METHOD FOR TREATMENT OF BLACK LIQUOR CONTAINING NO SULFIDE

摘要

The object is to aggregate/collect lignin from a black liquor containing no sulfide discharged in the cooking process of a pulp by a water treatment technique and to remove any organic material remaining in the filtrate to collect water, an acid and caustic soda. A black liquor is added with a mineral acid and, if necessary, a distillation water to adjust to pH 1 to 7. An aggregating agent is added to the resulting solution to cause the aggregation of lignin, and then filtering off lignin. Ozone is contacted with the filtrate to cause the oxidative decomposition of an organic material in the solution, and the remaining organic material is adsorbed onto active carbon to remove the organic material.