Juncus Pith: A Versatile Material for Automatic and Continuous Separation of Various Oil–Water Mixtures

It is extremely important to develop a facile and versatile strategy for effectively separating various oil–water mixtures. Here we report that the pith of juncus (which is also known as common rushes) can serve as a versatile material for oil–water separation. Under the action of capillary force and gravity, a piece of pith automatically and continuously separates not only immiscible oil–water mixtures but also surfactant-stabilized water-in-oil emulsions with high selectivity and desirable flux. The separation strategy is cost-effective and energy-efficient because it avoids the switch of wettability, the input of additional energy, and the use of low-surface-energy chemicals or special equipment. The unique capability of the pith is mainly attributed to the presence of three-dimensionally (3D) reticular texture with highly hydrophobic and superoleophilic properties. Owing to its easy availability and high effectiveness, juncus might be a promising material aiming for oil–water separation, water treatment, and purification of solvent or fuel, and so on.