Oil-in-water Pickering emulsions stabilized with functionalized multi-walled carbon nanotube/silica nanohybrids in the presence of high concentrations of cations in water

Functionalized multi-walled carbon nanotube (MWCNT)/silica nanohybrid was synthesized and proposed as a stabilizer for oil-in-water Pickering emulsion. Carbon nanotube-to-silica weight ratio was a decisive factor influencing the performance of the synthesized nanohybrid. The results showed an appropriate value of such a ratio for a sol–gel synthesized nanohybrid structure was 28–33%. The emulsion formation time was dictated by the adopted mixing strategy such that without any mixing or ultrasonication it took 12 days for stabilization to be established. Conversely, the use of ultrasonication accompanied by mechanical mixing reduced this time to less than 4 h. Another key factor pertained to the type of the cation contained in water. Bivalent cations, such as magnesium and calcium, changed the hydrophilic–lipophilic balance more intensely than the sodium univalent cation. The nanohybrid holds a great promise to be adopted in enhanced oil recovery (EOR) processes as it does not require any emulsifier and mechanical treatment.