Functionalization of a cast NaAl/binary ZnO/SiO2 nanohybrid with amine and Schiff base ligands as an adsorbent of divalent cations in water system

Casting method was used to synthesize a novel sodium alginate nanohybrid functionalized with aminated ZnO/SiO 2 Schiff base for adsorption of nickel (Ni 2+ ) and copper (Cu 2+ ) divalent cations in single and binary water systems. The cast Schiff base nanohybrids were investigated using FESEM, XRD, BET, FTIR, TGA, and XPS analyses. The influence of unfunctionalized binary ZnO/SiO 2 nano oxides and aminated Schiff base ligands formed by the reaction between salicylaldehyde and O-phenylenediamine on the adsorption of Ni 2+ and Cu 2+ cations was evaluated. The results confirmed that the aminated Schiff base ligands led to a higher adsorption ability of the cast nanohybrids containing interaction of divalent cations with nitrogen and oxygen atoms, as well as carboxyl and hydroxyl groups. The adsorption kinetics and isotherm for both cations followed a double-exponential model and the Redlich-Peterson model, respectively. The maximum monolayer capacity was found to be 249.8 mg/g for Cu 2+ cation and 96.4 mg/g for Ni 2+ cation. Thermodynamic analysis revealed an endothermic and spontaneous adsorption process with an increase in entropy. Furthermore, the synthesized Schiff base adsorbent could be easily reused over five times. The simultaneous adsorption in binary system exhibited a higher adsorption selectivity of the cast Schiff base nanohybrid for Cu 2+ cation compared to Ni 2+ cation. It was found that the removal percentages of Cu 2+ and Ni 2+ from industrial electroplating wastewater were 91.3 and 64.5%, respectively. Lastly, cost analysis of the synthesized nanohybrid was investigated.