Continuous removal of nanoplastics from industrial wastewater using electrophoretic deposition and particle-stabilized foam formation process

Micro- and nanoplastics have been found in nearly every environment on earth, from oceans to soil. While microplastics readily sediment and can be filtered, the removal of nanoplastics remains challenging. Nanoplastics also occur as intermediates in a range of industrial processes, such a polymer or latex production, and in consumer products, such as dispersion paints. A pathway to remove such small particles is to exploit their colloidal properties and use a combination of electrophoretic deposition with the formation of particle-stabilized foam. In this process, the localized pH changes at the electrode surface, induced by water electrolysis, enhances the hydrophobicity of the particles and promote their adsorption to nascent gas bubbles. Here, we demonstrate a continuous operation of this system and investigate in detail the influence of operation parameters on the efficiency of the removal process. In continuous systems operating with different total dispersion volumes of 2.5 L and 10 L, respectively, we achieve removal percentages exceeding 90 % for both nanoplastic model dispersions and industrial wastewater containing poly(methyl methacrylate) particles. We show that our process is particularly well suited for nanoplastic removal from industrial wastewater with high initial particle concentrations. We further establish that the removed particles consist of clean and unaltered polymer, demonstrating a direct recycling strategy for the removed nanoplastic waste from the industrial wastewater.