Preparation Of Multifunctional Magnetic Microspheres With Core-shell Structure For The Extraction Of Trace Pollutants In Environmental Water

Because of the complex composition of the environmental water bodies and the presence of pollutants in trace amounts,a pretreatment step is needed before analyzing by chromatography.In recent years,magnetic solid-phase extraction?MSPE?,which is based on solid-phase extraction?SPE?,has attracted more and more attention.Magnetic adsorbents are used in MSPE as the key to this technology.In this paper,according to the characteristics of pollutants?bisphenol and tetracycline compounds?in environmental water,a magnetic microsphere with a shell-core structure was designed,basing on the characteristics of bisphenols?BPs?and tetracycline antibiotics?TCs?,for the selective extraction and determination of trace pollutants in water combined with liquid chromatography.First,Fe₃O₄ magnetic nanoparticles were prepared by solvent thermal method,a thin layer of C shell is coated on the surface of Fe₃O₄ by hydrothermal synthesis method to obtain core-shell Fe₃O₄@C.This material had high saturation magnetization and good chemical stability in aqueous solution.At the same time,the synthesis time?8,12,and 24 h?was investigated on the synthesis of magnetic nanomaterial.The adsorption capacity of Fe₃O₄@C for bisphenols was investigated.The factors affecting extraction efficiency?adsorbent quality,eluent volume,solution pH value,etc.?were also optimized.The method for analyzing the environmental water samples of bisphenols were established combined with ultra-high performance liquid chromatography?UPLC?.The experimental results showed that the synthesized Fe₃O₄@C magnetic nanoparticles with a core-shell structure,the thickness of the shell about 5 nm,and the diameter of core about 150 nm.When synthesis time was 24 h,the carbon content was the highest,with the best extraction efficiency.The maximum adsorption capacity was about 9.25-10.68 mg g^-1,and the detection limits were 0.03-0.1?g L^-1.The standard recovery rate was 85.9-108.5%and RSDs 0.3-4.3%.In order to accurately detect tetracycline antibiotics in environmental water,FeO nanoparticles were modified on the surface of magnetic silicon microspheres?Fe₃O₄@SiO₂?.The key factors affecting extraction efficiency and the selectivity of magnetic material were investigated.Under the optimal conditions,the analysis method of TCs in water was established,combined with UPLC.Synthesized Fe₃O₄@SiO₂@FeO microspheres had well-defined core-shell structure,and the maximum saturation magnetization value was 35.5 emu g^-1.The modified FeO particles were well dispersed on the surface of the silicon shell,with uniform particle size of 5 nm.The Fe₃O₄@SiO₂@FeO had excellent selectivity for TCs in water.When the amount of adsorbent was 7.5 mg,at pH 3-9,with using 10%-MEOH:20%-ACN:70%-0.02 mol L^-11 oxalic acid solution as the eluent,the magnetic material had the highest extraction efficiency for three TCs.The method showed good linearity in the range of 0.133-333?g L^-1?R>0.999?,and the detection limits were 0.027-0.1070?g L^-1.