A novel magnetic buoyant-bead flotation method for the removal of typical microalgae from harmful algal blooms

In recent years, harmful algal blooms(HABs)caused by the eutrophication of water bodies have been occurring, which not only damage the ecological environment, but also threaten human health. To control HABs simply and efficiently, a novel magnetic buoyant-bead flotation method was developed in this study. A magnetic floatable bead of Fe3O4/CCP was first prepared, and then was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometer and X-ray photoelectron spectroscopy. Subsequently, this study examined the removal effects of three kinds of floatable bead (closed-cell perlite (CCP), Fe3O4/CCP and Fe3O4/CCP +CPAM) on three typical microalgae (Chlorella vulgaris, Microcystis aeruginosa and Anabaena flos-aquae) in water bloom. The results confirmed that the removal rate of Fe3O4/CCP +CPAM was 27.28%, 45.79% and 42.71% higher than that of Fe3O4/CCP in the removal of three microalgae, respectively, while it was 32.26%, 50.49% and 46.91% higher than that of CCP, respectively. In addition, CPAM concentration, the amount of Fe3O4/CCP, stirring time, and stirring speed were found to have significant effects on the removal of three microalgae. The orthogonal experiments further revealed that the CPAM concentration exerted the most significant impact on the removal rate while using the proposed magnetic buoyant-bead flotation method. Under the optimal experimental conditions, the removal rate of C. vulgaris, M. aeruginosa and A. flosaquae using Fe3O4/CCP was 98.01%, 97.96% and 97.58%, respectively. Finally, the removal mechanism of microalgae by the combination of Fe3O4/CCP+CPAM was given. This study can provide a new idea for effectively removing harmful microalgae from water blooms or harvesting the microalgae.