Effect of gas rate and impeller speed on bubble size in frother-electrolyte solutions

•Bubble size was determined for electrolyte-frother mixtures in a lab scale mechanical flotation cell.•Bubble size decreased with the addition of frother to a sea salt solution, but increased when frother was added to NaCl.•These different trends were assumed to be caused by various break-up or coalescence phenomena.•Bubble coalescence was shown to mask the effect of frother on bubble break-up at low frother concentration.•Differences in bubble size was highly dependent upon cell operating conditions.