Electrochemical Speciation Control of LCO-Derived NADES Leachate: Cyclic Voltammetry, Chronopotentiometry, Cobalt Speciation and Screening LCA Data
Description
This dataset supports a study on chemical-reductant-free electrochemical speciation control for cobalt recovery from lithium cobalt oxide (LCO)-derived natural deep eutectic solvent (NADES) leachate. The study tested whether galvanostatic electroreduction can convert dissolved Co(III)-rich species into more recoverable Co(II)-rich species without adding an external chemical reductant, and whether the added electrochemical burden is justified when assessed per unit of precipitable cobalt. The dataset includes time-resolved cyclic voltammetry (CV), chronopotentiometry/galvanostatic treatment data, UV-vis/ICP-OES cobalt speciation tables, and a screening life-cycle/economic assessment workbook. The CV files provide time, potential, current and working-electrode potential data for evaluating electrochemical accessibility. The CP files record potential/current responses over 2,400 s treatment runs, enabling calculation of voltage behaviour, plateau stability, charge input and energy demand. The speciation tables report Co(III) and Co(II) concentrations before and after treatment across current and catholyte-volume conditions, including replicate measurements and reduction efficiencies. The data show that LCO-derived NADES leachate is electrochemically active and that galvanostatic treatment shifts cobalt speciation from Co(III) toward Co(II). Fluorine-minimization pretreatment reduced total fluorine from 1.60 to 0.15 wt% and soluble fluoride from 151.3 to 5.76 mg L-1 before leaching. NADES leaching dissolved 94.7% of the feed mass and produced leachate containing about 15.32 g L-1 Co. Electrochemical treatment achieved approximately 39.56-95.04% Co(III)-to-Co(II) conversion, while total dissolved cobalt recovery remained high at 99.60 +/- 1.53%, indicating oxidation-state redistribution rather than cobalt loss. Conversion increased with current but decreased with catholyte volume, supporting normalized current dose, I/V, as a useful scale-up descriptor. The LCA workbook is foreground screening assessment. Although electroreduction-assisted recovery has a higher per-batch climate burden than direct precipitation, it produces more precipitable cobalt. Normalized to cobalt output, electroreduction lowered climate impact intensity from about 48.0 to 27.1 kg CO2-eq kg-1 Co at 80% NADES recovery and from about 28.9 to 18.1 kg CO2-eq kg-1 Co at 90% recovery. The dataset can be used to replot electrochemical traces, calculate charge and energy metrics, reproduce cobalt speciation mass balances, compare current/volume effects, and test foreground LCA assumptions for NADES-assisted cobalt recovery.
Files
Steps to reproduce
The LCO black mass was first conditioned to reduce fluorine-related side effects before NADES leaching. Pretreatment involved ethanol-water washing (1:1 v/v, 40 C), Cyrene extraction at 85 C to remove PVDF binder, and mild Ca(OH)2 conditioning at pH 10 to immobilize residual fluoride as CaF2. Fluorine removal was tracked by combustion ion chromatography for total fluorine, ion chromatography or fluoride ion-selective electrode analysis for soluble fluoride, and supporting XPS, FT-IR and TGA analyses for surface and binder-associated fluorine species. The NADES leaching medium was prepared from betaine, citric acid and lactic acid in a 1:1:1 formulation, stirred at 60 C until homogeneous, then combined with aqueous lactic acid, citric acid and ascorbic acid solutions and diluted to 1 L. For leaching, 25 g of pretreated LCO black mass was mixed with 1 L of the hybrid NADES at 80 C for 60 min. The resulting leachate was filtered, and dissolved cobalt and lithium were quantified by ICP-OES. Electrochemical experiments were conducted in a divided H-cell using a DHElecChem7000 workstation. Filtered LCO-derived NADES leachate was used as the catholyte, with a graphite cathode of 10 cm2 immersed area, a Ti/RuO2 dimensionally stable anode, a FAB-PK-130 anion-exchange membrane, and 0.25 M Na2SO4 anolyte. Cyclic voltammetry used an Ag/AgCl reference electrode and scanned approximately 0.206-1.408 V vs Ag/AgCl at 10-100 mV s-1. Chronopotentiometry/galvanostatic electroreduction was then performed for 2,400 s at different applied currents and catholyte volumes to assess voltage response, current loading, solution inventory effects and cobalt conversion. After treatment, UV-vis spectra were collected from 200 to 900 nm. The Co(III)-associated region near 425 nm and the Co(II)-associated band near 500-540 nm were used as supporting indicators, while quantitative conversion was determined from ICP-OES-supported cobalt mass balance. Co(II) gain, Co(III) loss and total dissolved cobalt were compared to distinguish redox redistribution from precipitation, adsorption or analytical loss. Supporting spectroscopy and electrochemical impedance data were used to interpret coordination changes and mixed kinetic/transport control. The screening LCA used treatment of 1 L leachate from 25 g LCO black mass as the functional unit. Direct precipitation and electroreduction-assisted precipitation were compared at 80% and 90% NADES recovery. The foreground boundary included fresh NADES make-up, oxalic acid dihydrate, sodium carbonate, electroreduction electricity, and lifetime-allocated graphite cathode, Ti/RuO2 anode and membrane burdens. Climate impacts were calculated using IPCC 2021 GWP100 and ReCiPe 2016 climate-change factors, with one-at-a-time sensitivity analysis and 5,000 seeded Monte Carlo trials.
Institutions
- Shanxi UniversityShanxi, Taiyuan