Efficient Extraction Of Organic Acid Pollutants From Environmental Water By Ionic COFs

At present,organic acid pollutants are widely distributed in the environment,and their sources mainly include agricultural production,industrial production and human life.In this paper,several representative organic acids were selected as the detection target,such as perfluorinated organic compounds,phenoxy carboxylic acid herbicides and plant growth hormones.These pollutants are frequently used in human production and life.They are difficult to degrade and can migrate and accumulate with individuals,causing harm to the environment and human body.Here a new type of magnetic ion covalent organic framework was designed and synthesized and applied to the enrichment and detection of organic acid pollutants.In this paper we have firstly synthesized Fe₃O₄@EB-iCOF.It has been subjected to X-ray,N₂ adsorption analysis and magnetic test.The material then shows the advantages of ionic properties,large surface area and magnetic responsiveness.It has the potential of magnetic solid phase extraction（MSPE）for perfluorinated compounds（PFCs）.Combined with MSPE-HPLC-MS/MS,a new method for the determination of perfluorinated compounds was established.The method has good linearity（R²≥0.995）and good reproducibility（1.4～5.8%）in the working range of 1～1000 ng·L^-1.N=6),the detection limit was 0.1～0.8 ng·L^-1,and the recoveries of environmental water samples were 73.9～108.3%.Secondly,another novel ion covalent organic framework（Fe₃O₄@EB-TFB-iCOF）was synthesized.Magnetic solid phase extraction（MSPE）was also used to extract herbicide and plant growth hormone mixed organic acid pollutants in water.The optimum process conditions（such as adsorption time,solution p H,material dosage,etc.）of MSPE were studied.Under the optimum conditions,a simple and sensitive analytical method was developed with high performance liquid chromatography.The method had good linear regression（R²≥0.995）,high precision（1.53-3.80%,n=6）,and low detection limit(0.1-0.49 ng·m L^-1).The recoveries of environmental water samples（Heihu Spring,groundwater and irrigation water）were 73.3%-101.0%.In addition,selective adsorption experiments were carried out to explore the mechanism of such extraction experiments.Firstly,there is hydrogen bonding force between the material and the target object.Secondly,it is found through potential study that when p H is equal to 3,the material is positively charged and the target object has electrostatic attraction.In general,in this paper,a new type of ionic covalent organic frameworks was successfully synthesized for the first time and applied to the magnetic solid phase extraction experiment.Trace organic acids such as perfluorinated compounds,herbicides and plant growth hormone mixed acids in water samples were detected and analyzed respectively.The experimental results show that the treatment technology has high sensitivity,low detection limit and wide linear range,and the use of organic solvents is small.It is economical and environmentally friendly,and can achieve high extraction efficiency at the same time.