A cost-effective approach to recycle serpentine tailings: Destruction of stable layered structure and solvent displacement crystallization

In this work, the stable layer structure of serpentine, which seriously restricts the extraction of magnesium, was broken down, and a nearly 94% leaching efficiency of Mg was obtained by adding 5% fluorite powder. Compared with the system without fluorite, the Mg leaching efficiency increased by 36.42%. This result was achieved because the complexation of fluorinion (F − ) with Si in serpentine promoted a distorted tetrahedral orientation, which led to a loose crystal structure of serpentine and contributed to exposing more Mg for a remarkable increase in Mg recovery. It is suggested that fluorite powder could replace expensive assisted reagents in the leaching process, which would markedly decreased the cost. Moreover, an energy-efficient “solvent displacement crystallization” (SDC) method was employed to efficiently recover magnesium (99.04%) from pregnant solutions. At the same time, the reuse of fluorine-containing solutions was explored.