Interakcije mikroplastike i organskih onečišćivala u vodi

Nowadays, microplastics (MPs), plastic particles smaller than 5 mm, are a hot topic in the field of environmental science due to their abundance and widespread in the environment and the food chain, including the human organism. The greatest concern is the potential harmful and toxic effect MPs can have on both the environment and human health. Additionally, MPs can adsorb and transport other pollutants, possibly increasing overall toxicity compared to the toxicity of isolated MPs and pollutants. Hence, it is important to understand the adsorption process to properly assess the potential risk of MPs. Experimental results show that adsorption is mainly governed by weak hydrophobic, electrostatic, van der Waals and π-π interactions, and hydrogen bonds. However, due to system complexity and many influencing factors, the results often lack consistency and reproducibility, which makes it impossible to draw clear conclusions and build a predictive model for MPs adsorption. The computational chemistry studies on the adsorption of MPs are still at the early stages, but they are believed to provide further insights into the adsorption mechanism. In this thesis, polyethylene terephthalate (PET) MPs was chosen as one of the most frequently found types of MPs in the environment. Adsorption was studied using quantum mechanical (QM) and molecular dynamics (MD) methods. QM study revealed that the interactions are weak and local, mainly dependent on the pollutants ability to form multiple contacts with MPs. Further quantitative structure activity/property relationship (QSA/PR) modelling showed that the key pollutant properties governing the adsorption can be correlated to the size of pollutants and the number of proton donor/acceptor functional groups. On the other hand, MD study showed that, when the explicit water molecules are included, the adsorption is mainly controlled by the pollutant relative affinity for water and MPs. Additionally, the affinity also depends on the structure of MPs, as the aggregated PET model, made of thirty 5-mer, showed stronger capacity compared to the PET model made of one 150- mer chain. MD results showed similar trend as the experimental results. However, the difference in calculated interaction energies could not be quantitatively correlated with the difference in adsorption capacities. Overall, computational studies showed a great potential as a tool to help to understand adsorption mechanism, although more work is needed to further develop the model’s accuracy.