Mg2+ leaching and CO2 sequestration of magnesium tailings enhanced by external field coupled with pretreatment

The magnesium tailings, whose main phase composition is serpentine [Mg3Si2O5(OH)4], has lower reactivity than common minerals and solid waste, but rich magnesium content. It is of great significance for CO2 emission reduction and ecological environment protection to solve the problem of low leaching rate and carbon sequestration efficiency of Mg in the tailings. The strengthening effect of external field (microwave and ultrasound) and pretreatment (impregnation-calcination) on leaching of magnesium tailings and its mechanism were studied, which significantly improved the leaching efficiency of Mg(2+ )in tailings. The idea of CO2 heterophase absorption and sequestration was put forward, and the efficient of CO2 mineralization was achieved by using the leaching product, magnesium-rich leaching solution. The results showed that pretreatment of impregnation and calcination and external field (microwave and ultrasound) could promote the leaching reaction of magnesium tailings. Reaction mechanism analysis showed that microwave can accelerate the reaction rate, pretreatment and ultrasound induction can reduce the adverse effect of product layer on the reaction, and promote the leaching of Mg2+. The optimum leaching parameters (acetic acid concentration of 4 mol/L, temperature of 80 degrees C, liquid-solid ratio of 20, tailings particle size <125 mu m, microwave power of 1000 Wand ultrasound power of 500 W) were determined, and 66.64 % of Mg2+ leaching efficiency was achieved in 120 min. The CO2 heterophase absorption and sequestration method achieves high level fixation of CO2 from gas phase to solid phase at normal temperature and pressure, and forms a carbon sequestration product MgCO3 center dot 3 H2O with long-term stability.