Mild pyrolysis of cotton coated with graphene-like materials as a method to produce superhydrophobic and highly absorptive oil sorbents

In recent years, hydrophobized cellulose-based materials have been proposed as oil spill sorbents. We investigate the possibility of using cheap, industrialgrade, graphene-like materials (GM), such as graphite flakes (GrF), exfoliated graphene nanoplatelets (xGNP) and microwave-plasma turbostratic graphene nanoplatelets (mGNP) as hydrophobic agents for naturally hydrophilic cotton. From among investigated GM, mGNP showed the highest ability to form superhydrophobic coating due to small flake size and small amount of impurities. Furthermore, we showed that mild pyrolysis not only makes cotton more hydrophobic, but also increases its sorption capacity towards organic solvents and oils. Pyrolyzed and coated with mGNP and xGNP cotton showed exceptional superhydrophobic properties and water contact angle equal 148° and 142°, respectively, besides the sorption capacity towards motor oil of 46 g/g and 51 g/g, respectively. What is more important, the price of graphene oxide used in previous research is still very high (approx. 100 $/g), while the price of xGNP and mGNP is 0.45 $/g, 7.3 $/g, respectively. This difference may be crucial for the implementation of graphene-based sorbents in the remediation of massive oil spill remediation.