Enhanced selective removal of lead ions using a functionalized PAMAM@UiO-66-NH2 nanocomposite: Experiment and mechanism

Abstract

The pollution of water systems by lead ions poses a significant health hazard to humans and ecosystems. A new type of adsorbent was developed by grafting polyamidoamine (PAMAM) onto Zr(IV)-containing metal-organic frameworks ([email protected]2), which possesses many adsorption sites and a high specific surface area. This novel adsorbent can efficiently reach the adsorption equilibrium of Pb(II) in 50 min, and the maximum adsorption capacity for lead ions was determined to be 334.32 mg/g. The effects of pH, adsorbent quality, contact time, temperature, and background ions on adsorption were assessed using batch adsorption methods. The experimental data agreed with pseudo-quadratic kinetics and the Freundlich model, which proved that the adsorption behaviour was controlled by multilayer chemical adsorption. Simultaneously, the adsorbent undergoes spontaneous endothermic reactions with Pb(II). [email protected]2 demonstrated excellent selectivity in the removal of Pb(II) and maintained its removal efficiency even after being reused six times. Density functional theory calculations and characterisation analyses provided a quantitative basis for the selective removal of lead ions by [email protected]2. It was also concluded that the adsorption strength of the N group toward Pb(II) was in the order of primary amino group > secondary amino group > tertiary amino group. All of these results clarified that [email protected]2 could efficiently and selectively remove Pb(II) from aqueous solutions.