Enhancement of acid extraction of magnesium and silicon from serpentine by mechanochemical treatment

Acid leaching of serpentine ground for various times was conducted at room temperature using 1 N HCl and 1 N H₂SO₄ solutions, respectively. Dry grinding of the ore sample by a planetary ball mill results in a structural change from a crystalline state into an amorphous one. This change is attributed to local disordering around magnesium in the structure. This disordering leads to enhancement of extraction of both magnesium and silicon from the mechanically activated serpentine by the acid solutions. Concentrations of both elements in the mother solutions increase with an increase in grinding time. More than 90% of Mg and 70% of Si in the sample ground for 240 min can be extracted by leaching, while no significant extraction is achieved in the leaching of the non-activated sample. The (Mg/Si) molar ratio in the mother solution decreases as grinding progresses. The ratio levels off under prolonged grinding and is equivalent to almost two, which is the same as that for forsterite.