Coalescence of Charged Droplets in Agitated Liquid-Liquid Dispersions

Experimental studies have been performed to assess the effect of drop charge on turbulent drop coalescence. Although it is well known that surface charge can affect coalescence rates of Brownian particles in a quiescent medium, no studies have been found in the literature which explicitly examine charge effects on larger drops in turbulent media. Results demonstate that drop charge can substantially inhibit coalescence between drops in agitated dispersions. Moreover, this effect can arise solely from latent drop charges, which are attributed to the preferential adsorption of hydroxide ions onto the water-organic phase interface. Ionic strength and p H thus are shown to play a major role in determining coalescence rates bet ween agitated drops. Results also demonstrate that reliance on measurement of average drop sizes for the purpose of determining coalescence rate dependencies is a precarious practice. Strong size-dependent effects such as obtained here have the potential to suggest erroneous conclusions when conclusions are based on measurements of average drop sizes rather than of drop-size distributions.