Calcium lignosulfonate is obtained from soft wood processed in sulfite pulping method for producing paper. http://www.greenagrochem.com/calcium-lignosulfonate-manufacturing-process/

1. Calcium lignosulfonate §is obtained from soft wood processed in sulfite pulping method for
producing paper.
They small pieces of softwood is put into reaction tank to react with acidic calcium bisulfite
solution for 5-6 hours under the temperature of 130 degree Centigrade. During the process the
bisulfite ions reacted with native lignin to for sulfonated lignin, that is lignosulfonate. Also the
calcium ion stabilize the anionic lignosulfonate group. After complete reaction the insoluble cello
use and soluble calcium lignosulphonate is separated by filter.
After filtration the filtrate contains some lignosulfonate, bisulfite salts and reducing agent
monomers. Thus will add into sulfuric acid then through evaporation to evaporate the water and
sulfite like sulfur oxide.
Then the filtrate will be diluted with water for further purification by ultrafiltration when the
temperature is slightly going up. Ultrafiltration is liquid /liquid separation to separate the filtrate
by a semi permeable membrane.
Then the filtrate is added into diluted sulfuric acid to adjust PH the evaporate around 100 degree
Centigrade for spray dry.