Characterizing Frothers through Critical Coalescence Concentration (CCC)95-Hydrophile-Lipophile Balance (HLB) Relationship

Wei Zhang,James A Finch,Jan E Nesset,Ramachandra Rao

doi:10.3390/min2030208

Abstract

Frothers are surfactants commonly used to reduce bubble size in mineral flotation. This paper describes a methodology to characterize frothers by relating impact on bubble size reduction represented by CCC (critical coalescence concentration) to frother structure represented by HLB (hydrophile-lipophile balance). Thirty-six surfactants were tested from three frother families: Aliphatic Alcohols, Polypropylene Glycol Alkyl Ethers and Polypropylene Glycols, covering a range in alkyl groups (represented by n, the number of carbon atoms) and number of Propylene Oxide groups (represented by m). The Sauter mean size (D32) was derived from bubble size distribution measured in a 0.8 m3 mechanical flotation cell. The D32 vs. concentration data were fitted to a 3-parameter model to determine CCC95, the concentration giving 95% reduction in bubble size compared to water only. It was shown that each family exhibits a unique CCC95-HLB relationship dependent on n and m. Empirical models were developed to predict CCC95 either from HLB or directly from n and m. Commercial frothers of known family were shown to fit the relationships. Use of the model to predict D32 is illustrated.

Highlights

Flotation, widely used for processing mineral ores, is based on the capture of hydrophobic particles by air bubbles [1]
Bubbles in flotation machines in the absence of frother exhibit a wide, often bi-modal size distribution with a Sauter mean size ca. 4 mm which the addition of frother narrows to a mono-modal distribution of Sauter mean size typically ca. 1 mm [2]
The D32-C curves were consistent and the 95% confidence interval on the calculated CCC95 was 0.6 ppm or 0.0024 mmol/L, which is too small to indicate on subsequent plots

Summary

Introduction

Widely used for processing mineral ores, is based on the capture of hydrophobic particles by air bubbles [1]. In the process surface-active agents known as frothers are commonly employed to aid production of fine air bubbles which facilitate particle capture and transport. Bubbles in flotation machines in the absence of frother exhibit a wide, often bi-modal size distribution with a Sauter mean size (diameter, D32) ca. Treating flotation as a first order kinetic process, Gorain et al [3,4] showed that the flotation rate constant increased inversely with bubble size (1/Db) a dependence used in the JKSimFloat simulator [5]. Others have suggested an even stronger dependence, as high as 1/Db3 [6]

Results

Discussion

Conclusion