Superhydrophobic and Sustainable Nanostructured Powdered Iron for the Efficient Separation of Oil-in-Water Emulsions and the Capture of Microplastics

Abstract

The pollution of oceans and seas by oils and microplastics is a significant global issue affecting the economy and environment. Therefore, it is necessary to search for different technologies that can remove these pollutants in a sustainable way. Herein, superhydrophobic powdered iron was used to efficiently separate stabilized oil-in-water emulsions and, remarkably, capture microplastic fibers. High-energy ball milling of iron particles was applied to decrease particle size, increase the specific surface area, and produce a nanostructured material. This was combined with the liquid phase deposition of lauric acid to modify the surface free energy. The nanostructured powder showed superhydrophobicity (WCA = 154°) and superoleophilicity (OCA = 0°), which were fundamental in separating stabilized oil-in-water emulsions of hexane with an efficiency close to 100%. Because of the superhydrophobic/superoleophilic properties of the powdered iron and its intrinsic properties of being able to freely move and adapt to the different morphologies of microplastics under continuous stirring, this material can capture microplastic fibers. Thus, we present a novel dual application of a superhydrophobic material, which includes the capture of microplastics. This has not been reported previously and provides a new scope for future environmental sustainability.

Surface-functionalised materials for microplastic removal

“…In fact, we recently found that these extraordinary materials that mimic materials found in nature, such as Nelumbo nucifera (known as lotus leaf), can also be used to remove solid pollutants like MP. For the first time, we previously reported a superhydrophobic iron powder used to capture HDPE-MP fibres (Rius-Ayra et al, 2020). To obtain this powder, we used high-energy ball milling to decrease the size of the iron particles to close to 50 μm.…”