1. J. Zawała, M. Krzan, K. Małysa Institute of Catalysis and Surface Chemistry Polish Academy of Sciences ul. Niezapominajek 8, 30-239 Cracow, Poland Influence of Surfactant on Initial Accelerations, Shape and Velocity Variations of the Detaching Bubbles Cluster A Meeting, 22 September 2005, Poznań

2. Bubble Motion INDUSTRY  flotation  foam fractionation techniques  biotechnology  waste water treatment EVERYDAY LIFE  washing (detergents)  champagne  beer

3. Questions  What determine the bubble velocities?  How important is the type and concentration of the surfactant for:  accelerations of the bubble?  local velocities of the bubble?  terminal velocities of the bubble?  minimum adsorption coverages needed to full immobilization of bubble interface?  Is there any relation between velocity variations and deformation of the bubble?

4. What affects bubble motion?  viscosity of the continous phase  density  surface tension  properties of gas\liquid interface Velocity of the rising bubble is very sensitive for presence of surface active substance >10 % adsorption coverage can diminish bubble velocity 2 x Bubble motion in surfactant solutions

5. Uniform coverage  eq 35 cm  eq top u Motion leads to disequilibration of adsorption coverage Motion leads to disequilibration of adsorption coverage  terminal velocity 

6.  in = 0.075 mm lamp = 100 Hz i 200 Hz h solution  35 cm Experimental SET-UP PC CCD cameras video TV square glass column stroboscopic lamp syringe pump

7. Captured movies Detachment of the bubble in : distilled water stroboscop illumination frequency – 100 Hz

8. Captured movies Detachment of the bubble in : 1.5 M pentanol solution stroboscop illumination frequency – 100 Hz

9. Measurements L – distance from the capillary  x – distance between two subsequent positions of the bubble Velocity =  t = 0.01 s or 0.005 s L xx dvdv dhdh d h,d v – horizontal and vertical diameter

10. Shape deformations dhdh dvdv quantitative parameter characterizing the deformation degree of the bubble Deformation ratio =

11. Accelerations Stroboscop illumination frequency - 200 Hz Initial acceleration water pentanol 2*10 -3 M pentanol 5*10 -3 M c [M]a [cm/s 2 ]sd 0 (water)92564 2*10 -3 64048 5*10 -3 500110

12. Velocities Low pentanol concentrations: 3 stages of the bubble motion acceleration, deceleration and terminal velocity

13. Shape pulsations vs. local velocities for low concentrations: CORRELATION

14. Velocities

15. full immobilization of bubble surface Adsorption coverage

16. Velocities

17. Effect of concentration on shape pulsations acceleration U max deceleration U terminal 1.10 - 1.22 1.29 1.25 - 1.14 1.06 : vh dd : vh dd 61 mm 16 mm capillary2.5 mm 34 mm 84 mm 100 mm 157 mm 216 mm322 mm 7 mm 1). n-pentanol 1.5*10 -3 1). capillary3.5 mm7.5 mm 15 mm33 mm 61 mm 84 mm102 mm162 mm216 mm 325 mm 2). n-pentanol 5*10 -3 2).

18. CONCLUSIONS  Initial acceleration and terminal velocity of the bubble decreases with increasing concentation of surface active substances  Presence of maximum at the bubble velocity profiles is an indication that dynamic structure of adsorption layer was not yet established there  Shape variations - „Indicators” of establishment of dynamic structure of the adsorption layer (steady state non-equilibrium distribution of the surfactant adsorbed)  Lower adsorption coverages needed in the case of nonionic surface active substances for immobilization of the bubble interface

19. ACKNOWLEDGEMENTS Partial financial support: (grant 3 T09A 164 27) from Ministry of Scientific Research and Information Technology is gratefully acknowledged Participation in Cluster C Meeting was made possible by EC grant INCO-CT-2003-003355