Oxygen-vacancy hydroxyapatite for visible-light photocatalytic degradation of tetracycline with online spectral monitoring

In this study, OV-HAp with abundant oxygen vacancies (OVs) were prepared by calcining carbonate-doped HAp (CHAp), and the effects of calcination temperature, time and atmosphere on the formation of OVs in OV-HAp and the influence of OVs concentration on its photoelectrochemical properties were investigated in detail. The results showed that the calcination temperature and atmosphere play a major role in the generation of OVs in OV-HAp. Through changing the temperature or atmosphere, the optical absorption range of OV-HAp can be broadened to the visible light and the band gap can be reduced to 1.6 eV. OV-HAp obtained by calcining CHAp at 600℃ for 5 h under H2 atmosphere (OV-HAp-H2) exhibited the highest efficiency for tetracycline (TC) photocatalytic degradation (65.4%). h+ and ·O2– were demonstrated to be the main active species in the degradation process by radical trapping experiments. Meanwhile, an integrated platform for photocatalytic degradation of TC with online spectral monitoring was constructed, and the feasibility of online spectral monitoring the TC degradation was tentatively explored. This work will provide a theoretical and technical basis for the development of HAp-based high-efficient photocatalysts, and this is favorable for promoting their use by a large scale for water pollutant removal. Moreover, it will also open a new path for online spectral monitoring and kinetic study of photocatalytic degradation of organic pollutants.