HHXRF can effectively screen for ceramic contamination in glass recycling streams. Testing showed HHXRF can accurately quantify ceramic identifier elements like Zr, Sr, and Ti in samples, and detect these elements even in small 1mm fragments. While quantitative analysis requires more time, qualitative screening for ceramic elements' presence or absence could remove ceramic materials from cullet streams. This technique has been applied in industrial in-line XRF systems that can process over 28 tons of cullet per hour for sorting.

1. Screening for Ceramic and Leaded Contaminants in Glass
Recycling Streams Using Handheld X-Ray Fluorescence (HHXRF)
Analyzers
Dillon McDowell and Alex Thurston
ECNDT 2018

2. Overview
¡ The glass recycling industry and recycling process
– Dealing with contamination
– Ceramic glass issues
¡ Brief introduction to XRF
¡ Experiment overview
– CRM analysis
– Glass cullet analysis
¡ In-line system overview

3. Glass Recycling
¡ The majority of recycling concerns glass containers (bottles, jars, etc.)
– Primarily, soda glass
¡ Glass is recovered, sorted, and cleaned to be turned into furnace-ready cullet
¡ Soda glass can be completely recycled without any loss of quality
¡ On average, newly produced glass containers consist of ~33% recycled content
¡ Material recovery facilities (MRFs) may process as much as 20+ tons of cullet per hour
¡ Material quality is key to hitting efficiency targets and reducing process cost
Solution Recycling, 11-1-2017, <http://www.solutionrecycle.org/why-recycle/>

4. Contamination and Ceramic Glass
¡ A variety of techniques that handle
different types of contamination
– Magnetic sorting (metallic contamination)
– Vacuum suction and vibrating screens
(light materials — paper, plastic, etc.)
– Visual/infrared sorting (opaque materials
— stones, gravel, etc.)
¡ Some materials are difficult to separate
through automated techniques
– Other glass types (borosilicate, leaded
crystal)
– Ceramic glasses
¡ Ceramic glasses are increasingly common
in a variety of products
– Cookware
– Manufactured goods
– Electronics (smartphone screens)
¡ Ceramic glass has many of the same
physical properties as recyclable glass
(weight, density, appearance, etc.)
¡ However, it also has…
– Different chemistry (unique ceramic
elements)
– A higher melting point (doesn’t fully melt in
a furnace)

5. Ceramic Glass Issues
¡ Increases the downtime of furnaces and/or may irreparably damage them
¡ Large risk to cutting systems
– Water-cooled scissors may be damaged attempting to cut into ceramic glass
¡ The final product is rendered defective and unusable by impurities
– Glass products with ceramic may crack or shatter (sometimes explosively)
G. Bonifazi, “Imaging spectroscopy based strategies for ceramic glass contaminants removal in glass recycling”, Waste Management,
vol. 26, pp. 627-639, June, 2005.
Monofrax services, 1-8-2017, <http://monofrax.com/services/>

6. X-ray Fluorescence Spectroscopy
¡ First demonstrated in 1912
¡ First handheld systems appeared in the late 1990s
¡ Exciting a sample with X-rays generates a
fluorescence response unique to the elements in
the sample
¡ Measuring that response provides compositional
information
¡ Used for various commercial applications
– Metals/alloys
– Soil/geologic samples
– Consumer products

7. Instrumentation
¡ Olympus Vanta™ handheld XRF analyzer
– Model: VCR (rhodium (Rh) anode, silicon drift detector (SDD)
system)
– 8 mm excitation point (down to 3 mm with collimation)
¡ Used “Soil” method as basis for testing
– Compton normalization technique
– Typically used to test SiO2-based samples
– Offers various excitation conditions (beams) for a variety of
elements
¡ Testing performed using the Vanta portable Work Station
– Enables consistent sample presentation
– Closed-beam system while in the Work Station

8. Experiment
¡ Gauge the effectiveness of HHXRF in identifying various elements
– Ceramic identifiers: titanium (Ti), zirconium (Zr), strontium (Sr), and zinc (Zn)
– Additional identifiers: iron (Fe), copper (Cu), and lead (Pb)
¡ Stage 1: Certified material
– Test certified glass samples (NIST 610, NIST 612)
– Establish a baseline calibration
¡ Stage 2: Test recovered ceramic glass samples
– Use the calibration from the previous stage
– Sample composition also verified through lab testing (ICP)
– Focus on effects of sample size and analysis time

