Synthesis of lignin-based polyurethane/graphene oxide foam and its application as an absorbent for oil spill clean-ups and recovery

Superhydrophobic and superoleophilic foam-like materials are attracting significant interest as promising absorbent for oil spill clean-up from water bodies. In this work, we report the synthesis of lignin based polyurethane (LPU) foam and its surface modification to form a superhydrophobic and superoleophilic sorbent, for use in spill clean-ups. The interior matrix of the LPU foam substrate was grafted with adhesive polydopamine-reduced graphene oxide (rGO) and octadecylamine (ODA), which reacted to transform the LPU foam skeleton to a superhydrophobic and superoleophilic 3-D structure. The resulting foam (designated as LPU-rGO-ODA) was shown to retain the interconnected porous structure, with a water contact angle of 152°. Spectroscopic and microscopic analyses were conducted to investigate the structure and morphology of the foam. Sorption experiments with crude oil, engine oil, kerosene and chloroform showed that the LPU-rGO-ODA foam was an excellent oil sorbent with a sorption capacity of 26–68 times its own weight, which was much greater than that of a commercial non-woven polypropylene sorbent. The LPU-rGO-ODA foam also exhibited a high selectivity to oil sorption and excellent reusability over repeated sorption-squeezing cycles. The absorbed oils in the sorbent could be removed and collected simply by squeezing the oil-laden sponge, and the foam sorbent became ready for reuse in next sorption cycle. As such, LPU-rGO-ODA foam is expected to be a promising oil sorbent for potential applications in oil-spill clean-ups.