Preparation Of Functionalized Magnetic Materials And Its Applications In Separation And Preconcentration Of Trace Heavy Metal

With the development of economy,environmental issues,food and drugs safety have become a serious problem,which seriously affected the quality of people's life.Heavy metal pollution has attracted nationwide attention.Especially,cadmium,lead and mercury are typical heavy metal elements,which have hazardous effects on human health and the environment is now being increasingly revealed.AFS has the characteristics of good precision,simple operation and lower cost.However,In the face of complex matrix samples or analyte of low concentration,it is necessary that some separation and enrichment methods should be involved prior to determination for better sensitivity and selectivity.Fe₃O₄ has a wide range of applications in environmental monitoring and other fields owing to many superiorities including small size effect,large specific surface area and high adsorption capacity,and magnetic materials can easily separated from the solution in the presence of an external magnetic field.This paper aims to develop functionalized magnetic materials combining AFS to preconcentration seperation heavy metal water sample in environment.Research contents were as followed:1.Fe₃O₄/SiO₂/TMS-EDTA nanoparticles was prepared and used as the adsorbent for the preconcentration of trace amount of Pb?II?and Cd?II?ions prior to its determination by hydride generation atomic fluorescence spectrometer.Fe₃O₄/SiO₂/TMS-EDTA nanoparticles characterized with FT-IR,SEM.Various parameters affecting MSPE were optimized systematically,under optimal conditions,enrichment factors were 83.3 and 66.7 for Pb?II?and Cd?II?ions,respectively.The obtained linearities were 0.12-15 ng mL-1 for Pb?II?and 0.10-4.0 ng mL-1 for Cd?II?.The LODs?3??was 0.030 ng mL-1 and 0.028 ng mL-1 for Pb?II?and Cd?II?ions,respectively.Also,the resultant repeatability expressed as relative standard deviations?RSD,n=7?were calculated as 2.72% and 3.41% for Pb and Cd,respectively.The method has been successfully applied to determination of Pb and Cd in water samples?tap water and lake water?.2.L-Cysteine functionalized Fe₃O₄ magnetic material?Fe₃O₄/Cys?via a one-pot solvothermal route,which were used as adsorbents coupled with hydride generation atomic fluorescence spectrometer for the removal of Pb?II?and Cd?II?ions from aqueous solutions.Fe₃O₄/Cys magnetic materials were characterized by FTIR.The main factors affecting the signal intensity have been investigated and established.Under the optimum conditions,the adsorption capacity of Pb?II?and Cd?II?ions were found to be 9.91 mg g-1 and 5.89 mg g-1,respectively.The linear range of Pb?II?and Cd?II?ions were 0.1-50 ng mL-1 and 0.15-30 ng mL-1 with relative standard deviations were 2.94% and 3.53%?n = 7?,respectively.The detection limit of Pb?II?and Cd?II?was 0.069 ng mL-1 and 0.11 ng mL-1,respectively.It can be concluded that the Fe₃O₄/Cys magnetic material could be used as a very promising and high effective materials for Pb?II?and Cd?II?determination.3.A new method was developed for the determination of trace mercury in natural water samples by coupling solid phase extraction?SPE?to hydride generation atomic fluorescence?HG-AFS?using oxidized multi-walled carbon nanotubes?ox-CNTs?micro-column as sorbent.Various experimental conditions that influence the solid-phase extraction and determination of trace mercury had been studied in detail,including pH of the solution,flow rate and volume of sample,volume and concentration of eluent and interfering ions.Under the optimum conditions,an enhancement factor of 30 was obtained with a sample consumption of 5.0 mL.The detection limit?3??was 7.13 ng L-1 for mercury.The precision?R.S.D?of 7 replicate measurements of 0.1ng mL-1 Hg?II?was 1.51%.The method was successfully applied to the determination of trace mercury in natural water samples with satisfactory results.