Removal of sodium diclofenac from aqueous medium using layered double hydroxide : a thermodynamic and theoretical approach.
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Date
2022
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Abstract
In this study, an adsorbent based on layered double hydroxide (Co–Al–NO3]-LDH) was synthesized by the co-precipitation method at constant pH
8.0±0.5. This new material was used for the removal
of diclofenac from water. The X-ray difraction pattern of [Co–Al–NO3]-LDH revealed a basal spacing of 0.859 nm. Equilibrium time was reached after
120 min for an initial concentration (C0) of diclofenac
of 500 mg L−1, and the pseudo-second order model
best ftted the kinetic data obtained at C0 values of 100,
250, and 500 mg L−1. The isotherms performed at 15,
25, 35, and 45 °C showed an increase in the maximum
adsorption capacity (Qmax=494.9 mg g−1) up to 25 °C,
but at temperatures above 25 ºC, the Qmax value was
not increased. Equilibrium data were ftted using the
Langmuir, Freundlich, and Sips models, and the change
in standard free energy of adsorption was estimated
from the Langmuir constant, corrected for the equilibrium activity coefcient, while the changes in standard
enthalpy and entropy of adsorption were calculated from
the van’t Hof equation. Adsorption studies as a function
of nitrate concentration at two C0 values (50 and 500 mg
L−1) showed that the increase in nitrate concentration
led to a decrease in the Qmax of diclofenac, showing that
nitrate competes with diclofenac for the adsorption sites.
Theoretical studies were carried out using four diferent
confgurations of the diclofenac molecule approaching
the surface of [Co–Al–NO3]-LDH. The interaction distance between diclofenac and [Co–Al–NO3]-LDH of
2.0 Å presented the lowest energy.
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Keywords
Adsorption, Mechanism
Citation
BRUZIQUESI, G. G. O. et al. Removal of sodium diclofenac from aqueous medium using layered double hydroxide: a thermodynamic and theoretical approach. Water, Air and Soil Pollution, v. 233, artigo 363, 2022. Disponível em: <https://link.springer.com/article/10.1007/s11270-022-05776-6>. Acesso em: 11 out. 2022.