Study On Photoelectric Catalytic Performance Of TiO₂ Nanotubes And Treatment Of Typical Microalae In Ship's Ballast Water

Marine environmental pollution is a severe challenge that has been faced since global integration and a key link in protecting the global environment.The inactivation treatment of microorganisms in ship's ballast water is a difficult problem faced for major shipping countries.At present,many treatment technologies cannot meet the safety,practical,economic,effective and friendly environmentally acceptable standards proposed by the IMO.Therefore,research on new ballast water treatment technology is urgently needed.The use of photoelectrocatalytic(PEC)technology to degrade wastewater in the environment is a new technology in recent years,which can be carried out under normal temperature and pressure without secondary pollution and has a wide range of treatment,although this technology has become a hot research direction of water treatment at home and abroad,and researchers from various countries attach great importance to it.However,this technology has great potential and feasibility for the treatment of ship's ballast water,and there is no relevant research in relevant institutions at home and abroad.In this paper,Ti metal is selected as the research object,Ti O₂ Nanotube Arrays(TNTs)are prepared by anodizing method,and the TNTs are annealed,then the TNTs photo-electrocatalysis degradation or inactivation of target pollutants is studied.Based on the above content,this research mainly carried out the following aspects:First,a new type of anodic oxidation electrolyzer device was made and designed,and a digital program-controlled electric motor was specially designed to precisely control the position of the anode and cathode.The Ti mesh(25×30×0.5mm)and Ti sheet(25×30×0.3mm)were selected as the anode,and the stainless steel steel plate was selected as the cathode(80×170mm).TNTs were prepared by anodizing method,and optimized anodizing The conditions for preparing TNTs are:voltage 30V,spacing 2cm,and anodizing time 1h;the length of TNTs prepared by Ti mesh is about 1.36?m,and the tube diameter is about 20-40 nm.The length of TNTs prepared from Ti sheet is about 3.09?m,and the tube diameter is about 67-72nm.The prepared TNTs are neat and uniform,arranged in order,and have a good specific surface areaSecondly,a new type of microwave annealing bath device with simple structure and low cost was designed and manufactured.The material of this device is heat-insulating ceramic material,and the inside contains an annealing chamber made of silicon carbide material.High-purity quartz sand is added between the device and the annealing chamber,which can not only transmit microwaves,but also effectively prevent heat dissipation.The experimental results show that the optimal single annealing time can be shortened by about 10 to 45 minutes by using this device for annealing.Meanwhile,select high and low power microwave annealing conditions for the nanotube arrays prepared by Ti mesh and Ti sheet respectively and systematically explore the PEC performance of Ti mesh and Ti sheet after microwave annealing.The results show that the degradation efficiency is related to annealing time and temperature,and the size of the photocurrent is positively related to the degradation efficiency of TNTs.In addition,TNTs prepared from Ti sheet have better PEC degradation performance and stability.Furthermore,select TNTs prepared from Ti sheet,and use muffle furnace annealing as annealing conditions to study in detail the effect of the tube length,integrity and crystal form of the nanotubes on the degradation of methyl orange by PEC.The photoelectrocatalytic test found that compared with the length of other TNTs in the experiment,the length is 2.90?m with a bias voltage of 0.4V,and the degradation rate of PEC reaches 98%at 28 minutes.At this time,the photoelectric catalytic performance is the best;it also proves that the integrity of TNTs is essential for photogenerated electrons The separation of holes can promote the separation of PEC,which has an impact on the degradation of PEC.In the PEC degradation experiment with the preferred orientation of the unit cell,the degradation rate of P-TNTs reached 98%and took24 minutes,while R-TNTs took 40 minutes,indicating The PEC degradation efficiency of P-TNTs is better than that of R-TNTs.Finally,the study uses TNTs to inactivate microalgae in ships'ballast water through PEC,and explores the effects of different experimental conditions on the inactivation.The results show that the higher the light intensity,the better the inactivation efficiency.When PEC is 8minutes,the inactivation efficiency at 100%light intensity reaches 99.45%;too high a concentration of microalgae will seriously hinder the inactivation efficiency of PEC,the concentration of microalgae is 106/ml,PEC 10min,the inactivation rate is 22.35%;the appropriate temperature has an impact on the performance of the initial treatment of PEC inactivated microalgae;TNTs can be reused,with high degradation effect and stability.After repeated experiments,the inactivation rate of TNTs can reach more than 99%after 10 min.The research work in this paper is expected to provide certain design concepts and basic research and development for the design of new PEC devices and annealing devices in the future;to provide research directions for PEC technology to scientifically and effectively inactivate microorganisms in ship's ballast water.I also hope to find a new and ideal treatment method for the treatment of ship's ballast water,and make some contributions to the protection of the marine environment.