Synthesis and evaluation of recoverable activated carbon/Fe3O4 composites for removal of polycyclic aromatic hydrocarbons from aqueous solution

Abstract

Three different synthesis methods were employed to prepare magnetic powder and granular activated carbons (MPAC and MGAC) as recoverable adsorbents to remove polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. The MPAC and MGAC composites were characterized by XRD, and the XRD patterns confirmed the presence of Fe 3 O 4 particles with cubic crystal structure on the adsorbents surface. FE-SEM images showed that the magnetic composites had spherical morphologies, with clusters of iron oxide nanoparticles formed in the ACs pores and distributed evenly on their surface. FTIR spectra of the PAH-loaded adsorbents revealed that the analytes were attached to the surfaces of MPACs and MGACs by π - π and H- π interactions formed between the PAHs and functional groups of the adsorbents. All the synthesized magnetic ACs were very effective in removing PAH compounds from aqueous solution with removal percentages between 87.2% to 99.3%. The precipitation method of magnetization resulted in the highest PAHs removal efficiency (99.3%) using PAC as the base AC, while the co-precipitation method of magnetization provided the highest PAHs removal efficiency (98.3%) using GAC as the base AC. The PAHs desorption tests indicated that low molecular weight PAHs were more easily desorbed from the magnetic ACs ranging from 38.1 to 60.1%, compared with high molecular PAHs ranging from 23.4 to 57.2%. This shows that the increase in the number of PAH rings would lead to the formation of more covalent bonds between the adsorbate and the adsorbent. • Six types of magnetic activated carbon particles were successfully synthesized and characterized. • All the synthesized magnetic adsorbents were able to strongly remove PAHs from the aqueous solutions. • The adsorption results indicated that the PAHs have a strong affinity to the surface of the magnetic activated carbons. • All the magnetic activated carbons could be rapidly and efficiently separated from the solutions by a magnetic field. • Desorption of five- and six-ring PAHs from the magnetic activated carbons were lower than three- and four-ring PAHs.