Oleic acid-modified layered double hydroxide for Pickering emulsion: (II) Emulsification behavior

English Layered double hydroxides (LDHs) are plate -like particles, being potential Pickering emulsifiers. Surfactant modification can regulate their surface properties, and thus can influence their emulsifying behavior. However, there is a lack of full understanding on the correlation between the surface modification of LDHs and their emulsification behavior. In the current work, one LDH and five oleic acid (OA) -modified LDH (LDH@OA) samples were chosen as emulsifiers, and emulsifying tests for pentadecane (oil) -water mixtures were performed at different oil/water volume ratios (1/9-9/1) and solid dosages (Cs, 1.00-10.0 g/L). The type, droplet size, and stability of emulsions were determined. The interfacial adsorption energy (Delta Gad) and the coverage of solid particles for droplet surfaces (Rcov) were estimated, and the oil -water interfacial tension and viscoelastic moduli were determined. Results showed that LDH and LDH@OA particles can emulsify the oil -water mixture, forming coalescence -stable Pickering emulsions. The emulsion type is only determined by the solid wettability, independent of the oil/water ratio and Cs. The OA modification can change the wettability of LDH from hydrophilic to hydrophobic, thereby can regulate the type of emulsions from oil -in -water (O/W) to water -in -oil (W/O).