X-ray fluorescence analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed-circuit-board ash

摘要

A method for the quantitative analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed-circuit-board ash by X-ray fluorescence (XRF) spectrometry using loose powder was developed. The printed-circuit-board samples were converted to ash pyrolytically in porcelain crucibles by sequential heating using a gas burner and electric furnace, and then were ground with a ball mill. The calibrating standards were prepared by adding the appropriate amounts of NiO powder and aqueous standard solutions containing Co, Pd, Ag, and Au to the base mixtures of Al_2O_3 (5.0 mass%), SiO_2 (49 mass%), CaCO_3 (11 mass%), Fe_2O_3 (3.3 mass%), and CuO (30 mass%) as a matrix. Then, 10g of the resulting mixtures were dried and homogenized for 90min with a V-type mixing machine. Specimens for XRF analysis were prepared from the so-called loose-powder method in which powder samples were compacted into a hole (12.0-mm diameter and 5.0-mm height) in an acrylic plate and covered with a 6-μm thickness of polypropylene film. Matrix effects were corrected using the intensity value of Compton scattering for PdKα, AgKα, and AuLβ_2, and that of background scattering at 35.8° (2θ) for CoKα and NiKα. The detection limits corresponding to three times the standard deviation of the blank intensity were 2.5-45μgg~(-1)s. The proposed method was validated against the pressed-powder-pellet method by comparing the calibration curves. Moreover, the concentrations of Co, Ni, Pd, and Ag determined using the proposed XRF method were approximately the same as those resulting from an atomic-absorption-spectrometric analysis.