Hydrophobic aerogels for oil-spill clean up – synthesis and characterization

Hydrophobic aerogels were synthesized, characterized by IR, surface areas, relative pore size distributions and decomposition behavior. The materials were then tested for oil absorbing capacity in oil salt-water mixtures for applications to oil-spill clean up processes. Aerogels containing the CF3(CH)2-group (CF3-aerogel) were successfully synthesized using (CH3O)4Si and nominally 30, 10, 1.5 mol% CF3(CH2)2Si(OCH3)3 in CH3OH by a NH4OH catalyzed reaction followed by supercritical extraction with CH3OH. The aerogels were found to be hydrophobic based on water absorption and sessile drop experiments. By IR, the CF3(CH2)2-group was found to be intact after the gelation process and after supercritical drying. Si–OH-groups were also found in all cases, with decreasing amounts with increasing amounts of the CF3(CH2)2-group. Heating under air caused the 30% CF3-aerogel to decompose, where the transition temperature from hydrophobic to hydrophilic appeared around 375–400 °C, which corresponded to disappearance of the CF3(CH2)2-moiety bands in the IR. Treating oil and salt-water mixtures with the aerogel at an oil to aerogel ratio of 3.5 showed that all CF3-aerogels cleanly separated the oil from the water, regardless of CF3(CH)2-group concentration. This indicates that CF3-aerogels can absorb oil as much as 237 times their weight, much more than previously determined.