MEMBRANE PROCESS FOR CAUSTIC SODA RECYCLING

In the list of the largest volume chemicals consumed worldwide caustic soda ranks in the top ten. Sodium hydroxide is being consumed among other applications for the edible oil and fat refining, in the soap industry as well as in the beverage industry (bottle washing). Most of the caustic soda is produced by electrolysis, where for every kg of caustic 890 gramms of chlorine are produced. Recent measures of environmental protection and diminishing acceptance of products containing chloride leads to reduction in chlorine demand. Consequently, a shortage in caustic supply is unavoidable. KREBS SWISS has been engaged since some time with a new membrane process for caustic soda recycling, based on the principle of ultrafiltration resp. nanofiltration. Some fields of application are listed. Finally the way how to proceed as well as some results are presented.