Since the start of the global COVID-19 pandemic, extensive quantities of face masks have been used and discarded. Most of these masks end up in landfills, causing a high environmental impact and no benefits. However, there are alternative ways to deal with this waste in a more sustainable way. For example, valorisation of face masks through pyrolysis has received special attention because it offers efficient application to produce a liquid oil that can be used as a diesel substitute and a solid char that can be used as an activated carbon substitute after activation. In this context, this study applies the Life-Cycle Assessment methodology to quantify and analyse the environmental impacts of different treatment scenarios based on the pyrolysis of surgical masks and FFP2 masks. It also compares their environmental performance with the conventional practice of landfilling. The scenarios studied include both thermal and catalytic pyrolysis by using sepiolite, a low-cost material abundant in Spain. Data on the pyrolysis process were obtained from laboratory experiments. It was found that the use of the produced oil as a diesel substitute very significantly reduces the environmental impact in all pyrolysis scenarios. Consequently, the pyrolysis of face masks can reduce the environmental impact caused by the treatment of this waste material. Furthermore, the thermal pyrolysis performs environmentally better than the catalytic pyrolysis. In all scenarios, freshwater ecotoxicity and marine ecotoxicity are the environmental impact categories that cause the highest environmental impact overall.

This research aims to develop a new strategy to valorize wasted COVID-19 masks based on chemical recycling by pyrolysis to convert them into useful products. First, surgical and filtering face piece masks, as defined in Europe by the EN 149 standard (FFP2), were thermally pyrolyzed at temperatures of 450, 500, and 550 °C, and the yields of valuable solid (biochar), liquid (biooil), and syngas products and their characteristics were determined. At low temperatures, biochar formation was favored over biooil and syngas production, while at high temperatures the syngas product yield was enhanced. The highest yield of biooil was found at a pyrolysis temperature of 500 °C, with both surgical and FFP2 masks achieving biooil yields of 59.08% and 58.86%, respectively. Then, the pyrolysis experiments were performed at 500 °C in a two-stage pyrolysis catalytic reactor using sepiolite as a catalyst. Sepiolite was characterized using nitrogen adsorption–desorption isotherms and Fourier-transform infrared spectroscopy. Results showed that the two-stage process increased the final yield of syngas product (43.89% against 39.52% for surgical masks and 50.53% against 39.41% for FFP2 masks). Furthermore, the composition of the biooils significantly changed, increasing the amount of 2,4-Dimethyl-1-heptene and other olefins, such as 3-Eicosene, (E)-, and 5-Eicosene, (E)-. Additionally, the methane and carbon dioxide content of the syngas product also increased in the two-stage experiments. Ultimately, the effect of sepiolite regeneration for its use in consecutive pyrolysis tests was examined. Characterization data showed that, the higher the use-regeneration of sepiolite, the higher the modification of textural properties, with mainly higher changes in its pore volume. The results indicated that the pyrolysis of face masks can be a good source of valuable products (especially from biooil and syngas products).

