Polyethyleneimine (PEI)-conjugated-poly(glycidyl methacrylate) (PGMA) brushes were grafted onto crosslinked chitosan (CCS) microspheres for the efficient removal of Cu(II) ions from aqueous solutions.Functional PGMA brushes containing dense and active epoxy groups were firstly grafted onto the CCS microsphere surface via surface-initiated atom transfer radical polymerization (ATRP),followed by the conjugation of polyethyleneimine (PEI) to the PGMA brushes by the ring openning reaction of epoxy groups with the amino groups of PEI.Success in each functionalization step was ascertained by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR),X-ray photoelectron spectroscopy (XPS),scanning electron microscopy (SEM) and water contact angle measurements.Batch adsorption results showed that solution pH values had a major impact on copper adsorption by the PEI-c-PGMA grafted CCS microspheres with the optimal removal observed above pH 5.5.The CCS-g-PGMA-c-PEI microsphere was found to achieve the adsorption equilibrium of Cu(II) at about 0.5 h,much faster than about 4 hours on the CCS microsphere.At pH 5.5 and with an initial concentration 0.1~4.0 mmol·mL-1,the maximum adsorption capacity of Cu(II) ions,derived from the Langmuir fitting,on the PEI-c-PGMA grafted microspheres was around 2.74 mmol·g-1 at temperature of 25oC.With the inherent versatility of surface-initiated ATRP [1] and good adsorptive property of amino-group compounds,[2] the CCS microspheres can be readily functionalized with copious amino groups as adsorptive sites for enhanced adsorption capacity to heavy metal ions.