GÉ

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CENTRE EUROPÉEN DE RECHERCHE ET D'ENSEIGNEMENTDE GÉOSCIENCES DE L'ENVIRONNEMENT

C E R E G E

Nanofiltration and adsorption for water treatment – The need fornanotechnologies

Armand MASION* ; Jean-Yves BOTTERO* ; Jérôme ROSE* ; Mélanie AUFFAN& ; JérômeLABILLE* ; Mark R WIESNER&

* CEREGE UMR 6635 CNRS-Aix-Marseille Université. Europole de l’Arbois BP 8013545 Aix-en-Provence France. International Consortium for Implications ofNanotechnology (CNRS-CEA)& Center for the Environmental Implications of NanoTechnology (CEINT). PrattSchool of Engineering. Nicholas School of the Environment. Duke University. Box90287. 120 Hudson Hall . Durham, NC 27708-0287 . International Consortium forImplications of Nanotechnology (CNRS-CEA)

Environmental Nanotechnology

MembranesAdsorbentsOxidantsCatalystsEnergySensingAnalytical

•Water•Waste•Soil treatment

A definitionThere is no universal definition of a nanoparticle, but one is: "Aparticle having one or more dimensions of the order of 100nmor less".

There is a note associated with this definition: "Novel propertiesthat differenciate nanoparticles from the bulk materialtypically develop at a critical length scale of under 100 nm".

Why makes nanoparticles unique ?

0

10

20

30

40

50

60

70

80

90

100

0 40 80 120 160 200

Diameter (nm)

% d

'ato

mes e

n s

urfa

ce Surface

Volume

High Surface area

High Surface reactivity

properties ≠ atnano and micro scale

ex : Gold

Inert (microscopic scale)

Active Surface(3 - 4 nm)

20 100

Why makes nanoparticules unique ?

Environmental benefits of nanotechnology :pollution treatment

•Proportion of tube wells thattested positive for As inBangladesh (i.e., >50 µg/L).Map prepared by UNICEF-Dhaka onthe basis of 51,000 field tests•At least 25 million peopledrink tube well (TW) watercontaining As > 50 ug/L.•Arsenic-related diseases :short term : skin lesions,respiratory illnesses, and eyeproblems, long term: cancer(skin, bladder, lung, and otherinternal organs), heart diseaseand neurological disorders.•WHO : 10 µg/l, … but

Nanoparticles and water treatment• Example of arsenic:

Nanoparticles and water treatment

• Difficulties to decrease [As]<10 µg/l• Adsorbent: Iron oxides and oxy-hydroxides

Akaganeite=FeOOHGoethite=FeOOH; ferrihydrite etc…

3 to 4 As/nm2 =>10 µg/l

Iron oxides as adsorbents

• Mechanisms of As adsorption

Fe

Fe

FeFe

As

As

As

Fe

As

H

HO

OO

H

H O

Fe Fe

As

H

HO

H

HOO

H

H O

Fe Fe

As

H

HO

H

HOH

H O

H

H O

X-ray Absorption Spectroscopy

(O. Proux)

0.01

0.1

1

10100

Diametre (nm)

mmol/g

Rétention de l'AsIII

par des particules de magnétite

Effet surfacespécifique

Qua

ntité

d'a

rsen

ic a

dsor

béA

mou

nt o

f As

adso

rbed

Diameter (nm)

Iron oxide NP : strong adsorption capacity

0.02

0.3

2

Per unit of mass...

The surface available toadsorb As is larger for NP

100 m2/g

20 m2/g

3 m2/gSpecific surfacearea effect

Iron oxide NP : strong adsorption capacity

0.01

0.1

1

10100

Diametre (nm)

mmol/g

Rétention de l'AsIII

par des particules de magnétite

Effet surfacespécifique

Qua

ntité

d'a

rsen

ic a

dsor

bé

0.01

0.1

1

0.001

0.01

10100

Diametre (nm)

mmol/m2mmol/g

Rétention de l'AsIII

par des particules de magnétite

Effet surfacespécifique

Effet reactivité de surface

Qua

ntité

d'a

rsen

ic a

dsor

bé

Per unit surface...

Different adsorptionmechanisms NP<20nm

10 As/nm2

4 As/nm2

Per unit mass...

The surface available toadsorb As is larger for NP

Am

ount

of A

s ad

sorb

ed

Diameter (nm)

Specific surfacearea effect

Surface reactivityeffect

Adsorption of AsIII at the surface of iron oxide NP

γ-Fe2O3 (nano-maghemites)

• 6 nm, 174 m2/g• FeIII

• Spinel Structure

• Pyramidal

As (OH) 3

10-7

10-6

10-5

0.1

1

10

0 2 10-4 4 10-4 6 10-4 8 10-4 1 10-3

Cad

s (mol

/m2 )

As concentration at equilibrium (mol/L)

Cads (arsenic/nm

2)

~ 10 AsIII / nm2

High density ofadsorption sites

Auffan et al., Langmuir 2008

Cad

s (mol

/m2 )

As concentration at equilibrium (mol/L)

10% : most reactive sites

100% : all the adsorption sites

EXAFS, As K-edge

2 4 6 8 10 12

100%

10%

k(Å-1)

k2 .chi

(k)

100%

1.7 ± 0.3 Fearound As

3.3Å

Fe Fe

As

10%

3.1 ± 0.5 Fearound As3.4Å

Fe Fe

AsFe Fe

Identification of the adsorption sites

As occupies the vacant tetrahedralsurface sites

16 18 20 22 24 26

21.3 21.4 21.5

Inte

nsity

(a.u

.)

2 theta (°) - Co K(!)

0.6

0.7

0.8

0.9

1.0

Taux occupation Fe (III) tetra

0.5

21.3 21.4 21.5

Inte

nsity

(a.u

.)

