Green sodium hydroxide for industrial purposes. A short review

Sodium hydroxide is the most common strong base used in the chemical industry worldwide. Industrially, it is produced by variations of the electrolytic Chlor-Alkali process, which have important differences in terms of environmental sustainability. We begin this review by exploring the three primary techniques linked with the Chlor-Alkali process (current traditional production of NaOH). Additionally, we carried out a comparative study considering the use of these process to obtain a sodium hydroxide with both a low carbon footprint and environmental impact (green NaOH). Moreover, alternative processes for NaOH generation or recovery are discussed, including the causticization with sodium trititanate, whose comparative parameters indicate it is the most sustainable process to produce NaOH. Furthermore, sustainable desalination, electrolysis of brine, bipolar electrodialysis membrane, and production of NaOH from coal fly ash enriched in gallium were evaluated. Electrolysis of sodium carbonate was considered as a technology under investigation. Finally, we conclude this short review with a comparative discussion on the importance of conventional technologies and the respective advances in the production of “green NaOH”.