A Comparison of Methods for the Characterisation of Waste-Printed Circuit Boards

Abstract

Electronic waste is a growing waste stream globally. With 54.6 million tons generated in 2019 worldwide and with an estimated value of USD 57 billion, it is often referred to as an urban mine. Printed circuit boards (PCBs) are a major component of electronic waste and are increasingly considered as a secondary resource for value recovery due to their high precious and base metals content. PCBs are highly heterogeneous and can vary significantly in composition depending on the original function. Currently, there are no standard methods for the characterisation of PCBs that could provide information relevant to value recovery operations. In this study, two pre-treatments, smelting and ashing of PCB samples, were investigated to determine the effect on PCB characterisation. In addition, to determine the effect of particle size and element-specific effects on the characterisation of PCBs, samples were processed using four different analytical methods. These included multi-acid digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, nitric acid digestion followed by X-ray fluorescence (XRF) analysis, multi-acid digestion followed by fusion digestion and analysis using ICP-OES, and microwave-assisted multi-acid digestion followed by ICP-OES analysis. In addition, a mixed-metal standard was created to serve as a reference material to determine the accuracy of the various analytical methods. Smelting and ashing were examined as potential pre-treatments before analytical characterisation. Smelting was found to reduce the accuracy of further analysis due to the volatilisation of some metal species at high temperatures. Ashing was found to be a viable pre-treatment. Of the four analytical methods, microwave-assisted multi-acid digestion offered the most precision and accuracy. It was found that the selection of analytical methods can significantly affect the accuracy of the observed metal content of PCBs, highlighting the need for a standardised method and the use of certified reference material.

Investigation of the Impact of Electrochemical Hydrochlorination Process Parameters on the Efficiency of Noble (Au, Ag) and Base Metals Leaching from Computer Printed Circuit Boards

“…Thus, the composition of the disintegrator-crushed raw material fractions with a particle size d < 90 µm depends on both the PCB batch and the number of times it is crushed. Moreover, it should be noted that the content of individual metals in PCBs, given in the literature [49], varies widely. It is associated not only with the methods of preliminary grinding of the raw material, but also with the sampling and leaching method for transferring metals into a solution for quantitative analysis.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…A paper by Van Yken et al compared numerous methods for the analysis of waste printed circuit boards. 222 This included any pre-processing methods ( e.g. ashing, smelting or no pre-processing), acid decomposition method (nitric acid, aqua regia and hydrofluoric acid, sulfuric acid and hydrogen peroxide (piranha solution) and a microwave assisted digestion) and the measurement technique (XRF or ICP-OES).…”

Chemical Characterization of an ARDUINO® Board and Its Surface Mount Devices for the Evaluation of Their Intrinsic Economic Value

“…Regarding the metal fraction, numerous scientific articles, reviews, and book chapters in the literature present the results of various chemical characterizations [4,5,[8][9][10][11][12][13]. These papers analyze different types of electronic boards, from those in televisions to computers and smartphones.…”