9. Stage 1 — Certified Materials
¡ Samples chosen for variety
¡ Initial readings used to established calibration
factors; the samples were retested using
corrections
¡ Each sample was tested for 30 seconds in
beams 1 and 2 (60 seconds total per test)
¡ Values shown are the averages of 10 repeat
tests
¡ Samples are quite thin (~3 mm), so multiples
were used to minimize thickness biasing for
initial calibration
¡ Overall, very consistent response from HHXRF
NIST 610
Element Assay (ppm) +/- 2σ XRF (ppm) +/- 2σ
Ti* 437 30 496.8 84.8
Zr[8] 440 2 445.4 16
Zn* 433 4 428 12
Pb 426 1 427 12
Cu 415 29 443 10
Fe 458 9 447.4 18
Sr 515 0.5 437.6 15.2
NIST 612
Element Assay (ppm) +/- 2σ XRF (ppm) +/- 2σ
Ti* 50.1 0.8 122.75 58
Zr[8] 36 1.3 46.8 4
Zn[9] 40 5 36.8 4
Pb 38.6 0.2 41.6 4
Cu* 35 3.3 36 2
Fe 51 2 43.6 6
Sr 78.4 0.2 83.2 4

10. Stage 2 — Recovered Glass Ceramic Samples
¡ Samples were provided from a major producer/recycler
of glass and glass ceramic products
¡ Samples were independently assayed by supplier using
ICP-MS
¡ Samples consisted of:
– #1: Heavy ceramic glass (high Zr, Sr, and Ti)
– #2: Leaded crystal glass (high Pb)
– #3: Light ceramic glass (high Sr)
¡ In addition, a certified pure quartz (SiO2) sample was
tested to ensure that no false positives were reported
by the analyzer
¡ Samples were tested using only 1 beam at various test
times to test the effect of long vs. short analysis for
sorting purposes

11. Sample 1 — Heavy Ceramic Glass
Sample 1 — Glass Ceramic (High Zr, Sr, Ti)
XRF Concentrations
Element ICP Result 30 Sec +/- 2σ 10 Sec +/- 2σ 3 Sec +/- 2σ
Ti 2705 71041.6 1884.4 71647.4 3297.2 71326.8 6047.6
Zr 11105 24020 1656 23403.8 2754.4 23627 5140.4
Zn 3856 6890.2 158 6910.2 275.6 6993.2 512.4
Pb - 208.8 27.6 208 48 221.8 89.2
Cu - 188 28.4 198 50 192.6 92.4
Fe 314 - - - - - -
Sr 77034 >10% 9415.2 >10% 15659.6 >10% 29120.4

12. Sample 2 — Leaded Crystal
Sample 2 — Leaded Crystal Glass (High Pb)
XRF Concentrations
Element ICP Result 30 Sec +/- 2σ 10 Sec +/- 2σ 3 Sec +/- 2σ
Ti 118 - - - - - -
Zr 222 - - - - - -
Zn - 94.5 45.5 125 80 - -
Pb 205069 >10% 19880.4 >10% 35518 >10% 68998.4
Cu - - - - - - -
Fe 287 411 77.6 393 135.2 541 260
Sr 161 - - - - - -

13. Sample 3 — Light Ceramic Glass
Sample 3—Light Glass Ceramic (Low Sr)
XRF Concentrations
Element ICP Result 30 Sec +/- 2σ 10 Sec +/- 2σ 3 Sec +/- 2σ
Ti - - - - - - -
Zr - 155.4 10 154.6 17.6 156.6 32.4
Zn - 46.4 4 49.4 6 45.4 11.2
Pb - - - - - - -
Cu - - - - - - -
Fe 70 23.8 6 21.4 10 31.5 20
Sr 1099 1695.8 57.2 1698.2 98.8 1712.6 184

14. Small Fragment Testing
¡ Broke off a small fragment of each sample
(~1 mm diameter) and repeated stage 2
¡ Goal was to simulate the smallest
fragment that may be present in a cullet
stream
– Can also mimic possible inclusions that
may appear in final container products
¡ Results largely qualitative but
demonstrate detection capabilities of
ceramic elements

15. In-Line XRF Systems
¡ The technique shown here has already been
scaled to an in-line system: the
X-STREAM™ XRF analyzer
¡ Used currently for both scrap and glass sorting
¡ Uses multiple source/detector arrays instead of
a single source/detector (like in HHXRF)
¡ Goal is qualitative analysis:
– Identify the presence/absence of ceramic
elements
– Remove ceramics from a cullet stream using
an air blast
¡ Can process as much as 28 tons/hour

16. Summary
¡ The nature of ceramic contamination is localized fragments with a high concentration of
ceramic elements (Zr, Zn, Sr, and Ba)
¡ HHXRF can effectively screen ceramic elements
– Accurate quantization, while achievable, requires more sample preparation and testing time
– Sorting/screening can be done effectively through qualitative testing using XRF
¡ HHXRF can identify even small fragments of ceramic material
– Maintain consistent detection of common ceramic tracers
¡ Technique can be scaled to in-line systems
– Qualitative sorting based on fluorescent signal from ceramic elements

17. Olympus is a registered trademark, and Vanta and X-STREAM are trademarks of
Olympus Corporation.