Jeffrey S. Spangenberger

Assessing Potential Nanoparticle Release During Nanocomposite Shredding Using Direct-Reading Instruments

This study was conducted to determine if engineered nanoparticles are released into the air when nanocomposite parts are shredded for recycling. Test plaques made from polypropylene resin reinforced with either montmorillonite nanoclay or talc and from the same resin with no reinforcing material were shredded by a granulator inside a test apparatus. As the plaques were shredded, an ultrafine condensation particle counter; a diffusion charger; a photometer; an electrical mobility analyzer; and an optical particle counter measured number, lung-deposited surface area, and mass concentrations and size distributions by number in real-time. Overall, the particle levels produced were both stable and lower than found in some occupational environments. Although the lowest particle concentrations were observed when the talc-filled plaques were shredded, fewer nanoparticles were generated from the nanocomposite plaques than when the plain resin plaques were shredded. For example, the average particle number concentrations measured using the ultrafine condensation particle counter were 1300 particles/cm3 for the talc-reinforced resin, 4280 particles/cm3 for the nanoclay-reinforced resin, and 12,600 particles/cm3 for the plain resin. Similarly, the average alveolar-deposited particle surface area concentrations measured using the diffusion charger were 4.0 μm2/cm3 for the talc-reinforced resin, 8.5 μm2/cm3 for the nanoclay-reinforced resin, and 26 μm2/cm3 for the plain resin. For all three materials, count median diameters were near 10 nm during tests, which is smaller than should be found from the reinforcing materials. These findings suggest that recycling of nanoclay-reinforced plastics does not have a strong potential to generate more airborne nanoparticles than recycling of conventional plastics.

Mass balance and composition analysis of shredder residue.

The process of shredding end-of-life vehicles to recover metals results in a byproduct commonly referred to as shredder residue. The four-and-a-half million metric tons of shredder residue produced annually in the United States is presently land filled. To meet the challenges of automotive materials recycling, the U.S. Department of Energy is supporting research at Argonne National Laboratory in cooperation with the Vehicle Recycling Partnership (VRP) of the United States Council for Automotive Research (USCAR) and the American Plastics Council. This paper presents the results of a study that was conducted by Argonne to determine variations in the composition of shredder residue from different shredders. Over 90 metric tons of shredder residues were processed through the Argonne pilot plant. The contents of the various separated streams were quantitatively analyzed to determine their composition and to identify materials that should be targeted for recovery. The analysis established a reliable mass balance for the different materials in shredder residue.