2 theta (°) - Co K(!)

0.6

0.7

0.8

0.9

1.0

Taux occupation Fe (III) tetra

0.5

100%

10%

0%

Experimental

Nano-maghémite

Vacant tetrahedral Fe(III) surface sites

21.3 21.4 21.5

Inte

nsity

(a.u

.)

2 theta (°) - Co K(!)

0.6

0.7

0.8

0.9

1.0

Taux occupation Fe (III) tetra

0.5

"New" adsorption sites

Larger particle

Theoretical

Proposed sorption mechanism...

10% d’As 100% d’As

Particle size increases

Radius increases by 8-10%Surface energy diminihes by 8-10%Nano

6 nm 6,5 nm

Nano-maghémite

Reactivity of Fe2O3 nanoparticles

Arsenic adsorption themodynamically stabilises NPs,

« like crystal growth ».

Decrease of surface energy is probably the leading mechanism.

When Ø of 0.5nm, surface energy of 8%

Decreases the surfaceenergy significantly

Saturation of theadsorption sites with As

Increases the size of NP+ 0.5 nm

Surface reactivity: C.Chanéac

Nanoparticles in water treatment• Use of crystalline nanoparticles :

– High reactivity– Nanoparticles can exhibit particular properties:

magnetic systems for the recovery of the pollutantloaded nanoparticles.

– Possibilities to re-use (NaOH pH 12, 3 or 4 times)Sorption efficiency by 25 % after each regeneration (‘erosion’,dissolution)

No mud to dehydrate

Superparamagnetic properties

Nanoparticles and filtration

• Membranes and nanoparticles

Raw waterIN OUT

Treated water(permeat)

(Water treatment…)

Organic membranes: low costCeramic membrane: thermal chemical resistance

Oxane process

CH3COOH

Al AlO

O

O OC

CH3

AlumoxanesAlumoxanes

Large Mineral

Boehmite (γAlOOH)

Lépidocrocite (γFeOOH) → (Alumoxanes®) (Callender et al., 1997)

→ (Ferroxanes®) (Rose et al., 2001)

top-downapproach

Micrometers Nanometers

Membrane making using nanoparticles

Ceramic membrane made from ‘metal-oxane’ nanoparticles

Particule ‘templating’

2 µm

Pore size < 4 nm, MWCO < 1,000

Cortalezzi, Rose, Barron and Wiesner, Membrane Science, 2002DeFriend, Wiesner, and Barron, Membrane Science, 2003

From A.Barron (Rice Univ.)

Important : mono dispersesuspension of Oxane

nanoparticles

CracksSintering

From the mineral to the smallparticles

Lepidocrocite + AA (in excess) 24 hours.

100011001200130014001500160017001800

Inte

nsity (

arb

.un

it)

Wave number (Cm-1)

10

22

11

65

12

60

14

21

15

85

iron acetate

acetate

Lep+AALep

DifferenceC-O-Fe

C-O-O

0

2000

4000

6000

8000

10000

12000

3 13 23 33 43 53 63 73

Angle 2?

coun

ts

lépidocrociteferroxanes

7,88Å

6,26Å

(020) clivage

Acetic acid

Acetic acid

Acetic acid

Acetic acid

Lepidocrocite Ferroxane®

Membrane propertiesAfter firring at 300°C

22-28 nm10-20 nmPore size

60-100 nm28 nmParticule size

FerroxanesAlumoxanes

Flux : 5,9.10-5 m3/m2.s (P=0,7bar)

Ferroxanes

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25

0 0.2 0.25 0.75 1

Perm

eabili

ty (

nm

2)

[Ferroxane] for the coating (mg)

Whatman Anodisc 100nm

Membrane making

• A second effect: surface reactivity

transformation

• Surface reactivityFiltration of 5.10-4 mol.L-1 (Na2CrO4) solution

% Cr fixed 40,4

NCr fixed by nm2 0,159

surface sites density 3,5

Membranes made from nanoparticles

Perspectives

1. Control of the pore size distribution2. Synthesis of doped membranes: reactive membranes.3. Combination of nanoparticles to create membranes with

various properties (UV sensitive, magnetic, reactive…)

Biological effects

Wanted and unwanted

Oxidation of iron

Structural stabilityin contact with E.coli

maghemites

nZVI

Increasingtoxicity

Maghemite Maghemite

Oxidative stress

Magnetite MaghemiteOxidation

Release of Fe (II)

Fe° Green rust

LepidocrociteγFeOOH

MagnetiteFe3O4

Dissolution Recrystallization

Oxidation

OxidativestressRelease of

Fe (II)

Fe°

Fe3+

Fe2+

Fe3+

magnetites

Surface reactivity vs biological responseNano-maghemites

nZVI Fe°

Nano-magnetitesFe3

2+/3+O4

γ-Fe23+O3

0

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120E.Coli Qc1301Sauvage

Control7 mg/L70 mg/L

175 mg/L350 mg/L700 mg/L

Perc

enta

ge o

f via

ble

cells

***

***

*****

***

Nano-magh Nano-magnet nZVI

7 mg/L70 mg/L

175 mg/L

0

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80

100

120E.Coli Qc1301Sauvage

Control7 mg/L70 mg/L

175 mg/L350 mg/L700 mg/L

Perc

enta

ge o

f via

ble

cells

***

***

*****

***

Nano-magh Nano-magnet nZVI

7 mg/L70 mg/L

175 mg/L

Cytotoxicity

Oxidative stress

Cytotoxicity test E.coli

Conclusion and Perspectives

• NP promising materials: nano-specific bindingsites for enhanced pollution removal; tayloringadsorbants for specific purposes.

• Membrane pore size distribution controlled by NP• "Reactive" (doped) membranes• NP for disinfection ?

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