Alumina nanoparticles immobilization onto the NaX zeolite and the removal of Cr (III) and Co (II) ions from aqueous solutions

•Facilitate the use and reuse of alumina nanoparticles as an adsorbent, by immobilization.•Improving the NaX zeolite performance by immobilization of alumina nanoparticles on it.•Maximizing the removal of Cr (III) and Co (II) ions from aqueous solution by optimizing the experimental conditions.•Kinetics and equilibrium studies for the removal of Cr (III) and Co (II) ions.

The immobilization of alumina nanoparticles onto the NaX zeolite granules, using the sol–gel and a physical method, for the removal of Cr (III) and Co (II) was investigated. Alumina nanoparticles immobilized zeolite (ANIZ) was characterized by SEM/EDX, XRD and AAS. The results suggested the formation of nanoscale alumina (∼30–50 nm) on the zeolite (loading ∼8–10 wt%) and the stability of the zeolite structure after the immobilization of alumina nanoparticles. ANIZ showed a good capacity for the removal of metal ions. Kinetic and equilibrium data were best fitted with the pseudo second order model and the Langmuir model respectively.