Iron-rich clay mineral synthesis using design of experiments approach

The precipitation of iron-rich clay minerals has been reported in various geologic environments. However, large quantities of these minerals are not widely accessible to study their thermodynamic properties and thus improve our understanding of these particular geological systems. To obtain sufficient amount of iron-rich minerals, their synthesis can be foreseen. A design of experiments and surface response methodology was used in this study to find optimum synthesis conditions for these clay minerals. Three parameters were considered: quantity of OH-, synthesis time and temperature. The quantity of OH- had the largest influence on the synthesis result. The amount of 2:1 type clay mineral with respect to 1:1 type clay mineral increased with OH/Fe molar ratio. Time and temperature had less significant impact on the synthesis outcome, yet the formation of 2:1 type phase was favored at short synthesis time (1 day) and high temperature (160 degrees C). The findings suggested that the kinetic of 2:1 type clay mineral phase formation with respect to 1:1 type phase was faster, yet the precipitation was strongly dependent on the availability of the reactants.