1

Wastewater treatment by nanoporous-crystalline

polymer materials

Christophe DanielDipartimento di Chimica e Biologia

Università di Salerno84084 Fisciano (SA)

“Wastewater treatment byadvanced technologies and risk

assessment framework”

04/09/2017- Salerno

Outline

� Part I: Nanoporous crystalline polymers�Which polymers?

�Nanoporous crystalline phases (structure, preparation)

� Part II: Sorption properties of nanoporous crystalline

polymer materials (aerogel, fiber, powder, …)

� Part III: Photodegradation activity of composite aerog els�N-doped TiO 2

3

Removal of organic micro-pollutantsfrom wastewater/groundwater�Biodegradation/phytodepuration�Coagulation-precipitation�Filtration�Adsorption�Chemical reduction/Oxydation (ozone, Fe0, TiO2, ….)�…..

Adsorption is (the most) widely process used forwastewater treatment for two main reasons:

�Simple design�Low initial investment cost

Types of adsorbents:�Natural: charcoal, clays, zeolites,….�Synthetic: activated carbon , polymeric materials, …..

4

Nanoporous crystalline phases withgood sorption capacity have been obtained

for two commercial polymers

� Syndiotactic polystyrene (s-PS) : δδδδ (1994), εεεε (2007)

� Poly(2-6-dimethyl-1,4-phenylene) oxide (PPO): 2011

Nanoporous ( microporous ) crystalline polymers

Polymeric adsorbentsSome examples of polymeric adsorbents: �Polystyrene–divinylbenzene copolymers�Cyclodextrin polymers (CDPs)�Cellulose-based materials�….

Syndiotactic polystyrene (sPS)

CH2C H CH2CH CH

CH2C H CH2CH CH

The first synth etic polymer f or which the is otacticity wasrecognize d and defined (Natta, Corrad ini, 1953) T= 24 0 °Cbut very slow crystallizationm

SYNDIO TACTIC P OLYSTYR ENE

Ishihara et al. (1986) T= 27 0 °Cfast crysta llizationX= 30 -60%

Very complex poly morphic behav ior(4 crystalli ne forms)

mC

Ishihara et al. (1986)

Electronic Control UnitPCB ConnectorsCellular Phone Antenna

produced by Idemitsu with trade-named Xarec® (7000 t/year)

Tm= 270 °CXc= 30-60%

fast crystallization

6

Poly(2-6-dimethyl-1,4-phenylene)oxide (PPO)

Tg = 212-218 °C

NO CRYSTALLIZATION

FROM THE MELT

One of the world's five largest engineering plastics

(Production capacity (2002): 150000 tons/year)

car body panels

General Electric (1966)

produced by Sabic with trade-named Noryl®

Pump partsFiltration housing

7

Preparation of nanoporous crystalline phases�STEP 1: Crystallization of polymer with organic solvents

-solution (film casting, gel, …)-treatment of solid polymer (liquid, vapor)

s-PS s-PS

�STEP 2: Removal of solvent (guest) molecules-evaporation-exchange with a volatile solvent (i.e. acetonitrile)-supercritical CO2

PPO

FORMATION OF CO-CRYSTALS

8

Nanoporous crystalline phases

5 10 15 20 25 30 35 40

δδδδ

sPS/CS2

sPS/styrene

sPS/decalin

2θ (deg)

Inte

nsity

(a.u

.)

Co-crystals

Nanoporousphase

Determination of crystalline structurefrom X-ray diffraction measurements

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

20

40

60

80

100

nanoporous δ powder

Relative pressure (P/P0)

N2

adso

rbed

(cm

3 g-1 S

TP

)

Non porous powder

X-ray diffractionN2 Sorption (77K)

Higher BET value due to the porous crystalline structure

9

Nanoporous crystalline phases of s-PS

isolated cavities

Lateral view

Top view

δMacromolecules

1997, 30, 4147

cavitiesvolume ≈ 120 Å3

channels

ρρρρδδδδ ≈≈≈≈ ρρρρεεεε ≈≈≈≈ 0.98 g/cm 3 < ρρρρam =1.05 g/cm 3

εChem. Mater.2008, 11, 3663

channelsdiameter ≈ 5 Å

10

Nanoporous-crystalline samples�Like other nanoporous materials (like zeolites or activat ed carbon)

• Powders�“Like” other thermoplastic polymers

• Films

• Aerogels

• Fibers non-woven fabric

fiber coil

staple

Aerogel

Possible applications� Air/water purification� Active packaging

11

Higher sorption in δδδδ samples due to the nanopores of the crystalline phase

1,2-dichloroethane

8100 8100 8100 8100 ppm

100 100 100 100 ppm

POWDERS: Fast sorption kinetics but bad handling characteristicsFILMS: Good handling characteristics but slow sorption kinetics

