Sodium lignosulfonate (lignosulfonic acid, sodium salt) is used in the food industry as a de-foaming agent for paper production and in adhesives for items that come in contact with food. It has preservative properties and is used as an ingredient in animal feeds. It is also used for construction, ceramics, mineral powder, chemical industry, textile industry (leather), metallurgical industry, petroleum industry, fire-retardant materials, rubber vulcanization, organic polymerization

Sodium Bisulfite Pulping Process

The additive (lignosulfonic acid, sodium salt),is  naturally anionic surfactant of high molecular polymer, rich in sulfo  and carboxyl group and has better water-solubility, surf-activity and dispersion capacity.Could be used for construction, ceramics, mineral powder, chemical industry, textile industry (leather), metallurgical industry, petroleum industry, fire-retardantmaterials, rubber vulcanization, organic polymerization,metallurgical industry, petroleum industry, fire-retardant materials, rubber vulcanization, organic polymerization. ,also could used as animal feed additives due to its antimicrobial and preservative properties.

The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites (SO3 2−) or bisulfites (HSO3−), depending on the pH. In this case, the counterion is Sodium (Na+). The cooking liquor is prepared by adding the counter ions as hydroxides or carbonates. The relative amounts of each species present in the liquid depend largely on the relative amounts of sulfurous used.

For Monovalent (M+) hydroxides, MOH:

MHSO3 + MOH → M2SO3 + H2O

Sulfite pulping is carried out between pH 1.5 and 5, depending on the counter ion to sulfite (bisulfite) and the ratio of base to sulfurous acid. The pulp is in contact with the pulping chemicals for 4 to 14 hours and at temperatures ranging from 130 to 160 °C (266 to 320 °F), again depending on the chemicals used.

Chief among sulfite process byproducts are lignosulfonates, which find a wide variety of industrial uses. Sodium Lignosulfonate is recovered from the spent sulfite by decanting (to remove insoluble material) and
evaporation, the latter to increase the solids content to around 50%. (The solids content of the original material recovered from the spent sulfite liquor is less than 10%.
Further processing may involve adjusting the pH and spray drying, depending on the target industrial application.

Applications of Sodium Lignosulfonate

1.Could work as plasticizer in making concrete and making concrete to maintain the ability of concrete  flow with less water.Also used during the production of cement, where they act as grinding aids in the cement mill and as a rawmix slurry deflocculant (that reduces the viscosity of the slurry).

2. Could be used in lead batteries to acts on crystallization of the lead sulfate thus increase the battery to get a much longer life-time.

3. Could used as a filler and binder in ceramic tiles, resins to fiber boards, casting sand and in fodder pellets.

4.Work as dust-suppression roads as well as in dusty processes within industry. Lignosulfonate is used as a dispersant in products like fodder, disperse pesticides, dyes,carbon black, and other insoluble solids and liquids into water.

5. Could reduce the viscosity of mineral slurries is used to advantage in oil drilling mud, where it replaced tannic acids from quebracho (a tropical tree).

6. Could be used for the production of plasterboard to reduce the amount of water required to make the stucco flow and form the layer between two sheets of paper. The reduction in water content allows lower kiln temperatures to dry the plasterboard, saving energy.

7. Lignosulphonates could work as a binder of powder and granular materials: for iron ore powder, lead and zinc powder, pulverized coal, coke Toner pressure on the ball; extrusion of cast iron, cast steel sand repression; mud-brick wall and floor tiles molding; mineral aggregate into a ball and provides high strength, good stability, lubrication and mold good results.