Preparation And Application Of Strongly Basic Anionic Magnetic Microspheres

Magnetic solid phase extraction is an innovative separation and purification technique that utilizes functionalized magnetic microspheres as adsorbents.By applying an external magnetic field,these microspheres can be directly separated from the matrix,thus achieving the objectives of separation,purification,and enrichment.Magnetic solid phase extraction offers several advantages over traditional column chromatography,such as simplicity,time efficiency,and the elimination of centrifugal filtration.This technique has a wide range of potential applications in the fields of trace pollutant analysis,detection,separation,and purification.Magnetic ion exchange technology,which combines magnetic solid-phase extraction and ion exchange techniques,is characterized by its rapid adsorption and separation capabilities.In this study,quaternary ammonium-functionalized magnetic microsphereswerepreparedusingN-（trimethoxysilylpropyl）-N,N,N-trimethylammonium chloride as the functional monomer.Based on different application requirements,the surface of the magnetic microspheres was modified to prepare strong base ion exchange magnetic microspheres and strong base molecularly imprinted polymer magnetic microspheres.The adsorption performance of acetic acid and sildenafil was studied,with details provided below:（1）To develop an adsorbent and method for the deep removal of trace acetic acid fromdimethylacetamide（DMAC）aqueoussolutions,quaternary ammonium-modified magnetic microspheres were prepared as adsorbents for extracting low-concentration acetic acid from DMAC aqueous solutions.N-（trimethoxysilylpropyl）-N,N,N-trimethylammonium chloride was employed as the functional monomer to synthesize ion exchange magnetic microspheres（Fe₃O₄@Si O₂@N（CH₃）₃⁺）through a two-step sol-gel method.The synthesized microspheres were characterized using characterization techniques such as Scanning Electron Microscope（SEM）,Fourier Transform Infrared Spectroscopy（FT-IR）,X-Ray Diffraction（XRD）,X-ray Photoelectron Spectroscopy（XPS）,and Vibrating Sample Magnetometer（VSM）.The prepared microspheres were then used to adsorb acetic acid,and the adsorption performance was optimized.Experimental results show that the prepared microspheres have a spherical structure and a saturation magnetization intensity of 40.49 emu/g.The quaternary ammonium salt was successfully modified on the surface of the magnetic microspheres.Under conditions of acetic acid concentration at 30 mg/L,adsorbent dosage of 1 g/L,and a temperature of 45°C,the maximum adsorption capacity was 11.06 mg/g.Tests for recyclability indicate good stability of the ion-exchange magnetic microspheres.Adsorption experiments of acetic acid in DMAC wastewater were carried out.When the mass concentration of acetic acid in water and DMAC wastewater is 0.006%,the removal rate is 100%,providing a new method for the removal of acetic acid in industrial DMAC wastewater.（2）To develop magnetic microspheres with selective adsorption capabilities for sildenafil,N-（trimethoxysilylpropyl）-N,N,N-trimethylammonium chloride（50%methanol solution）was employed as the functional monomer,sildenafil as the template molecule,tetraethyl orthosilicate（TEOS）as the crosslinker,and combined with silica-coated magnetic microspheres and initiator to synthesize sildenafil magnetic molecularly imprinted material（MMIP）.The material structure and properties were characterized using scanning electron microscopy（SEM）,Fourier-transform infrared spectroscopy（FT-IR）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,vibrating sample magnetometry（VSM）,and thermogravimetric analysis（TGA）.By incorporating magnetic solid phase extraction（MSPE）with high-performance liquid chromatography（HPLC）,the adsorption performance of sildenafil was investigated.The results showed that the prepared MMIPs were uniform in size with an average diameter of 322.3 nm,and a saturation intensity of 44.70 emu/g.Under the conditions of an initial concentration of sildenafil of 25 mg/L and a temperature of 18°C,when the adsorption time was 20 minutes and the amount of MMIP was 10 mg,the MMIP showed good adsorption performance for sildenafil with a maximum adsorption capacity of 22.62 mg/g.Meanwhile,through repeated use experiments,it was demonstrated that after 8 cycles of use,the reusability could still reach 88.5%,indicating that MMIP could be reused.