VOC sorption from Aqueous Solutions

s-PS powder withnanoporous δδδδ-form

s-PS powder withnon porous ββββ-form

nanoporous δδδδ-form

non porous ββββ-form

12

Aerogels for Water Purification

AEROGELS: High porosity solid materialsPREPARATION : Solvent removal from a gel using supercritical conditions

Adv. Mater., 2005, 17, 1515

AEROGEL WITH POROSITY UP TO 99.5%

sPS/Toluene: 10/90 g/gρ = 0.865 g/cc

GEL

100% sPSρ = 0.10 g/ccAEROGEL

supercriticalCO2

)1(100S

Pρρ−=

ρ = apparent densityρS= polymer density

Porosity:

12

13

High T

SOLUTION GEL

Low T

Thermoreversible (Physical) Gels

Crystalline cross-links between

polymer chains ensure gel formation

Cooling

Heating

Solvent

extraction

Polymeric aerogels physically cross-linkedby crystalline phases

AEROGEL WITH

CRYSTALLINE REGIONS

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Structure of sPS aerogels with δδδδ-form

2 µm

Fibrillar Morphology20 nm < D < 200 nm

Macropores Nanofibrills

Nanopores(V ≈≈≈≈ 120 Å3)

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N2 Sorption (77K)

sPS sample BET (m2/g)

Non porous powder 4

δ-powder 43Non porous aerogel 70δ-aerogel (P=91%) 270

δ-aerogel (P=98.5%) 348

0.00 0.05 0.10 0.15 0.20 0.25 0.300

20

40

60

80

100δ aerogel (P=98%)

δ aerogel (P=90%)

Non porous aerogel (P=90%)

δ powder

Relative pressure (P/P0)

N

2 ad

sorb

ed (

cm3 g

-1 S

TP

)

Non porouspowder

s-PS

60 65 70 75 80 85 90 95 100100

200

300

400

500

600

700

800

BE

T (

m2 /g

)

P (%)

δ s-PS

PPO

High BET valuesup to 750 m 2/g

can be obtained

PPO/s-PS BET values

16

Visualization of the sorption capacityof nanoporous aerogels

H2O/Azulene

t = 0

t = 2 hours

t = 20 hours

Porosity = 90%

Blue molecule having nearly the same sizeof the crystalline cavity of the δ phase (0.2 nm3)

Azulene

WITH NANOPORES

WITHOUTNANOPORES

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DCE sorption kinetics from100 ppm aqueous solution

0 500 1000 1500 2000 2500 3000 3500 4000t1/2/L (s1/2/cm)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

MD

CE (

t) /M

DC

E (

)

8

P = 98.5% P = 90%P =80%

�

�

D=1.0 10-5cm 2/s

D=1.7 10-7cm 2/s

100 ppm

+

D=1.2 10-8cm 2/s

D=8.4 10-8cm 2/s

apparent diffusivity increases with porosity

Daerogel >>>>DFilm (Daerogel, P = 98.5% ≈ 107 x DFilm )

Aerogels for water purificationSorption of VOC from dilute aqueous solutions

17Chem. Mater. 2008, 20, 577

Activated Carbon

1 10 100 1000DCE concentration (ppm)

0

5

10

15

DC

E e

quili

briu

m u

ptak

e g/

100

g sP

S

aerogel withonly macropores

Aerogel with macro and micropores (δ form)

Equilibrium 1,2-dichloroethane(DCE) sorption

Sorption occurs only in crystalline nanopores

Aerogel with macro andnanopores (δ form)

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Oil spill recoverynonwoven polypropylene sorbents

Oil uptake: x4-x10

Absorption in macroporesnon-clathrating molecules (e.g, white mineral oil)

0.01 0.1 1 100

100

200

300

400

500

600

Aerogel δδδδ

P=81%

Aerogel δδδδ

P=91%

g of

whi

te-m

iner

al-o

il/ 1

00g

of p

olym

er

time (hours)

Film δδδδ 35 µµµµm

!Aerogel preparation procedure is not

easily applicable to a large scale industrial production

(cost, difficulty, use of large amount of solvents, …)

with respect to benchmarkPP sorbents

δδδδ s-PS aerogelsare also effective with

VOCs dissolved in water

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Fibers with Nanoporous Crystalline PhaseFibers prepared by

Idemistsu Kosan Co., Ltd through a spun bond line

flexible fibers with 3-20 µµµµm diameter

5 10 15 20 25 30

Inte

nsity

(a.

u.)

2θ (deg)

8,5

8,2

8,4

10,1

10,2

10,2 CHCl3

THF

CH2Cl

2

5 10 15 20 25 30

Inte

nsity

(a.

u.)

