Facile preparation of superhydrophilic and superoleophobic sand for efficient oil-water separation

Abstract

Superhydrophilic-superoleophobic materials possess unique advantages in oil-water separation due to their water permeability and oil repellency. In this study, superhydrophilic-superoleophobic sand (CQS) was prepared using a facile and rapid mixing-drying coating method. Quartz sand was modified with polydopamine (PDA) as the hydrophilic binding agent, fluorosurfactant (FS-50) as the oleophobic agent, and CaCO3/SiO2 to construct hierarchical surface roughness. The CQS exhibited a water contact angle of 0° and an oil contact angle of 154°, which resulted in a slightly increased water adhesion capacity and a significantly reduced oil adhesion capacity. Owing to its selective wettability towards oil and water, the CQS was capable of directly separating immiscible oil-water mixtures and oil-in-water emulsions with high separation efficiency (99.5 % and 98.5 %, respectively), driven by gravity. Moreover, immiscible oil/oil mixtures could be effectively separated by the CQS as well, expanding its application to separating immiscible organic liquids with different polarities. Additionally, the CQS demonstrated good reusability and superior stability against acid, alkali, salt, hot water and mechanical abrasion. These properties ensured its applicability in complex environments. The CQS, with exceptional separation capability and stability, holds promising prospects for future applications in related separation field.