Removal of phenols in water using chitosan-conjugated thermo-responsive polymers

A chitosan-conjugated thermo-responsive polymer containing 15% chitosan, PNIPAAm-15CS, was used for the removal of different phenols in water. The polymer was synthesized by a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-mediated condensation of poly(N-isopropylacrylamide-co-acrylic acid) and chitosan in the aqueous solution (pH 6). At 30 degrees C. phenol, 4-methylphenol, 4-methoxyphenol, and 4-chlorophenol were converted to dark brown oxidized compounds by the tyrosinase-induced enzymatic reaction and subsequently bound to the amino moiety of PNIPAAm-15CS. In the presence of 1.0 g L-1 PNIPAAm-15CS and SO kU L-1 tyrosinase, phenols (20 mg L-1) decreased to undetectable levels (<0.01 mg L-1) within 2 h. By the vigorous mixing of the solution at 40 degrees C, the polymer deposited and became a small coagulate that can be easily taken up from water. Accompanying the polymer deposition, the oxidized compounds were completely (>98%) removed. The proposed method was successfully applied to the removal of phenols from wastewaters. (C) 2010 Elsevier B.V. All rights reserved.