Efficient removal of nanoplastics from industrial wastewater through synergetic electrophoretic deposition and particle-stabilized foam formation

Microplastic particles have been discovered in virtually all ecosystems worldwide, yet they may only represent the surface of a much larger issue. Nanoplastics, with dimensions well below 1 µm, pose an even greater environmental concern. Due to their size, they can infiltrate and disrupt individual cells within organisms, potentially exacerbating ecological impacts. Moreover, their minute dimensions present several hurdles for removal, setting them apart from microplastics. Here, we describe a process to remove colloidally stable nanoplastics from wastewater, which synergistically combines electrophoretic deposition and the formation of particle-stabilized foam. This approach capitalizes on localized changes in particle hydrophilicity induced by pH fluctuations resulting from water electrolysis at the electrode surface. By leveraging these pH shifts to enhance particle attachment to nascent bubbles proximal to the electrode, separation of colloidal particles from aqueous dispersions is achieved. Using poly(methyl methacrylate) (PMMA) colloidal particles as a model, we gain insights into the separation mechanisms, which are subsequently applied to alternative model systems with varying surface properties and materials, as well as to real-world industrial wastewaters from dispersion paints and PMMA fabrication processes. Our investigations demonstrate removal efficiencies surpassing 90%.