Hydrothermal synthesis of photoactive nitrogen- and boron- codoped TiO2 nanoparticles for the treatment of bisphenol A in wastewater: Synthesis, photocatalytic activity, degradation byproducts and reaction pathways

• Published in: Applied catalysis. B, Environmental Environmental, 2019-02, Vol.241, p.598-611
• Main Authors: Abdelraheem, Wael H.M., Patil, Meghshyam K., Nadagouda, Mallikarjuna N., Dionysiou, Dionysios D.
• Format: Article
• Language: English
• Subjects: Bisphenol A; Degradation byproducts; Nitrogen- and boron- codoped TiO2; Reaction pathways; Reuse; Treatment; Water
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2018.09.039

[Display omitted] •Anatase N- and B- codoped TiO2 with visible light activity was hydrothermally synthesized.•N and B atoms were introduced onto TiO2 lattice via substitution and interstitial mechanisms.•Bisphenol A was successfully removed by simulated solar light/2.0NBT-350 in wastewater.•Six degradation byproducts, including two new compounds, were identified by LC/Q-TOF-ESI-MS.•Oxidation routes included hydroxylation, ring elimination, and opening. Hydrothermal technique was employed for the synthesis of N- and B-codoped TiO2 at different atomic percentages and calcination temperatures (350 and 400 °C). Borane tert-butylamine complex was used as a novel precursor for the dopant atoms. The photocatalytic activities of catalysts were evaluated for destruction of bisphenol A (BPA) spiked in clean water and in secondary treated wastewater influent (SWI) collected from the Groundwater Replenishment System GWRS (Orange County, CA, USA), the world's largest water purification system for indirect potable reuse. Results of X-ray photoelectron spectroscopy (XPS) revealed the incorporation of N and B atoms onto TiO2 lattice via substitution of O and/or Ti, and interstitial incorporation mechanisms. Carbon doping (graphite-like carbon; O-C = O) was also evidenced from XPS spectra. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) revealed pristine TiO2 and all doped TiO2 existed in anatase structure. The anatase phase of catalysts was further confirmed by simulation of selected area electron diffraction (SAED) of the catalysts and reported anatase TiO2 using the simulation software CrysTBox (v 1.10). Among all prepared catalysts, 2.0NBT-350 (N + B = 2.0%, calcination = 350 °C) possessed the smallest particle size (12.9 nm), largest BET surface area (108.5 m2/g) and highest visible-light absorption (i.e., λ > 400 nm). Simulated solar light/2.0NBT-350 system exhibited the maximum removal of BPA (0.1 μM) at the optimum catalyst dose of 0.8 g/L in clean water, over three consecutive degradation reuse cycles without any noticeable decrease in its photocatalytic activity. BPA was also successfully removed in SWI water, however with slower kinetics due to hydroxyl radical quenching effect of dissolved organic and inorganic species present in the SWI matrix. Degradation byproducts were identified by LC/Q-TOF-ESI-MS analysis. Six byproducts were found in the reaction mixture, with two compounds were newly identified in the current study.