Laboratory batch and column experiments were conducted to investigate the feasibility of using bare Al2O3 (Al) and ZnO (Zn) nanoparticles (NPs) and modified Al2O3 (Al–H) and ZnO (Zn-H) NPs with humic acid (H) for an in situ immobilization of Cd2?, Cu2?, and Ni2? in single and multiple (competitive) solutions in a sandy loam soil. The results showed that, compared to control (blank) soil, metal removal increased with the four amendments (Al, Al–H, Zn, and Zn-H). In single solutions, the order obtained for the four amendments was Ni2?[Cd2?[- Cu2?, while the order in competitive solutions was Cu2?[Cd2?[Ni2?. We utilized sorption isotherms, sequential extraction procedure, TCLP (leachability) and PBET (bioavailability) tests, and leaching column tests to evaluate the mobility and availability of Cd2?, Cu2?, and Ni2? in the four amended soils. Sorption equilibrium isotherms could be described using the Freundlich model in most cases. After the 56-day incubation period, leachability and bioavailability of the heavy metals were determined. Additionally, compared to control soil samples, TCLP and PBET decreased in most of the amended soils. Aging (time effect) reduced leachability and bioavailability of most of the treatments. In some cases, amendments reduced the exchangeable and organic fractions yet increased the residual and oxide fractions. The retardation factors (Rf) obtained in leaching column experiments were used as an estimate of solute movement in amended soils. From the four amendments, Zn and Zn-H were selected for the leaching experiments. Results revealed that Zn-H along with Cd2?-multiple (multi) had the lowest Rf and the highest mobility associated with the lowest adsorption. This phenomenon may be related to both the increase in the specific and non-specific adsorption and to the precipitation reaction. These nano-amendments have the potential to be used as efficient sorbents in removing heavy metals from aqueous solutions and ZnO and Zn-H nanoparticles a
