Frothers and Frother Blends: A Structure---Function Study

The presence of frother, either singly or as a blend, is common to most mineral flotation processes. Frothers have two main functions: provide target hydrodynamic conditions and promote froth stability. In the thesis hydrodynamics is measured by bubble size and gas holdup and froth stability by water overflow rate. These functions are related to frother chemistry, or more particularly, molecular structure. However, the structure – function link is not well understood and forms the theme of the thesis.;A methodology is developed to link one hydrodynamic function, bubble size reduction represented by CCC95 (critical coalescence concentration 95%), to frother structure represented by HLB (hydrophile-lypophile balance). The results indicate each frother family has a unique CCC95-HLB relationship. Empirical models are developed to predict CCC95 either from HLB or directly from frother structural parameters. Commercial frothers are shown to fit the relationships.;Use of dual-frother systems to achieve independent control over the two frother functions is tested. Blends of Alcohols with Polypropylene Glycols (PPG) and Polyethylene Glycols (PEG) are selected in pre-mixed and base/additive styles. The base/additive system 1-Butanol/PEG (EO > = 4) gives the independence sought but not 1-Butanol/PPG which causes an increase in bubble size. To explain the bubble size effect, frother partitioning is determined. This is achieved by development of two analytical techniques: high pressure liquid chromatography (HPLC) and nuclear magnetic resonance spectrometry (NMR) associated with total organic carbon analysis (TOC). The 1-Butanol/PPG blends show strong partitioning to the froth which corresponds to the increase in bubble size.;New frothers are synthesized to test the structure-function relationship by combining three groups: linear Alkyl-Ethoxy-Propoxylates (CnEO 1POm) and Alkyl-Propoxy-Ethoxylates (CnPO mEO1). It is found that varying the number of PO groups, the length of Alkyl group chain, and the position of PO and EO could affect the two functions.