The removal of copper, lead and cadmium by apple residues (AR) was investigated to evaluate cation exchange capacities. The effects of solution pH, ionic strength, ligands and co-ions were studied in batch experiments. Apple residues were modified with phosphorus (V) oxychloride to improve their physicochemical properties and greatly enhance the capacity of metal removal. Adsorption equilibria were established rapidly initially and decreased markedly after 1 h. Column experiments were carried out in a glass column filled with AR and modified AR to evaluate the metal removal capacity. The influences of the feed concentration, chemical treatment and ligand were also studied. After exhaustion of the residues, the columns were regenerated successfully by a simple elution procedure. (C) 1998 Elsevier Science Ltd.