Hydroxysodalite nanoparticles (ZW5, ZW10, ZW15, and ZW20) with different crystallite sizes (46.43, 54.98,
62.69, and 64.12 nm, respectively) were hydrothermally synthesized from an aluminum waste. Also, different
mmoles of sodium metasilicate pentahydrate as a silicon source (23.58, 47.17, 70.75, and 94.34, respectively)
were utilized. In addition, chitosan composites with hydroxysodalite nanoparticles were synthesized (CZW5,
CZW10, CZW15, and CZW20). XRD, EDS, and FT-IR were utilized to recognize the synthesized products and
their functional group. Besides, FE-SEM and BET techniques were utilized to recognize the morphology and
surface textures of the synthesized products. Moreover, Ni(II) and Pb(II) ions were successfully separated from
aqueous solutions using the synthesized products. The atomic absorption spectrophotometer was used for the
quantitative determination of Ni(II) and Pb(II) ions before and after the adsorption processes. In the case of Ni
(II), the maximum adsorption capacities of ZW5 and CZW5 were 7.74 and 10.21 mg/g, respectively. But, their
values in the case of Pb(II) were 12.41 and 17.85 mg/g, respectively. The kinetic study proved that the pseudosecond-
order and intra-particle diffusion models are more convenient to describe the adsorption of Ni(II) or Pb
(II) ions using ZW5 or CZW5. Besides, equilibrium study proved that Langmuir isotherm greatly exceeded
Freundlich in the description of the adsorption processes. Moreover, reusability study proved that these adsorbents
are stable, promising, and can be used many times without losing its adsorption capacity toward Ni(II)
or Pb(II) ions.