Selective adsorption and photodegradation of salicylic acid by a novel magnetic molecularly imprinted mesoporous TiO2 co-doped with silver nanoparticles and carbon nanotubes (Fe3O4@mTiO2-Ag-CNTs-MIPs) under visible light

A novel magnetic molecularly imprinted mesoporous TiO₂ co-doped with silver nanoparticles and carbon nanotubes (Fe₃O₄@mTiO₂-Ag-CNTs-MIPs), was successfully prepared for the selective adsorption and photodegradation of salicylic acid (SA). The morphological and physicochemical properties of the prepared composite were characterized by SEM, FT-IR, XRD, VSM, UV–Vis DRS, EIS and XPS. The adsorption and photodegradation performance of Fe₃O₄@mTiO₂-Ag-CNTs-MIPs towards SA was investigated. The results showed that Fe₃O₄@mTiO₂-Ag-CNTs-MIPs could achieve the specific adsorption of SA with the selectivity coefficient higher than 2. Compared with Fe₃O₄@mTiO₂, the photodegradation efficiency of Fe₃O₄@mTiO₂-Ag-CNTs-MIPs for SA under visible light was significantly improved, indicating that the doping of CNTs and Ag together with the loading of MIPs could enhance the photocatalytic performance of the prepared composite. Under the irradiation of visible light (300 W) for 150 min, the degradation rate of SA (5 mg/L) in 50 mL of solution (pH 3) by Fe₃O₄@mTiO₂-Ag-CNTs-MIPs (15 mg) was up to 98.41 %. Moreover, the degradation rate of the recovered Fe₃O₄@mTiO₂-Ag-CNTs-MIPs for SA was still 87.12 % after five cycles. The primary active species for the photodegradation of SA by Fe₃O₄@mTiO₂-Ag-CNTs-MIPs were ${\text{O}}_{\text{2}}^{\bullet \text{-}}$ and h⁺, and the potential degradation pathways of SA were elucidated by high-resolution UPLC-MS. Overall, this study constructed a promising photocatalyst Fe₃O₄@mTiO₂-Ag-CNTs-MIPs, which was expected to effectively degrade the pollutant SA in wastewater treatment.