Surface functionalised adsorbent for emerging pharmaceutical removal: Adsorption performance and mechanisms

Abstract

А highly effective adsorbent (PPhA) was designed using “acid catalyst” functionalisation and tested for six emerging PhCs (sulfamethoxazole (SMX), carbamazepine (CBZ), ketoprofen (KP), naproxen (NPX), diclofenac (DCF) and ibuprofen (IBF)) in a batch study. Characterisation results (BET, SEM, FTIR, XRD and pHzpc) showed that the functionalisation process generates a microporous material with a multitude of new functional groups (such as phosphate and phosphonate) present on the surface. Adsorption capacity reached near maximum within 10 min while equilibrium was obtained in 60 min. Findings suggest that the mass transfer was governed mainly by intraparticle diffusion processes through formation of H-bonds, π–π and n–π electron donor–acceptor interactions. A pH influence study showed that electrostatic interactions played a minor role in the overall removal mechanism. The magnitude of E was <8 kJ mol−1 for all studied PhCs, indicating that adsorption is mainly due to physisorption. Equilibrium data were best represented by the Freundlich model and the theoretical monolayer adsorption capacities were 17.193, 17.685, 19.265, 17.657, 21.116 and 23.332 mg g−1 for SMX, CBZ, KP, NPX, DCF and IBF, respectively. Based on these results, this PPhA is proposed as an excellent adsorbent for PhC removal.