One-step synthesis of PI@Fe3O4 composite microspheres and practical applications in Cu(ii) ion adsorption

Abstract

Polyimide(PI)@magnetite(Fe₃O₄) composite microspheres have been successfully synthesized from poly(amic acid) triethylamine salts (PAAS) and Fe(III) ions by a facile one-step solvothermal process. Furthermore, the formation mechanism of the PI@Fe₃O₄ composite microspheres has been investigated. The morphology and structure of the samples were both characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopy (IR). The results obtained show that the surface of magnetite could be successfully coated with polyimide and the coating could permeate throughout the crystals via a self-assembly process. The size of the composite microspheres was found to increase upon increasing the concentration of PAAS. The thermal properties of the composite microspheres were studied via thermogravimetric analysis (TGA) and the magnetic properties were determined by a vibrating sample magnetometer (VSM). Even though the saturation magnetization of the PI@Fe₃O₄ composite microspheres is lower than that of pure Fe₃O₄, the microspheres coated with PI exhibit an increased stability. In addition, basic hydrolysis of the composite microspheres has been carried out and the Cu(II)-adsorption properties of the composite microspheres before and after hydrolysis have been investigated. In doing so, it could be determined that the adsorption capacity of hydrolyzed composite microspheres increases from 5.84 mg g⁻¹ to 24.63 mg g⁻¹.