Shigaite, natroglaucocerinite and motukoreaite-like layered double hydroxides as Pickering emulsifiers in water/oil emulsions: A comparative study

摘要

Layered double hydroxides with the chemical composition [M62+Al3(OH)(18)](SO4)(2)Na(H2O6)(6))]center dot 6H(2)O (M2+ = Zn, Mn, Mg) were synthesized by co-precipitation with increasing pH and ripened at 90 degrees C. X-ray diffraction patterns confirmed the high crystallinity and expected basal distances of the samples. Microscopic techniques (SEM and TEM), confirmed the platelet-like morphology with submicrometric dimensions along the platelets and nanometric dimensions in the basal directions, also confirmed by the Scherrer equation. Additionally, the hydrodynamic diameter of particles was analyzed by dynamic light scattering, zeta potential, dissolution and buffering studies were conducted in acid media. The submicrometric particle sizes increased in the order Mg/Al LDH Zn/Al LDH similar to Mn/Al LDH and platelet-like particles were used to formulate oil/water Pickering emulsions. Confocal microscopy was used to monitor the emulsions' formation and stability over time. The particles' size and the solubility effects were used to explain the emulsion formation and the buffer effect produced by the slow dissolution of LDH submitted to the acid medium, with preservation of the emulsified medium against small pH variations.