Dominance of hydrophobic attraction in attachment of microbubbles and Graphene oxide (GO)

This paper presents the synthesis of GO-coated microbubbles which would be useful for environmental remediation and enhanced heat transfer applications. The mechanism of microbubble-GO attachment including electrostatic interactions, hydrophobic attraction, contact angle and Gibb's free energy were determined. Preliminary experiments indicated that water alone is not favourable, which thus necessitated the use of a bridging surfactant. The optimum attachment between microbubbles and GO occurred at the GO's isoelectric point (IEP) in the ionic liquid as surfactant (IL), in which the IL concentration allowed GO to achieve maximum hydrophobicity. Therefore, it is inferred that hydrophobic attraction is the dominant force for microbubble-GO attachment with minor contributions from electrostatic interactions. Further studies showed that the longest carbon chain length IL, i.e. 1-Dodecyl-3-methylimidazolium chloride ([C₁₂mim]Cl) produced the most conducive environment for microbubble-GO attachment at its IEP concentration of 350 ppm.