Transformation of Silicate Ions into Silica under the Influence of Acid on the Structure of Serpentinite

Abstract

The process of transformation of the silicate components of the crystal lattice structure of chrysotile during its quantitative interaction with aqueous solutions containing various stoichiometrically required amounts of sulfuric acid (SRA H2SO4) calculated with respect to the magnesium content in the composition of chrysotile is investigated. It has been shown by IR spectroscopic, X-ray phase, thermal and chemical methods of investigation and analysis that, with quantitative interactions of chrysotile and sulfuric acid, first of all, the “brucite layer” of the molecular structural structure of chrysotile is exposed to acid at SRA H2SO4 = 0.1–0.3. As a result of ion exchange processes, acidic silanol (≡Si–O–H) or disilanol (=Si=(O–H)2) bonds are formed. These acid groups form one-dimensional silicate chains with transverse bridges (≡Si–O–Si≡), where the angles (Si–O–Si = 180°C) straighten, which are recorded in the IR spectra in the region of characteristic absorption of 1220–1250 cm−1 silica. The association of the resulting acid groups into silicate chains, dimers, and trimers with transverse bridges, leads to the appearance of colloidal silica particles in the system, which cause some inhibition of the dissolution of layered magnesium hydrosilicate in sulfuric acid solutions containing H2SO4˃ 0.3 SRA.