Synthesis and Characterization of γ-Fe₂O₃/Carbon Hybrids and Their Application in Removal of Hexavalent Chromium Ions from Aqueous Solutions

Abstract

Magnetic Fe(2)O(3)/carbon hybrids were prepared in a two-step process. First, acetic acid vapor interacted with iron cations dispersed on the surface of a nanocasted ordered mesoporous carbon (CMK-3). In the second step, the primarily created iron acetate species underwent pyrolysis and transformed to magnetic iron oxide nanoparticles. X-ray diffraction, Fourier-transform infrared, and Raman spectroscopies were used for the chemical and structural characterization of the hybrids, while surface area measurements, thermal analysis, and transmission electron microscopy were employed to determine their physical, surface, and textural properties. These results revealed the preservation of the host carbon structure, which was homogenously and controllably loaded (up to 27 wt %) with nanosized (ca. 20 nm) iron oxides inside the mesoporous system. Mössbauer spectroscopy and magnetic measurements at low temperatures confirmed the formation of γ-Fe(2)O(3) nanoparticles exhibiting superparamagnetic behavior. The kinetic studies showed a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these magnetic mesoporous hybrids and a considerably increased adsorption capacity per unit mass of sorbent in comparison to that of pristine CMK-3 carbon. The results also indicate highly pH-dependent sorption efficiency of the hybrids, whereas their kinetics was described by a pseudo-second-order kinetic model. Taking into account the simplicity of the synthetic procedure and possibility of magnetic separation of hybrids with immobilized pollutant, the developed mesoporous nanomaterials have quite real potential for applications in water treatment technologies.

High-performance iron oxide–graphene oxide nanocomposite adsorbents for arsenic removal

“…This can be ascribed to the enhanced surface area and pore volume with the increase of iron oxide content in the composites as shown below, which lead to the enhanced contact of GO surface with air for combustion. Meanwhile, it can also result from the existence of iron oxide on the GO surface, which acts as catalysts for the carbon combustion since their exothermic oxidation takes place at lower temperatures [36]. Similarly, the uniform distribution of iron oxide is also confirmed in FeO x -GO-36 having a lower iron oxide content (see Figure S5).…”

“…[36]. The infrared spectra of FeO x -GO-36, FeO x -GO-60, and FeO x -GO-80 all show a broad band with the peak maximum at 1578 cm -1 , corresponding to aromatic C=C stretch in GO [23].…”

“…Typical substrates include low-cost abundant ones, such as naturally occurring minerals [21], activated carbons [22], graphene oxide (GO) [23][24][25][26][27][28][29][30][31][32][33], and cellulose [34], as well as some specially synthesized costly ones, such as mesoporous carbons [35,36], carbon nanotubes [37], macroporous silica [38], etc. Such nanocomposite adsorbents facilitate their more convenient separation following adsorption.…”

Redox Properties of Iron-Based Materials in Water Treatment Technologies: An Overview of Laboratory Versus Field Experiences

“…3). In order to be able to detect chromium, the 1,5-diphenylcarbazide method is used that is based on the reaction of dissolved Cr(VI) with 1,5-diphenylcarbazide molecules in acid solution leading to the formation of a red−purple chromium 1,5-diphenylcarbazide complex that is measured spectroscopically at 540 nm [31], [32]. The calibration curve is initially determined by using the absorbance spectra of standard chromium solutions (Fig.…”

Superparamagnetic iron oxide nanoparticle-loaded polyacrylonitrile nanofibers with enhanced arsenate removal performance

“…18 To avoid these problems, the dispersion and fixation of iron oxide nanoparticles over porous supports has been a common strategy in the development of safe and efficient arsenic adsorbents. [19][20][21][22] Among the several available supporting materials, electrospun polymeric nanofibers present high surface area able to interact easily with the inorganic particles and improve the contact time with the contaminated media. Electrospinning is a well-established and versatile process that has been used to produce ultrafine fibers including microfibers (>1 m) or nanofibers (<1000 nm).…”