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The adsorption mechanisms of organic micropollutants on high-silica zeolites causing S-shaped adsorption isotherms

An experimental and Monte Carlo simulation study

Journal Article (2020)
Author(s)

Nan Jiang (TU Delft - Sanitary Engineering)

M. Erdös (TU Delft - Engineering Thermodynamics)

O. Moultos (TU Delft - Engineering Thermodynamics)

R. Shang (TU Delft - Sanitary Engineering)

T.J.H. Vlugt (TU Delft - Engineering Thermodynamics)

Sebastiaan Heijman (TU Delft - Sanitary Engineering)

Luuk Rietveld (TU Delft - Sanitary Engineering)

Research Group
Sanitary Engineering
Copyright
© 2020 N. Jiang, M. Erdös, O. Moultos, R. Shang, T.J.H. Vlugt, Sebastiaan Heijman, L.C. Rietveld
DOI related publication
https://doi.org/10.1016/j.cej.2019.123968
More Info
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Publication Year
2020
Language
English
Copyright
© 2020 N. Jiang, M. Erdös, O. Moultos, R. Shang, T.J.H. Vlugt, Sebastiaan Heijman, L.C. Rietveld
Research Group
Sanitary Engineering
Volume number
389
Pages (from-to)
1-9
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Abstract

The adsorption of organic micropollutants (OMPs) on high-silica zeolites is characterized by adsorption isotherms with various shapes. The occurrence of an S-shaped adsorption isotherm indicates the lack of adsorption affinity for OMPs at low, environmentally relevant equilibrium concentrations. In this study, S-shaped isotherms were observed during batch experiments with 2,4,6-trichlorophenol (TCP) and FAU zeolites. This is the first time that an S-shaped isotherm is reported for the adsorption of OMPs on high-silica zeolites. Monte Carlo (MC) simulations in the grand-canonical ensemble were used to obtain a better understanding of the mechanism of the S-shaped adsorption isotherms. From the MC simulation results, it was observed that multiple TCP molecules were adsorbed in the supercages of the FAU zeolites. It was found that the π-π interactions between TCP molecules give rise to the adsorption of multiple TCP molecules per supercage, and thus causing an S-shaped adsorption isotherm. Simulations also revealed that water molecules were preferentially adsorbed in the supercages and sodalite cages of the FAU zeolites. FAU zeolites with a higher Al content adsorbed a higher amount of water molecules and a lower amount of TCP, and showed less pronounced S-shaped isotherms.