Nanocrystalline structured ethylene glycol doped maghemite for persistent pollutants removal

Abstract

In this study, a new type of maghemite (γ-Fe₂O₃) nanoparticles, doped with ethylene glycol (EG) were investigated. The nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and N₂ adsorption/desorption technique for their morphological, structural, mineralogical and textural properties and examined in multiple adsorption/desorption cycles. Factors such as pH of the environment, adsorbent dosage and initial concentration of pollutant were studied. In case of γ-Fe₂O₃ the nanoparticles diameter is found to be in the range of 120–180 nm, while EG functionalized γ-Fe₂O₃ revealed an average diameter of about 50 nm by SEM analysis, confirmed also by TEM evaluation. The FT-IR investigation confirms the functionalization of γ-Fe₂O₃ with EG and EG presence within γ-Fe₂O₃ structure. The BET results show a substantial increase (ca. 2.9 fold) of the surface area for the nanoparticles that were synthesized in the presence of EG as opposed to EG-free nanoparticles. The maximum removal efficiency of 97.38% was obtained at pH 4 and at initial RY84 concentration of 10 mg L⁻¹. The adsorption is slower in wastewater effluent. The adsorption of RY84 onto magnetic adsorbent was better fitted by pseudo-second order (PSO) model for the adsorption test at concentration above 20 mg L⁻¹. However, at low dye concentrations, the experimental data were fitted slightly better by the Elovich model. The recyclability results showed that after 8 repeated experiments the adsorbent retained same very good activity, being a promising adsorbent for wastewater treatment.