Adding Rare Earth Oxide Markers to Polyoxymethylene to Improve Plastic Recycling through Tracer-Based Sorting

Area of Science:

• Materials Science
• Polymer Chemistry
• Recycling Technology

Background:

• Polyoxymethylene (POM) is a high-performance engineering plastic with significant market value.
• POM's immiscibility with other plastics and low production volume hinder its effective separation from mixed plastic waste streams.
• Current minimal recycling rates for POM highlight the need for advanced sorting solutions.

Purpose of the Study:

• To demonstrate the feasibility of tracer-based sorting (TBS) for enhancing the separation efficiency of low-volume, high-value polymers like POM.
• To evaluate yttrium oxide (Y2O3) and cerium (IV) oxide (CeO2) as tracers for POM.
• To assess the suitability of Y2O3 for industrial TBS implementation.

Main Methods:

• Embedding Y2O3 and CeO2 tracers into the POM matrix at varying concentrations (0.1–1000 ppm).
• Conducting mechanical tests on tracer-doped POM samples.
• Analyzing tracer detectability and dispersibility using a portable X-ray fluorescence spectrometer (p-XRF).
• Optimizing p-XRF detection time and tracer concentration.
• Simulating thermal treatment to assess tracer fate and recovery.

Main Results:

• Y2O3 and CeO2 were successfully embedded into the POM matrix.
• Optimized detection parameters allowed for effective tracer identification using p-XRF.
• Mechanical properties of POM were minimally affected by the presence of tracers at tested concentrations.
• Y2O3 exhibited a low loss ratio after simulated thermal recycling processes.

Conclusions:

• Yttrium oxide (Y2O3) is a suitable tracer for the industrial application of tracer-based sorting (TBS) in polyoxymethylene (POM) recycling.
• TBS offers a promising solution for improving the separation and recycling rates of valuable, low-volume engineering plastics.
• Further research can focus on scaling up TBS for industrial implementation with Y2O3.