Heat Exchanger Fouling and Cleaning – 2011 June 05 - 10, 2011

Influence of soluble polysaccharides

on the adherence of particulate soils

Y. Touré, P.G. Rouxhet, C.C. Dupont-Gillain and M. Sindic

yetioman.toure@doct.ulg.ac.be

II- Experimental procedures

Presentation outline

III- Results and discussion

I- Introduction

IV- Conclusion

I- Introduction

Who is concerned ?

• Particulate soils• Microorganisms

Why ?

The cleaning efficiency influences:

• final quality of the products,• absence of cross-contaminations,• batch integrity.

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- IntroductionBackground

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- IntroductionBackground

Assess the influence of soluble polysaccharides on particulate soils adhesion

Improve:

• understanding of mechanisms affecting soiling

• cleanability

I- IntroductionObjectives

II- Experimental procedures

Material

Model of soluble polysaccharide: dextran from Leuconostoc mesenteroides; PM: 500 000 Da

Model of surfaces  :

• glass (hydrophilic),

• polystyrene (hydrophobic)

Model of particulate soils  : quartz (10-30µm)

Surfaces

PolystyreneGlass

Immersion dextran 80mg/l, 1h

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

Fouling

Drying, nitrogen

Redrying, nitrogen

Conditioned ?

No

Yes

Substrate pretreatment

Yes

Quartz particles (10-30µm)

Suspension à 15% without dextran)

Suspension (15%) with dextran (80 mg/l)

3 cycles , washing-decantation (MQ) – supernatant elimination

surfaces pretreated fouling

Suspension (15%) reconstitution

Gentle agitation

Storage, 72 h , 4°C

Dextran present ?

Yes or no

Suspension (15%) with dextran and washed

Soil preparation andtreatment

Pretreated surfaces

Soiling

Particulate soilsSoiling procedure

FLOW

Radial-flow cell (90 ; 190 ; 390 ml/min)

Drying, 30 min in dark, 19 ± 5°C, 39% H

Picture I

Cleaning method

r

Excel

Drying after cleaning

Pretreated surfaces

Drying, 30 min in dark, 19 ± 5°C, 39% H

OK ?

Soiling

LUCIAResult

Particulate soils

Yes

No

Radial-flow cell (90 ; 190 ; 390 ml/min)

Picture II

MATLAB

picture I

Data processing

rCritical 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

Contact angles on the substrates in the indicated state 

Glass ≠ Polystyrene, whatever substrate treatment

Glass

Polystyrene

Size and shape of adhering aggregates

Histograms (% in number) of the lateral size of the soiling entities formed on glass and polystyrene (equivalent diameter of the contour)

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90

Heig

ht (µ

m)

Eqdiameter (µm)

Polystyrene Glass

Height of the soiling entities formed on glass and polystyrene plotted as a function of their lateral dimension (equivalent diameter of the contour)

• Height and lateral size, larger on polystyrene than glass

• No distinction between samples involving the same substrate

NB: Larger population, density • glass: 51±4 drops/mm2, • polystyrene: 33±4 drops/mm2

D50% were:• 30µm on glass,• 55µm on polystyrene

• 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.

Critical detachment radius

Bare surfaces surfaces with dextran Quartz without dexran    

Quartz with dextran    Quartz with dextran and whased    

IV- Conclusion

• Surface hydrophobicity influences aggregates morphology and adherence.

study of wider range of concentrations is in progress

• 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

Thank you for your attention !