Preparation Of Functional Fibers With Microwave-Assisted Method And Its Application To Detection Of Cu(?) In Vegetables

In view of the current heavy metal pollution problem,especially the vegetable pollution problem caused by soil heavy metal pollution,the existing analysis and detection methods still have many shortcomings,so it is particularly important to establish a method with good accuracy,high sensitivity,simple operation and low cost.It is of great value and practical significance to carry out the preparation of new adsorption functional materials and use it in combination with spectrophotometry,which can effectively increase the detection range of spectrophotometry.In this study,polyacrylonitrile fibers were used as raw materials,and hydroxyurea,2-aminopyridine,and 5-amino-2-methoxypyridine were used as ligands.Three types of adsorption functional fibers were prepared by microwave-assisted method: PAN-HDU,PAN-TAP and PAN-FAMP.The synthesis conditions were optimized by orthogonal experiment with 5 factors and 4 levels.The adsorption functional fibers were characterized by infrared spectroscopy,scanning electron microscopy,X-ray diffraction,thermogravimetric analysis,Zeta potential and elemental analysis.The measurement results of the adsorption properties of the three fibers showed that the optimal pH for Cu(?)ion adsorption by the PAN-HDU fiber was 6 and reached equilibrium at 120 min.At pH=2,PAN-TAP and PAN-FAMP fibers adsorbed the largest amount of Cr(?)ions.The adsorption equilibrium time of PAN-TAP fiber was 60 min,and PAN-FAMP was 30 min.In addition,0.5 mol/L hydrochloric acid can completely elute Cu(?)adsorbed on PAN-HDU,and after 5 desorption adsorption cycles,the adsorption amount is more than 90% of the initial adsorption amount.The desorption rate of PAN-TAP and PANFAMP by 4 mol/L hydrochloric acid was above 70%.Then the non-linear fitting of experimental data of adsorption functional fibers was performed.Three fibers conformed to the pseudo-second-order kinetics and Langmuir isothermal adsorption model,which showed that the adsorption process was mainly chemical adsorption.The theoretical adsorption of PAN-HDU at 25? is 219.08 mg/g,the theoretical adsorption of PAN-TAP at 25? is 287.14 mg/g,and the theoretical adsorption of PAN-FAMP at 25? is 282.38 mg/g.The results of adsorption thermodynamics show that the adsorption process proceeds spontaneously,the temperature increase promotes the adsorption,and the irregular interlayer adsorption of the micro-interface of the solid-liquid system is enhanced.The XPS analysis results show that the main adsorption mechanism of PAN-HDU fibers is due to the chelation of Cu(?)ions by N and O atoms,and the adsorption mechanism of PAN-TAP and PAN-FAMP fibers is due to ion exchange and chelation.A method for detecting Cu(?)ion in vegetables was established by combining PAN-HDU fiber with spectrophotometry.The optimal conditions of the PAN-HDU fiber pre-enrichment column were optimized,and the content of Cu(?)ions in 6 vegetables was detected in combination with spectrophotometry.The results were basically the same as those obtained by ICP-AES.The precision and spiked recovery experiments show that the method has good accuracy and precision,and provides a reliable technical solution for the adsorption of functional fibers in food heavy metal detection.