Recyclable Joule heated low shrinkage carbon nanofiber aerogels for microscale oil/water separation

Abstract

• A freeze-shaping method for fabricating CNFA was proposed. • A novel CNFA was designed by directly using 1D CNF with a vine-wrapped tree structure. • Hydrophobic-lipophilic CNFA with lightweight, high porosity, great elasticity, and high Joule-heating efficiency was obtained. • The cyclic stability of CNFA was proved to be high efficiency Joule-heated adsorption for microscale levels acetone (87%) and DMF (92%). Aerogels have shown great potential as oil adsorbents but their application to the removal of microscale oil from water and their recycling remains problematic. The present work proposed a freeze-shaping method for fabricating carbon nanofiber aerogels (CNFAs) based on the direct use of one-dimensional (1D) carbon nanofibers (CNF) rather than carbonization of polymer aerogels. This technique greatly reduces volume shrinkage and increases the three-dimensional (3D) structural stability of the material. Carbon nanotubes (CNT) and gelatinized starch were incorporated in these aerogels as a conductive enhancement agent and binder, respectively, forming a “vine (CNT)-wrapped tree (CNF)” structure that improved mechanical and Joule-heating performance. The effects of glutaraldehyde added to aerogels as a cross-linking agent on mechanical properties and microstructure were also systematically investigated. The optimized CNFAs combined with low density, high porosity, good elasticity, and superior Joule-heating efficiency along with suitable adsorption capacity, excellent selectivity, and cycling stability. This material was able to selectively remove 87% and 92% of microscale acetone and dimethylformamide (DMF), respectively, from the water after nine cycles of adsorption and Joule-heating. The present work demonstrates a novel means of designing and fabricating a low shrinkage CNFA with outstanding Joule-heating performance having potential practical applications in the remediation of organic pollution.