Fluorescence labeling of polymers for automatic identification in - - PowerPoint PPT Presentation
Fluorescence labeling of polymers for automatic identification in mixed plastic waste streams. Thermal and photochemical stability. A. Arenas, F.R. Beltrn, V. Alczar, M.U. de la Orden, J. Martnez Urreaga PolCA. Technical University of
4th International Conference on Sustainable Solid Waste Management, Limassol, 23–25 June 2016
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Source: Plastic Europe
Introduction
Mechanical (secondary) recycling is the best alternative for most plastics. The new EU targets are very ambitious and represent a big scientific and technological challenge.
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Introduction
Nowadays manual and automated separation processes are used for the sorting. Automated processes are cheap but their actual separation capacity is still far away from 100 %. In recent years, different methods based on the use of fluorescent markers have been proposed for the identification and automated sorting of different plastics waste.
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Introduction
DIAPOSITIVA 3
Recovered HDPE
HDPE is growing in the recycling market because it is easy to be recovered and reprocessed and there are applications for the recycled plastic, for instance in the packaging of cleaning products (not in food packaging).
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The tracer
We have studied the use of fluorescent tracers to aid in removing certain HDPE products. Among the required conditions for the tracer, the following can be highlighted: 1. The fluorescent emission must be clearly distinguishable. 2. The emission intensity should be high enough to keep the concentration of tracer to a ppm level. 3. The fluorescent tracer must be easily incorporated into the plastic. 4. The migration of the tracer to the environment must be minimal. 5. The fluorescent labeling must be resistant against thermal, photochemical and hydrothermal degradation.
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Tracers
Fluorescence of commercial products
400 450 500 550 600 650 Intensity (a. u.) Wavelength (nm) Acetone Irganox B900 HDPE-Irg
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Tracers
Two markers were evaluated. Rhodamine 6G is a commercial cationic fluorescent dye, which was introduced into HDPE in two ways, either directly or immobilized in a layered silicate montmorillonite
Rhodamine-6G (R6G)
HDPE
Irganox B900 + CaCO3
R6G-modified clay
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Tracers
Synthesis of quinacridone with C14 substituents (V-Quin)
H3COOC COOCH3 OH HO H3COOC COOCH3
N N O O H H
C14H29 C14H29
N N O O H H
C14H29 C14H29 N H H3COOC COOCH3 H N C14H29 C14H29 (commercial) NH2 C14H29 (commercial) 2 3 4 5 1 60% 88% 76% 78%
The second marker (V-Quin) was a quinacridone synthesized in the laboratory with C14 substituents for improving the stability in HDPE.
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Results
Fluorescence emission spectra (λex = 510 nm) corresponding to HDPE labeled with R6G-modified clay, measured before (black) and after (red) 100 h of photochemical degradation.
Fluorescence and stability of labeled plastics
550 600 650 700 750 800 Intensity (a. u.) Wavelength (nm) 0 h 100 h HDPE-Irg
HDPE labeled with R6G-Clay. Photochemical degradation
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Results
Evolution of the fluorescence emission of HDPE-R6G (λex = 510 nm) during the hydrothermal degradation at 80 oC.
Fluorescence and stability of labeled plastics
550 600 650 700 Intensity (a. u.) Wavelength (nm) 10 20 236 308 HDPE-Irg Time (h) 100 200 300 400 Intensity (a. u.) Time (h)
Solution Plastic
Time evolution of the emission intensity (λex = 510 nm) of HDPE marked with R6G and its immersion medium during the hydrothermal degradation.
HDPE labeled with R6G without clay. Hydrothermal degradation
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Results
Time evolution of the emission intensity of the immersion media (λex = 510 nm) during the hydrothermal degradation of HDPE marked with R6G and R6G-modified clay.
Migration of R6G
100 200 300 400 Intensity (a.u.) Time (h)
R6G C-R6G
Not encapsulated Encapsulated
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Results
Evolution of the fluorescence emission of HDPE marked with V- Quin (λex = 350 nm) during the hydrothermal degradation at 80 oC.
Fluorescence and stability of labeled plastics
400 450 500 550 600 650 Intensity (a. u.) Wavelength (nm) 10 20 188 308 HDPE-Irg Time (h)
HDPE labeled with V-Quin. Hydrothermal degradation
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Results
Retention of the fluorescence emission of HDPE marked with R6G and V-Quin during the hydrothermal degradation.
Stability with R6G and V-Quin
100 200 300 400 0.2 0.4 0.6 0.8 1.0 Relative intensity (I/I0)
Time (h)
V-Quin R6G
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Conclusions
1. The fluorescent tracers rhodamine-6G and V-Quin allow the correct identification of the marked HDPE in mixed plastics streams. 2. The good stability of the fluorescent emission indicates that the marked plastics will be properly detected even after a long lifetime. 3. The intercalation of rhodamine-6G between clay nanosheets reduces the leaching of the tracer during the hydrothermal degradation. 4. V-Quin shows better stability and better anchoring to polyethylene than rhodamine-6G. 5. The fluorescent labeling of some products can be very useful for improving the recycling of HDPE.
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Tracers
Characterization
the modified montmorillonite.
2 4 6 8 10 400 800 1200 1600 Intensity(a. u.) 2 θ CNa C-R6G
200 400 600 800 20 40 60 80 100 Weight (%) Temperature (°C) CNa C-R6G R6G Thermogravimetric traces corresponding to unmodified clay (CNa), R6G and CNa modified with R6G XRD traces corresponding to unmodified clay (CNa) and CNa modified with R6G
DIAPOSITIVA 16
AlP + 3 H2O → Al (OH)3 + PH3