The adsorption characteristics of platinum(IV) and palladium(II)from aqueous solutions onto the ethylenediamine-modified magnetic chitosan nanoparticles (EMCN) have been investigated. The magnetic chitosan nanoparticles were prepared by adding the basic precipitant of NaOH solution into a W/O microemulsion system. The transmission electron microscope showed that the diameter of EMCN was from 15 to 40 nm. The adsorption experiments indicated that the maximum adsorption capacity occurred at around pH 2.0 for both Pt(IV) and Pd(II). Due to the small diameter and the high surface reactivity, the adsorption equilibrium of Pt(IV) and Pd(II) onto the EMCN reached very quickly. The maximum loading capacity of EMCN for Pt(IV) and Pd(II) was determined to be 171 and 138 mg/g, respectively. Sorption isotherms were determined both in single component with pure metal solutions and bicomponent systems with different Pd/Pt mass ratios. The results showed that the sorbents had a greater affinity for Pt(IV) than for Pd(II). The total sorption capacity was comparable to that of each metal individually, indicating that the metals compete for the same sorption sites. It was found that 0.4 M HNO3-1.0 M thiourea solution provided effectiveness of the desorption of Pt(IV) and Pd(II) from EMCN, while 5 M ammonia exhibited the highest selectivity for the tested metal ions. (C) 2010 Elsevier B.V. All rights reserved.