A Simple Process to Prepare High‐Efficiency Durable Oil–Water Filter

Abstract A simple process is designed to conveniently prepare a high‐efficiency oil–water filter to satisfy the need to separate oil from large amounts of oily wastewater. In this strategy, a porous sand core (SC) is selected as the substrate, and a hydrophilic sodium alginate gel layer is introduced to uniformly cover the outer and inner surfaces of the SC by briefly and successively soaking the SC into sodium alginate solution and CaCl₂ solutions. Significant underwater ultra‐oleophobicity is achieved by combining a hydrophilic gel coating with a rough surface microstructure. This modified filter exhibits excellent oil–water separation ability. The SCs with various pore sizes exhibit a separation efficiency of nearly 100% when filtering various oil–water mixtures and oil‐in‐water emulsions, and a water flux of approximately 200–5000 L m^–2 h^–1 depending on the pore size of the SC and the operating pressure. Moreover, the filter reveals excellent chemical stability, excellent mechanical strength, ease of cleaning, and strong durability, thereby making it a potential candidate for large‐scale applications in wastewater treatment.