Removal of lipophilic extractives from debarking wastewater by adsorption on kaolin or enhanced coagulation with chitosan and kaolin

Abstract

Finnish kaolin samples of two different size fractions, fine (<0.063mm) and coarse (<2mm), were tested as adsorbents and coagulant aids for the removal of lipophilic extractives from debarking plant wastewater. In the adsorption tests (24h, 20g/L), commercial talc (Finntalc F15) removed slightly more extractives (46%) than the fine kaolin (42%), whereas the coarse kaolin removed only 28% of the extractives. In the coagulation–flocculation studies, the chitosan coagulant alone removed 85–89% of the lipophilic extractives, the optimum dosage being in the range of 30–85mg/L based on turbidity. 87–91% of the lipophilic extractives were removed in the presence of 2 or 5g/L kaolin. However, kaolin addition improved the removal of resin acids. The charge quantity of the wastewater correlated with the required dosage of chitosan at the two different sampling times. Both the fine and coarse kaolin fraction significantly increased the settling rate of the chitosan flocs.