IMPROVED PROCESS FOR PRODUCTION OF PURE AMORPHOUS AND HYDROPHOBIC SILICA FROM QUARTZ

摘要

Process for production of amorphous silica from quartz or other SiO2 base raw material includes the following steps: heating (calcinations step) of quartz or other SiO2 base raw material with MgCl2 or other metallic chlorides of group II in the periodic table, commonly referred to as MeCl2, at a temperature of 800 - 1300 °C wherein the weight ratio of MeCl2 to SiO2 is equal to or greater than 2 and the presence of water vapour in excess of the stoichiometric amount needed; leaching at temperatures preferable between 50 and 150 °C of the produced silicate with HCl to form a solution of MeCl2 with insoluble silica; separation of insoluble silica from the solution; recycling of MeCl2 to the heating step and the HCl solution to the leaching step; whereby hydrophobation of the silica is obtained by adding of hydrophobation chemicals, either during the leaching step prior to separation or during repulping after separation, or to a dry product. The other metallic chlorides used in the process may be such as BeCl2, CaCl2, SrCl2 and BaCl2.