Super-wetting properties of functionalized fluorinated graphene and its application in oil-water and emulsion separation

Recently, two-dimensional graphene derivatives obtained by the chemical functionalization of fluorinated graphene (FG), owing to its rich surface chemistry, have been receiving increasing attention. Herein, we have extended the FG derivative library to dithiocarbamate-functionalized FG (FG-DTC) by a one-step in situ route under room temperature conditions using carbon disulphide and diethylamine as precursors. The covalent binding of sulphur moieties via the partial defluorination of FG, including the pendent dialkyl units resulted in a low surface free energy (9.0 mJ m(-2)) with a water contact angle of 150 +/- 3 degrees. The superhydrophobic FG-DTC powder exhibited excellent repellency toward corrosive aqueous liquids. The non-polar solvent adsorption and water rejection properties of FG-DTC were utilized for selective oil uptake from oil-water mixtures. The dispersion processability of the FG-DTC material was integrated into a macroporous polydimethylsiloxane (PDMS) polymer sponge. The FG-DTC-PDMS sponge was utilized to selectively adsorb less-dense oils on the surface of water and heavy solvents underwater, which makes it a potential candidate for treating oily wastewater under various conditions. The resultant hydrophobic PDMS sponges exhibited selective oils/organics sorption efficiency in the range of 4.8 to 12.1 g g(-1) with excellent reusability and an adsorption capacity of greater than 90% even after 10 cycles. The robustness of the hydrophobic modified PDMS sponges was evaluated under tough physical deformations, followed by chloroform sorption, and demonstrated 99% efficiency. The cooperative merits, including the hydrophobic macropore walls of the PDMS network after the fine coating of FG-DTC, were explored towards emulsion (toluene in water) separation. The outcomes from this work provide vital insights into surface-engineered fluorinated graphene nanosheets for self-cleaning applications with a major emphasis on oils/organics and emulsion separation.

Automated summary

Chemically functionalized fluorinated graphene derivatives have been synthesized and shown to have superhydrophobic properties for selective oil adsorption from oil-water mixtures. The resulting PDMS sponge with FG-DTC coating demonstrated efficient oily wastewater treatment with excellent adsorption capacity and reusability.