A facile surface modification approach to fabricate durable underwater superoleophobic stainless steel mesh for efficient oily wastewater purification

Acidic, alkaline, salty and hot oily water originated from industrial oily wastewater, petroleum spills and meal oily waste sewage have caused heavy environmental pollutions and energy waste. Underwater superoleophobic stainless steel mesh (SSM) is one kind of promising materials to purify above oily wastewater; however, it is still a challenge to prepare durable underwater superoleophobic SSM towards acid, base, salt, high temperature or abrasion. Herein, a durable underwater superoleophobic SSM (TA-PF-SSM) was prepared using tannic acid (TA) and paraformaldehyde (PF) via a simple and mild wet chemical immersion method. Surface morphologies show a few differences compared with those of pristine SSM. The underwater superoleophobic TA-PF-SSM can be utilized to separate various kinds of oil/water mixtures that water phase can be acidic/alkaline (pH = 1, 4, 10 and 13), salty and even hot. Separation efficiencies can reach 99.98% without any obvious declines after tens of cyclic separations, and also do not decrease after sand paper abrasion with a load of 200 g for 10 cycles. In addition, the TA-PF-SSM can also be applied to separate meal waste oily water at 80°C and crude oil/water at 50°C. And it shows excellent self-cleaning property towards crude oil. This study not only provides a simple surface modification method to prepare durable underwater superoleophobic material, but also proposes a TA-PF-SSM that can be applied to purify oily wastewater from industry, meal wastes and petroleum spills.