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A method for preparing emulsions with a narrow droplet size distribution (span) without repetitive membrane permeation, by controlling the premix emulsion viscosity and membrane permeation rate (MPR), flux, was provided. The mean emulsion viscosity and the MPR are some of the main factors that control the wall shear stresses responsible for droplet break up in premix membrane emulsification (PME). Hence, striking a balance between these two factors is important for preparing monodispersed emulsions. When the emulsion viscosity and the viscosity ratio of the phase were low, the emulsion droplet size and polydispersity decreased linearly with PMR until MPR of 60 m3/m2h at which the most monodispersed emulsions (d50 =5.80, span = 0.24) were prepared. Beyond this the droplet size decreased further while polydispersity became higher, due to the uncontrolled wall shear stresses at higher MPR. Increasing the disperse phase viscosity (i.e., high viscosity ratio) lowered the shear stresses in the pores that the emulsion droplet size polydispersity became higher. Whereas, increasing the mean emulsion viscosity enabled us achieve the most monodispersed emulsions (d50 =5.80, span = 0.24) at lower MPR of 10 m3/m2 h. At low MPR the wall shear force could be increased by increasing the mean emulsion viscosity and emulsions with a small span could be prepared. Therefore, in this study it was proved possible to prepare highly monodispersed emulsions by adjusting the mean emulsion viscosity and MPR, without repetitive permeation, in PME. |
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