Regeneration/reuse capability of monolithic carbon xerogels-metal nanocomposites for crude oil removal from oil-in-saltwater emulsions

This work is focused on the development of monolithic carbon xerogels-metal composites for oil removal through adsorption and regeneration processes from oil-in-saltwater emulsions. In this way, three carbon materials with and without metal content (Ni and/or Ce) were prepared by a sol-gel method, namely XCe (carbon xerogel with 18 wt.% of cerium), XCeNi (carbon xerogel with 18 and 4 wt.% of cerium and nickel, respectively), and X (free metal-carbon xerogel). Crude oil adsorption was tested by batch adsorption experiments, varying different operational conditions, including pH, temperature, and amount of monolithic composite and its nature. Regeneration studies were done through oxidation method using air in a thermogravimetric analyzer under isothermal and nonisothermal conditions. From N2 adsorption isotherms it was found that all materials presented a type Ib behavior distinctive of microporous materials. Adsorption results show that crude oil removal increased with the increase of metal content in the composite for all experimental setups. Also, crude oil decomposition was successfully assessed, obtaining the main decomposition peak at 150°C during nonisothermal runs. For isothermal experiments, the three monolithic carbon xerogels achieved 100% conversion of the crude oil adsorbed for all temperatures, whereas raw crude oil only decomposed 60%. The catalytic activity of three monolithic carbon xerogels was corroborated with effective activation energy calculations, which was reduced by 24.9%, 32.5%, and 52.4% from virgin crude oil decomposition to decomposition adsorbed on the samples X, XCe, and XCeNi, respectively.