Enhanced photocatalytic degradation of tetrabromobisphenol A by tourmaline–TiO₂ composite catalyst

The TiO₂ supported on tourmaline composite catalyst was successfully prepared by a sol–gel method and was characterized by scanning electron microscopy, X-ray diffraction and nitrogen adsorption–desorption analysis. The results showed that the addition of tourmaline increased crystallite sizes of TiO₂. Furthermore, the photocatalytic activity of the tourmaline–TiO₂ composites obtained was evaluated by the degradation of tetrabromobisphenol A (TBBPA). Compared with bare TiO₂, the tourmaline–TiO₂ composites exhibited the excellent photocatalytic activity for the degradation of TBBPA and this degradation enhanced was correlated with the tourmaline dosages and the optimum photocatalyst is found to be T(20%)-TiO₂ catalyst. It implied that the higher dosage of tourmaline facilitated migration of charge carriers and higher photon-to-electron conversion efficiency. The photocatalytic reaction followed pseudo-first-order kinetics and the Langmuir–Hinshelwood model. The photodegradation efficiency of TBBPA enhanced with the increase in pH value. Additionally, metal ions influenced the photocatalytic degradation of TBBPA by T(20%)-TiO₂ catalyst, Cu²⁺ could accelerate TBBPA degradation, whereas inhibited by Mn²⁺ and Fe³⁺. Importantly, five intermediate products of TBBPA at m/z 463, 355, 293, 255 and 137 were observed by HPLC–MS/MS. The possible photodegradation pathway of TBBPA by tourmaline–TiO₂ composite catalyst was proposed. Generally, the incorporation of mineral with spontaneous permanent poles to TiO₂ with photocatalytic activity offers a promising technology to the practical application of TiO₂ in contamination control.