Enhanced adsorption and degradation of nonylphenol on electron-deficient centers of photocatalytic surfaces

Abstract

Boron doped TiO2 was used for enhanced adsorption and degradation of nonylphenol. It was found that boron from boric acid was doped into TiO2 crystal lattice as interstitial boron, introducing more Lewis acidic sites as electron-deficient centers. Further characterization found that boron doping not only improved its Lewis acidity but also enhanced the photocatalytic activity both in light absorption and lifetime of the photogenerated charges. Boron doped TiO2 possessed 1.8 times adsorption capacity over TiO2 due to faster adsorption kinetics, both of which fits Langmuir model. And the adsorption on TiO2 and boron doped TiO2 follows pseudo-first-order and pseudo-second-order, respectively. The adsorption process was further studied using in situ infrared, the results showed phenolic hydroxyl groups was dissociative absorbed on TiO2, while phenolic hydroxyl was coordinated to boron on boron doped TiO2. In two hours of degradation, 99.4% of nonylphenol was removed on boron doped TiO2, the degradation rate of which was 1.5 times that of TiO2. The TOC removal was 89.5%, suggesting most of nonylphenol was mineralized. Proposed degradation pathway showed the degradation mechanism was complicated. The reusability maintained well after three repeating degradation.