Leaching of sulfidic backfill at the Thalanga Copper-Lead-Zinc mine, Queensland, Australia

The placement of sulfidic waste below the groundwater table ensures limited interaction with the hydrosphere and suppression of sulfide oxidation. However, if sulfidic waste is placed above the groundwater table and remains uncovered, the backfill becomes part of the unsaturated zone and is exposed to atmospheric oxygen and leaching. This study aims to establish the leaching behaviour of sulfidic waste placed above the groundwater table and the impact of such leachate on the local aquifer at the Thalanga base metal mine. Mining of the Thalanga copper-lead-zinc deposit resulted in a large final mining void (600 m × 150 m × 70 m) and extensive underground workings. The underground workings were partly filled with tailings and the open pit was partly backfilled with acid producing sulfidic waste rock. In addition, the pit serves as a sink for acidic run-off from adjacent waste rock piles and mine workings. To date, the backfill of sulfidic waste rock placed into the pit has not been capped with benign materials and for most of the dry season, the surface of the backfill is covered by melanterite-type efflorescences. Results of kinetic column leach experiments conducted on the sulfidic waste indicate that Cd, Cu, Zn and SO4 rich waters migrate from the backfilled sulfidic waste into the local unconfined aquifer. However, the seepage of alkaline (pH 7.3 - 8.0), high conductivity (>10 000 µS/cm) tailings waters into the remaining pit void clearly shows that the acid leachate originating from the sulfidic waste rock does not impact beyond the waste repository and its immediate environment. Geochemical modelling implies that minimal or no mixing occurs between the acid waste rock leachate and the alkaline tailings waters

High-Resolution pit water quality model for the Highway Reward Mine, Queensland, Australia

Field and laboratory data combined with computational modelling have been used to predict the pit water quality for the Highway Reward mine. Open pit mining of the Highway Reward copper-gold deposit has produced a final mining void with a diameter of 600 m and a depth of 280 m. This void will be left to fill with ground and surface water once pumping of pit water ceases. Several leaching tables were constructed to simulate weathering reactions and surface water run-off in the major pit wall units during a 200-day leaching experiment. To date, about three-quarters through the experiment, combined run-off from these cells has reached a pH <4, corresponding to actual present day pit water pH values and chemistries. While sulfide oxidation in the pitwalls leads to an acid, metal-rich leachate, bicarbonate-rich groundwater inflow during the dry season acts as a buffer. Acid generating salts appear to have only a small impact on the overall pit water chemistry. The kinetic test data have been combined with measured pit water chemistry data, measured surface and seasonal groundwater inflows, climatic data, and calculated pit lake surface area and volume to produce a high-resolution pit water quality model. This high-resolution pit water quality model will aid in the mine decommissioning process

Fluorinated polysulfonamide based single ion conducting room temperature applicable gel-type polymer electrolytes for lithium ion batteries

Single ion conducting polymer electrolytes (SIPEs) comprised of homopolymers containing a polysulfonylamide segment in the polymer backbone are presented. The polymer structure contains –C(CF3)2 functional groups that due to better solubility allow for effective lithiation, yielding well-defined materials. An optimized polymer electrolyte membrane was fabricated as a 3 : 1 blend of single ion conducting polymer and PVdF-HFP, which exhibits a high ionic conductivity of 0.52 mS cm−1 and an impressive lithium ion transference number of 0.9, as well as a 7Li self-diffusion coefficient of 4.6 × 10−11 m2 s−1 at 20 °C. The presented polymer electrolyte has superior oxidative stability and long-term stability against lithium metal, thus facilitating operation in LiNi1/3Mn1/3CO1/3O2 (NMC111)/lithium metal cells at 20 °C and 60 °C, thereby clearly demonstrating the application potential of this class of materials

Ionic liquid plasticizers comprising solvating cations for lithium metal polymer batteries

Ternary solid polymer electrolytes (TSPEs) with ionic liquids (ILs) including alkyl-based ammonium cations and low coordinating anions suffer from the lack of Li+ ion coordination by the ILs compared to the immobile polymer backbone, in terms of Li+ ion transport. Thus, solvating ionic liquids (SILs) with an oligo(ethylene oxide) side chain attached onto the cation were prepared to improve the interaction between Li+ and the IL and accelerate Li+ transport in TSPEs. A variety of methods, such as pulsed field gradient nuclear magnetic resonance spectroscopy, Li metal plating/stripping and measurements of Sand's times were used to show that Li+ ion transference numbers increase with the oligo(ethylene oxide) side chain length in SIL-based TSPEs, which results in faster Li+ ion transport and translates into much slower lithium depletion at a given current, thereby delaying the onset of fast dendrite growth of lithium metal

Cation-Assisted Lithium-Ion Transport for High-Performance PEO-based Ternary Solid Polymer Electrolytes

N-alkyl-N-alkyl pyrrolidinium-based ionic liquids (ILs) are promising candidates as non-flammable plasticizers for lowering the operation temperature of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs), but they present limitations in terms of lithium-ion transport, such as a much lower lithium transference number. Thus, a pyrrolidinium cation was prepared with an oligo(ethylene oxide) substituent with seven repeating units. We show, by a combination of experimental characterizations and simulations, that the cation's solvating properties allow faster lithium-ion transport than alkyl-substituted analogues when incorporated in SPEs. This proceeds not only by accelerating the conduction modes of PEO, but also by enabling new conduction modes linked to the solvation of lithium by a single IL cation. This, combined with favorable interfacial properties versus lithium metal, leads to significantly improved performance on lithium-metal polymer batteries

Toward adequate control of internal interfaces utilizing nitrile-based electrolytes

Methods to control internal interfaces in lithium ion batteries often require sophisticated procedures to deposit coating layers or introduceinterphases, which are typically difficult to apply. This particularly holds for protection from parasitic reactions at the current collector,which reflects an internal interface for the electrode composite material and the electrolyte. In this work, electrolyte formulationsbased on aliphatic cyclic nitriles, cyclopentane-1-carbonitrile and cyclohexane-1-carbonitrile, are introduced that allow for successful suppressionof aluminum dissolution and control of internal interfaces under application-relevant conditions. Such nitrile-based electrolytesshow higher intrinsic oxidative and thermal stabilities as well as similar capacity retentions in lithium nickel–manganese–cobalt oxideLiNi3/5Mn1/5Co1/5O2 (NMC622)||graphite based full cells compared to the state-of-the-art organic carbonate-based electrolytes, even whenbis(trifluoro-methane)sulfonimide lithium salt is utilized. Moreover, the importance of relative permittivity, degree of ion dissociation, andviscosity of the applied electrolyte formulations for the protection of current collector interfaces is emphasized