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Frother Function-Structure Relationship: Dependence of CCC95 on HLB

A prime function of frothers is reducing bubble size in flotation systems. The objective of this project is to relate bubble size reduction – summarized by CCC95 (Critical Coalescence Concentration) – to frother structure represented by HLB (Hydrophilic-Lypophilic Balance). The experimental frothers - aliphatic alcohols (1-Alcohol) and Polyglycols (Polypropylene Glycols and Propylene Glycol Ethers) - were selected to give a wide range in structure-related parameters n (number of carbons in alkyl groups) and m (number of propylene oxide groups). Bubble size (Sauter Mean Diameter D32) was measured in a 700 L mechanical flotation cell – a Metso RCSTM 0.8 m3 pilot unit. The D32 data were fitted to a 3-parameter model to determine the CCC95 which represents the concentration giving the minimum D32. The HLB was calculated using the Davies equation. A CCC95-HLB relationship dependent on frother family was demonstrated. To extend to commercial frothers whose structures are uncertain, NMR spectroscopy was used to identify the frother family and estimate the HLB. It appears that the CCC95 value for a commercial frother can be estimated directly from its molecular structure by using NMR spectroscopy.

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