Phase-separation mechanism of water-in-oil droplets on a mesh with selective wettability by dripping

Abstract

Developing technologies of high-efficiency and low-cost oil/water separation has attracted much attention due to the environmental damage caused by oil pollution. General filtration can be coupled with selective wettability to improve oil/water separation efficiency and reduce energy consumption. However, accumulated liquid obstruction is problematic for the commonly used ‘Gravity-driven mode’ method, reducing permeate flux and separation efficiency. Hence, we experimentally analyze the phase-separation mechanism of an alternative (‘Dripping mode’) method by studying the impact dynamics of water-in-oil compound droplets on the metallic mesh with selective wettability. Firstly, the effect of selective wettability on the impact dynamics is studied. We focus on two crucial behaviors in practical application: oil/water separation and water-core expulsion. Their typical regimes are classified according to the outcomes, and theoretical models are proposed to explain the thresholds of these regimes. The max-volume quantitative prediction model of separated oil is established, and the model’s error is illustrated. Additionally, the feasibility of separating heavy oil (i.e., high viscosity & density oil) is discussed.