Surface forces and measuring techniques

In this chapter we are concerned with interactions between particles, including air bubbles. Such interactions occurring across aqueous solutions are of special interest since they determine phenomena in mineral processing, including froth flotation (Leja, 1982; Schulze, 1984). The most important types of colloidal forces will be introduced and discussed together with short descriptions of the most commonly used techniques for studying such interactions. This field is large and subject to extensive research and the account given here is therefore necessarily very concise. The interested reader will find more extended treatments in some of the books and research articles referred to in the text. Some results obtained from surface force measurements will also be provided in order to illustrate what can be learned from such studies. In flotation we are dealing with complex systems comprising, in addition to the minerals to be separated, the gangue or non-mineral containing material, other suspended solids, electrolytes, and dissolved and adsorbed polymers. The object of the flotation process, to separate unwanted material from the desired product, is usually facilitated by introduction of additives like surfactants and polymers to tthe already complex system. These components interact with one another in a variety of ways. This leads to formation of various molecular aggregates (micelles, polymer-surfactant complexes, etc.) and to adsorption at air-liquid and solid-liquid interfaces (Fig. 1), which affect the interactions between the constituents in the flotation system.An account is given on the interactions between particles, including air bubbles. Such interactions are of special interest because they determine phenomena in mineral processing, including froth flotation. The most important types of colloidal forces are introduced and discussed together with short descriptions of the most commonly used techniques for studying such interactions. Some results obtained from surface force measurements are also provided in order to illustrate what can be learned from such studies.