José Soeiro de Carvalho

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.

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.

A comprehensive study of the environmental radioactivity covered in a distance up to 20 km from a point source—two stacks of a coal-fired power plant. Airborne particulate matter was collected, and the element composition on the 30 cm soil profile was determined. The range of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K from the studied areas varies from 8 Bq/kg to 41 Bq/kg, 5 to 72 Bq/kg and 62 to 795 Bq/kg, respectively. The activities values are increased by 44% for ²²⁶Ra, 37% for ⁴⁰K, and 75% for ²³²Th in the prevailing wind direction. For some elements, the respective concentration in the soil is above the maximum permissible level for all types of soil use, particularly for the arsenic concentration. The deposition flux ranged from 0.36 to 5.70 (g m⁻² per month) in the first sampling campaign and from 0.02 to 3.10 (g m⁻² per month) for the second sampling campaign. Maps on the spatial distribution of gamma dose rates, radionuclides activity concentrations, deposition flux and trace metals in topsoil were developed for the study region. These maps are in accordance with higher values in specific locations in the vicinity of the coal-fired power plant, showing the influence of point sources, and for locations within 6 and 20 km from the stacks, particularly in the prevailing wind direction.

Over the past few decades there has been some discussion concerning the increase of the natural background radiation originated by coal-fired power plants, due to the uranium and thorium content present in combustion ashes. The radioactive decay products of uranium and thorium, such as radium, radon, polonium, bismuth and lead, are also released in addition to a significant amount of 40K.Since the measurement of radioactive elements released by the gaseous emissions of coal power plants is not compulsory, there is a gap of information concerning this situation. Consequently, the prediction of dispersion and mobility of these elements in the environment, after their release, is based on limited data and the radiological impact from the exposure to these radioactive elements is unknown. This paper describes the methodology that is being developed to assess the radiological impact due to the raise in the natural background radiation level originated by the release and dispersion of the emitted radionuclides. The current investigation is part of a research project that is undergoing in the vicinity of Sines coal-fired power plant (south of Portugal) until 2013. Data from preliminary stages are already available and possible of interpretation.

Mining activity always has high impact on its surroundings, beingwaste deposition the cause of multiple and complex problems to the environment. One...