A highly efficient TiOX (X = N and P) photocatalyst for inactivation of Microcystis aeruginosa under visible light irradiation

Harmful algae pollution has become the most concerned environment issue as the serious eutrophication spreads in natural waters all over the world. Highly efficient TiO₂ photocatalysis is considered as a promising technique to achieve the inactivation of harmful algae using light energy. Herein, we prepare TiOX (X = N and P) photocatalyst with high activity via a facile sol-gel method in an oxygen deficient environment. The results show that the oxygen deficient environment can enhance the doping process, and the N and P can be successfully doped into TiO₂ crystal by controlling the calcination temperature. The as-prepared TiOX particles can be assembled to a porous structure with a high specific surface area, which is beneficial to the adsorption of algal cells. The substitution of oxygen and the oxygen containing functional groups gives rise to disorder of the TiO₂ crystal, thus tuning the light absorption capacity and promoting the separation of photogenerated charge carriers. Among the TiOX photocatalysts, the TiOX prepared at 550 °C exhibits the best photocatalytic performance with an algal inactivation rate of 81.5% for Microcystis aeruginosa following 6 h visible light irradiation, which can be attributed to the good synergetic effect of adsorption and photocatalysis. The deformation in algal morphology and disorder in cellular metabolism further confirms the inactivation process. The TiOX photocatalyst is also found to be able to effectively remove cytotoxins, which demonstrate that it holds substantial promise for the remediation of harmful algae polluted water.