Electrochemical water treatment for scale removal Cosmelina - - PowerPoint PPT Presentation

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Electrochemical water treatment for scale removal Cosmelina - - PowerPoint PPT Presentation

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C a e n - R o u e n UR ABTE UR ABTE EA 4651 EA 4651 Aliments Bioprocds Toxicologie Environnements Electrochemical water treatment for scale removal Cosmelina GONCALVES DA SILVA a , Otavio GIL a , Benot RIFFAULT a , Daniel CHATEIGNER b

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UR ABTE EA 4651

C a e n - R o u e n

UR ABTE EA 4651

Aliments Bioprocédés Toxicologie Environnements

a Normandie Univ, UNICAEN, ABTE, France b Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, France c Calor SAS-Groupe SEB, France

Cosmelina GONCALVES DA SILVAa, Otavio GILa, Benoît RIFFAULTa, Daniel CHATEIGNERb, Dominique GELUSc, Stéphane LEBOEUFc, Thomas CORDIERc, Guy DUCRUETc

Electrochemical water treatment for scale removal

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CONTEX

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Hard water Scale deposits CaCO3 Mg(OH)2

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SLIDE 3

Source: Own work , from Skippy le Grand Gourou, [CCO] via Wikimedia Comm.

CONTEX

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Hardness Rating

  • f

French Counties Soft < 15 26 % Moderately Hard 15 - 30 31 % Hard 30 - 40 34 % Very Hard > 40 9 %

74 % Hard water map

Note: 1 of = 10 mg L-1 CaCO3

43 %

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CONTEX

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Scale deposits damages…

F Biological: F Material:

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CONTEX

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Solutions…

w Chemicals/inhibitors w Membrane systems w Degassing w Electrochemical electrolysis Application: water softening

  • R. Ketrane, B. Saidani, O. Gil, L. Leleyter, F. Baraud, Desalination, 249 (2009) 1397.
  • I. Zaslavschi, H. Shemer, D. Hasson, R. Semiat, J. Membrane Sci., 445 (2013) 88.
  • D. Hasson, V. Lumelsky, G. Greenberg, Y. Pinhas, R. Semiat, Desalination, 230 (2008) 329.
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Anode Cathode

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Solutions…

w Electrochemical water electrolysis At the anode:

H2O(l) g 2H+ + ½O2(g)↑ + 2e-

At the cathode:

2H2O(l) + 2e- g H2(g)↑ + 2OH-

(aq)

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CONTEX

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Solutions…

w Electrochemical precipitation

Calcium carbonate precipitation:

Ca2+

(aq) + CO3 2- (aq) g CaCO3(s)i

Displacement of calco-carbonic equilibrium:

HCO3

  • (aq) + OH-

(aq) g CO3 2- (aq) + H2O(l)

CaCO3 precipitation = OH- consumption è H+ excess (òpH)

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CONTEX

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  • ERCA2 electrolyser (by Lyonnaise des Eaux)

Moderate softening 33% of treatment w Electrochemical precipitation Application: water distribution

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CONTEX

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  • Present work:

w Electrochemical precipitation High softening ≈ 90% of treatment Application: small heating devices

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EXPERIMENT

AL

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Treated water Pump# 1 Pump# 2 Cell Power source Cathode Anode Level detector Filter

Set up

Non treated water supplier Caen tap water (40 of )

  • Hardness degree: MColortest™,

Merck

  • pH: CyberScan pH 510,

Eutech Instruments w Total current intensity w Water flow rate

  • G. Dominique, Patent No. FR3005665(A1), Nov. 21, 2014.
  • G. Dominique, Patent No. EP2803761(A1), Nov. 19, 2014.
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RESULT

S

Hardness and pH evolution with treatment time

Current intensity = 0.5 A Flow rate = 30 mL min-1

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After 20 min è òHardness and pH

Results comparing

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Effect of the total current intensity

Flow rate = 30 mL min-1

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ñ Current è òHardness and pH

After 60 min of treatment 90% of treatment

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Effect of the flow rate

Current intensity = 0.5 A

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ñ Flow rate è ñHardness and pH

After 60 min of treatment 97% of treatment

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Theoretical pH calculation

To treat 90% of the water scale è 90% of [Ca2+]:

Considering that: [HCO3

  • ] = 349 mg L−1 = 5.7 10-3 mol L−1 (determined by titration)

[Ca2+] = 169.33 mg L−1 = 4.2 10-3 mol L−1 (determined by ICP-AES)

Experimental pH values (2.6 - 3.3) ≈ Theoretical pH (2.7)

ä

HCO3

  • and Ca2+ ions initial concentrations ratio

pH = - log(1.8 [Ca2+] - [HCO3

  • ])

Theoretical pH = 2.7

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SEM imaging and XRD analysis

Current intensity = 0.5 A Flow rate = 30 mL min-1

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100% Calcite

  • r

Calcite + Aragonite

  • S. Ouhenia, D. Chateigner, M.A. Belkhir, E. Guilmeau, C. Krauss, J. Cryst. Growth, 310 (2008) 2832.

CaCO3

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CONCLUSI

ONS

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w The system allows us to choose the final hardness setting the total current intensity or water flow rate; w A high water softening can be obtained; w The final pH depends on the bicarbonate and calcium ions initial concentrations ratio; w Depending on the final hardness/pH desired, different applications can be conceived.

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Thank you for your attention!

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