High-efficient nanoemulsions separation by surface manipulation of sands

Oil-in-water (O/W) nanoemulsions, prevalent in the cosmetics, pharmaceutical, and petroleum industries, present significant threats to aquatic ecosystems and human health upon their inadvertent release into the environment. However, the nanoscale droplet size and robust interfacial film of nanoemulsions confer exceptional stability, rendering their separation a formidable challenge. Developing an economical and efficient method to remove nanoemulsions is crucial, offering a cost-effective and energy-saving alternative to traditional techniques. Here we present a sand filtration system integrating oleophilic and oleophobic sands, achieving cost-effective, high-flux, and efficient separation of nanoemulsions. The synergistic effect of hydrophobic silane treatment and a rough surface structure endows the oleophilic sands with exceptional oil absorption capacity. Meanwhile, the hydration layer on the oleophobic sands confers strong anti-oil adhesion properties in aqueous environments, facilitating swift water permeation. Remarkably, under gravity alone, the mixed rough sand filter (MRSF) achieves a separation flux exceeding 2519 L.m^-2.h^-1 with a separation efficiency of up to 98.7 %. This work offers a promising approach for achieving high-flux, efficient nanoemulsion separation.