Amphiphilic cellulose and surfactant mixtures as green frothers in mineral flotation. 1. Characterization of interfacial and foam stabilization properties

The stabilization of the froth phase is among the most important aspects for efficient separation in flotation. While the behavior of froth stabilization reagents has been thoroughly studied, there have only been minimal changes to their formulations in the past decades. Simultaneously, there is an increasing need for both more efficient processes due to declining ore grades and more sustainable methods due to increased environmental awareness. The current commercially applied frothers consist mainly of aliphatic alcohols and oligomeric glycol ethers. The present manuscript proposes a profound change to the state-of-art frother formulations by introducing the first ever detailed interfacial characterization of an aqueous polymer-surfactant (PS) mixture consisting of a nonionic amphiphilic polymer and a nonionic surfactant pair to be used as a flotation frother. The polymeric component of the mixture is a biodegradable cellulose derivative, namely hydroxypropyl methyl cellulose (HPMC), produced from sustainable sources. In the first part of this series, the dynamic surface tension, bubble size distribution and foam stability were measured for PS-mixtures with various compositions and concentrations. This work shows that the interaction of the components in this unique PS-system results in significant improvements to foam formation behavior compared with commercial frothers, including: i) a synergistic decrease of surface tension; ii) accelerated diffusion of surfactants to the air-liquid interface; iii) bubble size reduction; and iv) a self-stabilizing foam phase.