METHOD FOR LIGNIN PURIFICATION Russian patent published in 2023 - IPC D21C11/00 

FIELD: chemical industry.

SUBSTANCE: invention is directed to a process for obtaining a purified lignin salt from alkaline waste liquor from the chemical pulping of lignocellulosic raw materials. The method includes the steps of reducing the pH value of the spent liquor to form a precipitated lignin suspension, filtering the precipitated lignin to form a filter cake containing lignin and the filtrate, admixing the filter cake containing lignin to a diluting liquid to form an alkaline lignin agglomerate colloid, carrying out an alkaline agglomerate colloid lignin by large-pore membrane filtration, and extracting the concentrate of purified lignin salt.

EFFECT: invention allows avoiding the use of finely porous ultrafiltration membranes and all the difficulties associated with them, separating a relatively pure lignin product as a result of holding lignin agglomerates on a large-pore membrane and allowing low molecular weight organic and inorganic components to pass through and thereby removing them, and avoiding acid washing and the use of sulfuric acid, which would distort the chemical balance of the pulp mill supplying the spent liquor.

14 cl, 1 dwg, 2 tbl, 2 ex