Process for the production of high purity silica from waste by-product silica and hydrogen fluoride

A process for the purification of silica, comprising the steps of:

• obtaining a first-purity silica containing impurities as a by-product from a wet process phosphoric acid process;
• reacting said first-purity silica with hydrogen fluoride in the presence of sulfuric acid to minimize the formation of hydrofluosilicic acid to produce a gaseous silicon tetrafluoride and a mother liquor containing said impurities;
• separating said gaseous silicon tetrafluoride from said mother liquor, said impurities remaining in said mother liquor;
• contacting the removed gaseous silicon tetrafluoride with water substantially free of impurities to form a slurry of hydrofluosilicic acid and a second-purity silica of a purity higher than said first-purity silica;
• and
• separating said second-purity silica from said hydrofluosilicic acid.

A process for increasing the purity of silica obtained from a process for preparing wet process phosphoric acid, comprising the steps of:

• reacting said silica with hydrogen fluoride in the presence of sulfuric acid to minimize the formation of hydrofluosilicic acid for an amount of time sufficient and at a temperature effective to produce gaseous silicon tetrafluoride and a mother liquor containing impurities;
• separating said gaseous silicon tetrafluoride from said mother liquor with the impurities remaining in said mother liquor;
• contacting said gaseous silicon tetrafluoride with water substantially free of impurities in a clean environment for an amount of time sufficient and at a temperature effective to form purified silica and hydrofluosilicic acid;
• separating said purified silica from said fluosilicic acid to produce a separated purified silica and hydrofluosilicic acid;
• and
• washing said separated purified silica with water substantially free of impurities to produce a washed purified purity silica.