The sixth lecture in the module Particle Technology, delivered to second year students who have already studied basic fluid mechanics. Membranes and Colloids covers the different types of particle related pressure driven membrane separations and models of flux decay and fouling. Colloidal behaviour using the DLVO theory is also covered, including colloid stability.

1. Membranes & Colloids Chapters 4 & 13 in Fundamentals Watch this lecture at http://www.vimeo.com/10202852 Visit; http://www.midlandit.co.uk/particletechnology.htm for further resources. Course details: Particle Technology, module code: CGB019 and CGB919, 2nd year of study. Professor Richard Holdich R.G.Holdich@Lboro.ac.uk

3. Surface and internal fouling

4. Polarisation flux models & enhancement

7. viruses 0.05 to 0.5 microns

8. colloidal silica 0.02 to 1 micron

9. macromolecules 0.01 to 0.5 microns

10. ions <0.01 microns

12. 0.05 to 10 microns generally

13. Ultrafiltration

14. 1 to 50 nano-metres

16. Cells - unstirred and stirred

19. Crossflow filtration

22. Crossflow filtration

23. Permeate flux decay

24. Filtration fundamentals Why can’t we simply measure Rm for each medium?

26. Surface and internal fouling

27. Polarisation flux models & enhancement

30. Membrane internal fouling?

31. Membrane secondary membrane

33. Surface and internal fouling

34. Polarisation flux models & enhancement

36. Rejection R = 1 - Np/Nb

37. Equilibrium flux response

38. Membrane film theory

39. Membrane simple circuit

40. Membrane feed & bleed

41. Diafiltration

42. Diafiltration Stirred tank displacement washing only: e.g. washing times given a flux rate of 50 l m-2 h-1 and tank volume of 1000 litres Area (m2): 1 10 20 t(hrs) C(ppm) C(ppm) C(ppm) 0 500 500 500 1 476 304 184 2 452 184 68 4 409 68 9 6 370 25 1

43. Membrane cleaning

44. Membrane & other SLS

45. Membrane surface filter

46. Membrane surface filter - slots

48. Surface and internal fouling

49. Polarisation flux models & enhancement

51. Increase diameter but decrease density – net enhanced rate

52. COAGULATION

53. v

55. Fixed layer +ve ions

56. Diffuse layer after…

57. Shear layer

58. Zeta potential – measured by moving particle in field,

60. Electrical repulsion where the Zeta potential is used extensively above, together with the particle diameter, dielectric constant of the system and the Debye-Hückel function –which is a function of ionic conditions.

62. Dimensionless interaction energy

64. Primary minimum

65. and maximum

66. Curve 2

67. Primary and

68. Secondary minimum

69. Single maximum

70. Curve 3

71. Primary minimumWhich colloid is the most stable?

74. Often assessed by the Zeta potential

76. Surface and internal fouling

77. Polarisation flux models & enhancement