Oil-phase cyclic magnetic adsorption to synthesize Fe3O4@C@TiO2-nanotube composites for simultaneous removal of Pb(II) and Rhodamine B

In this work, to simultaneously remove organic dyes and Pb(II) from wastewater, a series of magnetic Fe 3 O 4 @C@TiO 2 -nanotube composites were designed and successfully synthesized via a new facile oil-phase cyclic magnetic adsorption (OCMA) method. The structural properties of the synthesized composites were investigated by different characterization methods systematically. It was found that Fe 3 O 4 was uniformly deposited on the inner walls of TiO 2 nanotubes. Although a Type III band alignment was formed in the catalysts, Fe 3 O 4 @C@TiO 2 -nanotube composites exhibited enhanced light absorbing ability and enlarged absorption edge due to efficient separation of h + and e − , which was verified by UV–Vis (Ultraviolet–visible) and PL (Photoluminescence) spectra. Decontamination experiments of 1FeCTi showed that more than 98% of RhB and about 92% of Pb(II) ions could be removed through adsorptive removal in the dark equilibrium period and further elimination during the illuminating period. The pseudo-first-order model, L-H model and adsorption-reaction model were established to describe the adsorption of Pb(II) in the dark, photodegradation of RhB and further elimination of Pb(II), respectively. A four-step mechanism was proposed to describe the decontamination process of Pb(II) during the illuminating period according to the final forms of Pb (Pb δ1 , Pb δ2 , Pb 0 and PbO). Finally, it was found that the photocatalytic activity would be maintained in the recycle experiments due to the existence of 1FeCTi@PbO heterostructure.