Studies On The Preparation Of BiOBr-based Floating Composites And Photocatalytic Inhibition Of Algae Under Visible Light Irradiation

With the continued eutrophication of water resource environment,the harmful algal blooms（HABs）happens worldwide and subsequently causes filter-clogging or water quality deterioration.Cyanobacterial blooms produced algae toxins which are seriously threatening human and aquatic organism health by oral,skin absorption,drinking water,and other ways.Various technologies of the alga-killing have been used to prevent and remedy cyanobacterial bloom,and to conserve water resource environment effectively.However,the applications of classical technologies are proved to be cost-consuming and injurant-producing,these methods are quite difficult to recover and recycle.Thus,focusing on new alga-killing methods to overcome the classical technology gap is crucial.In this study,under the irradiation of visible light,the photocatalytic performance of the as-prepared floating photocatalysts（EP-Bi₂S₃/BiOBr and 3D BiOBr/rGAs）to remove algae was evaluated with the dominant species in algal bloom（Microcystis aeruginosa）as test species.The main contents are as follows:1.Bi₂S₃/BiOBr-expanded perlite（EP-Bi₂S₃/BiOBr）composite material is synthesized by a solvothermal method.The influence of morphology,structure and elemental component were characterized by XRD,FESEM,DRS and TEM.Alga-inhibiting experiment reveals that the chlorophyll-a removal efficiency of M.aeruginosa was 70.2%in 5 h using 1 g?L^-1 EP-Bi₂S₃/BiOBr under visible light,and the content of dissolved organic matter（DOM）dramatically decreased.It explains that could effectively restrain the growth of M.aeruginosa.Furthermore,after 7 days floating force test still had very high floatation ratio about 81%.2.A series of BiOBr/reduced graphene aerogels（BiOBr/rGAs）was fabricated using a two-step method.Various analysis methods such as XRD,FESEM,DRS and XPS were used to adequately characterize the as-prepared samples.The results show that the structure of BiOBr/rGAs is too loose to be self-assembled with the increase of BiOBr content.The sample under 10.2:1 of mass ratio shows the highest activity,and the chlorophyll-a removal efficiency is 93.1%.Based on three-dimensional fluorescence spectroscopy,intra-cellular（IDOM）or extra-cellular（EDOM）is obviously reduced.3.The paper analyses the change of fluorescence regional integration（FRI）on DOM during the photocatalytic process,and further infer the mechanism for the photocatalytic inhibition of algae assisted with EP-Bi₂S₃/BiOBr and BiOBr/rGAs under visible light.The mechanism may be photocatalysts produce free radicals and the photogenerated holes in the photon excitation,which can damage cell outer membrane and the intracellular substances could be dissolved.Further,the intracellular substances had been mineralized by free radicals or holes that lead to apoptosis.