Heat of Immersion as a Method to Quantify Wettability for Particulates: Effect of Temperature and Surfactant

Heats of immersion of three different silica particles with three different wettabilities are measured at different temperatures to examine one critical assumption concerning the temperature dependence of the heat of immersion. In addition, surfactants are added to the water and the effect of surfactant concentration on the heat of immersion is measured. One particularly noteworthy aspect of the current study is that some measurements were made at temperatures greater than 100°C and hence pressures higher than atmospheric with no more difficulty than measurements made at atmospheric pressure. Using heat of immersion as a qualitative measure of wetting is appropriate.  However, without measurement of the values of liquid-solid interfacial energy with temperature as well as the gas-solid interfacial energy with temperature, conversion to the contact angle directly is not appropriate. However, for the same surface, using this approach to quantify contact angle as a function of temperature is likely appropriate if the contact angle is measured using some other method at one temperature, at least over the limited temperature range (up to 150°C) explored in this study.