Chitosan-conjugated thermo-responsive polymer for the rapid removal of phenol in water

Chitosan-conjugated thermo-responsive polymers (PNIPAAm-CSs) containing 2.0-8.7% (w/w) chitosan were readily synthesized by the condensation of chitosan and poly(N-isopropylacrylamide-co-acrylic acid) with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. PNIPAAm-CSs were water-soluble at 30 °C, while they deposited above the lower critical solution temperature (LCST, ca. 34 °C in 50 mM sodium phosphate, pH 6.8). Tyrosinase-induced phenol oxidation was performed in the dilute aqueous polymer solution at 30 °C for the rapid binding of oxidized compounds to the amino moiety of PNIPAAm-CS. By heating and shaking the solution, the polymer containing highly concentrated oxidized compounds deposited and agglutinated to a condensed coagulate. Increasing polymer concentration and chitosan content in the polymer increased the removal of phenol and its oxidized compounds. When 1.0 g of PNIPAAm-CS containing 8.7% chitosan was employed for treating 1 l of contaminated water, the concentration of phenol (19 mg l−1) was reduced below the detection limit (0.08 mg l−1) within 2 h.