Cloud-point Extraction and

Characterization of Nanomaterials

from Waterfrom Water

Yu Yanga, Paul Westerhoffa, Kiril Hristovskib

aSchool of Sustainable Engineering and the Built Environment,

Arizona State University, Tempe, Arizona 85287-5306, United States

bCollege of Technology and Innovation, Arizona State University at the

Polytechnic Campus, Mesa, AZ 85212,United States

1

Outline

• Introduction of Cloud-point Extraction (CPE)

• Demonstration of CPE on Extraction of Gold

Nanoparticles

• CPE on a Variety of Water and Characterization • CPE on a Variety of Water and Characterization

of Nanoparticles

• Summary

• Future Work & Potential Application

2

Potential Release of Nanomaterial from

Semiconductor Industry

• The use of chemical-mechanical polishing (CMP) agents

may lead to potential release of nanoparticles to water.

• Some existing methods are capable of detecting nano • Some existing methods are capable of detecting nano

particles (e.g. single particle ICP-MS), but still needs

development to count small nanoparticles (NPs) of Al or

Si based CMP.

• To characterize nanomaterials in the water, an enrichment

method may be beneficial.

3

Benefits of Pretreatment Method for

Nanomaterial Characterization1) Enrichment of nanoparticles into a clean phase to facilitate analysis.

2) Separation of nanoparticle from metallic ions

3) Non invasive method (i.e. does not change size or shape of nanoparticles)

4)Currently such methods are lacking for nanomaterials in aqueous systems or biological fluids, perhaps with exception of ultra-high speed centrifugation.

4

What is Cloud-point Extraction (CPE)?

• A surfactant – Trition 114 can be used for CPE (Liu., et al., Chemical Communication, 2009).

Surfactant : Triton 114

• When the temperature increases above the temperature - cloud point (CPT), the micelles become dehydrated and aggregates, forming cloudy phase.

• Cooling down and centrifuge� phase separation

• Nanoparticles move from water phase to surfactant phase

5

Demonstration of CPE on Nanomaterial

Extraction• Effectively used in a variety of nanoparticles suspended in

deionized water, including CdSe/ZnS, Fe3O4, TiO2, Ag, Au,

C60,SWCNT.

• No size change of nanoparticles (e.g. silver nanoparticles)TEM Images

Before Centrifugation After Centrifugation

TEM Images

Chao et al., Analytical Chemistry, 20116

Literature Reports of Factors Affecting

Recovery Rate

Effect of pHEffects of humic acid and

initial silver concentration

7Chao et al., Analytical Chemistry, 2011

The importance of recovery rates may vary based upon applications. Low

recovery rates may be acceptable in some cases (e.g. characterization of

nanoparticles).

Objectives and Approach

1. Objective: To extract nanoparticles existing in

rivers, tap, and waste waters (i.e., prospecting

for nanoparticles in water)

2. Approach: Apply CPE to nanopure water with

known nanoparticles and then to characterize

NPs by electron microscopes in more complex

“real” matrix after CPE.

8

Cloud-point Extraction Process

22oC

Supernatant

Step 1.

Adding

surfactant

(Triton 114) to

get a final

concentration of

5% (W/V)

Step2.

Water bath

at 40 °C for

30 minutes

(Ojeda.,et.al., Microchimica Acta, 2012)

Surfactant

Phase

Step 3.

Cooling down,

and centrifuge

9

Example of CPE: Recovery Rate of Au

Nanoparticles from Nanopure water

After

CentrifugationBefore

Centrifugation

60%

80%

100%

Reco

very

Rate

DI + Au NPs

0%

20%

40%

60%

Surfactant phase Supernatent

Reco

very

Rate

10

Characterization Results

• Nanoparticles in river water after CPE

• Nanoparticles in drinking tap water after CPE

• Nanoparticles in treated wastewater after CPE

11

Salt River Sample

Energy (keV)

Counts

108642

2000

1500

1000

500

0

C

Cu

CuCu

O

FeFe SiAlK Mn

Mn

Mn

Mg

Na

Ca

Ti

Ti

Ti

Ti

SP

Zn

Zn

Cl

EDX (R1-10-3-2txt.txt)

