Precious, strategic and toxic elements in electronic waste: bibliometric evaluation, proposition of reference material and direct analysis by laser-based techniques and fluorescence spectrometry

Abstract

Waste electrical and electronic equipment (WEEE) is among the fastest growing types of solid waste in the world. In addition, this is a complex waste stream when it comes to recycling, due to the large variety of valuable materials and toxic elements present in plastics, metals, glass, ceramics, etc. In this context, the chemical analysis of electronic waste and issues involving the management of this matrix were discussed in this thesis: (1) initially, bibliometric resources were used to evaluate the different topics involving the handling of electronic waste and the evolution of world research; (2) as well, given the lack and difficulty of producing materials to ensure the traceability of measurements and validation of analytical methods, an electronic waste reference material was produced and evaluated following all standards established by ISO guides 30 - 35; (3) finally, different techniques of direct analysis such as laser-induced breakdown spectroscopy (LIBS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray spectrometry (XRF) were used to develop analytical methods for elementary determination in printed circuit board (PCB) and liquid crystal display (LCD) samples. Bibliometrics proved to be an efficient resource for analyzing past research topics, emerging research hotspots and assess the current status of electronic waste research. Studies involving the analysis of critical elements (e.g. In, Pd, rare earths) and the development of reference materials for e-waste have been identified as gaps in the current literature, which are addressed and discussed in this thesis. New univariate (multi-energy calibration, MEC) and multivariate (data fusion using partial least squares regression, PLS) calibration strategies have been proposed for direct analysis of e-waste samples (i.e. PCB and LCD), through elemental analysis and chemical mapping within the sample surfaces. Considering the applicability, advantages and limitations of each analytical technique used, combined with appropriate chemometric tools, it was possible to propose new methods for analyzing complex matrices such as e-waste, which make it possible to minimize or even eliminate possible interferences, with analytical performance similar or superior to those existing traditional alternatives.