Unlike conventional immobilization methods [15,36], here we
presented an effective method with PAA treatment of synthesizing
the TiO2 catalyst particles attached to the silica surface by covalent
bonds. As the result, the Fe3O4/SiO2/TiO2 catalyst can be efficiently
recovered and recycled in liquid. Upon completion of the RhB degradation
reaction, the magnetic properties of the photocatalysts
can afford a straightforward way for isolating the catalyst. The particles
of the catalyst can be collected within a few minutes by using
a permanent magnet (Fig. S2). The photoactivity of the compound
remained unchanged after magnetic separation, washing and
drying.