Adenosine-functionalized UiO-66-NH2 to efficiently remove Pb(II) and Cr(VI) from aqueous solution: Thermodynamics, kinetics and isothermal adsorption

A new zirconium-based adsorption material (UiO-66-AMP) was prepared by modifying UiO-66-NH 2 with 5-adenosine to effectively remove Pb(II) and Cr(VI) from wastewater. The SEM, EDS, XRS and FT-IR characterization confirmed the successful synthesis of UiO-66-AMP. We conducted a sets of experiments to test the adsorption effectiveness of UiO-66-AMP for Pb(II) and Cr(VI). The maximum adsorption capacity of UiO-66-AMP for Cr(VI) (pH=2) and Pb(II) (pH=4) are 196.60 and 189.69 mg/g, respectively. The adsorption process conforms to the pseudo-second-order and Langmuir models, which indicates that the adsorption is a single-layer chemical process. Gibbs free energy ( ∆G) indicates that the adsorption of Pb(II) is an exothermic reaction , while the adsorption of Cr(VI) is an endothermic reaction . At the same time, the adsorbent maintains excellent adsorption capacity at least after 4 cycles. The good adsorption performance of UiO-66-AMP towards the metal ions was attributed to the surface complexation and electrostatic interactions. Therefore, the new adsorbent has obvious application prospect to remove Pb(II) and Cr(VI) from wastewater.