Transcript Influence of soluble polysaccharides on the adherence of particulate soils Y. Touré, P.G.

Influence of soluble polysaccharides
on the adherence of particulate soils
Y. Touré, P.G. Rouxhet, C.C. Dupont-Gillain and M. Sindic
[email protected]
Heat Exchanger Fouling and Cleaning – 2011
June 05 - 10, 2011
Presentation outline
I- Introduction
II- Experimental procedures
III- Results and discussion
IV- Conclusion
I- Introduction
Background
Who is concerned ?
• Particulate soils
• Microorganisms
Why ?
The cleaning efficiency influences:
• final quality of the products,
• absence of cross-contaminations,
• batch integrity.
I- Introduction
Background
Understanding the interactions in order to :
• reduce equipment fouling,
• reduce interruptions of production process for cleaning,
• improve the efficiency of cleaning and disinfection,
• develop easy-to-clean surfaces.
I- Introduction
Background
Study of soluble macromolecules
associated with a suspension of particles:
• may give practical information on the interaction of surface nature
and particle surface properties
• may give an insight into the physico-chemical mechanisms involved
• may clarify the role of the soluble macromolecules involved in
particles adherence
• may open the way to designing and evaluating easy-to-clean
surfaces
I- Introduction
Objectives
Assess the influence of soluble polysaccharides on
particulate soils adhesion
Improve:
• understanding of mechanisms affecting soiling
• cleanability
II- Experimental procedures
Material
Model of soluble polysaccharide: dextran
from Leuconostoc mesenteroides; PM: 500 000 Da
Model of particulate soils : quartz (10-30µm)
Model of surfaces :
• glass (hydrophilic),
• polystyrene (hydrophobic)
Substrate pretreatment
Surfaces
Glass
Polystyrene
Immersion (RBS50 2% à
50°C), 10 min
Sonication, 10min
+ MQ rinse
Washing, alcohol
+ immersion, 30 min
+ MQ rinse
Immersion, piranha mixture
10min + MQ rinse
Drying, nitrogen
Immersion dextran
80mg/l, 1h
Yes
Conditioned ?
No
Redrying, nitrogen
Fouling
Soil preparation and
treatment
Suspension (15%) with
dextran and washed
Quartz particles (10-30µm)
Suspension à 15%
without dextran)
Suspension (15%) with
dextran (80 mg/l)
Gentle agitation
Storage, 72 h ,
4°C
3 cycles , washing-decantation
(MQ) – supernatant elimination
Suspension (15%)
reconstitution
Yes
Dextran
present ?
Yes or no
surfaces pretreated
fouling
Soiling procedure
Pretreated surfaces
Soiling
Particulate soils
Cleaning method
Drying, 30 min in dark, 19
± 5°C, 39% H
Picture I
Radial-flow cell (90 ;
190 ; 390 ml/min)
FLOW
r
Data processing
Pretreated surfaces
Particulate soils
Soiling
Drying, 30 min in dark, 19
± 5°C, 39% H
picture I
Radial-flow cell (90 ;
190 ; 390 ml/min)
Drying after
cleaning
Picture II
Excel
Result
Yes
MATLAB
LUCIA
OK ?
No
r
Critical detachment
radius
Methods of characterization
• Contact angle
• Scanning electron microscopy (SEM)
• Individual size measurements
• Size measurements on a large population
III- Results and discussion
Wetting properties
80
Water
70
Dextran solution
60
Contact angle (°C)
50
40
30
20
10
Dextran solution
0
Bare Glass
conditioned
Glass
Water
Bare
Polystyrene
Conditioned
Polystyrene
Contact angles on the substrates in the indicated state
Glass ≠ Polystyrene, whatever substrate treatment
Size and shape of
adhering aggregates
Glass
Polystyrene
45
• No distinction between samples
involving the same substrate
40
Height (µm)
35
30
25
20
• Height and lateral size, larger
on polystyrene than glass
15
10
Polystyrene
5
Glass
0
0
10
20
30
40
50
60
70
80
90
Eqdiameter (µm)
Height of the soiling entities formed on glass and
polystyrene plotted as a function of their lateral
dimension (equivalent diameter of the contour)
Histograms (% in number) of the lateral size of
the soiling entities formed on glass and
polystyrene (equivalent diameter of the contour)
D50% were:
• 30µm on glass,
• 55µm on polystyrene
NB: Larger population, density
• glass: 51±4 drops/mm2,
• polystyrene: 33±4 drops/mm2
Critical detachment radius
Bare surfaces surfaces with dextran
Quartz without dexran
Quartz with dextran
Quartz with dextran and whased
• Adhering much more firmly on glass compared to polystyrene
• Substrate influence: polystyrene with dextran increased slightly the
adherence, while the opposite was observed with glass
• Influence of particles conditioning: no effect on adherence, whatever
substrate and particles are conditioned or not with dextran.
IV- Conclusion
• Surface hydrophobicity influences aggregates morphology and
adherence.
• Presence of dextrane (80mg/L) :
- Conditioning polystyrene substrate: slightly increases the adherence
- Conditioning glass substrate: slightly decreases
- Conditioning powder…presence in the suspension: no effect
study of wider range of concentrations is in progress
Thank you for your attention !