Flotation behaviour of fine particles with respect to contact angle

► We probed the flotation behaviour of particles from 0.2 to 50 μm. ► We examined the flotation rate and recovery as a function of particle size and contact angle. ► A minimum contact angle θcrit exists for flotation to occur. ► The critical contact angle is a result of an energy barrier for the initiation of the three phase line of contact. ► The critical contact angle increases as particle size decreases.