Synthesis and Optimization of a Highly Stable and Efficient BN/TiO2 Nanocomposite for Phenol Degradation: A Photocatalytic, Mechanistic and Environmental Impact Study

Abstract

Different BN/TiO2 nanocomposites were prepared hydrothermally, and their ratio was optimized to get the best photocatalytic performance towards phenol degradation. They were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning and transmission electron microscopies coupled with energy dispersive x-ray units, BET surface area, and UV-Vis diffuse reflectance. The bandgap energy was reduced from 3.35 to 2.95 eV due to the formation of the B-O-Ti bond. This allowed the exploitation of the visible light and inhibited the TiO2 e(-)/h(+) recombination, and consequently, the photocatalytic activity of TiO2 was dramatically improved. Almost 90 % mineralization of 20 ppm phenol solution was achieved within 30 min under simulated sunlight. The as-prepared composite showed excellent stability and reusability. Mechanistic analysis indicated that O2.- and h(+) played a crucial role in phenol degradation. The nanocomposite ' s biocompatibility and environmental impact were evaluated by analyzing its potential toxicity in vivo using the zebrafish embryos. 96-hpf acute toxicity assays, including the mortality rate assay (to obtain the LC50 values) and teratogenic assays (to obtain the No Observed Effect Concentration, NOEC) was conducted. The LC50 value for BN/TiO2 was 482.5 mg L-1, and the NOEC was 100 mg L-1. Based on LC50 value and according to the Fish and Wildlife Service (FWS) acute toxicity rating scale, the photocatalyst is "practically not toxic."