Separation of Silica from Liquid Media
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.
Sodium silicate can be removed from water with AMBERSEP™ 21K XLT Strong Base Anion Resin.
For streams that have a high organic content and are prone to surface fouling, AMBERLITE™ HPR9200 Cl 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 removal of silica from salt solutions has been described using a metal-hydroxide-loaded ion exchange resin.1 AMBERSEP™ G‑26 (H) Resin is a tough and versatile cation resin for this application.
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 AMBERSEP™ IRC748 Resin in the sodium form after the brine is acidified to a pH of 2–3.
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 → H2SiCl2 + SiCl4
2 H2SiCl2 → 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.