Production of Oil-in-Water Emulsions with Varying Dispersed-Phase Content using Confined Impinging Jet Mixers

Abstract

This work reports for the first time on the use of Confined Impinging Jet Mixers (CIJM) for the production of emulsions with dispersed-phase content up to 80 wt %, in both the surfactant-poor and -rich regimes, following the exposure to varying CIJM hydrodynamic conditions. It was observed computationally and experimentally that the CIJM capacity resulted strictly dependent on the mass jet flow rate (W jet > 176 g/min) and the pre-emulsion droplet size (>10 μm). CIJM emulsification performance remained (almost) unaffected by the variation in the oil mass fraction. All systems showed the lowest droplet size (∼8 μm) and similar droplet size distributions under the highest W jet. Conditionally onto the Tween20 availability, the emulsion d 3,2 was primarily determined by formulation characteristics in the surfactant poor-regime and by the CIJM energy dissipation rate in the surfactant-rich regime. In conclusion, this study offers further insights into the CIJM suitability as a realistic alternative to already-established emulsification methods.

Formation of Pickering and mixed emulsifier systems stabilised O/W emulsions via Confined Impinging Jets processing

“…It should be highlighted that, as previously discussed, the pre-emulsions containing 0.10 wt.% silica phase separated immediately after their preparation, whereas, in our previous work, we showed that although the emulsions stabilised by only 0.01 wt.% Tween20 remained stable after CIJs processing (d3,2 ~ 25µm), these phase separated during the storage period, i.e. 40 days (Tripodi et al, 2019). Thus, there is a clear evidence that the combination of the emulsifiers (even at concentrations where each of them on their own do not give a stable emulsion microstructure) aids in prolonging the emulsion stability, although in this case the droplet size was not entirely retained (Figure 7.B).…”

“…On the other hand, as the ε̅ th increased (highlighted areas in Figure 3), the droplet size reduction became more pronounced and all systems reached the lowest droplet size (~10 µm) at the highest value of ε̅ th regardless of particle concentration and oil content. In a recently published study (Tripodi et al, 2019), it was demonstrated that the jet collision was compromised at low ε̅ th , resulting in relatively poor mixing conditions and ultimately impeding CIJs emulsification capacity (within this energy dissipation rate range) . Contrarily, as higher levels of ε̅ th are approached (i.e.…”

“…In contraposition, Confined Impinging Jets (CIJs) have shown the potential of overcoming both of these limitations. In CIJs two (either the pure oil and water phases or two pre-emulsion) jets collide at high velocities within a confined geometry (Tripodi et al, 2019). CIJs exploit the energy dissipated upon impingement as the driving force for the turbulent production of emulsions rather than the application of high-levels of shearing, pressure or cavitation (Tripodi et al, 2019).…”

“…In CIJs two (either the pure oil and water phases or two pre-emulsion) jets collide at high velocities within a confined geometry (Tripodi et al, 2019). CIJs exploit the energy dissipated upon impingement as the driving force for the turbulent production of emulsions rather than the application of high-levels of shearing, pressure or cavitation (Tripodi et al, 2019). Due to the confined mixing volume, droplets experience rather uniform disruptive forces, resulting in the high throughput production of emulsions with tailored microstructural features (e.g.…”

“…More recently, it has also been shown that CIJs processing allowed the production of dilute emulsions having an average droplet dimension within the nano-size range (~700 nm) but only if coupled with an ultrasound treatment (Siddiqui et al, 2017). An additional study investigated the use of CIJs for the production of emulsions with dispersed phase content up to 80%, in the surfactant (Tween20)-poor and -rich regime, hydrodynamic conditions as well as residence times (Tripodi et al, 2019). In this work, CIJs operation could induce droplet size reduction only when the process took place within the identified optimal processing window (i.e.…”