Inactivation Effect And Mechanism Of Ultraviolet-Catalyzed Modified Nano-TiO2 Modified On Microorganisms In Ballast Water

Ballast water carries a large number of harmful organisms and spreads among different water bodies all over the world,posing a great threat to the safety of Marine environment and human health.As an effective means of ballast water treatment,UV has the advantages of high efficiency,no secondary pollution and no corrosion to the cabin.However,in the case of high turbidity,UV radiation alone will greatly reduce the inactivation effect.In order to make up for these defects,modified nano TiO₂ photocatalyst was prepared.Typical bacteria and microalgae in ballast water were treated by UV and modified nano TiO₂,and the factors affecting photocatalytic effect and inactivation mechanism were studied.It provides a theoretical basis for seeking an efficient ballast water disinfection process.Cu-TiO₂,N-TiO₂ and Cu/N-TiO₂ nano-photocatalysts were prepared and characterized.Escherichia coli was used as the inactivating target to study the inactivating energy of modified photocatalyst.Then the response surface method was used to optimize the Times of coating,heat treatment temperature and heat treatment time of the supported photocatalyst.The results showed that the surface morphology,particle size and sterilization effect of the modified nanometer photocatalyst were improved.Doped Cu and N can increase the photocatalytic activity of the catalyst.The double doping effect of Cu/N-TiO₂was higher than that of Cu-TiO₂and N-TiO₂,the logarithmic sterilization rate at 20 s was 0.98 log and 1.42 log higher than that of Cu-TiO₂ and N-TiO₂,respectively.High activity supported Cu/N-TiO₂ photocatalyst was prepared with stainless steel fiber felt as the support under optimized conditions,which provided a foundation for the establishment of ballast water treatment system.The UV/Cu-N-TiO₂ ballast water treatment system was established.Typical bacteria and microalgae in ballast water were used as inactivation targets.The results showed that the sterilization and algal killing effects of UV/UV/Cu-N-TiO₂ ballast water treatment system were significantly improved compared with UV and UV/TiO₂.The processing time to achieve the same inactivation effect was shortened by at least 8 s compared with the UV alone.The sterilization effect of UVC/UVA/Cu-N-TiO₂ system is the best.At 20 s,the logarithmic inactivation rates of escherichia coli,brucella duchenne,protodinoflagellate microphylla and trichoderma were 5.67 log,2.12 log,0.71 log and 0.89 log,respectively.The content of lipid peroxides(MDA)increased,the activity of superoxide dismutase(SOD)decreased rapidly,and the chlorophyll a of microalgae was degraded rapidly.Therefore,UV/Cu-N-TiO₂ system has a good effect on the disinfection of ballast water,which has great practical application value and prospect.