Water-in-Oil Pickering Emulsions Stabilized by Divalent Metal Phenylphosphonate Particles

Phenylphosphonates of zinc (Zn-PPh), calcium (Ca-PPh) and magnesium (Mg-PPh) were synthesized by the hydrothermal method. Samples showed characteristic X-ray diffraction (XRD) patterns of layered compounds with basal spacing in the range of 14-15 Å. According to Fourier transform infrared spectroscopy (FTIR), all compositions showed the presence of characteristic bands attributed to phenyl aromatic rings, phosphonate and lattice metal-oxygen (M-O) vibrations. Different concentrations of phenylphosphonate particles were applied to stabilize water-in-oil Pickering emulsions using vaseline oil in different w/o fractions. The three particle types showed greater affinity for the oil phase (wettability) and the ability to stabilize the emulsions via the Pickering effect. Ca-PPh particles contained a greater emulsified fraction after 20 days of evaluation. This result can be attributed to the particle morphology observed by scanning electron microscopy (SEM). The fibrous morphology of Ca-PPh particles is believed to increase the steric hindrance effect at the surface around the droplets, while the Zn-PPh and Mg-PPh layered particles tended to form clusters.

Keywords:
water-in-oil emulsion; Pickering emulsion; layered and fibrous phenylphosphonates