Alginates are the water-soluble salts of water-insoluble alginic acids. Alginic acids form the framework of brown algae, which grow in cold seawater.
These brown algae are collected and dried by hand or mechanically. The alginic acid is converted into soluble sodium salt and extracted. These solutions are purified using filtration and decantation. There are three different methods to isolate the products:
- Precipitation as calcium alginate, washing out the calcium ions with acid,
- neutralisation of the alginic acid to obtain the desired alginate
- Precipitation of the alginic acid using sulphuric acid, neutralisation of the alginic acid to obtain the desired alginate
- Precipitation of the sodium alginate with alcohol
We obtain sodium alginate mainly from China.