Recent and Ongoing Research for Use of PC4 and

Recycled Carpet FiberPeter G. Green, Ph.D.

Dept. Civil & Environmental EngineeringUniv. California at Davis

Acknowledgements toColleagues: Prof. Sanjai Parikh and Prof. Tom YoungFunding from: California Carpet Stewardship, Bob Peoples 1

My background:Degrees in Chemistry 1984 and Physical Chemistry 1989

Since then, I’ve been analyzing trace chemicals in assorted samples=> Heavy metals, pesticides, persistent pollutants, volatiles, etc…

Both basic and applied research in environmental science and engineering=> projects in air quality, drinking water, wastewater, and waste treatment

Moved to University of California, Davis, in 2000Broadened areas to include agriculture, ecology, and human health

Up-to-date instrumentation including ICP-MS, GC-Q-TOF-MS and LC-Q-TOF-MS=> Including high resolution and/or isotope ratios for greater understanding

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TOPICS:

PC4 (from PET carpet) added to soil – impact and concerns

(Calcium is beneficial to some crops/plants; some soil is too acidic.)

However, are there ill-effects?

Other trace chemicals – PFAs and BFRs, (most) persistent, toxic, bioaccumulative

Can the concentration of these in PC4 be decreased?

Can the residual plastic composition (all

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Antimony (Sb) is used as acatalyst in production ofPET – the leading fiber in carpet

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Added PC4 to a mildly acidic Sacramento Valley ag soil.

Sprouted lettuce, then to soil/mixture – 10 replicates.

Three treatments: soil as is, soil + 5% PC4, soil + 5%

CaCO3 – amounts which shifted pH to neutral

Grew ok, though not better.

3 out of 10 died.

Elevated Na and root swelling. (Less Al & As in leaves).

High Sb in roots. No other elements of concern.

Not as much Ca delivered to leaves as by CaCO3.

(Did deliver Ca well to roots.)8

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Was there a very high concentration of Sb in the PC4?

No, but it was highly bio-available to the plant.

Yes, enough to merit warning labels for human consumption

Why isn’t this seen directly from PET packaging?

After processing into fine carpet fiber, there is far more surface area.

After a decade of aging, in air and with light(s), the PET is degraded.

One might pre-wash the carpet to lower the Sb which is in the PC4?

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Does Sb vary from batch to batch?

Week-to-week study in underway from 3 participating facilities

Samples prepped last Wednesday…

Results to be emailed to me this Monday

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So, if one could avoid Sb …(non-PET should help, or non-Sb PET – tested by XRF)

Then, are there other trace chemicals of concern to consider?

Our leading concerns would be PFAs and BFRs:

perfluoroalkyl compounds (diverse, many uses, persistent, and groundwater concern at ng/L)

brominated flame retardants, especially PBDEs(poly brominated diphenyl ethers)

We tested replicate samples of two PC4s and found both of these groups of compounds

…at concentrations 10 times as high as in household dust

Could they be eliminated somehow?

⇒ High-temperature furnace (500 to 700C, 900 to 1300 degrees F)

(These conditions are used for bulk material treatment; cents per pound large scale) 14

Initial PC4

Charred PC4500 C, 2 Hr, N2

CaCO3(99%, ACS)

#1 PC4 “charred” 2 hours at 500C with air excluded – changes, but not resulting in CaCO3 only

Plastic signal not removed from IR spectra . Different composition, plastics more resistant to thermal degradation?

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Initial PC4

Charred PC4500 C, 2 Hr, N2CaCO3(99%, ACS)

#2 PC4 “charred” 2 hours at 500C with air excluded – results look close to CaCO3 only

Plastic signal removed from IR spectra (maybe tiny remnant) 16

PC4 (PET) - Untreated

PC4 (PET) – Charred 500 °C

PC4 (PET) – Charred 600 °C

99% Pure Calcium Carbonate

Plastics and other organics

Calcium Carbonate

General Infrared (IR) Band Assignments

Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) Spectroscopy

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PC4 (PET) - Untreated

PC4 (PET) – Charred 500 °C

PC4 (PET) – Charred 600 °C

99% Pure Calcium Carbonate

Plastics and other organics

Calcium Carbonate

General Infrared (IR) Band Assignments

Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) Spectroscopy

1800

1650

1500

1350

1200

1050

900

Absorbance

Wavenumber (cm

-1

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Peak Area %mass PET*

RCC SoCal - Untreated 0.20 13.6%

RCC SoCal - Ashed 500 °C 0.00

Infrared analysis with spatial resolution near the diffraction limit –Using Synchrotron Radiation at the Advanced Light Source, Berkeley National Laboratory

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Locations with high percentage of acidic soils, pH < 6(California’s are primarily in high mountains and forests.)

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PC4 as percentage replacement for either cementor aggregate (fines) in concrete

[Profs. Sabbie Miller and John Harvey]

Start with small-scale tests for assessing proportions (e.g. 5%, 15%)

Then larger-scale with controlled curing conditions – up to 90 days

Properties assessed will include:

(i) coefficient of thermal expansion(ii) drying shrinkage(iii) workability(iv) flexural strength(v) compressive strength(vi) void volume(vii) specific gravity

Concrete specimens will be prepared by curing mixtures in a 25°C chamber with >80% relative humidity. For mechanical tests, namely flexural strength and compressive strength, tests will be performed at 7 and 28 days, and longer, to capture the effects of strength development. 21

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PC4 Concrete Project withProf. Sabbie Millerand Prof. John Harvey

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Thank you.

Questions?

Peter G. Green, Ph.D.PGGreen(at)UCDavis.edu

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Recent and Ongoing Research for Use of PC4 and �Recycled Carpet FiberSlide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Thank you.��Questions?