Hydrothermal conversion of chrysotile to amorphous silica or brucite

Abstract

Chrysotile (Mg₃Si₂O₅(OH)₄) was treated hydrothermally in acid or alkaline hydroxide solution. By hydrothermal treatment in 1 M HCl, HNO₃ or H₂SO₄ solution at 180°C for 48 h chrysotile changed to amorphous silica by complete extraction of magnesium component and its fibrous morphology was held in spite of changing chemical composition. The maximum specific surface area (S_BET) of the fiberous amorphous silica was 127 m²/g. It was converted to Mg(OH)₂ by complete dissolution removal of silica component in 20 M NaOH or KOH solution at 180°C for 48 h and the fiberous morphology of chrysotile disappeared.