Chitosan fibers were treated with chloroacetic acid to prepare partially substituted carboxymethyl chitosan fibers. Fibers with different levels of carboxymethylation were prepared by controlling the ratio between the fiber and the amount of chloroacetic acid. The absorption properties of the modified fibers for Cu(II) ions were studied at different concentrations, temperature, time, and pH. Results showed that the carboxymethylated chitosan fibers were more effective than the original chitosan fibers in removing Cu(II) ions from aqueous solutions. (c) 2006 W.iley Periodicals, Inc.