Study on flocculation mechanism of tailings slurry in ferric chloride solution

The presence of a significant quantity of clay colloids in the tailings slurry results in an unusually sluggish consolidation process under self-weight. Therefore, containment within an artificial dam is necessary for the tailing slurry, posing a substantial hazard. It is imperative to reconsider the methods of disposing of tailing slurry due to the intricate physicochemical interactions and charged surfaces exhibited by clay colloids upon contact with water. To elucidate the mechanism of soil–water interaction in tailings slurry, a comprehensive set of macroscopic and microscopic experiments was conducted. The results from sedimentation experiments on tailings in the presence of ferric chloride at different concentrations indicate that as the concentration increases, both the initial settling rate and void ratio decrease continuously after sedimentation stabilization, accompanied by a decrease in absolute zeta potential. This phenomenon can be attributed to decreasing solution pH and increasing Fe3+ concentration with higher solution concentration, resulting in positive charges on clay particles' edge charges. Under Fe3+ influence, double-layer thickness decreases, while electrostatic forces between particles weaken. Consequently, sedimentation transitions from face-to-edge to face-to-face configuration occur, reducing aggregation diameter and porosity, which subsequently lowers both sedimentation rate and stable sedimentation porosity of the tailings slurry.