Direct Force Measurement between Hydrophobic Glass Sphere and Covellite Electrode in Potassium Ethyl Xanthate Solutions at pH 9.2

Froth flotation is the most widely used method of separating minerals from one another. The basis of this process is to control the hydrophobicity of the minerals to be separated. The most commonly used measure of hydrophobicity is the water contact angle (θ), which is usually measured on polished mineral surfaces using either sessile drop or captive bubble technique. However, contact angle is a thermodynamic property and, therefore, it is difficult to use it for predicting a kinetic process such as flotation. For this reason, most of the flotation models published in the literature fail to incorporate the role of hydrophobicity. However, recent investigations conducted at Virginia Tech led to the development of a flotation model, which includes contributions from hydrophobic forces [1]. Here the term hydrophobic force should be distinguished from hydrophobicity. Since its first measurement by Israelachivili and Pashley in 1982 [2], many investigators conducted surface force measurements between surfaces of different hydrophobicities. Rabinovich and Yoon [3] and Yoon and Ravishankar [4] reported a relationship between hydrophobic force and θ. Such information is critical for developing reliable flotation models.