Fabrication of Magnetite-Graphene Oxide/MgAl-Layered Double Hydroxide Composites for Efficient Removal of Emulsified Oils from Various Oil-in-Water Emulsions

The oil contamination caused by surfactant-stabilized oil-in-water (O/W) emulsions are of increasing concern because of their persistent stability and high transportability. In this study, magnetic three-dimensional composites, which contain magnetite (Fe₃O₄) particles, grapheme oxide (GO), and MgAl-layered double hydroxides (MgAl-LDHs), were fabricated and applied as adsorbents to remove emulsified oils from various oil-in-water (O/W) emulsions. Transmission and electron scanning microscopies, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and ζ-potential analysis techniques were utilized to characterize MGO/MgAl-LDH composites. The particle–interface interaction was characterized by interfacial rheometer. Oil removal study results showed that the maximum removal efficiency for the crude oil was a mass ratio of LDHs/MGO = 1:1, while the maximum removal efficiencies for decane and white oil were a mass ratio of LDHs/MGO = 1:3. Under a suitable mass ratio of LDHs to MGO, 98–99% of emulsified oils could be removed by MGO/MgAl-LDH composites. Experimental data were best fitted to the Langmuir isotherm model. Thermodynamic analysis indicated that the adsorption process was both exothermic and spontaneous. The emulsified oil removal efficiencies were increased with increasing ionic strength. In addition, MGO/MgAl-LDH composites could maintain good oil removal efficiency after reusing over five cycles, indicating their great potential for use in an oily wastewater treatment.