Hypothesis

Super-hydrophilic/underwater super-oleophobic materials composed of biomass show great advantages for the treatment of oily wastewater due to their inherent fouling resistance. However, the development of three-dimensional materials from biomass for oil–water separation is still a challenge. It is universally acknowledged that constructing a rough structure on the surface of hydrophilic substrates would significantly improve the underwater oleophobicity and oil–water separation performance.

Experiments

In this work, a three-dimensional lignin/cellulose aerogel (LCA) was developed through sol–gel method with freeze-drying. The rough microstructure and 3D interconnected network composed of lignin and cellulose impart excellent underwater superoleophobicity to LCA for efficient oil–water separation.

Findings

The introduction of lignin to cellulose aerogel could effectively enhance its surface roughness, water permeation speed and underwater oil contact angle. Especially, the swelling properties of the hydrogel could be regulated by modulating the content of lignin, which could further control the pore size of aerogels to optimize the separation flux. The as-prepared aerogel showed remarkable performance in separating various oil–water mixtures and oil-in-water emulsions, with a separation flux of 7646 ± 167 L·m⁻²·h⁻¹ and oil rejection rate >99 %. These excellent properties combined with its facile fabrication make LCA a promising candidate for the treatment of oily wastewater.