Preparation Of Functionalized Ferrite And Its Application To Detection/Removal Of Heavy Metals And Organic Pollutants

In recent years,environmental pollution has been plaguing people.Nano-materials with its specific surface area,strong adsorption capacity and other superior performance in the detection and removal of environmental pollutants aspects has been more and more attention.In this study,the functionalized three-dimensional magnetic hollow porous ferrite nanoparticles?MHPS-NiFe₂O₄?were designed and synthesized by simple one-step hydrothermal method and applied to the simultaneous detection of multiple heavy metal ions?Cu2+,Cd2+,Cr3+,Co2+? Zn2+?in the actual sample;Simultaneous removal of inorganic pollutants?Cu2+,Cd2+,Cr3+ and Zn2+?and organic pollutants?CIP?,Enfloxacin?ENR?and Norfloxacin?NOR?in water.The basic research of this paper is as follows:1.)The functionalized magnetic hollow porous nanospheres?MHPS-NiFe₂O₄?was successfully prepared by simple one-step hydrothermal method and characterized by a variety of methods.The characteristic peak of ferritic nickel with spinel structure are shown in the XRD spectrum.The morphology of the MHPS-NiFe₂O₄ can be clearly observed on the SEM image and the broken microsphere image further shows that it is a hollow porous nanosphere morphology formed by the self-loading of nanoparticles.The results show that the surface of MHPS-NiFe₂O₄ is modified by a large number of amino groups and oxygen-containing functional groups,which is beneficial to enhance the adsorption performance of adsorbents.In the hysteresis loop analysis,the saturation magnetization?Ms?of MHPS-NiFe₂O₄ is about 10.12emu·g-1,which can be separated from the solution by magnet and is easy to be used.The possible growth mechanism of MHPS-NiFe₂O₄ is presumed to dissolve Fe3+ and Ni2+ in ethanol at the initial stage of the experiment to form a homogeneous solution.Under hydrothermal conditions,CO?NH2?2 decomposes into NH3 and CO2 bubbles.Fe3+ and Ni2+ ions nucleated at high temperature and self-assembled into NiFe₂O₄ nanoparticles.Secondly,many NiFe₂O₄ nanoparticles are aggregated and gradually deposited on the bubble surface.Then,the hollow porous Ni Fe₂O₄ microspheres were slowly grown in situ on the surface of the nucleus.In addition,urea as a modifier can also provide a functional group such as-NH2 and-C=O by hydrothermal method to improve its adsorption capacity.2.)The functionalized magnetic hollow porous ferrite nanoparticles?MHPS-NiFe₂O₄?were used as adsorbents for solid phase extraction of five heavy metal ions,and the simultaneous detection of five kinds of metal ions was carried out by ICP-OES.MHPS-NiFe₂O₄ has high magnetic response,good water dispersibility and has good adsorption properties to Cu2+,Cd2+,Cr3+,Co2+ and Zn2+ metal ions.The adsorption rates of MHPS-NiFe₂O₄ on Cu2+,Cd2+,Cr3+ and Zn2+were more than 95%,Co2+ was more than 80% under the optimum extraction conditions?the amount of adsorbent was 200 mg,the pH of solution was 5 and the adsorption time was 50 minutes?.When 2.5 mol · L-1HAc: 0.25 mol · L-1HCl?2:1,v/v?was used as the elution solvent,the elution volume was 10 mL and the elution time was 20 min.Metal ion recovery rate were more than 80%.Under the optimum extraction conditions,the enrichment factor of this method is 6.And the detection limits for Cu2+,Cd2+,Cr3+,Co2+? Zn2+ were as low as 0.015 ?g · L-1,0.13 ?g · L-1,0.062 ?g · L-1,0.035 ?g · L-1 and 0.46 ?g · L-1.The method has good reproducibility,the relative standard deviation?RSD?was 3.87%.The satisfactory recoveries of the five heavy metals?Cu2+,Cd2+,Cr3+,Co2+ and Zn2+?in the actual samples?cabbage,lettuce,apples,seawater?were in the range of 92-108%.3.)?MHPS-NiFe₂O₄?was used to remove various inorganic and organic pollutants such as Cu2+,Cd2+,Cr3+ and Zn2+ ions,ciprofloxacin?CIP?,enfluoride Desmethyl?ENR?and norfloxacin?NOR?.MHPS-NiFe₂O₄ showed excellent adsorption properties to the target.All the targets could be removed by more than 80% in the solution pH of 5 and the adsorption time of 60 minutes.In this paper,the adsorption of MHPS-NiFe₂O₄ on single metal ions/organic pollutants,the adsorption of multiple heavy metal ions/organic pollutants,and the simultaneous removal and continuous adsorption processes of various inorganic and organic pollutants in the mixed system are discussed in detail.In the adsorption isotherm study,four metal ions follow the surface of the monolayer adsorption Langmuir adsorption isotherm model,while the three organic pollutants follow the heterogeneous adsorption of the Freundlich adsorption isotherm model.Cr3+/ENR is preferentially adsorbed by MHPS-NiFe₂O₄ and has stronger affinity with MHPS-NiFe₂O₄ in the binary or multi-component system.For the same type of contaminants,the adsorption capacity of each target is reduced due to the competitive effect in the multicomponent system.Due to the different adsorption mechanism of inorganic pollutants and organic pollutants,the adsorption of four kinds of metal ions during the simultaneous removal and continuous adsorption of the mixed system does not affect the adsorption of the three organic compounds,and vice versa.Finally,the possible adsorption mechanism between the target and MHPS-NiFe₂O₄ was deduced by analyzing the infrared spectrum of before and after adsorption of adsorbent.The removal of organic pollutants was due to hydrogen bonds and intermolecular hydrogen bonds.Metal ions were mainly attributed to metal ions with-NH2 or-C=O groups of MHPS-NiFe₂O₄.