Study On The Preparation Of Phptocatalytic Microreactor And Its Application In Environmental Monitoring Of Water Sample

Water quality analysis is important for monitoring of water pollution.Most water quality monitoring items,including organic phosphor,heavy metal and COD etc,need sample pretreatment.Traditional pretreatment technologies such as high temperature and high pressure digestion.Microwave digestion always need strong acid,which will cause environmental pollution.Also they need special equipments,which are time consuming and energy costing.Recently,photocatalytic oxidation technology is widely used in environmental analysis as a pretreatment technology due to its well-known advantages of environmental,efficient and nontoxic.It becomes more effective,flexible and portable when integrated with microreactor technology.In this paper,main work is the preparation of photocatalytic microreactor and its application in detection of organic phosphor and heavy metals.In the first chapter,a review is made to introduce the common pretreatment technologies for water quality monitoring,the principle and influence factors of photocatalytic oxidation,the combination of photocatalytic oxidation technology and microreactor technology,and the detection methods for organic phosphor and heavy metals.In the second chapter,we investigated the fabrication of photocatalytic microreactor by coating nano-TiO₂ film in microfluidic channel with sol-gel process.The photocatalytic performance of the prepared TiO₂ coating microreactor was monitored with the degradation rate of methylene blue.In the process of sol-gel,the flow rate and retention time of hydrothermal treatment of sol coated microchannels were optimized.The effect of coating thickness and doping of Si on the photocatalytic performance of the microreactor were also invesgated.The photocatalytic microreactor fabricated under the optimized condition showed good photocatalytic performance.The highest degradation rate of methylene blue in the microreactor reached up high to 97.1%.However,the stability of the TiO₂ film in the microchannel coated with sol-gel process is not good enough.The reproducibility of the MB degradation rate in the same microreactor was only 26.7%?RSD,n=7?.So it is not applicable to real sample.In the third chapter,we prepared a photocatalytic microreactor coated with nano-TiO₂powder.By using UV-LED as light source,UV-VIS spectrophotometer as detector,an microfluidic analysis system based on TiO₂ coated microreactor has been established.Organic phosphorus?chlorpyrifos?in water sample had been detected in the microfluidic analysis system.Influence factors including light intensity,flow rate and pH of organic phosphorus sample,flow rate of ammonium molybdate with ascorbic acid had been investigated.Different concentration of standard phosphate have also been measured under the optimized condition and showed a good linear relationship in the range of 0.05-5 mg/L,the regression equation of standard phosphate is y=0.1125x+0.1702,R²=0.9904.Detection limit of standard phosphate is0.013mg/L,and the recovery of chlorpyrifos is 80.0%.Several Organic phosphorus have been detected in this microfluidic analysis system with good sensibility.It takes40 minutes to complete the whole process of measurement including degradation of organic phosphorus sample.In the fourth chapter,an microfluidic analysis system based on photocatalytic microreactor with electrochemical detection of heavy metals has also been established.The concentration of Cd²⁺in Cd²⁺-EDTA water sample has been measured in this analysis system.Influence factors including light intensity,flow rate and pH of water sample,flow rate of the oxidant have been investigated.Under the optimal condition,the degradation of EDTA in water sample rate up to 92.6%.The regression equation of the current for Cd²⁺is i_p=13.22c+0.0001,R²=0.9994?The detection limit of Cd²⁺is 0.0025mg/L.The sample volume needed for the electrochemical detection of Cd²⁺is only 0.3mL.The total analysis time for one measurement is about 60min.In the last chapter,I summarized the works described in the chapters forehead,presented the innovation points of my works,and outlined the prospect of photocatalytic microreactor.