Construction of surface oxygen vacancies by bimetallic doping combined with ellagic acid modification to enhance the photocatalytic degradation of ethinyl estradiol by TiO2

In this paper, two surface oxygen vacancy-rich TiO2 composite photocatalysts were successfully constructed by solid thermal reduction ((R-Vo)TiO2) and bimetallic doping (Nd-Fe-(D-Vo)TiO2). The oxygen vacancies were characterized in detail using XPS, Raman, EPR and STEM. The results show that the excellent photocatalytic performance of Nd-Fe-(D-Vo)TiO2 deriving from its doping energy and surface oxygen vacancies. Nd-Fe-(D-Vo) TiO2 could degrade 58 % of phenol within 120 min, which was much greater than 15 % of TiO2 and 27 % of (RVo)TiO2. Three composite photocatalysts, TiO2@EA, (R-Vo)TiO2@EA and Nd-Fe-(D-Vo) TiO2@EA, with better visible light absorption and photocatalytic performance were further obtained by bonding ellagic acid (EA) to the surface of TiO2. Nd-Fe-(D-Vo)TiO2@EA could almost completely degrade ethinyl estradiol within 20 min with a high minimization degree of 84 %. The possible sites of ethinyl estradiol attacked by free radicals were predicted by theoretical calculation combining with high-resolution mass spectrometry analysis, and the possible degradation mechanism was proposed.