Monolithic ceramic electrode for electrochemical deactivation of Microcystis aeruginosa

Algae bloom is a major environmental problem that may occur in both freshwater and marine water, and thus it is important to develop effective manners for deactivating algae. In this study, we investigated the monolithic ceramic electrode (MCE) for electrochemical deactivation of Microcystis aeruginosa, a typical alga found in aquatic system. The results demonstrated that the MCE contained the mixed Magnéli-phases of Ti₄O₇, Ti₅O₉ and Ti₉O₁₇, which could achieve efficient and stable deactivation of M. aeruginosa cells and removal of chlorophyll-a. The chlorophyll-a removal was shown to be positively correlated with the current density applied, reaching the maximum efficiency of 89.2% at reaction time of 120 min. The 8-day re-cultivation experiments showed the dependence of deactivation performance on total coulombs, and the coulombs in excess of 77.4 C could completely deprived the M. aeruginosa cells of propagation and proliferation. As shown from atomic force microscopy (AFM), scanning electron microscopy (SEM) and flow cytometric (FC) measurement, the algal cells underwent an irreversible damage of cell structure, isolation of intracellular components and dissolution of cytoplasm-like substances after being attacked by electrochemically produced oxidative species. The solution pH was observed to increase from 8.0 to 9.8 during 120-min electrolysis, which should be the consequence of leakage of cytoplasm containing a variety of small-molecule substances such as protein-, humus-, and sugar-like matters, indicated by 3D excitation-emission matrix (EEM) fluorescence spectra. This study provides a promising electrode material for effective electrochemical deactivation of algae in potential application of water purification.