Controlling Bubble–Solid Surface Interactions with Environmentally Benign Interfacial Modifiers

The influence of two biopolymers (xanthan gum and locust bean gum) on the interaction between bubbles and graphite has been elucidated using a combination of direct measurement techniques. Bubble–surface collisions (monitored using high speed video capture) reveal that when graphite is exposed to low concentration solutions of the two polymers, the time scale of bubble attachment is prolonged by 1–2 orders of magnitude, and the final receding water contact angle achieved on such surfaces is reduced by approximately 30 deg. Single bubble flotation studies confirm the significant effect of such aspects of bubble–particle collisions on the collection efficiency of graphite particles, with marked reduction in flotation recovery across the particle size range, with greatest effect on the coarser particle sizes. The differences in performance of the two polymers in reducing bubble–particle attachment is seen to be partly due to variation in adsorbed layer coverage of the two polymers on the graphite surface, as revealed by atomic force microscopy imaging. Both polymers can be expected to perform well in the prevention of flotation of graphitic/carbonaceous minerals.