Superhydrophobic and superoleophilic carbon nanofiber grafted polyurethane for oil-water separation

The oil contamination in water and industrial wastewater is a concern for the environment. The role of carbon nanofiber (CNF) grafted onto polyurethane (PU) for oil absorption was investigated under ambient conditions. Superhydrophobic and superoleophilic materials based on CNF grafted PU were synthesized by a dip coating for oil/water separation. The synthesized materials were characterized by SEM, FTIR, BET and by a dynamic oil separation setup. Surface grafting with CNFs substantially increased the surface area of PU by nearly 31X (9 m²/g to 276 m²/g), which also decreased the average pore size in the PU matrix from 2567 Å to 36 Å. The decrease in pore size significantly improved the capillary action of the synthesized CNF grafted PU and provided almost no chance for water to pass. CNF grafted PU has successfully separated oil from different oil/water models and displayed absorption capacity up to 50 times to its own weight. The absorbed oil can be recovered by squeezing CNF grafted PU, which retains its original shape after releasing the pressure, and thus it was successfully used multiple times. The flexibility and the mechanical stability of the material allows it to be used for the continuous separation of oil from oil-contaminated water.