Hydrothermal and Laser-Guided Janus Membrane with Dual Wettability for Unidirectional Oil/Water Separation.

The development of a Janus membrane with contrasting chemical functionality/or wettability on opposite faces has shown great promise as a passive and energy-efficient oil/water separation technology. Notably, one side of the membrane is designed hydrophilic (i.e., water-attracting in air and underwater oleophobic) and the other hydrophobic (i.e., water-repelling in air and underwater oleophilic). The distinctive surface wettability features of the membrane allow it to repel water and attract oil without consuming energy, thus making it an attractive technology for passively separating oil/water mixtures. The hydrophobic face of the membrane captures oil droplets while allowing water to pass through, and the hydrophilic side attracts water droplets and allows oil to pass. Nonetheless, crafting a Janus membrane is complex, tedious, and expensive. To overcome these limitations, an easy and inexpensive two-step fabrication process for the Janus membrane is proposed in this work. The first step involves creating a superhydrophilic face by the hydrothermally guided deposition of nanoneedles on either side of a commercially available hydrophobic carbon sheet. In the second step, the double-faced surface is subjected to a pulsed laser to create conical micropores studied for oil/water separation. The fabricated membrane is economically affordable and environment friendly. Besides being energy-efficient (as the separation process works passively), the membrane demonstrates an efficient oil/water separating performance. The potential application of this work is diverse and impactful, encompassing wastewater treatment, oil spill cleanup, and various industrial separation processes.