Removal of heavy metal (Hg(II) and Cr(VI)) ions from aqueous solutions using Fe2O3@SiO2 thin films as a novel adsorbent

Abstract

Abstract In this work, plasma-enhanced chemical vapor deposition method was used for synthesizing Fe2O3@SiO2 thin films as a novel adsorbent for removal of heavy metal mercury(II) and hexavalent chromium ions from water samples. To that end, crystalline structure, chemical state, morphology, optical and magnetic property of deposited film were characterized using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV–vis spectrophotometer (UV–vis), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) system respectively. Then, the effects of some parameters such as the initial pH, the initial content of metal, the synthesized adsorbent dose, the contact time, the temperature and the ionic strength were analyzed for a batch adsorption system. The adsorption data was modeled by different models using the origin nonlinear software version 6.1. The results indicated that, the adsorption kinetics was well fitted by the pseudo second-order model, while the adsorption isotherm was well fitted by the Brouers–Sotolongo model. Moreover, it was found that the maximum adsorption process capacities of metal ions on adsorbent were 335.5 8 mg g−1 for Hg(II) and 152.8 mg g−1 for Cr(VI). It was also noted that, the mechanism of adsorption was complex where several types of interaction between ions and the surface of the prepared adsorbent were involved. Also, based on the results of the desorption studies it was speculated that adsorbent could be easily regenerated using eluents.