Nanocomposites of a new organosoluble polyetherimide and epoxide‐functionalized magnetite for removal of Co(II) Ions: Kinetic and thermodynamic investigations

Abstract

This study reports the synthesis and characterization of the novel polyetherimide obtained from a new aromatic dianhydride monomer, 2,6‐bis‐(isobenzofuran‐1,3‐dione‐5‐yl)pyridine, and 2‐(5‐(3,5‐diaminophenyl)‐1,3,4‐oxadiazole‐2‐yl)pyridine (POBD). Magnetite nanoparticles were modified by γ‐glycidoxypropyl trimethoxysilane (GPTMS) to gain a core‐shell structure (Fe3O4@GPTMS). Magnetic nanocomposites (MNCs) containing different wt% of Fe3O4@GPTMS were then prepared. Structure, morphology and magnetic properties of the obtained nanoparticles and MNCs were studied by Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction, and vibrating sample magnetometry methods. The capability of MNC 25 wt% to remove Co(II) cations was shown under optimal pH (7.0), contact time (45 min), adsorbent dosage (50 mg) and initial metal ion concentration (3.0 ppm). The adsorption kinetics followed the pseudo‐second‐order kinetic equation and the adsorption isotherm was best described by the Langmuir model with a maximum adsorption capacity of 1.33 mg g−1. According to the thermodynamic study, the adsorption process was spontaneous, endothermic and entropy favored in nature (ΔG = −2.96 kJ mol−1; ΔH = 19.63 kJ mol−1; ΔS = 75.80 J mol−1). The intraparticle diffusion and Boyd kinetic models revealed that the adsorption mechanism is intraparticle diffusion which is controlled by film diffusion. MNC 25 wt% was regenerated by stirring the Co(II)‐complexed adsorbent in an acidic medium for 1 h followed by magnetic decantation and washing steps. The adsorption–desorption cycles were repeated seven times and the re‐generated sorbent was re‐used under optimal conditions. The average extraction efficiency (E%) of the five consecutive runs was 85.8%, indicating the sorbent recovery by 93.5% after five cycles. POLYM. COMPOS., 40:3166–3181, 2019. © 2018 Society of Plastics Engineers