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 °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 ^·, ¹O₂, and [Formula: see text]) 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.