Ionic Liquid As Surfactant In Pickering Emulsions Stabilised By Silica Particles.

Ihebie, Chidimma

Abstract

Investigations were carried out on the use of ionic liquid as an adsorbing surfactant in Pickering emulsions stabilised by silica particles. Colloidal silica nanoparticles, Ludox CL (positively charged) and Ludox HS-30 (negatively charged), and 2 μm silica particles were used for both the aqueous dispersion studies in ionic liquid and emulsion studies.
Ludox CL and Ludox HS-30 dispersions in aqueous 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (IL) was studied. Ludox HS-30 formed stable, less turbid dispersions while Ludox CL formed unstable, more turbid dispersions with sedimentation at higher IL concentrations.
Dynamic light scattering was used to characterize both Ludox CL and Ludox HS-30 dispersions. The results showed that as the IL concentration increased, the zeta potential values for Ludox CL changed from +34 mV to reduced negative values while zeta potential values for Ludox HS-30 shifted from -30 mV to lower negative values. The particle size increased with increasing IL concentration in both Ludox CL and Ludox HS-30, indicating particle aggregation and decreased dispersion stability.
Emulsions studies with silica particles and octane was done at octane to water volume ratio of 1:1. Ludox HS-30 formed stable oil-in-water (o/w) emulsions at intermediate IL concentrations ranging from 2.5 × 10-2 M to 2.0 × 10-1 M, while Ludox CL formed unstable o/w emulsions at all the IL concentrations investigated.
For investigations with micron-sized silica particles, stable o/w emulsions were formed at IL concentrations from 3.9 × 10-4 M to 5.0 × 10-2 M for both the powdered particle method and when particles were originally dispersed in octane. However, when particles were initially dispersed in water, no stable o/w emulsions were observed except at IL concentration of 5.0 × 10−2 M. More stable o/w emulsions were obtained by keeping the IL concentration constant at 1.56 × 10-3 M than at 1.25 × 10-2 M while varying the particle concentration. The results indicate that the IL was acting as an adsorbing surfactant in Pickering emulsions with Ludox HS-30, micro-sized silica particles originally dispersed in octane and the powdered particles method but could not effectively act as a surfactant when the micron-sized silica particles were initially dispersed in water.

Citation

Ihebie, C. (2024). Ionic Liquid As Surfactant In Pickering Emulsions Stabilised By Silica Particles. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/5077513

• Thesis Type: Thesis
• Deposit Date: Mar 11, 2025
• Publicly Available Date: Mar 17, 2025
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/5077513
• Additional Information: Department of Chemistry; University of Hull
• Award Date: Aug 28, 2024