More efficient adsorption media are needed for removing dissolved phosphorus in surface water runoff. We studied the use of cationized pine bark as a sorbent for dissolved phosphorus in water. Cationized pine bark was prepared by treating extracted milled pine bark with polyallylamine hydrochloride (PAA HCl) and epichlorohydrin (ECH) in aqueous medium. Attachment of PAA HCl to the bark was monitored by percentage of weight gain and nitrogen content. Changes in bark surface chemistry were characterized by zeta potential and inverse gas chromatography measurements. Energy dispersive x-ray analysis and scanning electron microscopy were used to determine changes in chemical composition and morphology of the cationized bark. The cationized bark showed a decrease in the dispersive component of the surface energy and a barely measurable change in the surface acid-base properties. In the pH range 2.5 to 7.9, the cationized bark showed a positive zeta potential, which changed to negative at pH 7.9 or higher. By comparison, the zeta potential of control extracted bark remained negative throughout the pH range of 2.5 to 9. We propose that the reaction of bark with PAA HCl results in a surface network of fixed cationic sites of quaternary ammonium that have mobile chloride ions as counter anions. Preliminary results from batch adsorption experiments indicate that cationized milled bark has an estimated maximum adsorption capacity of approximately 12.65 mg phosphate/g, which compares favorably with that of other well-known phosphorus sorbents. (C) 2004 Wiley Periodicals, Inc.