2θ (deg)

8,6

8,6

8,7

16,2

16,5

16,4

20,6

20,6

20,6

Solventtreatment

5 minNative Fibers

Solventremoval

αααα form co-crystals

30 min inCH3CN

δδδδ form5 10 15 20 25 30

Inte

nsity

(a.

u.)

2θ (deg)

6.713.5

11.6

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N2 sorption (77K)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

20

40

60

80

100

120

140

160

180

200

220

Relative pressure (P/P0)

Q

uant

ity a

dsor

bed

(cm

3 ·g-1 S

TP

)

Nanoporousfiber

Native

Sample BET (m2/g)Native fiber 1

Nanoporous fiber 165

0 1000 2000 3000 4000 5000 60000.0

0.5

1.0

1.5

2.0

2.5

3.0

Native

DC

E w

eigh

t upt

ake

(%)

time (min)

10 ppm

Nanoporous

DCE uptake after 60 minutesNative fibers: 0 wt%Nanoporous Fibers: 1.4 wt%

DCE sorption kinetics from10 ppm aqueous solution

Fibers with Nanoporous Crystalline Phase

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500 1000 1500 20000

1

2

3

4

5

6

DC

E w

eigh

t upt

ake

(%)

time (minute)

AerogelP=90%

Nanoporous Fibers

P=98.5%

Comparison of Fiber-Aerogelsorption properties

DCE sorption kinetics from10 ppm aqueous solution

500 1000 1500 20000

1

2

3

DC

E w

eigh

t upt

ake

(% g

/mL

)

time (minute)

Nanoporous Fibers

Aerogel P=90%

P=98.5%

DCE uptake per mass unitUptake Aerogel > Uptake Fibers

DCE uptake per volume unitUptake Aerogel << Uptake Fibers

Important for water purification processes:cartridge filtration units have a fixed volume

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Comparison of nanoporous fiber-GACsorption properties

Cin

Cout

% of removal(Cin-Cout)/Cin

0 50 100 150 200 250 300 350 400 450 50080

85

90

95

100

% r

emov

alC

in (ppb)

sPS GAC

% removalsPS : 97.2%GAC : 94.5%

Tetrachloroethene

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Part III

16.00-16.30 Synthesis and characterization of photo catalysts for wastewater treatmentVincenzo Vaiano, Department of Industrial Engineerin g, University of Salerno

Photodegradation activity of composite aerogelsPhotocatalyst systems are highly promising for the elimination

of hazard environmental pollutantsespecially for the degradation of

biorecalcitrant organic contaminants

Practical engineering applications require that photocatlyst particlesmust be fixed on bulky support materials (organic or inorganic) tosimplify their recovery from the treated water or to avoid damages to

the re-circulation pumps.

Dispersion of photocatalyst nanoparticlesin monolithic aerogels

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s-PS/N-TiO 2 (NdT) composite aerogels

NdT powders

Polymersolubilization

at 100°C

Sonication at room

temperature

sPS cylindricalmold

gel formationat room

temperature

CO2supercriticalextraction

NdT powders

Polymersolubilization

at 100°C

Sonication at room

temperature

sPS cylindricalmold

gel formationat room

temperature

CO2supercriticalextraction

s-PS s-PS/NdT (90/10)

NdT nanoparticlesuniformly dispersed withinthe fibrillar polymer network

Submitted to Process Safety and Environmental Protection

25

Photocatalytic activity ofs-PS/N-TiO 2 composite aerogels

Phenol degradation

N-TiO2 composite weight: 4 g/L

Solution Volume: 75 ml

C0Phenol=50mg/l

P= 1 atm

T=25°C

Qair=150 Ncc/min

sPS

NdT (powder)

10NdT/s-PS

UV-light ON

Dark

Increase in degradation ability of NdT/s-PS aerogel could be related to a decrease of NdT

aggregate size when the photocatalyst is dispersed in aerogel matrix

SAME RESULT WITH VISIBLE LIGHTSubmitted to Process Safety and Environmental Protection

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TAKE HOME MESSAGES

Particularly suitable as filter sorption medium toremove traces of pollutants from water (and moist air)

Sorption properties of materials based on sPS and PPO nanoporous crystalline phases make them

interesting for VOC removal from water.

Simple and scalable preparation procedures of microporous sPS fibers with excellent sorption properties and safe macroscopic morphology

s-PS aerogels are an efficient support ofphotocatalyst nanoparticles

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Dipartimento di Chimica e Biologia, Università di Salern oGaetano Guerra , Vincenzo VendittoMarina Pellegrino, Wanda Navarra

Department of Industrial Engineering, University of Salerno(Photocatalyst)Vincenzo Vaiano, Olga Sacco

Acknowledgements