Eco-friendly separation layers based on waste peanut shell for gravity-driven water-in-oil emulsion separation

Developing a feasible and eco-friendly separation layer for the purification of emulsified oily wastewater is urgently needed and remains a great challenge. Herein, a biodegradable and superwettable separation layer was developed based on waste peanut shell via a facile method of mechanical grinding. The obtained peanut shell layer possessed a micronano structured surface with natural underwater super-oleophobicity (Oil contact angle of 150 +/- 5 degrees) due to the mass transfer channels and hydrophilic substance of peanut shell. Under gravity, the layer separated immiscible oil/water mixtures exhibited a desirable flux rate (2636.9 L m(-2).h(-1)) and high separation efficiency (>99.5%) for disposing of a surfactant stabilized water-in-oil emulsion. Moreover, this layer maintained stable reusability after 55 cyclic operations. This successful creation of a peanut shell separation layer might provide new insights into the design of biomaterial separation layers for oily wastewater purification and resource utilization of agricultural residue. (C) 2020 Elsevier Ltd. All rights reserved.