Formation of variable-composition iron(III) hydrosilicates with the сhrysotile structure

Abstract

The process of formation of iron hydrosilicates (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was studied. It was shown that the stage of coprecipitation of magnesium and iron hydroxides in the presence of silica nanoparticles forms poorly crystallized layered Mg–Fe double hydroxides having Fe³⁺ ions in the octahedral sites. Hydrothermal treatment of the mixtures of coprecipitated hydroxides and silica nanoparticles gives rise to layered hydrosilicates, where Fe³⁺ ions occupy both the octahedral (preferentially) and tetrahedral sires. The possibility of the formation and a fairly stable existence of the variable-composition layered hydrosilicate (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was shown to correlate with the stability range of its precursor brucite-like Mg–Fe layered double hydroxide.