Wood extractives recovery from flotation of thermo-mechanical pulp process water

Wood extractives were recovered by solvent extraction from a concentrated solution obtained from flotation of TMP process water. The influence of pH, solvent polarity and the cationic surfactant dodecyltrimethylammonium bromide (DTAB) were investigated. DTAB decreased the recovery of extractives presumably by binding them at the solvent-water interface. The effect of pH on recovery of wood extractives was consistent with the dissociation of resin and fatty acids, increasing their water-solubility at alkaline pH and limiting recovery by solvent extraction. The effect of solvent polarity on extraction reflected the polarity of resin and fatty acids. Triglycerides were poorly recovered overall which can be explained by their location at the core of wood extractive colloids and by hydrophobic interaction with DTAB. Maximum recovery of wood extractives was achieved by extraction with a 60:40 mixture of ethyl acetate and heptane at pH 6 which recovered 88 %, 36 % and 10 % of the resin acids, fatty acids and triglycerides respectively.