Preparation of novel flower-like BiVO4/Bi2Ti2O7/Fe3O4 for simultaneous removal of tetracycline and Cu2+: Adsorption and photocatalytic mechanisms

(T)o improve the visible light utilization and adsorption capacity for combined pollutants (Tetracycline and Cu2+), novel flower-like BiVO4/Bi2Ti2O7/Fe3O4 composite has been successfully synthesized for the first time via a simple two-step process, surfactant-free hydrothermal route and solvothermal method. The crystal structures, chemical compositions, morphologies, optical and photocatalytic properties of the as-prepared samples were characterized by the techniques of XRD, XPS, SEM, HRTEM, BET, UV-vis DRS, and Photocurrent tests (PT). The synthetic sample with 4:1:20 (S5) mass ratio of BiVO4/Bi2Ti2O7/Fe3O4 possessed the highest adsorption capacity and photocatalytic performance simultaneously in all of the as-prepared composites. Adsorption experiment (model 1 and model 2) suggested that there was not only competitive adsorption but also synergistic adsorption mechanisms between Cu2+ and TC. Compared to pure BiVO4, and BiVO4/Bi2Ti2O7, BiVO4/Bi2Ti2O7/Fe3O4 displayed more superior photodegradation efficiency with 97.22% removal of TC (10 mg/L) in 60 min, where the optimal conditions were catalyst dosage 1.00 g/L and initial pH at 6.0. In addition, radical trapping experiments revealed that the photo-induced active species superoxide radical (O-center dot(2)-) and holes (h(+)) were the predominant active species in the photocatalytic system. These features demonstrate that the BiVO4/Bi2Ti2O7/Fe3O4 has great application potential for combined pollutants' removal from water. (C) 2018 Elsevier Inc. All rights reserved.