Magnetic Fe/Fe3C@C Nanoadsorbents for Efficient Cr (VI) Removal

Abstract

Magnetic carbon nanocomposites (α-Fe/Fe3C@C) synthesized employing fructose and Fe3O4 magnetite nanoparticles as the carbon and iron precursors, respectively, are analyzed and applied for the removal of Cr (VI). Initial citric acid-coated magnetite nanoparticles, obtained through the co-precipitation method, were mixed with fructose (weight ratio 1:2) and thermally treated at different annealing temperatures (Tann = 400, 600, 800, and 1000 °C). The thermal decomposition of the carbon matrix and the Fe3O4 reduction was followed by thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, Raman spectroscopy, SQUID magnetometry, and N2 adsorption–desorption isotherms. A high annealing temperature (Tann = 800 °C) leads to optimum magnetic adsorbents (high magnetization enabling the magnetic separation of the adsorbent from the aqueous media and large specific surface area to enhance the pollutant adsorption process). Cr (VI) adsorption tests, performed under weak acid environments (pH = 6) and low pollutant concentrations (1 mg/L), confirm the Cr removal ability and reusability after consecutive adsorption cycles. Physical adsorption (pseudo-first-order kinetics model) and multilayer adsorption (Freundlich isotherm model) characterize the Cr (VI) absorption phenomena and support the enhanced adsorption capability of the synthesized nanostructures.

Magnetic carbon Fe3O4 nanocomposites synthesized via Magnetic Induction Heating

“…Lorentz peak deconvolution: D, G, FWHM (full width at half maximum), and the relative intensities of the peaks (ID/IG). Low ID/IG values (ID/IG tends to zero in amorphous carbon) together with the decrease of G from 1600 cm -1 (graphitic carbon) to around 1510 cm -1 (completely disordered carbon) 25,26 , support the conclusion of the amorphous nature of the carbon coating obtained through the performed MIH procedure. One of the characteristic properties of carbon materials (graphene, nanotubes, graphite and carbon black) is their high electrical conductivity 27 .…”

“…Finally, Cr (VI) absorption test were performed employing a UV-Vis spectrophotometer (UV-16, LAN OPTICS) with a wavelength range from 190 nm to 1100 nm . The experimental procedure is described in 25 . In brief, a colour reagent (1,5- Then, the solutions were mechanically stirred and aliquots of 1 mL were collected at different times, the adsorbent was separated by a hand-held magnet, and the solution was filtered by a 0.22 μm syringe filter.…”

Enhancement of Mass Transfer Process for Photocatalytic Reduction in Cr(VI) by Electric Field Assistance

“…Various physical and chemical techniques such as photocatalysis [ 12 ], biological treatment [ 13 ], electrodialysis [ 14 ], membrane filtration [ 15 ] and adsorption [ 16 ] have been applied for the removal of Cr(VI) from industrial wastewater. Compared with other methods, photocatalytic reduction can be carried out under mild reaction conditions to convert highly-toxic Cr(VI) into low-toxic Cr(III), achieving the essential removal of Cr(VI) [ 17 ].…”

Induction heating: an efficient methodology for the synthesis of functional core–shell nanoparticles

“…To the best of our knowledge, the only systems derived from the use of nanoparticles under an AMF are TiO 2 -decorated Fe 3 O 4 , 17 and a carbon Fe 3 O 4 nanocomposite. 18 However, no literature on magnetic nanoparticles acting as the substrate for the growth of metal, metal oxide or metal carbide shells is available.…”