A study of magnesium dissolution from serpentinites composed of different serpentine group minerals

Abstract

An innovative approach to the acid processing of serpentinites was applied to serpentinites samples consisting largely of one or two species of the three important serpentine group minerals (Mg, Fe)3Si2O5(OH)4: chrysotile, lizardite and antigorite. The innovation lies in keeping a serpentinite sample grinded (100–200 μm) in a state of quiescence for different periods of time (0, 10, 30, 60, and 240 min) in the solution prepared by a ten-minute agitation of this sample in the boiling leach solution (95 °C) of hydrochloric acid (HCl 8–10%). The influence of this period of quiescence on serpentine minerals dissolution was judged from the amount of magnesium measured in the solution. The data derived from experimental studies have revealed that serpentinites composed of chrysotile and lizardite minerals display the higher degree of magnesium extraction in comparison to the ones largely made up of antigorite mineral. Furthermore, 30 min proved to be the period of quiescence that is sufficient for recovering up to about 97 % of the total magnesium present in serpentinites comprised of chrysotile and lizardite minerals. This study highlights the importance of identifying serpentine polymorphs constituting serpentinites in achieving higher yields of magnesium under mildly acidic conditions.