Removal of emerging pollutant dibutylhydroxytoluene from water with CNT/TiO2 catalysts in a visible LED photoreactor

For the photocatalytic degradation of antioxidant 2,6-di-tert-butyl-hydroxytoluene (BHT), several TiO2-based composites have been prepared in MWCNT from titanium isopropoxide and ethanol via supercritical CO2 synthesis followed by calcination at 400 degrees C. TEM and XRD showed uniform coverage of CNT by 10 nm TiO2 particles in the anatase form, and spectral analyses revealed the formation of CNT/TiO2 structure. Further, synthesized material displayed significant visible light absorption and absorption edge shifted to longer wavelengths. Once the material was characterized, the effect of adsorption and photochemical degradation of BHT was investigated in the wavelength range from 400 to 700 nm, in batch mode, by monitoring the concentrations of BHT as a function of time. CNT/TiO2 composites were more efficient than commercial TiO2 P25 in the photodegradation of the antioxidant. In particular, CNT50/TiO250, a composite with 50% by weight of CNT, was the best catalyst, stable, and completely degrading BHT within 30 min of exposure to visible light. The role played by different reactive oxidative species (h(+),OH center dot,O-1(2), and O-2(center dot-)) in the photocatalytic reaction was also studied by using appropriate radical scavengers that inhibited the corresponding active species. Superoxide radical was found the main oxidizing agent.

Automated summary

In this study, TiO2-based composites were synthesized through supercritical CO2 synthesis, showing uniform coverage of CNT by TiO2 particles. The CNT50/TiO250 composite exhibited the best performance in photocatalytic degradation of the antioxidant BHT, with complete degradation within 30 minutes under visible light. Superoxide radical was identified as the main oxidizing agent in the photocatalytic reaction.