Search Results (4)

Global resource consumption continues to grow each year, exerting increasing pressure on their availability. This trend could lead to a shortage of raw materials in the coming years. Aware of the risks associated with this situation, the European Union has implemented policies and strategies aimed at diversifying its supply sources, including waste recycling. In this context, the present study was conducted with the objective of developing innovative processes to concentrate valuable metals present in the non-recovered fractions of waste electrical and electronic equipment (WEEE). Three types of samples were studied: washing table residues (WTRs), printed circuit boards (PCBs), and powders from cathode-ray tube screens (CRT powders). Several separation techniques, based on the physical properties of the elements, were implemented, including electrostatic separation, magnetic separation, and density and gravity-based separations. The results obtained are promising. For WTRs and PCBs, the recovery rates of targeted metals (Cu, Al, Pb, Zn, Sn) reached approximately 91% and 80%, respectively. In addition to these metals, other valuable metals, present in significant quantities, deserve further exploration. Regarding CRT powders, the performances are also encouraging, with recovery rates of 54.7% for zinc, 57.1% for yttrium, and approximately 71% for europium. Although these results are satisfactory, optimizations are possible to maximize the recovery of these critical elements. The techniques implemented have demonstrated their effectiveness in concentrating target metals in the treated fractions. These results confirm that recycling constitutes a viable alternative to address resource shortages and secure part of the supplies needed for the European Union’s industry. Full article

The paper presents a technological approach for obtaining sintered components with tailored electromagnetic features from electromagnetically active powders through the selective recycling of electronic waste, in particular scrap electronic components. Printed circuit board (PCB) scraps were submitted to a succession of grinding processes, followed by progressive magnetic and electrostatic separation, resulting two final fractions: metallic particles and non-metallic particles including different metallic oxides. Three types of powders were analyzed, i.e., powder after fine grinding, after magnetic separation and after electrostatic separation, which were further processed within a spark plasma sintering furnace in order to obtain solid disk samples. All samples contained several classes of oxides, and also residual metals, leading to specific thermal decomposition processes at different temperatures, depending on the nature of the oxides present in the studied materials. The chemical analysis of powders, via spectrometry with X-ray fluorescence—XRF, emphasized the presence of a mixture of metal oxides and traces of metals (mainly Ag), with concentrations diminishing along with the purification process. The most important analysis was related to dielectric parameters, and it was concluded that the powders obtained by the proposed technology could efficiently substitute scarce raw materials actually used as additives in composites, coatings and paints, mainly due to their high permittivity (above 6 in all frequency domains) and, respectively, dielectric loss factor (above 0.2 in all cases, in all frequency domains). We estimate that the technology described in this paper is a sustainable one according to the concept of circular economy, as it could reduce, by a minimum of 15%, the embodied GHG emissions generated from information and communications technology (ICT) devices by advanced recycling. Full article

Non-metallic fractions (NMFs) from waste printed circuit boards (PCBs) are mostly composed of cured resin and fiber. In this study, NMF material from a PCB was ground into powder and added into matrix asphalt to produce PCB-NMF-modified asphalt. To improve the compatibility of PCB-NMF and asphalt, a compatibilizer consisting of tung oil and glycerol was also developed. The optimum compatibilizer content was determined to be 8% by weight of the PCB-NMF through a series of laboratory tests, including the softening point, penetration, ductility, and softening point difference (SPD). The micro-mechanism of NMF powder-modified asphalt was analyzed through Fourier transform infrared spectroscopy (FTIR) and a scanning electron microscope test (SEM). The performances of PCB-NMF-modified asphalt were evaluated by the dynamic shear rheology (DSR) test and the low-temperature bending beam rheometer (BBR) test. The optimum compatibilizer content was 8% by weight of the NMF powder and the optimum content of NMF powder was determined to be 30% by weight of the asphalt based on a comprehensive evaluation. The results show that PCB-NMF can significantly improve stiffness, rutting resistance, high-temperature stability, and temperature sensitivity of asphalt material at an appropriate content. The BBR tests revealed that PCB-NMF slightly weakened the cracking resistance of asphalt at low temperatures. The SEM test showed that the addition of a compatibilizer can increase the compatibility by making the NMF powder evenly dispersed. The FTIR test results implied that a chemical reaction may not have happened between PCB-NMF, compatibilizer, and the matrix asphalt. Overall, it is a promising and sustainable way to utilize PCB-NMF as a modifier for asphalt material and reduce electronic waste treatment at a low cost. Full article

In this study, non-metallic materials of waste-printed circuit board powders (WPCBP) were successfully used as reinforcing filler to produce polypropylene (PP)–wood composites, and their effect on the weathering properties of PP composites were fully evaluated via oxidation induction time (OIT), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry, vicat softening point (VST), scanning electron microscopy, and mechanical properties analysis. The OIT analysis confirmed that the anti-thermal oxidative aging properties of PP–wood composites were decreased with the loading of WPCBP. Apart from that, the PP composite, reinforced with 30 wt.% of WPCBP, exhibited the highest value of active energy, which suggests that it is more sensitive to temperature and oxygen when compared with other PP composites. The mechanical properties analysis revealed that neat PP exhibited the poorest weathering properties after being subjected to UV exposure, and its retention rate of tensile strength and notched impact strength were only 70.6% and 59.6%, respectively, while WPCBP and wood flour (WF) could efficiently improve the retention rates of the mechanical properties of the PP composites when subjected to UV exposure. The visual appearance of the PP composites after being subjected to UV exposure showed more and smaller cracks with the loading of WPCBP and WF. The ATR-FTIR results revealed that the carbonyl index increased for all the weathered samples, and the more WPCBP was added into the PP composites led to a higher carbonyl index value, which might be due to the multivalent transition metals in WPCBP, which accelerate the photo-oxidation of the PP composites. The VST results show that both WPCBP and WF can effectively enhance the heat deformation resistance of the PP composites that have been subjected to UV exposure. Full article