Preparation and Microstructural Control of Waterborne Polyurethane/Graphene Aerogel for Efficient Oil Absorption

Graphene aerogel shows great potential for oil absorption and favorable microstructure is the key for realization of stable structure and excellent performance. In this work, tannic acid was used as a cross-linking agent to bridge the graphene oxide nanosheets and the waterborne polyurethane molecular chains, and a stable graphene aerogel was constructed after self-assembly and reduction reaction under suitable pH. The results show that the waterborne polyurethane/tannic acid/graphene composite aerogels (WTGA) prepared at different pH values have distinctly different properties. Compared with acidic condition and alkaline condition, WTGA prepared under neutral pH conditions has stable three-dimensional structure, due to the appropriate degrees of graphene oxide reduction and the effective construction of cross-linked network. The water contact angle of prepared WTGA reaches 133.2 o and it can withstand reiterative compression at 70% strain, exhibiting outstanding hydrophobicity and compression resilience. Meanwhile, the WTGA shows ultra-high absorption capacity for various oils and organic solvents, and the saturated absorption capacity for soybean oil can be up to 139.4 g/g. Significantly, the oil-saturated aerogel can be regenerated via simple squeezing for oil recovery, maintaining over 90% of its absorption performance after 10 absorption-desorption cycles, revealing a wide prospect of application in oil absorption.