Modified Metal-Organic Frameworks as an Efficient Nanoporous Adsorbent for the Removal of Naproxen from Water Sources

Abstract

In this paper, we synthesized nanoporous metal-organic frameworks modified with melamine (Mlm), UIO-66-NH2-Mlm (UN-Mlm), and investigated its application for adsorptive removal of naproxen (NPX) from aqueous solutions. The structure of nanoporous adsorbent was characterized via several analyzes and its modification with melamine was approved. The results of X-ray diffraction (XRD) confirmed that crystalline structure of the framework was maintained after modification with Mlm. Influential parameters such as contact time, pH effect, and etc. on NPX adsorption using modified nanoporous framework were investigated to find the desirable situations. A high adsorption capacity (114.94 mg g−1) was acquired for NPX at pH 5 and in 30 min under the optimum situations. The high absorption of UN-Mlm can be attributed to existence of interactions such as electrostatic, π–π and H-bonding interactions. Among the adsorption isotherms investigated for the adsorption process, Freundlich isotherm was recommended as an appropriate multilayer adsorption pattern for NPX. Also, through the adsorption kinetics studies, the adsorptive removal of NPX sample was corresponded to the pseudo-second-order model. Finally, this modified nanoporous framework was recycled by easy wash with methanol and reused with a slight change in the performance of absorption removal of NPX for at least three time that is very important in the industry.