Preparation Of Magnetic Nanoadsorbents And Its Adsorption For Cadmium Ions In Water

Magnetic Fe₃O₄ nanoparticles?Fe₃O₄ nanoparticles:Fe₃O₄ NPs?have large specific surface area,rich active sites,high magnetic response sensitivity,and can be quickly separated from the liquid phase by the action of an external magnetic field,which can be recycled and reused.Good for heavy metal ion adsorption.However,due to the hydrophilic groups on the surface of Fe₃O₄ NPs,the particles are easily agglomerated in aqueous solution,and have high chemical reactivity,which is sensitive to oxidants,thus limiting their application in heavy metal ion adsorption.Some polymers such as polypyrrole?PPy?,polyaniline?PANI?,etc.may be modified on the surface or modified by adding a surfactant to solve the problem that the particles are easily agglomerated.Adding surfactants such as sodium dodecylbenzene sulfonate?NaDBS?,polyethylene glycol?PEG?,hexadecane and trimethylammonium bromide?CTMAB?can improve the dispersion and chemical stability of Fe₃O₄ NPs.Polypyrrole is more porous to the surface due to its porous surface and more adsorption active sites on the surface.The surface of Fe₃O₄ NPs is modified to be hydrophobic after the addition of surfactant,and it is easier to polymerize with polypyrrole.Graphene oxide?GO?has a special network structure and a functional group with many surfaces to provide active sites for heavy metal ion adsorption.The magnetic nano-adsorbent prepared by the combination of Fe₃O₄ NPs,PPy and GO can simultaneously obtain the magnetic properties of Fe₃O₄ NPs and the strong adsorption properties of PPy and GO.The magnetic nano-adsorbent with the traditional adsorption material has the advantages of non-toxicity,high adsorption selectivity and good regeneration performance.In order to obtain an adsorbent with excellent performance,two kinds of magnetic nano-adsorbents for heavy metal cadmium ions were prepared by combining these three kinds of materials.The specific research contents are as follows:?1?Fe₃O₄ NPs were prepared by coprecipitation method and characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT-IR?,thermogravimetric analysis?TGA?and vibrating sample magnetometer?VSM?.The results show that the as-prepared Fe₃O₄ NPs are regular spherical structures with good dispersion and the average particle size of about 15 nm and have a saturation magnetization of 45 emu/g.?2?Preparation and characterization of Fe₃O₄/PPy composite nanoparticles:In the preparation process of Fe₃O₄ NPs,a suitable surfactant,polyethylene glycol 4000?PEG-4000?,was selected and compounded with PPy under mechanical stirring to prepare Fe₃O₄/PPy composite nanoparticles and carry out various characterizations.The prepared composite nanoparticles have an average particle diameter of about 130nm,and a plurality of Fe₃O₄ NPs are embedded in the polypyrrole microspheres.The composite nanoparticles are well dispersed,and the saturation magnetization is 4emu/g,which can be quickly separated by the action of an external magnetic field.?3?Preparation and characterization of Fe₃O₄/PPy/GO compounds:GO was prepared by an improved method of the conventional Hummers method.Due to the presence of more amino groups and hydroxyl groups on the surface of the graphene oxide,the complexation of Cd²⁺can be enhanced.It can be obtained by adsorbing Fe₃O₄/PPy nanoparticles on the surface of graphene oxide by stirring.The loading of graphene oxide can further increase the adsorption efficiency of cadmium ions,and can also be quickly separated from the aqueous solution by the action of an external magnetic field.?4?Adsorption and desorption of Cd²⁺by Fe₃O₄/PPy composite nanoparticles and Fe₃O₄/PPy/GO compounds:Adsorption and desorption of Cd²⁺on Fe₃O₄/PPy nanoparticles and Fe₃O₄/PPy/GO compounds experiment.Simultaneously,the adsorption and desorption experiments of pure GO on Cd²⁺were carried out,and the adsorption performance of the two adsorbents prepared was compared.In the adsorption experiment,a certain amount of the obtained Fe₃O₄/PPy nanoparticles,Fe₃O₄/PPy/GO compounds and pure GO were respectively dissolved in the Cd²⁺solution,and after stirring for a while,the supernatant was separated by a magnet.The absorbance of Cd²⁺at 228.8 nm was measured by flame atomic spectrophotometer,and the residual concentration was calculated by the relationship between absorbance and concentration,and the amount of Cd²⁺adsorbed by the remaining Cd²⁺concentration.The adsorbed nanoparticles were dried,dispersed in a 1mol/L hydrochloric acid solution,and desorbed under stirring.The absorbance of Cd²⁺at 228.8 nm was also measured by a flame atomic spectrophotometer.The maximum adsorption capacity of Fe₃O₄/PPy/GO compounds prepared after loading GO can reached 57.83 mg/g,and the slow release of Cd²⁺can be achieved under stirring,and the desorption efficiency reaches 88.9%.In this paper,Fe₃O₄/PPy composite nanoparticles and Fe₃O₄/PPy/GO compounds were prepared,and their adsorption and desorption properties for heavy metal Cd²⁺were studied.Compared with the traditional adsorbent,the preparation methods of Fe₃O₄/PPy nanoparticles and Fe₃O₄/PPy/GO compounds are simple,and the prepared two magnetic nanoadsorbents have high adsorption rate,no toxic and side effects,and can be well applied to adsorption of heavy metal ions in sewage.