Aurora Futuro

The high demand for electronic devices is generating a substantial amount of electronic waste, which contains spent printed circuit boards (PCBs). PCBs are mainly composed of metals, with copper (Cu) being the most representative. The Cu scarcity in the Earth crust and the so-called digital and energy transition create additional stress to find innovative approaches to overcome this global problem.In this study, Cu recovery from mechanically pre-concentrated PCBs residues was studied using sulfuric acid–hydrogen peroxide leaching followed by two alternative downstream routes: (i) direct cementation using steel wool and (ii) solvent extraction (SX) with the oxime-based extractant LIX 984N followed by stripping and cementation. Optimized leaching achieved 98±0.05% Cu extraction with high Zn co-leaching (93±0.02%). Direct cementation recovered 99±0.01% of dissolved Cu, corresponding to approximately 506g of Cu/ kg of concentrate, with 2% of Zn co-cementation. The SX–stripping–cementation route achieved high individual stage efficiencies (SX 93±0.003%), stripping 90±0.02%, cementation 91±0.01%) without Zn losses. On the other hand, with low overall Cu recovery - 390g of Cu/ kg of concentrate - due to dilution and cumulative transfer losses.The results demonstrate a clear trade-off between maximum Cu yield (direct cementation) and higher Cu/Zn selectivity (SX route), highlighting the importance of normalized mass balance comparison in PCBs recycling flowsheet design.

The exponential growth in the consumption of electronics, in combination with the reduction in their useful life, has led to a significant increase in the volume of electronic materials which are discarded. Printed Circuit Boards (PCBs) are modules composed of ceramic, polymer, and metallic materials of high economic value and with a great potential for damage to biotic and anthropic environments when inadequately discarded. The aims of this work were to study the main environmental impacts and the efficiency of mechanical operations in the electronic waste recycling process in optimizing the concentration of metallic copper. For this, the samples obtained were characterized according to their morphology and chemical composition, and subjected to physical and mechanical treatments: dismantling, grinding, separation by granulometry, density, and magnetic property. The environment impacts were estimated by the Life Cycle Assessment of the pre-treatment processes, associated with copper extraction operations in Waste Printed Circuit Boards (WPCBs). According to the results obtained, it is possible to infer that the NM + 1 mm Concentrated product presents in its metallic composition around 78% copper, which contributes to the efficiency of the hydrometallurgical extraction processes. It is noteworthy that the Concentrated class represents about 14% of copper (wt) taking into account the amount of 3.789 kg of PCB waste input material. The potential for reinsertion of the dust in the material recovery process is highlighted, given that the chemical composition of this particulate has a significant presence of metals. In general, it was found that due to the higher concentration (wt%) of the sample being allocated in the range of −0.15 mm + 0.05 mm, the elements Fe (18.30%), Si (10.73%), Ca (9.21%), and Cu (8.89%) stand out regarding the participation of the elemental composition of this fraction and also regarding the general composition of the sample. Furthermore, the generation of dust during the fragmentation process can be associated with occupational respiratory diseases when not managed. About the Life Cycle Assessment, in seven of the nine categories evaluated, crushing and screening activities accounted for more than 90% of the recorded impact values. In general, it is estimated that in the pre-treatment phase it generated 15.4 kg CO₂ eq.

In the Valongo Belt, with an extension of about 90 km, located very close to Porto, northern Portugal, dozens of ore deposits of various metallic minerals and coal were exploited in the 19th and 20th centuries. One of the metals most intensely exploited was antimony, with or without associated gold mineralization. This research intends to verify the extent of the current environmental legacy of ancient antimony mining. A typical old mine was selected. The main objectives were to verify whether the environmental legacy still manifests today, how natural processes contributed to an environmental dispersion of the mining footprint and whether the environmental legacy was absorbed by developments in a new landscape modified by anthropic activities. The topography of the area was captured using a Light Detection and Ranging (LIDAR) based drone system. The regional background was characterized by the geo-referenced chemical analysis of 157 soil samples, collected in a 35 × 35 m grid. The former mining area was characterized by 58 supplementary samples. The mining area is distinct from the background by higher antimony and zinc levels, constituting two distinct populations, as confirmed by statistical tests. In the samples collected in the industrial zone, six elements were considered contaminants: As, Cu, Mo, Sb, Sn and Zn. The concentrations of these elements were statistically examined using multivariate statistical analyses (principal component analysis and correspondence analysis). The main conclusions are: (a) the mining heritage area is discernible from the highly mineralized background; (b) in the mining zone, it is possible to distinguish the processing industrial area from the waste rock storage; (c) the natural processes of environmental dispersion were of little relevance; (d) the environmental legacy was smoothed and mostly incorporated into the new post-industrial landscape created by anthropic activities.

