PHYSICOCHEMICAL PROPERTIES OF SULPHATE WASTE LIQUOR AFTER SOAP EXTRACTION IN THE PRESENCE OF SURFACTANTS

During the wood delignification a multicomponent spent liquor (black liquor) is formed. Depending on the type of wood, black liquor is enriched with valuable extractives. The isolation of extractives from processing liquors and their conversion into biologically active substances, tall products is according to development trend of pulp and paper industry. It includes the introduction of scientific based technologies in manufacturing processes with reference to modern environmental protection requirements. Now the extraction efficiency of sulphate soap does not exceed 75–80% whereby the quality of obtained soap is low. Sulphate soap, especially extracted after hardwood cooking, contains a large amount of impurities. This complicates the process of soap treatment into valuable biologically active substances (beta-sitosterol, etc.). In the present work the addition of demulsifying and coagulating substances into the black liquor is proposed to intensify the hardwood sulphate soap extraction. The chemical colloidal characteristics of the obtained sulphate soap were investigated. Two critical micelle concentration (CMC) were found on the surface tension isotherms. The second critical micelle concentration (CMC2) in the concentration range of 0.9–1.0% CMC2 indicates the restructuring of micelles into a spherocylindrical shape. A comparative qualitative and quantitative analysis of the composition of sulfate soap obtained in industrial conditions and in the presence of selected additives in laboratory was carried out. Surfactants promote the extraction of phytosterol from black liquor obtained from hardwood species cooking. The influence of surfactant addition on the main physical and colloidal chemical characteristics of black liquor before and after isolation of sulphate soap is investigated. A decrease in viscosity and a de foaming of a black liquor solution is observed as a result of the addition of surfactant additives.