Jorge Vazquez-Arenas

The Effect of the Cu2 + ∕ Cu + Step on Copper Electrocrystallization in Acid Noncomplexing Electrolytes

in all of the solutions employed. In cyclic voltammetry, a larger reduction peak was obtained in the nitrate electrolyte, in comparison with the other two media. This higher current has been associated with the catalytic reduction of nitrate ions on recently deposited metallic copper. This effect was confirmed in the potential-step analysis. Despite the fact that Cu + is not thermodynamically stable in these three solutions, the reduction step Cu 2+ /Cu + has been considered as an electron-transfer reaction. The anion type has a direct effect on this electron- transfer reaction and consequently, on the electrocrystallization process; sulfates provoke the most important current decrease associated with the Cu 2+ /Cu + step and also strongly influence the nuclei formation, while the nitrate ions accelerate the Cu 2+ /Cu +

Electrochemical reactor with rotating cylinder electrode for optimum electrochemical recovery of nickel from plating rinsing effluents.

This study is devoted to analyze the metallic electrochemical recovery of nickel from synthetic solutions simulating plating rinsing discharges, in order to meet the water recycling policies implemented in these industries. These effluents present dilute Ni(II) concentrations (100 and 200 ppm) in chloride and sulfate media without supporting electrolyte (397-4202 μS cm(-1)), which stems poor current distribution, limited mass transfer, ohmic drops and enhancement of parasitic reactions. An electrochemical reactor with rotating cylinder electrode (RCE) and a pH controller were utilized to overcome these problems. The pH control around 4 was crucial to yield high purity nickel, and thus prevent the precipitation of hydroxides and oxides. Macroelectrolysis experiments were systematically conducted to analyze the impacts of the applied current density in the recovery efficiency and energy consumption, particularly for very diluted effluents (100 and 200 ppm Ni(II)), which present major recovery problems. Promising nickel recoveries in the order of 90% were found in the former baths using a current density of -3.08 mA cm(-2), and with overall profits of 9.64 and 14.69 USD kg(-1), respectively. These estimations were based on the international market price for nickel (

Chemical and surface analysis during evolution of arsenopyrite oxidation by Acidithiobacillus thiooxidans in the presence and absence of supplementary arsenic

18 USD kg(-1)).

Arsenopyrite weathering under conditions of simulated calcareous soil

Bioleaching of arsenopyrite presents a great interest due to recovery of valuable metals and environmental issues. The current study aims to evaluate the arsenopyrite oxidation by Acidithiobacillus thiooxidans during 240h at different time intervals, in the presence and absence of supplementary arsenic. Chemical and electrochemical characterizations are carried out using Raman, AFM, SEM-EDS, Cyclic Voltammetry, EIS, electrophoretic and adhesion forces to comprehensively assess the surface behavior and biooxidation mechanism of this mineral. These analyses evidence the formation of pyrite-like secondary phase on abiotic control surfaces, which contrast with the formation of pyrite (FeS2)-like, orpiment (As2S3)-like and elementary sulfur and polysulfide (Sn(2-)/S(0)) phases found on biooxidized surfaces. Voltammetric results indicate a significant alteration of arsenopyrite due to (bio)oxidation. Resistive processes determined with EIS are associated with chemical and electrochemical reactions mediated by (bio)oxidation, resulting in the transformation of arsenopyrite surface and biofilm direct attachment. Charge transfer resistance is increased when (bio)oxidation is performed in the presence of supplementary arsenic, in comparison with lowered abiotic control resistances obtained in its absence; reinforcing the idea that more stable surface products are generated when As(V) is in the system. Biofilm structure is mainly comprised of micro-colonies, progressively enclosed in secondary compounds. A more compact biofilm structure with enhanced formation of secondary compounds is identified in the presence of supplementary arsenic, whereby variable arsenopyrite reactivity is linked and attributed to these secondary compounds, including Sn(2-)/S(0), pyrite-like and orpiment-like phases.

Nanocomposite polymer electrolytes based on poly(poly(ethylene glycol)methacrylate), MMT or ZSM-5 formulated with LiTFSI and PYR11TFSI for Li-ion batteries

Mining activities release arsenopyrite into calcareous soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., Sn2−/S0) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (α, γ-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe3(AsO4)3)-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary α, γ-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in calcareous soil and environmental implications based on experimental data.

Multiscale Simulation Platform Linking Lithium Ion Battery Electrode Fabrication Process with Performance at the Cell Level

Novel poly(poly(ethylenglycol)methacrylate) (pPEGMA) nanocomposite electrolytes (NE) based on montmorillonite (MMT) and zeolite (ZSM-5) with lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (ionic liquid, PYR11TFSI) are synthetized using two different routes. Sonication technique is successfully used to introduce the fillers into the polymer matrix, provide uniform dispersion and shatter aggregates of nanofillers to ensure a polymer amorphous structure. The influence of the inorganic particle content (1, 3 and 5 wt%) and filler structure are discussed in terms of their thermal and morphological properties. SEM and TEM techniques reveal an efficient embedding of the fillers into pPEGMA, whereas analyses conducted with TGA/DSC, FTIR and XRD showed that for the binary systems BN-MMT and BN-ZSM-5 containing LiTFSI, the morphology of pPEGMA results into a crosslinking amorphous matrix where Li+ ion motion is hindered. This behavior stems from a strong interaction between the surface of the anionic nanofiller with methylene (CH2) groups from pPEGMA, and particularly anionic nanofiller with Li+. The addition of ionic liquid (IL) PYR11TFSI to ternary systems TN-MMT and TN-ZSM-5 abates the aforementioned interactions and leads to an increase of the interfacial layer separation, which grants flexibility to the polymer chains. These effects stem significantly enhancements in the ionic conductivities of TN-MMT (4.0 × 10−4 S cm−1) and TN-ZSM-5 (9.4 × 10−6 S cm−1) at 30 °C. The lower conductivity obtained for TN-ZSM-5 in comparison to TN-MMT is explained by considering that the introduction of (PYR11)+ to the host channels is blocked, since (PYR11)+ is larger compared to the diameter channel of ZSM-5 (≈0.56 nm), whereby only Li+ ions outside ZSM-5 can be efficiently transferred. Anisotropic conductivity is exhibited for these NE occurring by hopping motion through the formation of a weak coordination shell formed between ether oxygen and carbonyl oxygen from pPEGMA chain. These materials present adequate morphological, thermal and mechanical properties, and a significant enhancement of Li+ ion conductivity for green materials at room temperature to be considered as potential NE for Li-ion batteries.

Battery state of the charge estimation using Kalman filtering

A novel multiscale modeling platform is proposed to demonstrate the importance of particle assembly during battery electrode fabrication by showing its effect on battery performance. For the first time, a discretized three-dimensional (3D) electrode resulting from the simulation of its fabrication has been incorporated within a 3D continuum performance model. The study used LiNi0.5Co0.2Mn0.3O2 as active material, and the effect of changes of electrode formulation is explored for three cases, namely 85:15, 90:10, and 95:5 ratios between active material and carbon-binder domains. Coarse-grained molecular dynamics is used to simulate the electrode fabrication. The resulting electrode mesostructure is characterized in terms of active material surface coverage by the carbon-binder domains and porosity. The trends observed are nonintuitive, indicating a high degree of complexity of the system. These structures are subsequently implemented into a 3D continuum model which displays distinct discharge behaviors for the three cases. The study offers a method for developing a coherent theoretical understanding of electrode fabrication that can help optimize battery performance.