The use of disposable personal protective equipment (PPE) as a control measure to avoid transmission against COVID-19 has generated a challenge to the waste management and enhances plastic pollution in the environment. The research aims to monitor the presence of PPE waste and other plastic debris, in a time interval where the use of face mask at specific places was still mandatory, on the coastal areas of Granada (Spain) which belongs to the Mediterranean Sea. Four beaches called La Rijana, La Charca, La Rábita and Calahonda were examined during different periods. The total amount of sampled waste was 17,558 plastic units. The abundance, characteristics and distribution of PPE and other plastic debris were determined. Results showed that the observed amount of total plastic debris were between 2.531·10⁻² and 24.487·10⁻² units per square meter, and up to 0.136·10⁻² for PPE debris, where face masks represented the 92.22 % of the total PPE debris, being these results comparable to previous studies in other coastal areas in the world. On the other hand, total plastic debris densities were in the range from 2.457·10⁻² to 92.219·10⁻² g/m² and densities were up to 0.732·10⁻² for PPE debris. PPE debris supposed 0.79 % of the weight of total waste and the 0.51 % of total items. Concerning non-PPE plastic waste: cigarettes filters, food containers and styrofoam were the most abundant items (42.95, 10.19 and 16.37 % of total items, respectively). During vacation periods, total plastic debris amount increased 92.19 % compared to non-vacation periods. Regarding type of beaches, the presence of plastic debris was significantly higher on touristic/recreational than in fishing beaches. Data showed no significant differences between accessible and no-accessible beaches, but between periods with restrictive policy about mask face use and periods with non-restrictive policy data suggest significant differences between densities (g/m²) for PPE litter. The amount of PPEs debris is also correlated with the number of cigarettes filters (Person's r = 0.650), food containers (r = 0.782) and other debris (r = 0.63). Finally, although interesting results were provided in this study, further research is required to better understand the consequences of this type of pollution and to provide viable solutions to this problem.

A semi-industrial scale hydrocyclone with a 250 mm internal diameter was used to concentrate medium-grade celestine ore (75%–85% celestine) from the Montevive deposit of Granada (Spain) using a dense ferrosilicon (FeSi) medium. For this purpose, a Box–Behnken factorial design (BBD) was carried out, with the response variable being the Sr concentration measured by X-ray fluorescence (XRF), as well as the concentration of celestine measured by X-ray diffraction (XRD) of the mineral collected from the under (sunk) stream of the hydrocyclone. The experimental factors to be optimised were the density of the medium in the mixing tank (water, FeSi, and feed mineral) varying from 2.7 to 2.9 kg/L, the hydrocyclone inlet pressure from 0.8 to 1.2 bar, and the hydrocyclone inclination (from 15° to 25° from the horizontal). The range of densities of the dense medium to be tested was determined from previous sink–float experiments using medium-grade ore, in which the distribution of mineral phases with different particle size fractions was determined. To evaluate the separation behaviour, the following parameters were considered: the enrichment ratio (E), the tailings discarding ratio (R), and the mineral processing recovery (ε). From the factorial design and the response surface, the optimum parameters maximising celestine concentration in the under stream (78%), were determined. These optimised parameters were: a density of 2.75 kg/L for the dense medium, an inlet pressure of 1.05 bar, and a hydrocyclone inclination varying from 18° to 20°. Under these conditions, a 94% recovery of celestine (68% Sr) can be achieved. These results show that medium-grade celestine ore, accumulated in mine tailings dumps, can be effectively concentrated using DMS hydrocyclones and that the operating parameters can be optimised using a factorial experiment design. This study can contribute to reducing overexploitation of strategic mineral resources, avoiding blasting and environmentally damaging clearing, by applying a simple and sustainable technique.

This research aims to develop a new strategy to valorize wasted COVID-19 masks based on pyrolysis to convert them into useful products. First, surgical and FFP2 masks were thermally pyrolyzed at temperatures of 450-550 ?C with the purpose of determining gas, liquid (oil) and solid (char) yields. At low temperatures, solid yield was high, while at high temperatures the gas product was enhanced. The highest yield of liquid was found at an operating temperature of 500 ?C in both surgical and FPP2 masks pyrolysis. The liquid product yields were 59.08% and 58.86%, respectively. Then, the volatiles generated during thermal pyrolysis of residual masks were cracked over sepiolite as catalyst at a temperature of 500 ?C. The catalytic pyrolysis increased the yield of gas product (43.89% against 39.52% for surgical masks and 50.53% against 39.41% for FFP2 masks) and decreased the viscosity of the liquid product. Finally, the effect of sepiolite regeneration and reuse in consecutive pyrolysis tests was examined. Results showed that, with the higher regeneration-reuse of sepiolite, the catalyst was degraded obtaining a liquid product with higher molecular mass. This effect was hardly noticeable in the case of FFP2 masks.