Chitin-grafted-poly(methacrylic acid) (chi-g-PMAA) was synthesized and characterized as an adsorbent of paraquat. Chi-g-PMAA copolymers were prepared using various concentrations of ammonium cerium(IV) nitrate (Ce+4) to determine the optimal concentration of Ce+4. Grafting was verified by differential scanning calorimeter thermograms, FTIR, and solid-state 13C-NMR spectra. A representative chi-g-PMAA copolymer was neutralized to a sodium salt (chi-g-PMANa) and used to adsorb paraquat. The adsorption equilibrium data are strongly related to both the Langmuir and the Freundlich isotherms. The maximal adsorption capacity is 147.0 mg/g-adsorbent. This value exceeds those of Fuller's earth and activated carbon, which are the most common binding agents that are currently used for paraquat. The results suggest that chi-g-PMANa has potential as a paraquat adsorbent. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012