A green strategy for preparing durable underwater superoleophobic calcium alginate hydrogel coated-meshes for oil/water separation.

Superhydrophilic and underwater superoleophobic calcium alginate (CA) hydrogel-coated meshes (CAHMs) were prepared via a green dip-coating and self-assembly method without adding any toxic or expensive modifying agents. Since meshes possess intrinsic chemical inert characterisitics, the first CA layer was employed as a precoating and then continually facilitated deposition of CA hydrogel via coordination bonding to form extraordinary underwater superoleophobicity. All results proved that CA was introduced to generate both hydrophilic chemical compositions and rough structures onto resultant mesh surfaces. The obtained meshes, which possessed a underwater oil contact angle (UOCA) of ~154.3° and low oil sliding angle (OSA) of ~7°, could separate various oil/water mixtures with efficiency above 99% and maximum water flux up to 28,108.9 L·m·h. This separation process was spontaneous and only driven by gravity. Furthermore, as-prepared meshes still maintained high stability under corrosive organic solvents. These outstanding performances made it a promise for oil/water separation in the future.