WEEE under the prism of urban mining

Improving the service life of oxygen lance is a key assignment in electronic scrap smelting process. The degradation mechanism of 304, 310S, 316L, and 321 stainless steels in FeO_x-SiO₂-CaO-Al₂O₃ slag were experimentally studied at the range of 1300–1400 °C, in the air and at p_O2 = 10^-7 atm. The oxidation and dissolution of steel components, and the formation of (Ni,Fe)(Fe,Cr,Al)₂O₄ spinel phases caused steel degradation. The chrome oxide layers protected the stainless steel from further corrosion at high p_O2. 310S stainless steel had the best performance in the experimental conditions, and 321 stainless steel was also stable at low temperatures.

Pyrometallurgical processes have been widely recognised as the preferred technology for E-scrap recycling, and E-scrap smelting is usually accompanied by the formation of high-Al₂O₃-content slag. However, this slag can cause problems, such as refractory wear and even accelerated failure. Therefore, the corrosion mechanism of magnesia-chrome and alumina-chrome refractories in contact with FeO_x-SiO₂-CaO-Al₂O₃ smelting slag was experimentally studied in the range of 1300–1400 °C, in air (p_O2 = 0.21 atm) and at p_O2 = 10^-7 atm. The results showed that refractory-component dissolution and new phases formation were the major causes of refractory degradation. The dissolution of the refractory components increased along with both increasing temperature and decreasing Al₂O₃ concentration in the initial slag. When decreasing the p_O2, the dissolution of MgO and Al₂O₃ into the slag slowed down. New phases such as forsterite, anorthite, and spinel were detected at the interface between the slag and the bulk refractory. The formation of forsterite accelerated the refractory wear, whereas the newly formed (MgO,FeO)·(Cr₂O₃,Fe₂O₃,Al₂O₃) spinel phase acted as a protective layer against further corrosion. A lower Al₂O₃ concentration in the slag and a higher smelting temperature both densified the formed spinel layer. Additionally, a high oxygen partial pressure was beneficial to the formation of spinel in the magnesia-chrome refractory corrosion experiments. However, a low oxygen partial pressure was favourable for the formation of spinel on the surface of the alumina-chrome refractory materials. This study provides useful information for designing refractory materials and optimizing the processing parameters of E-scrap smelting.

The generation of waste electrical and electronic equipment (WEEE) has become a globally serious problem. Its adequate management has great importance for governments and organizations alike. Despite the available literature on models for estimating WEEE generation, such analysis and forecasting are scarce in the context of big organizations. The objective of this research is to estimate WEEE generation in organizations using the Market Supply model applied to a Brazilian federal agency. The agency's Asset Control System was the data source. These records allow organizations to effectively manage their WEEE, influencing the quality of generation estimate. A statistical analysis was carried to calculate the lifespan of the equipment in the system, observing a reduction in the lifespan of the most modern items. The model allows for estimating WEEE generation for the coming years in organizations, whilst providing lifespan profiles, meaning the probabilistic obsolescence rate of appliances. The results obtained, including the statistical analyses and the used methodology represent a valuable resource to organizations as a means to inform their decision-making process regarding the management of WEEE.

The COVID-19 pandemic and the ensuing lockdowns has drastically altered modern life. Increased use of telecommuting for work, education, and leisure has led to a surge in demand for electronic products, which has strained both global manufacturing supply chains and upstream mineral stocks and resources. In this paper, we discuss a prospective research and policy agenda that covers the technological, socio-economic, and regulatory aspects needed for an accelerated transition towards enhanced mineral resource efficiency and improved electronic waste management during the pandemic and its aftermath.

One of the current challenges in circular economy is the ability to transform waste into valuable products. In this work, waste of electrical and electronic equipment (WEEE) was used as a gold source to prepare stable gold nanoparticles (AuNP). The proposed methodology involves a series of physical and chemical separation steps, carefully designed according to the complex nature of the selected WEEE and the targeted product. In a first step, pins from microprocessors were separated by mechanical treatments, allowing to concentrate gold in a metallic fraction. A two-step hydrometallurgical method was subsequently performed, to obtain a Au (III) enriched solution. Such solution was used as a secondary raw material to obtain AuNP. For that purpose, a specific synthetic method was developed, adapted to the high acidity and ionic strength of the solution. Thanks to the use of two easily available reducing agents (sodium citrate and ascorbic acid) and a polymeric stabilizer (PVP), it was possible to obtain high purity AuNP presenting a mixture of well-defined spherical and triangular shapes. These AuNP were finally deposited onto glass substrates and present a sensitive response to refractive index changes in the environment, a necessary condition towards application in optical sensors. In summary, this upcycling case study demonstrates that e-waste can successfully replace primary raw materials to obtain highly valuable and useful nanomaterials. These results highlight the potential of urban mining as a sustainable and circular approach to the development of nanotechnologies.