Ti

Ca

Cu

Fe

O

60 ± 12 nm

12

Verde River Sample

202 nm

Fe +C +O, 93 nm

Energy (keV)

Counts

12108642

6000

4000

2000

0

C

Cu

CuCu

O

Fe

Fe

Si

Al

KMn

Mn

MgNa

Ca

Ti

Ti

Ti

Ti

SP

EDX (R25-05-03.txt)

Ti

Ca

Cu

Fe

O

13

Si

Water Sample from Tempe Canal

4 nm

The smallest particle containing

high concentration of Ti

Energy (keV)

Counts

6.04.02.0

5000

4000

3000

2000

1000

0

C

Cu

O

FeFe

Si

Al

KMn

Mn

Mn

MgNa

Ca

Ti

Ti

Ti

Ti

SP

EDX (HTC-04.txt)

Ti

K Ca

Si

FeAl

high concentration of Ti

14

Influent to Potable Water Treatment Plant (WTP)

- “between River and Tap Water”

Counts

3000

2500

2000

1500

1000 Ca

Cu

Cu

Cu

C

O

Na

Na

EDX (In-cloud-1.txt)

C+O+Ca and P,S,Na,Mg,Al

Energy (keV)

Counts

8.06.04.02.00.0

2500

2000

1500

1000

500

0

Ca

Ca

Cu

CuCu

Cu

Cu

C

O

Mg

Mg

S

SCl

Cl

Si

Si

Na

Na

Al

Al

PP

EDX (In-cloud-9.txt)

C+O+Si+Ca and P,S,Na,Mg,Al

Energy (keV)

8.06.04.02.00.0

500

0

Ca

CuMgMg

S

SCl

ClSiSi

15

Particles in Tap Water

Si+O

•One major

advantages of

Ti+O

Zr+Mn+Ca + O

advantages of

CPE in

characterization:

particle

enrichment

•Titanium and

silicon containing

particles were

frequently found.

16

Nanoparticles from Arizona Wastewater Treatment

Plants

78 nm

140 nm

Silica containing particles. The atomic ratios of elements �

80 nm

C O Si S Ca

29 16 4 2 117

More Nano- and Micron- Silica particles

in Wastewater

50 nm

Si + O

18

Summary of all the Particles Found

Major elements detected by EDX of

particulates(likely material)

Approximate

Particulate

Diameter (nm)

Location

Ti + O (Titanium dioxide) 4, 60 ± 12, 108 Salt, Verde River,

Canal, and tap water

Si + O (Silica) 50 - 220 wastewaterSi + O (Silica) 50 - 220 wastewater

C + Ca + O (Calcium carbonate) 61 - 109 River and tap water

Fe + C + O 93 River water

C+O+Si+Ca (Amorphous) 200 - 377 River, tape water, and

wastewater

* No silver/gold particles were identified.

19

Benefits over sp-ICP-MS : entire composition, shape, morphology of particles.

� Cloud-point extraction (CPE) by Triton 114 demonstrated the

ability to enrich gold nanoparticle from nanopure water about

18 times while preserving the size and shape.

� The most abundant nanoparticles identified so far were silica

and titanium containing particles with diameter in the range 4-

Conclusions

and titanium containing particles with diameter in the range 4-

99 nm.

� Other nanoparticles ranged from 30-65 nm contained a list of

major elements, including

calcium, magnesium, aluminum, iron, oxygen, sulfur, carbon,

and chloride.

20

Future Work

• To determine the total metal concentration in cloud phase by ICP-OES, prospecting nanomaterial concentration in water.

(e.g. concentration of silica NPs = Total concentration of silica × number of nano silica/ total concentration of silica × number of nano silica/ total number of silica particles).

• Apply CPE to semi-conductor waste streams, using simulated CMP wasted fluids after laboratory jar tests.

21

Acknowledgements

• SRC Funding: Task # 425.040

• NSF: CBET 1336542

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