Highly efficient removal of salicylic acid from pharmaceutical wastewater using a flexible composite nanofiber membrane modified with UiO-66(Hf) MOFs

The successful development of a cost-effective and efficient adsorbent is crucial for the optimal treatment of pharmaceutical sewage. In this study, a UiO-66(Hf)–NH2 nanocrystal modified composite nanofiber membrane (HfPNFM) was synthesized through electrospinning and solvothermal techniques, for the removal of salicylic acid (SA). The in-situ growth of UiO-66(Hf)–NH2 on the nanofibers led to a significant increase in the specific surface area of the composite nanofiber membrane. Furthermore, HfPNFM demonstrated exceptional flexibility and reusability, with the removal efficiency of SA still at 96.85 % even after ten cycles. The adsorption process of SA onto HfPNFM was well described by the pseudo-second-order kinetic model and Langmuir isotherm model, with a maximum adsorption capacity of 128.21 mg/g. In dynamic adsorption experiments, HfPNFM effectively removed 100 % of SA at a concentration of 50 mg/L. The chemical oxygen demand (COD) concentration of SA was reduced from 165.89 mg/L to 41.47 mg/L by two layers of HfPNFM filtration, below the standard for pharmaceutical wastewater discharge (GB: 21904-2008). X-ray photoelectron spectroscopy (XPS) revealed that electrostatic interactions, π-π interactions, hydrogen bond interactions, and metal complexation interactions between SA and HfPNFM were responsible for the adsorption. This highly effective composite nanofiber membrane has promising potential for pharmaceutical wastewater treatment.