Optimizing oil-water separation using fractal surfaces

TL;DR

This paper explores the use of disordered fractal materials with special wetting properties for efficient oil-water separation, achieving nearly 98% separation efficiency by leveraging their high volume availability and unique surface characteristics.

Contribution

It introduces a novel application of disordered fractal surfaces for oil-water separation, demonstrating superior efficiency over traditional micro-pillared surfaces through modeling and simulations.

Findings

Fractal surfaces exhibit high water contact angles, confirming hydrophobicity.

Oil can penetrate these surfaces effectively, indicating oleophilicity.

Separation efficiency reaches nearly 98%, outperforming non-fractal designs.

Abstract

Oil has become a prevalent global pollutant, stimulating the research to improve the techniques to separate oil from water. Materials with special wetting properties - primarily those that repel water while attracting oil - have been proposed as suitable candidates for this task. However, one limitation in developing efficient substrates is the limited available volume for oil absorption. In this study we investigate the efficacy of disordered fractal materials in addressing this challenge, leveraging their unique wetting properties. Using a combination of a continuous model and Monte Carlo simulations, we characterize the hydrophobicity and oleophilicity of substrates created through ballistic deposition (BD). Our results demonstrate that these materials exhibit high contact angles for water, confirming their hydrophobic nature, while allowing significant oil penetration, indicative of oleophilic behavior. The available free volume within the substrates vary from $60\%$ to $90\%$ of the total volume of the substrate depending on some parameters of the BD. By combining their water and oil wetting properties with a high availability of volume, the fractal substrates analyzed in this work achieve an efficiency in separating oil from water of nearly $98\%$, which is significantly higher compared to a micro-pillared surfaces made from the same material but lacking a fractal design.