This paper deals with the identification of low molecular weight compounds in spent chlorination liquor of kraft pulp, and the evaluation of acute toxicities of various bleaching effluents and their components. Thiolignin and holocellulose were used as the model substance of unbleached kraft pulp components.
The results are as follows :
1) The major components in spent chlorination liquor of thiolignin were oxalic acid and chloro-aliphatic acids.
2) Dichloromaleic acid and trichloroacetic acid were newly identified in spent chlorination liquors. These are originated from lignin in unbleached kraft pulp.
3) In the chlorination stage chloro-organic compounds are not originated from carbohydrate. The major components in spent chlorination liquor of holocellulose are glycolic acid and glyceric acid.
4) The toxicity of each spent liquor to Himedaka (Oryzias latipes) is in the increasing order of AP liquor (spent alkaline extraction liquor of chlorinated pulp), AL liquor (spent alkaline extraction liquor of chlorinated lignin), CL liquor (spent chlorination liquor of thiolignin), and CP liquor (spent chlorination liquor of kraft pulp).
5) Aliphatic acids, except chloromaleic acid and chlorofumaric acid, in spent chlorination liquors showed no toxicity. They are hardly responsible for the toxicity of bleaching effluents.
