Sprecher
Beschreibung
Microplastics, defined as plastic particles smaller than 5 mm, are a grave concern due to their accumulation in marine and terrestrial environments, posing significant ecological and health risks and potential to enter the food chain. Various strategies are being employed to combat this issue, including filtration, bioremediation, coagulation, and flocculation [1-3]. Herein, we have developed a model microplastic system comprised of 140 ± 6 nm polystyrene spheres dispersed in water and flocculated using Nanofloc®. Here, the polystyrene particles are analogs to the microbeads in commercial face washes. The role of Nanofloc® in this system is to induce flocculation, a process crucial for the aggregation and removal of the model microplastic from aqueous suspensions.
The polystyrene particles are negatively charged with Zeta potential - 58 mV for a particle volume fraction 1e-5. The Nanofloc® solution is highly positively charged; a 0.17 vol/vol % solution showed Zeta potential 56 mV. We prepared a series of polystyrene colloids and investigated their flocculation using scanning electron microscopy (SEM) and small-angle neutron scattering (SANS). The flocculation occurs within 10 seconds of adding Nanofloc®. SEM image of the suspension (inset, Fig 1), which exhibited complete flocculation, shows that the Nanofloc® uniformly covers the polystyrene particles with an interconnected network of compact and denser flocs. SANS studies were carried out as a function of polystyrene and Nanofloc® concentration. Fig.1 shows the SANS curve of the polystyrene particles with and without the addition of Nanofloc®. For samples with a high concentration of Nanofloc®, the intensity is random due to the quick settling of the flocs (data not shown). The scattering data for the particles with Nanofloc® was fitted using the Teixeira model for fractal aggregates, and a fractal dimension of 2.3 was obtained from the fit. This implies a faster diffusion process and the flocculation proceeds via reaction-limited cluster aggregation (RLCA).
References
1. Lapointe, M., Farner, J.M., Hernandez, L.M. and Tufenkji, N., Environmental science & technology, 54(14), 8719 (2020).
2. Rajala, K., Grönfors, O., Hesampour, M. and Mikola, A., Water Research, 183, 116045 (2020).
3. Risch, P. and Adlhart, C., ACS Applied Polymer Materials, 3(9), 4685 (2021).
