Highly efficient adsorption of Ag(I) from aqueous solution by Zn‐NDC metal–organic framework

Abstract

In this work, an adsorbent, an O-containing metal-organic framework (MOF) (Zn-NDC) was designed and prepared to recover Ag(I) with high performance to alleviate its high consumption and protect the environment. Its adsorption performance was accessed by batch adsorption experiment. The kinetic data fit well with the pseudo-first-order model, pseudo-second-order model, and moving boundary model. It is found that the overall adsorption rate was determined by liquid film diffusion. The maximum adsorption of Zn-NDC towards Ag(I) can be up to 844 mgÁg −1 , superior to many reported adsorbents. Besides, Sips model better fits with the experimental data, implying the adsorption process belongs to heterogeneous adsorption. Thermodynamic analysis indicates the adsorption process of Ag(I) is a spontaneous, exothermic, and entropy-driven process. Zn-NDC could selectively adsorb Ag(I) from a hybrid solution containing Ag(I), Co(II), Ni(II), Cd(II), Cr(III), Zn(II), and Mg(II). Moreover, Zn-NDC could be effectively reused up to three cycles with negligible change in adsorption capacity. Finally, the X-ray photoelectron spectroscopy (XPS) results show the electronic attraction and inner-sphere surface complexation are the main adsorption mechanism. Based on the above analysis, Zn-NDC could be regarded a cost-effective adsorbent for the Ag(I) removal.