Study On The Application Of Magnetic Composite Materials In The Adsorption And Preconcentration Of Heavy Metal Ions

The treatment and monitoring of heavy metal ions in water environment is closely related to the stability of whole ecosystem and safety and health of human beings.The application of magnetic composite materials shows rapid upward trend in the treatment and analysis of heavy metals in wastewater due to its advantages of magnetic properties,larger surface area,more active sites and high selectivity.In this paper,the present status of heavy metals pollution,and common treatment approach at present were introduced in briefly.Meanwhile,the application of magnetic composites in the treatment of environmental pollutants,enrichment and detection methods of heavy metals were elaborated emphatically.Then research on preparation and application of magnetic composite materials were carried out afterwards.The detailed contents in research are as follows:First of all,four magnetic materials,Fe₃O₄,Fe₃O₄/G,Fe₃O₄/PPy and Fe₃O₄/G/PPy,were synthesized and the adsorption properties of Cr?VI?on these materials were investigated under the condition of ultrasonic and stirring mode of dispersion,respectively.It is found that the application of ultrasonic can significantly improve the adsorption capacity of Cr?VI?on magnetic materials.The larger the magnetic moment of the material,the higher the degree of the enhancement in adsorption capacity.In addition,the effects of ultrasonic frequency,power and other factors on adsorption performance for magnetic material with different magnetic moment were highly significant.For example,the saturated amount of adsorption Fe₃O₄/G increased by 105% when applied ultrasonic frequency at 59 kHz compared to 40 kHz;and the adsorption capacity was increased by 120% when the ultrasonic power increased from 30 W to100 W.The thermodynamic data show that the adsorption of Fe₃O₄/PPy and Fe₃O₄@G/PPy in the two dispersion modes are in accordance with the Langmuir isotherm model,and the kinetic processes are consistent with the pseudo two order kinetics model.Subsequently,Fe₃O₄@SiO₂-IL1 and Fe₃O₄@SiO₂-IL2,were prepared by modified with imidazolium ionic liquid of 1-butyl-3-methylimidazolium dihydrogen phosphate and1-butyl-3-methylimidazolium three trifluoromethane sulfonate,respectively.Then a new method for highly sensitive determination of ultra trace Hg²⁺ based on the two material was established.The SEM,XRD and FT-IR spectra showed that the loading by ionic liquid only changed the surface morphology of Fe₃O₄ without transformation of the lattice structure.Enrichment experiments showed that the adsorption of Fe₃O₄@SiO₂-IL1 and Fe₃O₄@SiO₂-IL2 on 0.2 g L^-1 Hg²⁺ solution reached equilibrium at 30 and 60 min,respectively.Under the optimized experimental conditions,the detection limits of Hg²⁺ after preconcentration by the two materials were 0.25 ng L^-1 and 0.36 ng L^-1,respectively,and the relative standard deviations were 3.2% and 4.1%,respectively.The actual environmental water samples were tested,and the results of recovery were range in 95.8%¹06.7%.Finally,magnetic composites of ?-Fe₂O₃@MnO₂ was synthesized successfully by hydrothermal method and the enrichment of trace As?III?was discussed.The characterization of SEM,XRD and BET shows that the material surface is loose and porous spherical and the size is about 3 ?m,surface area and total pore volume were 121.926 m2 g-1 and 0.21 cm3 g-1,respectively.The adsorption time,initial concentration,pH,temperature,adsorbent dosage,eluent type and concentration,the interference ions were systematically studied.It is found that0.2 ⁵.0 g L^-1 As?III?can be completely enriched with high recovery based on the above materials in 10⁶0 min.Based on the established analytical method,the detection limit of As?III?was 0.25 ng L^-1,and the relative standard deviation was 3.2%.