Separation of Silica from Liquid Media

14

Si

Water/Wastewater

Sodium silicate can be removed from water with DOWEX™ 21K XLT Strong Base Anion Resin.

For streams that have a high organic content and are prone to surface fouling, DOWEX MARATHON™ MSA Anion Exchange Resin is recommended.

Unfortunately, silicate is very weakly ionic, so it is not selectively removed and resin capacity will be limited in the presence of most other anions. See the table of selectivity data. Removal is complicated by the polymeric forms that often occur.

Selective Silica Removal

Selective removal of silica from salt solutions has been described using a metal-hydroxide-loaded ion exchange resin1. DOWEX™ G 26 (H) Resin is a tough and versatile cation resin for this application.

Chlor-Alkali Brine

Silica (and alumina) can be present in chlor-alkali brines, interfering with the process to make pure chlorine gas and caustic soda. These impurities can be removed from brine with AMBERLITE™ IRC748i Resin in the sodium form after the brine is acidified to a pH of 2–3.

Catalysis Silane Inter-Conversation and Processing

Silanes are widely used chemicals, showing up in a variety of consumer products. Ion exchange resins are convenient tools for the production and inter-conversion of these valuable chemicals in a variety of reactions.

  • 2 HSiCl3 → H2SiCl+ SiCl4
  • 2 H2SiCl→ H3SiCl + HSiCl3
  • 2H3SiCl → SiH4 + H2SiCl2
  • Net: 4 HSiCl3 → SiH4 + 3 SiCl4

Chloro-silanes are interconverted with a weak base ion exchange functionalized resin where the tertiary amine group is believed to act as a reservoir of HCl and stabilizes the intermediate complex. AMBERLYST™ A21 DRY Resin is a chemical process-grade weak base resin with proven performance in this application.

 

1 "Method of purification of salt solution for electrolysis" by Oohara, C.; Matsuoka, T.; Kishi, T.; and Okuno, T. of Chlorine Engineers Corp., Ltd. European Patent Application EP 0 987 221 A1 (1999).

Silica is second only to oxygen in weight percentage of the Earth's crust. It is found in an enormous diversity of silicate minerals. The water soluble ionic forms of silicate are the sodium salts of the general form [SiO2(OH)2]2- but, depending on the pH and concentration, other polymerized species can also form.