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 superoleophobicity (Oil contact angle of 150 ± 5°) 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. [Display omitted] •This innovation brings a new way on agricultural waste treatment.•Waste peanut shells were used to fabricate separation layer for oily wastewater.•The production processing is eco-friendly, costless and simple.•The layer exhibits 99.5% emulsion separation efficiency and stable reusability.