The increasing demand for rare earth elements (REEs), which is associated with their economic importance and the supply risk, has motivated the research for alternative secondary sources of these elements. Coal and coal combustion ash have been pointed out as promising REE raw materials. This research seeks to understand REE fractionation, from feed coals to ashes, considering seasonal variations, and to assess the trends within the ash fractions that can be used for further beneficiation processes. Colombian commercial feed coals, combustion ashes, and their respective fractions were sampled from a Portuguese power plant and were characterized via petrographical, mineralogical, and chemical analyses. The total REE concentrations in the feed coals studied range between 6.97 and 23.15 ppm, while, in the ashes, they vary from 159.9 to 266.6 ppm. Fly ash (FA) from electrostatic precipitator (ESP) presented higher concentrations than the bottom (BA) and economizer (ECO) ashes. Furthermore, REEs and the LREE/HREE ratio increased slightly towards the back rows of the ESP. In the feed coals, the REEs are significantly correlated with ash, and they occur in micrometric phosphate minerals intermixed with clays. In the ashes, the REEs were mostly detected in micrometric particles, with P and Al-Si as the major components. The results from the fractioned samples show that the REEs were enriched in the fine (<25 µm) and nonmagnetic fractions of the ESP FA. A single trial combining sieving and magnetic separation enabled the attainment of a REE recovery of 53%, and a final enrichment factor of 1.25. Coal combustion ashes and their respective size fractions are promising REE raw materials; however, the REE oxide concentrations are below the economical cutoff of 1000 ppm.

The characterization of historical mine tailings provides important information for land-management decisions, in particular when considering potential reprocessing activities or the development of an environmental protection program. In addition, outcomes from such characterization may define the scope for a more detailed investigation. The present work describes the characterization of the waste material from the Cabeço do Pião tailings impoundment performed within the project ReMinE: Improve Resource Efficiency and Minimize Environmental Footprint. The purpose of the work was to investigate alternative mine waste management options such as the extraction of valuable resources from an environmental liability. The study involved the collection of 41 samples at different locations at two different depths, physical and chemical characterization of the wastes, natural leaching tests, and potential for acid generation. The results showed that, apart from the potential instability of the dyke (with an average slope of 35°), the drained solutions flowing by percolation contain very small particles with high arsenic contents that are being incorporated into the river sediments. In addition, these very fine-grained materials are available for the transport by the wind creating secondary sources of environmental contamination. This data is fundamental for economic and environmental assessment of the two main alternatives, reprocessing or removal.

Demand growth for metallic minerals has been faced with the need for new techniques and improving technologies for all mining life-cycle operations. Nowadays, the exploitation of old tailings and mine-waste facilities could be a solution to this demand, with economic and environmental advantages. The Panasqueira Mine has been operating for more than a century, extracting tungsten and tin ore. Its first processing plant, “Rio”, was located near the Zêrere river, where mineral-processing residues were deposited on the top hillside on the margin of this river in the Cabeço do Pião tailings dam. The lack of maintenance and monitoring of this enormous structure in the last twenty years represents a high risk to the environment and the population of the surrounding region. A field-sample campaign allowed the collection of data, and resulted from laboratory tests to use regression optimization. Re-mining the tailings by hydrometallurgical methods was considered to satisfy the two conditions of metal demand and environmental risk. The metal content in Cabeço do Pião was shown be enough for environmental restoration. The re-mining solution was studied, taking into account the technical, economic, social, and environmental aspects.

The recycling of Waste Printed Circuit Boards (WPCBs) constituent materials has been of increasing relevance, especially when associated to the also increasing volume of WPCBs, caused by factors such as the technological advancement and the reduction of estimated useful life of products. The WPCBs recycling plants use physical processing operations such as dismantling, crushing, sieving, magnetic, gravity and density separation for the recovery of metals. The main objective of this work was the evaluation of the efficiency of the copper enrichment of fractions obtained in the physical recycling process of WPCBs. According to the results obtained in the present study, it is indicated the use of the process of physical separation in fractions with particle size +1 mm, aiming at the enrichment of metallic fractions, especially the nonmagnetic fraction, once the concentrate NM + 1 mm fraction, presented a concentration of 78% of copper in its composition.