Dynamics of Micropollutant Adsorption to Polystyrene Surfaces Probed by Angle-Resolved Second Harmonic Scattering

Angle-resolved second harmonic scattering is used to probe the adsorption dynamics of aqueous cationic and anionic dye molecules onto polystyrene surfaces. The adsorptions of malachite green to negatively charged polystyrene and naphthol yellow S to positively charged polystyrene are both highly favorable, with Î"GAds values of -10.9 ± 0.2 and -10.27 ± 0.09 kcal/mol, respectively. A competitive displacement methodology was employed to obtain values for the adsorption free energies of various smaller neutral organic molecules, including the important micropollutant ascorbic acid, caffeine, and pentoxifylline. For charged adsorbers, electrostatic interactions appear to significantly contribute to adsorption behavior. However, electrostatic repulsion does not necessarily deter the adsorption of molecules with large uncharged moieties (e.g., surfactants). In these cases, the mechanism of adsorption is dominated by van der Waals interactions, with the surface charge playing a relatively minor role.

Citation

Cole, W. T. S., Wei, H., Nguyen, S. C., Harris, C. B., Miller, D. J., & Saykally, R. J. (2019). Dynamics of Micropollutant Adsorption to Polystyrene Surfaces Probed by Angle-Resolved Second Harmonic Scattering. The Journal of Physical Chemistry C, 123(23), 14362–14369. doi:10.1021/acs.jpcc.9b01146

Sponsors

This work was supported by the Director, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy (DOE) under contract no. DE-AC02-05CH11231 through the Chemical Sciences Division of the Lawrence Berkeley National Laboratory (LBNL), by the National Natural Science Foundation of China (NSFC) under grant no. 61775114, by KAUST under grant OSR-2016-CRG5-2992, and by CALSOLV (an affiliate of RESOLV) under Fund #56475. of the U.S. Department of Energy under Award Number DE-SC000493.