Esterification of cotton stalks with chlorosulfonic acid, phosphorus oxychloride, and their mixture was carried out with the aim to prepare cation exchangers for the removal of heavy metal ions from industrial waste water. Elemental analysis, Fourier transform infrared (FTIR) analysis, and sodium ions binding capacity were used to prove the occurrence of the esterification. The efficiency of the prepared cation exchangers to remove some heavy metal ions (strontium, arsenic, copper, and nickel) at different metal ion concentration, pH, contact time, and temperature was studied. The results showed that cotton stalks that contain both phosphate and sulfonate groups (phosphosulfonated cotton stalks) showed higher adsorption of the different heavy metal ions than cotton stalks containing sulfonate or phosphate on a separate basis. (c) 2006 Wiley Periodicals, Inc.