Characterization of a printed-circuit board by X-ray fluorescence and X-ray diffraction analyses for metal recovery

A printed-circuit board (PCB) powder sample obtained by cryo-milling was characterized to elucidate its elemental composition and the chemical states of its components for metal recovery. The major elements (Al, Si, Ca, Fe, Ni, Cu, Sn, Ba, and Pb) were characterized by X-ray fluorescence and X-ray diffraction analyses. The particle-size distribution histogram of the ground PCB exhibited two high frequencies corresponding to the 27-45 mu m and 250-500 mu m fractions, and the median size was 125 mu m. The elemental components of the PCB particles were categorized into four groups: (1) the elements concentrated in the coarse-particle fraction (Cu), (2) elements tending to accumulate in the moderately sized-particle fraction (Br and Sn), (3) elements concentrated in the fine-particle fraction (Fe), and (4) elements that prefer to concentrate in both the coarse- and fine-particle fractions or no particular fraction (Al, Si, Ca, Ni, Ba, and Pb). Based on the diffraction patterns of each fraction, Al existed as metallic Al and Al2O3 (corundum), Si as metallic Si, Ca as CaCO3 (calcite), Fe as Fe3O4 (magnetite), Ni as metallic Ni, Cu as metallic Cu, Ba as BaTiO3 (barium titanate), and Pb as PbZrO3 (lead zirconate). Moreover, multivariate statistical analyses (principal component and cluster analyses) revealed that the amorphous components comprised mainly Si, Ca, Br, and Sn. The elemental composition and crystalline-phase analyses revealed the following: (1) the metallic components were durable because of their high ductility and malleability; (2) the ceramic materials were concentrated in the fine-particle fraction owing to their fragile nature; (3) the PCB components exhibited different durability properties depending on their chemical states.