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Preparation of magnetic mesoporous composites from glycerol and iron(III) salt

Medeiros, Miguel A, Ardisson, José D, Lago, Rochel M
Journal of chemical technology and biotechnology 2020 v.95 no.4 pp. 1038-1045
Raman spectroscopy, X-ray diffraction, activated carbon, adsorbents, adsorption, aqueous solutions, desorption, differential thermal analysis, glycerol, heat treatment, indigo carmine, iron, leaching, magnetism, methylene blue, nitrogen, polymerization, porous media, pyrolysis, scanning electron microscopy, surface area, temperature, thermogravimetry, transmission electron microscopy
BACKGROUND: A process was developed to produce mesoporous composites with magnetic cores involving the following sequential reactions: glycerol polymerization/iron(III) reduction/polyglycerol pyrolysis/activated carbon production. RESULTS: Glycerol containing 1, 3, 5, or 8 mol% iron(III) was heat treated to 380, 600, or 800 °C. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction, Mössbauer spectroscopy, thermogravimetry/differential thermal analysis, Raman spectroscopy, and nitrogen adsorption/desorption results showed that the iron(III) salt promoted polymerization of glycerol up to 380 °C. At higher temperatures, up to 800 °C, three different processes simultaneously occurred: pyrolysis of polyglycerol, reduction of iron(III) ion (Fe³⁺) to Fe⁰ and Fe₃C, and activation of the carbonaceous matrix, yielding a composite with a BET surface area of 136 m² g⁻¹. Moreover, to verify a possible environmental application of the prepared composites and their ability to remain suspended in aqueous solution, they were tested as adsorbents of organic contaminants such as methylene blue and indigo carmine. The test results were satisfactory: 10 mg of the prepared composite (GFe3‐800) adsorbed up to 80% of the dye [10 mL of solution (50 ppm)] within 30 min of contact, and the composite could be removed from the system by simple magnetic attraction. CONCLUSIONS: Magnetic composites exhibited good dye adsorption, in addition, good resistance to acid leaching. © 2019 Society of Chemical Industry