Analysis of Plastic Pellets (Carriers for Water Treatment) Using FTIR and EDX

Significance of the Topic

Ensuring safe and reliable drinking water is a global priority. Wastewater recycling plays a critical role in extending potable water supplies. In biological treatment stages, plastic carrier pellets provide surface area for microbial biofilms that degrade organic pollutants. However, concerns over pellet degradation and the release of microplastics necessitate analytical methods to characterize material changes and surface contamination.

Study Objectives and Overview

This study demonstrates the combined use of Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) and energy-dispersive X-ray fluorescence (EDX) to compare unused and spent plastic carrier pellets. The goal was to identify bulk polymer composition, detect organic or inorganic additives, and reveal trace contaminants or surface wear acquired during water treatment.

Methodology and Used Instrumentation

Sample Types:

• Unused pellets (virgin polyethylene-based carriers).
• Used pellets recovered from a wastewater treatment plant after biological operation.

Used Instrumentation:

• IRTracerTM-100 FTIR spectrophotometer with Quest diamond ATR accessory.
• EDX-8000 energy-dispersive X-ray fluorescence spectrometer.

Key Measurement Conditions:

• FTIR-ATR: 4 cm⁻¹ spectral resolution, 100 scans, Happ–Genzel apodization, DLATGS detector.
• EDX: Rh X-ray tube target, voltage adjusted automatically (50 kV for elements Al–U, 15 kV for C–Sc), vacuum atmosphere, 10 mm analysis diameter, 100 s integration time.

Main Results and Discussion

FTIR-ATR Findings:

• Surface spectra of both pellet types indicate a mixture of polyethylene and cellulose, suggesting surface treatments or additives.
• Cross-sectional spectra reveal primarily polyethylene in both unused and used specimens, indicating bulk polymer consistency.

EDX Observations:

• Major elements consistent across unused and used pellets, confirming polyethylene matrix.
• Phosphorus signal detected in unused pellets (likely additive) was absent in used samples, implying leaching or abrasion during operation.
• Trace inorganic signals on used pellet surfaces point to adhered contaminants or wear products from the treatment environment.

These results demonstrate negligible alteration of the base polymer but highlight surface-level changes due to use, including additive loss and contaminant deposition.

Benefits and Practical Applications of the Method

The combined FTIR-ATR and EDX approach offers rapid, non-destructive qualitative and semi-quantitative analysis of polymeric carriers. Key advantages include:

• Quick identification of organic polymer types and surface treatments via FTIR.
• Detection of elemental composition and trace contaminants through EDX.
• Minimal sample preparation allows direct analysis of used materials.

Such methods support quality control of carrier manufacturing, monitoring pellet integrity during plant operation, and assessing microplastic release risks.

Future Trends and Application Possibilities

Emerging developments may include:

• Integration with Raman microscopy or hyperspectral imaging for spatially resolved surface analysis.
• Coupling with thermal desorption or pyrolysis GC-MS to identify organic additives and degradation products.
• Portable FTIR-ATR and handheld XRF instruments for in-field monitoring of carriers in treatment basins.
• High-throughput automated screening of carrier batches to ensure consistency and longevity.

Conclusion

This application note illustrates how FTIR-ATR and EDX can efficiently characterize both bulk and surface properties of plastic pellets used in wastewater treatment. While the core polyethylene structure remains intact after service, surface analyses reveal additive depletion and contaminant deposition. The complementary techniques deliver actionable insights for optimizing carrier design, enhancing treatment performance, and mitigating microplastic generation.