent iron for in situ remediation of vanadium (V)

Vanadium (V) pollution in underground water is continuously aggravated by the improper disposal of tailings, and microscale zero-valent iron (mZVI) after sulfidation and stabilization have been considered as a promising strategy to eliminate V(V) pollution. However, the transport and retention of mZVI after sulfidation and stabilization in porous media have not been elucidated, which is of significance to the practical application. Therefore, this study aimed to decipher the migration mechanism of sulfidated and xanthan gum-stabilized mZVI (SmZVI@XG) and evaluated its remediation performance for V(V). The introduction of XG substantially enhanced the stability of S-mZVI due to the formation of viscous polymer matrix via steric resistance and electrostatic repulsion. In contrast to the 79.3 % settling of S-mZVI at 10 min, the settling of S-mZVI@XG was only 12 % at 2 h. The transport of S-mZVI@XG was strongly affected by the grain size of porous media, flow rate of underground water, and ironic strength. S-mZVI@XG exhibited a 65.58 % effluent rate with a maximum transport distance of 447.9 cm in coarse sand and under flow rate of 10 m center dot d-1 and ionic strength of 10 mM. The retention mechanism of S-mZVI@XG in saturated porous media was mainly attributed to the interception. Besides, S-mZVI@XG possessed a greater performance for remediation of V(V) than S-mZVI, particularly for actual underground water. The findings could provide theoretical and technical insights into the practical application of mZVI materials for in situ remediation of V(V) pollution.