Positive Material Identification (PMI) Capabilities in the Metals Secondary Industry: An Analysis of XRF and LIBS Handheld Analyzers

Recycling is a critical part of obtaining a more circular economy. In the metals secondary industry, traditional equipment (a magnet, file, and/or grinding wheel) used to identify and sort materials at their end of life can aid in grouping metals (i.e. Al + Mg alloys, ferrous, high temperature alloys, etc.), but they are incapable of identifying the alloy's elemental composition; a necessity for preventing downcycling and maximizing secondary utilization rates. Handheld analyzers that utilize X-ray fluorescence (XRF) and spectroscopy (LIBS) technology may offer technological assistance that is helpful for achieving this level of analysis, often referred to as Positive Material Identification (PMI). This work tests the performance of these units under the challenging conditions present in yards (contaminated, unpolished, rugged scraps). These instruments, with their increasing safety settings, ruggedness, ease of point-click use and quick read times (for both XRF and LIBS) have significant potential, especially with ability to ID metal faster than cognitive recognition. Additionally, as unit costs of these instruments continue to decrease and the range of varying types of metal entering yards continues to widen, the return on investment becomes more immediate. However, extreme fluctuations of reported elemental compositions are being seen even when measurements have been taken in the same place consecutively; indicating that in their current state, they can inform content of material but aren't necessarily reliable for reporting accurate and precise compositional percentages.