Preparation of magnetic lignin/graphene aerogel and its adsorption properties to oil and organic solvents

The magnetic lignin/graphene aerogel (FLGA) was successfully fabricated via one-step hydrothermal synthesis and freeze drying. The results showed that the p-toluenesulfonic acid (P-TsOH) modified lignin was rich in hydrophilic oxygen-containing functional groups, which could be cross-linked with the functional groups in graphene to improve the selectivity and adsorption ability of graphene aerogels to oil and organic solvents. The well dispersed and immobilized Fe3O4 nanoparticles in the micro/nanopore structure of the aerogel enabled excellent magnetic properties which improved the recovery rate of the aerogel material under an external magnetic field is improved while maintaining a good adsorption capacity for substances such as oil. The introduction of Fe3O4 and modified lignin significantly improved the properties of graphene aerogel and resulted in lower density (7.75 mg/cm3), and improved the thermal stability of aerogels, making them excellent adsorption efficiency. The BET specific surface area of the modified lignin graphene aerogel was 64.82 m2/g and the average pore size is 5.88 nm. The BET specific surface area of FLGA was 17.78 m2/g and the average pore size is 8.31 nm when the content of Fe3O4 is 50% of GO. After 10 successive adsorption-desorption cycles, the specific surface area of FLGA became 10 m2/g and the pore size became 11.84 nm, The adsorption of ethanol, organic solvents and oil by FLGA was more efficient when the content of Fe3O4 is 16.7% of GO, which can reach 65.56–135.17 times of its own weight.