Is there any straight relationship between emulsion stability and zeta potential of emulsion droplets? Or other factors will also influence the emulsion stability other than the zeta potential. can we conclude only on the basis of zeta potential about the stability of the emulsion?
I am finding in some literature that a 30mv value of zeta potential is a must for emulsion stability. However few articles also have mentioned against this
The system which I am experimenting has a mixture of surfactant and particle. The primary reason for emulsion stabilization can be assumed to be electrostatic repulsion between the charged droplets for this system.
The actual factor of stability of disperse systems is the total potential energy of interaction of particles (solid, liquid). The maximum of the potential curve corresponds to the potential barrier. The larger the potential barrier, the more stable the emulsion and vice versa. The zeta potential is easily determined, but it is an indicator of the stability of the emulsion, indirectly at high values.
Best regards.
You need to go back into the literature to find the source of the "30 mV" rule. There are 2 areas where it does not apply - steric stabilization where the slipping plane in located in the polymer coating and nanoparticles (< 100 nm) where far more than 30 mV is needed to confer stability. See:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
The original literature is Thomas M. Riddick “Control of Colloid Stability through Zeta Potential: With a closing chapter on its relationship to cardiovascular disease” Volume 1 Livingston Publishing Company (1968). I attach the table (his Table 1) where you'll see that 30 mV only confers 'moderate stability' and he was referring to blood cells of 7 - 10 microns typically.
Other factors for emulsions include size, stabilizer concentration, density differences, chemistry etc so it's not simply an electrostatic affair. See also: Guidance to improve the scientific value of zeta-potential measurements in nanoEHS G L Lowry et al DOI: 10.1039/c6en00136j
Copies of Riddick's book can be obtained for $50. See:
http://customers.hbci.com/~wenonah/riddick/
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