In this study, the adsorptive removal of Zn²⁺, Cu²⁺, and Cr³⁺ metal ions from aqueous solutions onto NiO–MgO silica-based nanoparticles (SBNs) has been studied. The effect of several factors such as solution pH, initial concentration, contact time, and coexisting ions on the adsorbed amounts of single Zn²⁺, Cu²⁺, and Cr³⁺ ions have been investigated within an array of batch mode experiments. Interestingly, the adsorption of Cr³⁺ at high and low concentrations was very fast, and equilibrium was achieved within 2 min compared to Cu²⁺ and Zn²⁺ which needed 30 and 60 min to reach equilibrium, respectively. The adsorption equilibrium data fitted very well with the Sips adsorption isotherm model for Cu²⁺ and Zn²⁺, and the BET model for Cr³⁺ ions. The maximum uptake was maintained at 7.23, 13.76, 41.36 (ions per nm²) for Zn²⁺, Cu²⁺, and Cr³⁺, respectively. This equals to 37.69, 69.68, 209.51 (mg adsorbate per g adsorbent), respectively, showing the promising industrial application of those SBNs. Moreover, the adsorption uptake results increase with increasing the pH in the range of 7.0–11.0 for all investigated metal ions. The thermodynamic parameters such as the changes in Gibbs free energy (ΔGo), enthalpy (ΔHo), and entropy (ΔSo) were determined. The adsorption of Zn²⁺, Cu²⁺, and Cr³⁺ was spontaneous, endothermic, and physical for Cu²⁺ and Cr³⁺, while exothermic and chemical for Zn²⁺. The regeneration and reusability studies have proven that the NiO–MgO SBNs can be employed for the adsorptive of these metals repeatedly without impacting the adsorption capacity indicating their sustainability.

Title

Journal of Environmental Management

Publisher

Elsevier

Publisher Country

Netherlands

Indexing

Thomson Reuters

Impact Factor

4.865

Publication Type

Online only

Volume

268

Year

2020

Pages

110713