Adsorption of diclofenac on a magnetic adsorbent based on maghemite : experimental and theoretical studies.
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2018
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Abstract
In the present study, a magnetic adsorbent for diclofenac formed by maghemite (g-Fe2O3) nanoparticles
with high saturation magnetization (19.8 emu g 1) and specific area (79 m2 g 1) was synthesized by a
one-pot method through the precipitation of Fe2+ ions with NaOH solution followed by rapid oxidation
with hydrogen peroxide. The X-ray diffraction and Mo¨ssbauer spectroscopy data confirmed that the
adsorbent is formed solely by maghemite. The adsorption equilibrium time for diclofenac (C0 = 500 mg L 1)
was reached after 120 min, and the kinetic data were best fitted to the pseudo-first-order model. The
adsorption isotherms acquired at five different temperatures showed an increase in the maximum
adsorption capacity (261 mg g 1) until 298 K, but at higher temperatures, the maximum adsorption capacity
was not increased. The isotherm data were best fitted to the Langmuir and Sips models. Adsorption tests as
a function of solution pH showed a decrease in the diclofenac adsorption capacity with increasing solution
pH, suggesting that the hydroxyl anions compete with diclofenac molecules for the adsorption sites.
Diclofenac adsorption on maghemite was endothermic (67.31 kJ mol 1) and entropically driven (TDadsS1 =
96.33 kJ mol 1). Finally, theoretical calculations and infrared spectroscopy data suggest a physisorption
mechanism of diclofenac on the maghemite surface.
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LEONE, V. O. et al. Adsorption of diclofenac on a magnetic adsorbent based on maghemite : experimental and theoretical studies. New Journal of Chemistry, v. 42, p. 437-449, 2018. Disponível em: <http://pubs.rsc.org/en/content/articlelanding/2018/nj/c7nj03214e#!divAbstract>. Acesso em: 05 abr. 2018.