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"The potential to determine the gastric bioaccessibility (BA) of Tl, As, Pb(II), Cu(II), Zn(II) and Cd(II) using a simple extraction method was evaluated in selected samples from soils contaminated by mining and metallurgical wastes. The SBRC (Solubility and Bioavailability Research Consortium) test was used as a gastric BA comparative method versus a simple extraction method using HCl solution at pH 1.5. High cor- relations (r ≥ 0.98, p ˂ 0.01) were obtained between the two extraction methods for Cd(II), Cu(II), Tl and Zn(II), in all samples investigated. Bioaccessible As, however, only showed a high correlation in the metallurgical area (r = 0.99, p ˂ 0.01), but not in the mining area (r = 0.88, p ˂ 0.01). Conversely, Pb(II) showed a better correlation in samples from the mining area (r = 0.99, p ˂ 0.01) than in those of the metallurgical area (r = 0.92, p ˂ 0.01). Three experimental conditions of the extraction procedures ensured the high correlations observed: (1) Maintaining a strict pH control of 1.5 (± 0.1), (2) a stirring time of 1 h (± 1 min), and (3) filtration of the extraction mixture through a membrane of small pore size (0.05 µm). Bioaccessible Tl was detected in all samples, a fact that has not been reported before in these environments, and alerts to potential health risks not previously identified."

This work received funding from the European Unions Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 778045 , and from Portuguese funds from FCT / MCTES through grant UIDB/04085/2020 . J. Almeida acknowledges Fundação para a Ciência e a Tecnologia and EcoCoRe Doctoral program for her PhD fellowship PD/BD/135170/2017 . The sustainability of mining activities is compromised due to the high amounts of mining residues generated that have to be disposed of, often in open dams, that may cause environmental deterioration, e.g. release of toxic elements to water supplies. These residues are, however, secondary resources of raw materials. In the case of Panasqueira mine, they even are a source of tungsten, considered a critical raw material. The present work aims to assess the electrodialytic process efficiency for raw materials extraction from Panasqueira mine residues. Experiments were performed with 2 and 3-compartment electrodialytic reactors, applying current intensities between 50 and 100 mA, from 4 to 14 days, and sample suspensions enhanced with NaCl or effluent. Additionally, control experiments with no current application were carried out. The results showed that a 3-compartment reactor operating at 100 mA, with NaCl as supporting electrolyte, presented the highest extraction of copper (13%), tin (10%), tungsten (13%) and arsenic (63%). authorsversion published

Mining and metallurgy generate residues that may contain thallium (Tl), a highly toxic metal, for which it is currently not feasible to determine its geochemical speciation through X-ray absorption spectroscopy due to a combination of very low contents and the interference of accompanying high arsenic contents. Therefore, fractionation studies in residues and soils are required to analyze the mobility and bioavailability of this metal, which in turn provide information to infer its speciation. For this purpose, in this work a modification of the BCR procedure was applied to residues and contaminated soils from three mining zones of Mexico and two mining zones of Spain, spanning samples with acidic to alkaline pH values. The Tl extraction procedure consisted of the following fractions: (1) water-extractable, (2) easily exchangeable and associated to carbonates, associated to (3) poorly-crystalline and (4) crystalline Fe and Mn oxyhydroxides, and (5) associated to organic matter and sulfides; and finally a residual fraction as associated to refractory primary and other secondary minerals. The extracted contents were analyzed by Inductively-Coupled Plasma with Mass Spectrometry. Surprisingly, water-soluble, in Tl(I) oxidation state, was detected in most areas, regardless of the pH, a fact that has not been reported before in these environments, and alerts to potential health risks not previously identified. Most of the samples from a metallurgy area showed high levels of Tl in non-residual fractions and a strong correlation was obtained between extracted Mn and Tl in the third fraction, suggesting its association to poorly crystalline manganese oxides. In the majority of samples from purely mining environments, most of the Tl was found in the residual fraction, most probably bound to alumino-silicate minerals. The remaining Tl fractions were extracted mainly associated to the reducible mineral fractions, and in one case also in the oxidizable fraction (presumably associated to sulfides). Capsule: Soluble Tl(I) was found in all soil samples contaminated with either mining or metallurgical wastes. Additionally, in those affected by metallurgical wastes a very strong Tl-Mn correlation was found., Y. Cruz-Hernández is thankful to the Consejo Nacional de Ciencia y Tecnología (CONACYT) for the fellowship received to perform Ph.D. studies. The authors are grateful to the Mexican UNAM PAPIIT IG100215, the US-Mexico UC-MEXUS-CONACyT CN 15-44, and the Spanish National Plan for Scientific and Technical Research and Innovation CTM 2014-55321-P projects for the financial support to perform this investigation.

Made available in DSpace on 2020-12-12T01:43:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Iron mining residue was evaluated as a potential catalyst for heterogeneous Fenton/photo-Fenton degradation of sulfonamide antibiotics. The residue contained 25% Fe2O3 and 8% CeO2, as determined by X-ray fluorescence spectroscopy, as well as other minor phases such as P2O5, SiO2, and TiO2. X-ray photoelectron spectroscopy analysis revealed a lower content of iron oxides on the surface, which restricted interaction of the residue with H2O2. Despite this limitation and the relatively low specific surface area (26 m2 g-1) of the crude iron mining residue (without any pretreatment), the material presented high catalytic activity for Fenton degradation of sulfonamide antibiotics. The degradation was strongly dependent on the initial pH, showing the highest efficiency at pH 2.5. For this condition, a concentration of sulfathiazole below the detection limit was obtained within 30 min, under black light irradiation and using 0.3 g L-1 residue, with low H2O2 consumption (0.2 mmol L-1). The residue also provided highly efficient sulfathiazole degradation in the dark, with the concentration of the antibiotic decreasing to an undetectable level after 45 min. Simultaneous degradation of two sulfonamide antibiotics revealed higher recalcitrance of sulfamethazine, compared to sulfathiazole, but the levels of both antibiotics decreased to below the detection limit after 45 min. The residue was very stable, since no significant concentration of soluble iron was detected after the degradation process. Furthermore, high catalytic activity was maintained during up to five cycles, showing the potential of this material for use as a low-cost and environmentally compliant catalyst in Fenton processes. Institute of Chemistry São Paulo State University (UNESP), Araraquara National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) São Paulo State University (UNESP), Araraquara Institute of Chemistry São Paulo State University (UNESP), Araraquara National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) São Paulo State University (UNESP), Araraquara FAPESP: 2015/21732-5

The materials used to conduct kinetic study on the leaching of silver in the S2O32&minus, O2-Cu2+ system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated concentration of Ag = 71 g∙ton&minus, 1. The kinetic study presented in this paper assessed the effects of the following variables on Ag dissolution rate: particle diameter (d0), temperature (T), copper concentration [Cu2+], thiosulfate concentration [S2O32&minus, ], pH, [OH&minus, ], stirring rate (RPM), and partial pressure of oxygen (PO2). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 KJ∙mol&minus, 1 in a range between 288 K (15 &deg, C) and 328 K (55 &deg, C), which indicates that the dissolution reaction is controlled by the chemical reaction. With a reaction order of n = 0.4, the addition of [Cu2+] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S2O32&minus, ] in a range between 0.02 mol&middot, L&minus, 1 and 0.06 mol&middot, 1. Under the studied conditions, variables d0, [OH&minus, ] and RPM did not have an effect on the overall rate of silver leaching.