Effects of Particle Shape and Surface Structure on the Adsorption Properties of Polystyrene Microplastics

Model spherical polystyrene particles are studied to understand the interactions of microplastics with organic pollutants. Analysis of the experimental results presented in the literature is complicated since researchers use different types and concentrations of particles, durations of tests, etc. In addition, there is little information on the effect of the structure of the surface layer of polystyrene particles on the processes under study, and the question of the effect of the shape of polystyrene particles remains open. Here, we present the first results of a model experiment to study the effect of the shape and structure of the surface layer of polystyrene microspheres and non-spherical particles of 2 to 5 μm in size on the sorption properties in relation to model molecules of rhodamine B as a model organic pollutant. The properties of both the initial model polystyrene particles and the modified ones were studied by optical, transmission electron, and atomic force microscopy, as well as using the Brunauer-Emmett-Teller method (BET). The sorption process was studied by spectrophotometry, and the analysis of sorption curves was carried out using the Langmuir model. It is shown that the shape of polystyrene model particles does not have a significant effect on the sorption capacity. At the same time, the sorption processes of rhodamine B molecules are determined by the structure of the surface layer, which can be changed, for example, by exposing the polystyrene microspheres to N,N'-dimethylformamide.