Surface charge effect of nanogel on emulsification of oil in water for fossil energy recovery

Crosslinked polymeric hydrogels in nano-size, termed as nanogels, have significant technological applications by stabilizing Pickering emulsion. Herein, we present our experimental observations and the results of the emulsion stability analysis on the effects of nanogel concentration, oil-to-water ratio, nanogel charge, and ambient temperature. The nanogel with neutral-charge showed extraordinarily high emulsifying ability, interfacial tension between decane and water was reduced from 51.98 mN·m−1 to less than 6.04 mN·m−1, compared to 47.5 mN·m−1 by nanosilica. When treated with neutral-charged nanogel, the oil-in-water emulsion exhibited long-term stabilization, 90% emulsion remained after one month at room temperature, showing the highest stability among the reported literature of Pickering emulsions. However, inorganic silica nanoparticles displayed emulsion stability in minutes. Of particular interest was that the emulsion volume remained 82% after thermal treatment at 65 °C for 48 h. The resulting high emulsion stability was attributed to a combination of high hydrophilicity, sufficient steric repulsion, and high surface coverage of nanogel. These observations indicated that the resulting nanogel can be a promising candidate toward enhanced oil recovery.