Conjugated Microspheres FeTCPP–TDI–TiO2 with Enhanced Photocatalytic Performance for Antibiotics Degradation Under Visible Light Irradiation

Abstract

Toluene disocyanate (TDI) was used as a bridging molecule, a bridge bonding conjugated microsphere (FeTCPP–TDI–TiO2) was successfully prepared by grafting tetra-(carboxyphenyl) porphyrin iron (FeTCPP) on the surface of TiO2 microspheres. The FT-IR spectra revealed that the hydroxyl group (–OH) of TiO2 microspheres surface and the carboxyl group (–COOH) of FeTCPP reacted respectively with the active isocyanato groups (–NCO) of TDI to form a surface conjugated microsphere FeTCPP–TDI–TiO2. The UV–vis DRS analysis demonstrated that the formation of FeTCPP–TDI–TiO2 extended remarkably the photoresponse of as-prepared samples to visible light region. The photocatalytic activity of FeTCPP–TDI–TiO2 was evaluated using the photocatalytic degradation of norfloxacin (NFC), tetracycline (TC) and sulfapyridine (SPY) antibiotics in aqueous solution under visible-light irradiation. The results showed that, TDI, as a bond unit, was used to form a steady chemical bridging bond linking between FeTCPP and the surface of TiO2 microspheres, and the prepared catalyst exhibited higher photocatalytic activity under visible-light irradiation for antibiotics degradation in comparison with P25. The degradation of antibiotics all followed the pseudo first-order reaction model under visible light irradiation, and the degradation mechanisms of NFC, TC and SPY were also proposed.