Browsing by Author "Videla, Alvaro"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Iodide-assisted leaching of chalcopyrite concentrate in acidic chloride solution: Effect of different parameters on the copper extraction rate
    (2024) Martinez-Bussenius, Cristobal; Videla, Alvaro
    Chalcopyrite leaching has slow kinetics in sulfate media compared to other copper minerals. Studies have shown that these slow kinetics are caused by a passivation layer generated during the mineral 's dissolution and/or by its semiconductor properties. In the continuous search for regents to improve kinetics, the use of iodide in sulfate media has led to a significant improvement in the leaching rate of copper from chalcopyrite. However, no detailed information on the effect of the chloride concentration in this system has been informed so far. In this present work, the leaching of a chalcopyrite concentrate using iodide in chloride solution was evaluated, varying parameters such as temperature, particle size, the initial potential of the solution, chloride, iodide, and cupric ion concentrations. The results indicated a copper extraction of 75.8 % in 30 days in the presence of 50 g/L chloride, a 43.1 % more than in the absence of chloride (32.7 % extraction) obtained under the same conditions (100 mg/L I - , 0.5 g/L Cu 2+ , 9 g/L Fe 3+ , 1 g/L Fe 2+ , pH = 1.5, 35 degrees C and an initial potential solution of 700 mV vs SHE). Additionally, the most statistically significant factors on copper extraction in order of influence were temperature, iodide concentration, and chloride concentration. QEMSCAN-PMA analysis of the leached solids showed a significant amount of elemental sulfur and possible intermediate copper species of chalcocite and covellite, which are not observed for the leaching of chalcopyrite concentrate in the presence of iodide in sulfate media. The measurements of the chalcopyrite potential and the solution potential indicate that they are similar for high concentrations of Fe 2+ and for iodide concentrations higher than 200 mg/L in the presence of Fe 3+ . The chalcopyrite potential obtained for the central condition of this study indicates that the predominant iodine species was triiodide, which suggests that this was the main oxidant in this system.
  • No Thumbnail Available
    Item
    Modification of a commercial activated carbon with nitrogen and boron: Hydrogen storage application
    (2023) Morande, Arturo; Lillo, Patricio; Blanco, Elodie; Pazo, Cesar; Belen Dongil, Ana; Zarate, Ximena; Saavedra-Torres, Mario; Schott, Eduardo; Canales, Roberto; Videla, Alvaro; Escalona, Nestor
    The present study evaluates the effect of heteroatom doping (N and B) and thermal treatment modification of activated carbon, in different sequences over hydrogen storage capacity. All the materials were characterized by N2-physisorption, XRD, TPD, and XPS. H2 adsorption was measured at-196 degrees C and correlated with physico-chemical properties, while a density-functional theory model was employed to analyze the hydrogen adsorp-tion. Results have shown that there is an effect of the modification order on the storage capacity, which was related to increments of the specific surface area or the nature of the functional groups. An optimum nitrogen doping temperature was detected at 500 degrees C and was associated with the presence of pyridone groups. This sample had the highest hydrogen capacity ca. 2.34 % at 0.93 bar. Such value was extrapolated to 7.86 wt% at 30 bar using the Dubinin-Astakhov adsorption model, making it a promising material for hydrogen storage.
  • No Thumbnail Available
    Item
    Novel Indigenous Strains and Communities with Copper Bioleaching Potential from the Amolanas Mine, Chile
    (2024) Casas-Vargas, Julian C.; Martinez-Bussenius, Cristobal; Videla, Alvaro; Vera, Mario
    Bioleaching, a process catalyzed by acidophilic microorganisms, offers a sustainable approach to metal extraction from sulfide minerals. Chalcopyrite, the world's most abundant copper sulfide, presents challenges due to surface passivation limiting its bioleaching efficiency. Also, indigenous species and microbial communities may present high copper extraction rates and offer new possibilities for application in bioleaching processes. This study examines the bioleaching potential of microbial isolates and communities obtained from Amolanas Mine in Chile. Samples were collected, cultivated, and identified by Sanger sequencing. The bioleaching potential and biofilm formation of isolates and enrichments were evaluated on pyrite and chalcopyrite. The results show the isolation of nine Leptospirillum and two Acidithiobacillus strains. The bioleaching experiments demonstrated good copper bioleaching potentials of the Leptospirillum I2CS27 strain and EICA consortium (composed mainly of Leptospirillum ferriphilum, Acidiphilium sp., and Sulfobacillus thermosulfidooxidans), with 11% and 25% copper recovery rates, respectively. Microbial attachment to the surface mineral was not mandatory for increasing the bioleaching rates. Our findings underscore the importance of indigenous microbial communities in enhancing copper bioleaching efficiency.
  • No Thumbnail Available
    Item
    Quaternary nitrate and chloride molten salts for the next concentrating solar power plants: Corrosion considerations for the use of AISI 304L steel
    (2024) Castro-Quijada, Matias; Jullian, Domingo; Walczak, Magdalena; Pineda, Fabiola; Videla, Alvaro
    The study addresses the advancement in concentrating solar power (CSP) plants by transitioning from binary nitrate salts to nitrate and chloride quaternary salts, focusing on the corrosivity of four salts as evaluated by immersion testing of AISI 304L stainless steel. Four compositions of salts were evaluated, from solar salt to equimolar NaNO3-KNO3-NaCl-KCl, up to 21 days (500 h) at 500 degrees C in an open atmosphere, determining the corrosion kinetics using gravimetry. The morphology, chemical composition, and microstructure of the corrosion products were characterized using XRD, FESEM-EDS, and GD-OES. Exposure to the molten salt with 0 mol% Cl(Solar Salt) resulted in negligible corrosion kinetics, consistent with previous studies. The salt with 14 mol% Clcaused a stable corrosion product with a corrosion rate 30 times higher than without chloride. All quaternary salts exhibited a multilayer structure of the top surface with selective chromium (Cr) removal. Specimens exposed to salts with more than 29 mol% Cl- displayed a similar structure with Cr and iron (Fe) removal, resulting in more brittle layers and corrosion rates 90 to 250 times higher than the salt without chloride. GD-OES analysis confirmed Cl diffusion into the oxide layer, highlighting the role of pCl2(g) and pO2(g) in driving corrosivity. Based on the results, using in salts with 29 mol% Cl- at 500 degrees C is discouraged, while using 304L with 14 mol% Cl- in a cold tank may be considered.