•Novel chelating sponge PVA-M-H is prepared and characterized.•PVA-M-H has high adsorption capacity for Ni(II) and Cd(II).•Adsorption mechanisms of Ni(II) and Cd(II) on PVA-M-H are elucidated.•Effects of Ca2+ and Mg2+ on absorbing Ni(II) and Cd(II) are elucidated.•PVA-M-H performs perfect regeneration capacity after multiple uses. Novel chelating sponge (PVA-M-H) was prepared with polyvinyl alcohol by graft polymerization and nucleophilic substitution. E.A, SEM, FT-IR, 13CNMR, and XPS analyses were used to characterize PVA-M-H. The equilibrium adsorption capacities of PVA-M-H for Ni(II) and Cd(II) were 65.39 and 125.11mgg−1, respectively. Within the range of 278–308K, the adsorption enthalpy changes of Ni(II) and Cd(II) on PVA-M-H were about 36.39–37.72kJmol−1, and the free energy were about −13.27 to −1.7kJmol−1. Both pseudo-first- and -second-order equations fit the adsorption kinetic curves well, and the initial adsorption rates of Ni(II) and Cd(II) onto PVA-M-H were 17.83 and 34.81mg (gmin)−1, respectively. Although the presence of alkali-earth metal ions in solution decreased Ni(II) and Cd(II) removal, PVA-M-H still retained more than 60 and 80% of its adsorption capacity even as the concentration of Ca2+ and Mg2+ was up to 10mmolL−1, respectively. Both 0.1M HCl and 0.1M EDTA solution could desorb Ni(II) and Cd(II) from PVA-M-H effectively, and the adsorption capacity of PVA-M-H for Ni(II) and Cd(II) could still maintain more than 90% level without any obvious decrease at the fifth cycle.