With Fenton's reagent as the redox initiator, a granular hydrogel was prepared under ambient conditions, and then modified with polyaniline (PAN) to develop a composite adsorbent with enhanced adsorption selectivity for the heavy metals, such as the Cu-Ni system in this study. The results indicate that PAN-modified hydrogel shows decreasing adsorption kinetics, but with a comparable adsorption capacity for Cu(II). Moreover, the adsorption selectivity for Cu(II) exhibits an impressive improvement, with the selectivity coefficient (KCu-Ni) being enhanced by a factor of 6-7 (aniline:hydrogel = 1:20) for binary Cu-Ni and quaternary Cu-Ni-Cr-Zn systems. Finally, the adsorption and desorption characteristics were evaluated during multicycle adsorption processes.