High-purity silica and its manufacture

Abstract

Abstract PURPOSE:To produce high-purity silica in which extremely few radioactive impurities and ionic impurities are contained by performing silica-producing reaction always in a strong acid range in manufacture of said silica by a wet process. CONSTITUTION:An aq. alkali silicate soln. (A) (for example, an aq. sodium silicate soln. of about <=20wt% concn. expressed in terms of SiO2) is allowed to react with an acid (B) (for example, sulfuric acid, hydrochloric acid) at about 50-100 deg.C under the condition wherein the concn. of free acid is always kept at about >=1N. Then, the produced silica is filtered and after washing the obtained filter cake preferably with an acid, the filter cake is washed with water, dried and crushed to produce high-purity silica wherein (i) content of radioactive impurities (uranium and thorium, etc.) is <=10ppb and (ii) content of ionic impurities [alkaline (earth) metallic ions, chloride ion and sulfate ion, etc.] is such amount that the electrical conductivity (25 deg.C) of extracted water obtained by boiling and leaching the silica is value of 100muS/cm or less.

Inventors

• 👤 Hiroyuki Matsubara
• 👤 宏之 松原
• 👤 Genichi Sato
• 👤 源一 佐藤

Bibliographic Details