Chitosan beads (CB) possesses low defluoridation capacity (DC) have been Suitably modified by carboxylation followed by chelation with Ce(III) to enhance its DC. The carboxylated chitosan beads (CCB), which has a desirable DC of 1385 mgF(-)/kg, has been further chemically modified by incorporating Ce 31 ion into CCB (Ce-CCB) and its DC was found to be 4798 mgF-/kg, whereas raw chitosan beads (CB) possesses 52 mgF-/kg only. The maximum DC of Ce-CCB was observed at pH 7 and showed selectivity toward fluoride in presence of other coanions. The sorbent was characterized using FTIR and SEM with EDAX analysis. The sorption data was fitted with Freundlich and Langmuir isotherms and kinetic models. The calculated thermodynamic parameters, viz., Delta G degrees, Delta H degrees and Delta S degrees indicate the nature of fluoride sorption. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village to test the suitability of Ce-CCB at field conditions. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1114-1121, 2009