Study On The Application And Mechanism Of Bifenthrin Extraction By Different Anionic Imidazoles Polymerized Ionic Liquids Based On Infrared Spectroscopy

Compared with traditional solvents,ionic liquids have many unique advantages,such as zero vapor pressure,non-volatile,so-called“Green solvent”,good solubility and chemical stability,and large stable temperature range,wide electrochemical stable potential window,adjustable design of anion and Cation,and designability of structure-property.Because of these unique properties,the application research of ionic liquids is developing rapidly in the world.Polymer ionic liquids（PILs）have the advantages of both ionic liquids（Ils）and polymers,so they have good ionic and conductive properties.There are hydrogen bonds in the lattice of Imidazolium polymerized ionic liquids,which may break and recombine.The main contents of the paper are as follows:（1）The effect of ultrasound（US）on imidazole-based polymeric ionic liquids with different anions BF₄^-,PF₆^-and Br^-was investigated by FT-IR infrared spectroscopy.This is also to study the formation and breaking process of hydrogen bonds inside the polymer ionic liquid grid,and then measure the FT-IR spectra of water-free and water-free at different frequencies and times.These results show that when ultrasound is present.The polymerized ionic liquid breaks the hydrogen bond with the free water inside the grid,but the infrared spectrum of P[VEIM]PF₆changes little in terms of infrared spectrum,because for P[VEIM]PF₆,the PF₆^-It is extremely hydrophobic,so the free water content inside the grid is very small,and it is difficult to affect the hydrogen bond formed by the polymerized ionic liquid when it is acted on by ultrasound,but for P[VEIM]Br and P[VEIM]BF₄In terms of their hydrophilicity,in the presence of ultrasound,the hydrogen bond formed by the free water inside the polymeric ionic liquid will be greatly affected,and the most influential one is P[VEIM]Br,This is due to its greater hydrophilicity,so the hydrogen bond formed with the inside of the grid under the influence of ultrasound has the strongest influence.（2）The abuse of pyrethroid pesticide has attracted more and more attention in recent year.Excessive pesticides will enter waters through a variety of ways,and eventually endanger human health through the enrichment of food chain.Therefore,it is of great significance to establish a microextraction method for pyrethroid pesticide detection in environmental water samples.Three kinds of polymeric ionic liquids were successfully prepared,and characterized with infrared spectrometer（IR）and scanning electron microscopy（SEM）.Bifenthrin was used as a typical pyrethroid pesticide,and P[VEIm]PF6 was selected as extractant in the effervescent dispersive microextraction method.Combined with high performance liquid chromatography,the content of typical pyrethroid pesticide bifenthrin was detected in environmental water sample.The method was optimized by single factor optimization as follows:ionic liquid 0.2g,temperature 25℃,p H 7.0,and elution time10min.Under optimized conditions,limit of detection was 2.7μg/L,the equation is Y=76500X-1260,R²was 0.9965 and the concentrations were in the range of 5～100μg/L.The RSDs varied from 4.0 to 6.9%and extraction recoveries were 92.5-98.7%in environmental water samples.（3）Herein,we prepared three imidazolium-based polymeric ionic liquids（PILs）with different anions（P[VEIM]BF₄,P[VEIM]PF₆and P[VEIM]Br）,and analyzed their differential extraction efficiencies for bifenthrin through H-bonding induced effects.Three PILs all presented irregular block structure with rough surface and lower specific-surface area（SSA,11.2-18.7 m²/g）than carbon-based nanomaterials.They formed hydrogen bonds with free-water molecules in the lattice of PILs,including C_2,4,5-H...O-H,Br...H-O-H...Br,O-H...Br,C_2,4,5-H...F-P,P-F...H-O-H...F-P,C_2,4,5-H...F-B and B-F...H-O-H...F-B.After extraction,the O-H stretching-vibration peak was prominently intensified,whereas the C-H bond varied slightly in concomitant with prominently reduced B-F and P-F vibration.Theoretically,the C-H vibration should become more intense in the C_4,5-H...H₂O and C₂-H...H₂O bonds after extraction in contrast to before extraction.These contrary spectral changes evidence that after extraction,the hydrogen bonds between cations in the PILs and free-water molecules were broken,further yielding the H-bonding occurrence between bifenthrin and H-O-H in lattice.As a time indicator for the free-water binding and releasing process,the highest slope for the plot of It/I0 against time implied that the shortest time was required for P[VEIM]PF6 to reach an adsorption equilibrium.Overall,the strong hydrophobicity,small SSA and electrostatic-repulsion force for P[VEIM]PF₆are all not conducive to its efficient adsorption.Contrary to our expectation,P[VEIM]PF₆provided the highest extraction recovery for bifenthrin up to 92.4%among three PILs.Therefore,the above high efficiency was realized owing to the strongest H-bonding formation between P[VEIM]PF₆and bifenthrin.These findings/analyses promote our deep understanding of PILs-triggered differential efficiency through H-bonding induced effect.