Frother structure-property relationship: Effect of hydroxyl position in alcohols on bubble rise velocity

Abstract

The properties of flotation frothers depend on their structure. This paper forms part of our investigation into the frother structure-property relationship using bubble rise velocity as the property, the structure variation in this study being the hydroxyl group position in alcohols. Single bubble rise velocity profiles were measured in a 350cm column and velocity at 300cm determined to estimate the concentration at minimum velocity (CMV): a decreasing CMV means it requires less concentration to slow the bubble, and vice versa. Two kinds of alcohols, alkyl alcohols (straight- and branched-chain) and 1,ὠ-diols, were investigated using five and six carbon members. The general effect is that CMV decreases as the OH moves to a terminal position, in the case of 1,ὠ-diols this means the 1,2 structure. For the alkyl alcohols, the effect of OH position on CMV was greater for branched-chain compared to straight-chain members, and having the methyl branch as far as possible from the terminal OH gave the lowest CMV. The most significant effect on CMV was the position of the second OH in 1,ὠ-diols. Arguments based on surfactant molecule orientation and packing on the bubble surface and the role of hydrogen bonding in the case of 1,ὠ-diols are advanced to account for the effects on CMV. Some observations on frother design based on the findings are offered.