Photocatalytic degradation of nonylphenol ethoxylate and its degradation mechanism

Photocatalyst TiO2@g-CQDs were prepared by one-step sol-gel method using tetrabutyl titanate, anhydrous ethanol, hydrochloric acid and graphite carbon quantum dots and characterized by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), UV–visible diffuse reflectance spectra (UV-DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of nonylphenol ethoxylate (NPE10O) by TiO2@g-CQDs and the degradation path of NPE10O by time-of-flight mass spectrometry (TOF-MS) were investigated. In addition, the photocatalytic mechanism of TiO2@g-CQDs was discussed in detail and the major active species were identified. The results showed that when the doping amount of g-CQDs is 5%, the amount of TiO2@g-CQDs is 0.1 g·L−1, the initial concentration of NPE10O is 50 mg·L−1, and the power of the light source is 500 W, the degradation efficiency of NPE10O can reach 100% at 60 min, which indicates TiO2@g-CQDs have excellent photocatalytic properties. TOF-MS showed that NPE10O was mainly degraded by nonylphenol polyethoxycarboxylate (NPExC) and carboxylated alkyl oxidation products of nonylphenol ethoxy (CAyPEC) intermediates during photocatalytic degradation. Trapping experiment of active species demonstrated that OH is the major active component for photocatalytic degradation of contaminant.