Pickering Emulsion Gels Based on Halloysite Nanotubes and Ionic Biopolymers: Properties and Cleaning Action on Marble Surface

We have fabricated ecocompatible Pickering emulsions based on halloysite nanotubes and ionic biopolymers (chitosan and pectin) from renewable resources. The effect of pectin and chitosan on the Pickering emulsion was investigated by direct visualization of the oil droplets and by the thermodynamic characterization at the interface. Pectin enhances the Pickering emulsion stability, while a phase separation and nonhomogeneous gel was observed in the presence of chitosan. We have demonstrated that the Pickering emulsion in a pectin based gel phase is suitable for wax layer removal from a marble surface. A controlled cleaning is achieved by tuning the contact time between the gel and the marble surface. Due to its nonhomogeneous structure, chitosan-based gel does not show proper wax removal ability. This work opens up a new sustainable approach in preparing cleaning formulations for conservation of cultural heritage.