pXRF on printed circuit boards: Methodology, applications, and challenges.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Materials Science

Background:

• Waste Printed Circuit Boards (WPCBs) pose environmental challenges due to their complex chemical composition.
• Accurate determination of metal content in WPCBs is crucial for effective recycling and resource recovery.
• Traditional analytical methods can be time-consuming and require extensive sample preparation.

Purpose of the Study:

• To evaluate the efficacy of portable X-ray fluorescence (pXRF) for analyzing metal content in WPCBs.
• To compare pXRF results with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) as a reference method.
• To investigate the influence of particle size and sample preparation on pXRF accuracy.

Main Methods:

• Analysis of 10 metals (Cu, Fe, Sn, Zn, Pb, Ni, Sb, Cr, Mo, Pd) in WPCBs.
• Comparison of pXRF with ICP-MS after aqua regia digestion.
• Testing of three particle sizes (200 µm, 750 µm, 2 mm) and three sample preparations (tube, cup, loose powder).
• Validation using 8-16 independent replicates per condition.

Main Results:

• ICP-MS confirmed sample homogeneity and robust sampling at 200 µm particle size (RSD < 5%).
• pXRF showed low data dispersion at 200 µm particle size with loose powder preparation (RSD < 10% for key elements).
• pXRF deviation from ICP-MS was acceptable (<20%) for several metals (Cu, Sn, Zn, Pb, Ni, Sb, Mo) at 200 µm.
• Larger particle sizes (750 µm, 2 mm) required more repetitions due to homogeneity issues.
• pXRF in mining mode provided rapid, non-intrusive screening for coarser samples.

Conclusions:

• pXRF is a viable method for analyzing WPCB chemical composition, particularly at a 200 µm particle size.
• Loose powder sample preparation is sufficient for pXRF analysis at optimal particle sizes.
• pXRF offers a rapid, cost-effective screening tool for WPCB metal content, complementing more rigorous analytical techniques.