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)

Authors

N. Jiang Sanitary Engineering - CEG
M. Erdös Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering
O. Moultos Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering
R. Shang Sanitary Engineering - CEG
T.J.H. Vlugt Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering
Sebastiaan Heijman Sanitary Engineering - CEG
L.C. Rietveld Sanitary Engineering - CEG
Research Group
Sanitary Engineering (CEG) (TU Delft)
Copyright: © 2020 N. Jiang, M. Erdös, O. Moultos, R. Shang, T.J.H. Vlugt, Sebastiaan Heijman, L.C. Rietveld
DOI: https://doi.org/10.1016/j.cej.2019.123968
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Published Date

2020

Language

English

Faculty

Civil Engineering & Geosciences

Department

Water Management

Research Group

Sanitary Engineering

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.