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Adsorption of Gadolinium (Gd3+) Ions on the Dibenzo Crown Ether (DBCE) and Dicyclo Hexano Crown Ether (DCHCE) Grafted on the Polystyrene Surface: Insights from All Atom Molecular Dynamics Simulations and Experiments
, A. Boda, S.M. Ali, J.K. Singh
Published in American Chemical Society
Volume: 123
Issue: 19
Pages: 12276 - 12285
All atom molecular dynamics simulations and experiments were performed to understand the adsorption behavior of gadolinium (Gd3+) ion on the crown ethers grafted polystyrene (PS) surface. Two different types of crown ethers, viz., dibenzo crown ether (DBCE) and dicyclo hexano crown ether (DCHCE), were grafted separately on the PS surface to understand the adsorption behavior. We investigate the roles of Gd3+ ion concentration and grafting density (ρs) of the crown ether on the adsorption behavior of Gd3+ ion on the PS surface. The adsorption of Gd3+shows an increasing trend with increasing salt concentration, for all cases of crown ether grafting densities. The adsorption behavior follows the Langmuir isotherm model. The maximum amount of Gd3+ ion adsorption was observed to be 1.83 mg/g for DBCE and 2.02 mg/g for DCHCE at ρs = 2.07 mol/nm2. The maximum amount of Gd3+ ion adsorption on DBCE coated PS beads, in batch experiments, was found to be 1.76 mg/g, which is in good agreement with the theoretical results. The increase in ρs from 0.25 to 2.07 mol/nm2 shows an increase in the qmax value by ∼422% and 329% for DBCE and DCHCE, respectively. The optimum value of the crown ether grafting density is found to be 1.25 mol/nm2, beyond which the qmax saturates. We further investigate the dynamics of the Gd3+ ion by evaluating the diffusion coefficient (D) and mean residence time (τ). It was found that D decreases with increasing salt concentration for both DBCE and DCHCE. On the contrary, as expected, the τ value of Gd3+ increases with an increase in salt concentration. Overall, a 3-fold increase in τ was seen with increasing salt concentration. The potential of mean force analysis using umbrella sampling reveals favorable binding energy for higher grafting density of DCHCE compared to that of DBCE. © 2019 American Chemical Society.
About the journal
JournalData powered by TypesetJournal of Physical Chemistry C
PublisherData powered by TypesetAmerican Chemical Society