Revista de Engenharia Química e Tecnologia de Processos
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The Mass Transfer and Coalescence Time Scales in Binary Droplet Systems for Copper Extraction

Jussi Tamminen, Esko Lahdenperä, Tuomas Koiranen, Toni Kuronen, Tuomas Eerola, Lasse Lensu and Heikki Kälviäinen

In this work, we studied whether coalescence has a direct effect on mass transfer in copper extraction. The coalescence of pendant and sessile droplets containing diluted Acorga M5640 in an aqueous copper sulfate solution was recorded on video. The videos were analyzed to determine droplet rest times, sizes, and concentrations. Concentration measurements revealed that coalescence does not enhance mass transfer because coalescence is a rapid phenomenon. A comparison of the experiments performed with and without mass transfer showed that the coalescence dynamics are not affected by mass transfer. A bimodal rest time distribution was observed when the copper sulfate solution was in the continuous phase. The surface flows and cell-like structures observed on the droplet interface are presumed to be because of a Marangoni convection, which is caused by concentration changes because of extraction. The presence and absence of surface flow is anticipated to lead to a bimodal rest time distribution. The presence of surface flow improves coalescence probability because of very short binary droplet rest times.