Infrared Signature of the Cation−π Interaction between Calcite and Aromatic Hydrocarbons

Abstract

The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hydrocarbons having non-zero quadrupole moments by mineral surfaces. Direct evidence supporting such a mechanism is, however, limited. Using the model mineral calcite, we probe the cation-π interaction with adsorbed benzene, toluene, and ethylbenzene (BTE) molecules using attenuated total reflectance Fourier transform infrared spectroscopy. We show that the presence of calcite increases the energy required to excite the synchronized bending of aromatic C-H bonds of BTE molecules. The unique conformation of this vibrational mode indicates that the planar aromatic rings of BTE molecules are constrained in a tilted face-down position by the cation-π interaction, as further confirmed by density functional theory calculations. Our results suggest that the shift of the excitation energy of the aromatic C-H bending may be used as an infrared signature for the cation-π interaction occurring on mineral surfaces.

Synergistic effect of lignin incorporation into polystyrene for producing sustainable superadsorbent

“…78 Wang and coworkers introduced d C-H band shis (4 cm À1 ) in FTIR analysis as an indicator of the cation-p interaction between mineral surfaces and aromatic hydrocarbons. 75 Along with the observed vibrational movement at 746 cm À1 , KL-PS-Cu wavelengths illustrate another visible signal alteration at the characteristic peak of residual hydroxy moieties (3100-3550 cm À1 ) in Fig. 6c.…”

“…6c (the bending may happen in or out of paper which is shown as + and À). 75 In the absence of copper (grey line in Fig. 6c), light with a wavenumber of 746 cm À1 is needed to excite d C-H vibration for KL-PS.…”

Potential of Waste Oyster Shells as a Novel Biofiller for Hot-Mix Asphalt

“…The oyster shell powder (i.e., CaCO 3 ) with high calcium content is naturally hydrophilic material and tends to create strong bonds with hydrophobic organic compounds such as bitumen. The strong bonding between the calcite (mainly calcium sites) and adsorbate aromatic molecules most likely involved the carboxylic, hydroxylic, and amines groups; some van der Waals and electrostatic interactions may have also occurred [49,50]. This is a very interesting finding that necessitates further in-depth investigation.…”

“…The other fraction of the filler, i.e., the fine particles smaller than the thickness of the asphalt film, is distributed in the asphalt phase and is part of the binder component of the mixture [44]. [4,3] 117 µ m Dv 102.98 µ m Dv (50) 71.…”

“…The changing of such composition fraction implies that the aromatics in lighter fractions of asphalt were more probably changed to resins. In other terms, it seems that the aromatics were selectively interacted with OSP surface [49,50] and readily converted into resin-like structures (see Figure 7). The oyster shell powder (i.e., CaCO 3 ) with high calcium content is naturally hydrophilic material and tends to create strong bonds with hydrophobic organic compounds such as bitumen.…”