Thermal activation of g-C₃N₄-tourmaline to drive the Fenton reaction in the dark: promoting carrier migration through a polarization electric field and a heterojunction structure

Tourmaline is often used as a raw material for the Fenton reaction to degrade pollutants in water because of its high iron oxide content and low price. However, the inefficiency of tourmaline and secondary pollution seriously limit its further application. Promoting the Fenton reaction cycle is an effective way to address these issues. In this study, a series of g-C₃N₄-tourmaline (CN-T-<i>x</i>) samples were synthesized by ball milling and calcination, which were able to effectively degrade rhodamine B (RhB) in the dark through H₂O₂ activation. By temperature regulation, the degradation efficiency could be greatly enhanced. Catalyst CN-T-3 could degrade about 91% of RhB (10 ppm) within 5 min at 65 °C in the dark, which was 2.6 times that of CN-T-3 at 25 °C in the dark. Moreover, this degradation efficiency was also 3.6 and 6.9 times those of tourmaline and CN under the same conditions, respectively. Due to the combination of the heterojunction structure between tourmaline and CN and the polarization electric field of tourmaline, the electrons were transferred more easily from CN to the tourmaline surface at higher temperature, which in turn effectively improved the Fenton reaction cycle. This study constructed a heterojunction structure based on the comprehensive exploration of the distinctive characteristics of the polarization electric field and semiconductor properties of tourmaline for pollutant removal and also contributed an effective way for elevating the degradation efficiency through regulating the temperature in the Fenton reaction.