Probing the Effect of Water Recycling on Flotation through Anion Spiking Using a Low-Grade Cu–Ni–PGM Ore: The Effect of NO3−, SO42− and S2O32−

Water scarcity necessitates the recycling of process water within mineral processing practices. This may however come with its disadvantages for unit operations such as froth flotation as this process is water intensive and sensitive to water chemistry. It is therefore important to monitor the water chemistry of the recycle stream of process water and any other water source to flotation. Monitoring the concentrations of the anions in recycled process water is therefore important to consider as these are speculated to impact flotation performance. Batch flotation tests were conducted using synthetically prepared plant water (3 SPW) with a TDS of 3069 mg/L as the baseline experiment. 3 SPW contained 528 mg/LNO3− and 720 mg/L SO42−, other anions and cations, and no S2O32−. Upon spiking 3 SPW with selected anions, viz, NO3−, SO42− and S2O32−, it was noted that NO3− and SO42− exhibited threshold concentrations while S2O32− did not show a threshold concentration for both copper and nickel grade. Spiking 3 SPW with 352 mg/L more of NO3− to a total 880 mg/L NO3− concentration resulted in the highest copper and nickel grade compared to 3 SPW while increasing the S2O32− from 60 to 78 mg/L increased nickel and copper grade. 720 to 1200 mg/L SO42− and 528 to 880 mg/L NO3− were deemed the concentration boundaries within which lies the threshold concentration above which flotation performance declines with respect to metal grades, while for S2O32− the threshold concentration lies outside the range considered for this study. Anion distribution between the pulp and the froth did not seem to impact the recovery of copper or nickel. Notably, the correlation between the concentrate grades and anion distribution between the froth and the pulp seemed to be ion dependent.

Hydrotalcites with heterogeneous anion distributions: a first approach to producing new materials to be used as vehicles for the successive delivery of compounds

ABSTRACTHydrotalcites with heterogeneous distributions of anions between their layers were synthesized. Some synthesis parameters were studied to verify their influence on the anionic segregation properties of the hydrotalcites. The nature of the divalent cation and the crystallization method were most relevant. Zinc, in contrast to magnesium, assisted in discriminating carbonates and attracting nitrates to form hydrotalcites with heterogeneous distributions using microwave irradiation. Furthermore, the identification of this kind of hydrotalcite could be easily verified by determining the presence of a double reflection in the 003 X-ray diffraction (XRD) maximum, which definitively characterized a heterogeneous anion distribution. Finally, the reason as to why in some cases the hydrotalcite presented two reflections in the 003 XRD peak was elucidated.

Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing of Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites

Mixed anion compounds in the Fm-3m vacancy ordered perovskite structure were synthesised and characterised experimentally and computationally with a focus on compounds where A = Cs+. Pure anion Cs₂SnX₆ compounds were formed with X = Cl, Br and I using a room temperature solution phase method. Mixed anion compounds were formed as solid solutions of Cs₂SnCl₆ and Cs₂SnBr₆ and a second series from Cs₂SnBr₆ and Cs₂SnI₆. Single phase structures formed across the entirety of both composition series, with no evidence of long range anion ordering observed by diffraction. A distortion of the cubic A2BX6 structure was identified in which the spacing of the BX6 octahedra changes to accommodate the A site cation without reduction of overall symmetry. Optical band gap values varied with anion composition between 4.89 eV in Cs₂SnCl₆to 1.35 eV in Cs₂SnI₆, but proved highly non-linear with changes in composition. In mixed halide compounds it was found that lower energy optical transitions appeared that were not present in the pure halide compounds, and this could be attributed to lowering of the local symmetry within the tin halide octahedra. The electronic structure was characterised by photoemission spectroscopy, and Raman spectroscopy revealed vibrational modes in the mixed halide compounds that could be assigned to particular mixed halide octahedra. This analysis was used to determine the distribution of octahedra types in mixed anion compounds, which was found to be consistent with a near-random distribution of halide anions throughout the structure, although some deviations from random halide distribution were noted in mixed iodide-bromide compounds, where the larger iodide anions preferentially adopted trans configurations.

Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing of Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites

Mixed anion compounds in the Fm-3m vacancy ordered perovskite structure were synthesised and characterised experimentally and computationally with a focus on compounds where A = Cs+. Pure anion Cs₂SnX₆ compounds were formed with X = Cl, Br and I using a room temperature solution phase method. Mixed anion compounds were formed as solid solutions of Cs₂SnCl₆ and Cs₂SnBr₆ and a second series from Cs₂SnBr₆ and Cs₂SnI₆. Single phase structures formed across the entirety of both composition series, with no evidence of long range anion ordering observed by diffraction. A distortion of the cubic A2BX6 structure was identified in which the spacing of the BX6 octahedra changes to accommodate the A site cation without reduction of overall symmetry. Optical band gap values varied with anion composition between 4.89 eV in Cs₂SnCl₆to 1.35 eV in Cs₂SnI₆, but proved highly non-linear with changes in composition. In mixed halide compounds it was found that lower energy optical transitions appeared that were not present in the pure halide compounds, and this could be attributed to lowering of the local symmetry within the tin halide octahedra. The electronic structure was characterised by photoemission spectroscopy, and Raman spectroscopy revealed vibrational modes in the mixed halide compounds that could be assigned to particular mixed halide octahedra. This analysis was used to determine the distribution of octahedra types in mixed anion compounds, which was found to be consistent with a near-random distribution of halide anions throughout the structure, although some deviations from random halide distribution were noted in mixed iodide-bromide compounds, where the larger iodide anions preferentially adopted trans configurations.

A redox-generated biomimetic membrane potential across polypyrrole films

An artificial membrane potential was generated through redox-regulating anion distribution on the two sides of a polypyrrole film.

The lanthanide hydride oxides SmHO and HoHO

Metal hydride oxides are an interesting class of compounds with potential for hydride ion conduction and as host materials for luminescence. SmHO and HoHO were prepared from mixtures of the sesquioxides Ln2O3 and the hydrides LnH2+x at 1173 K as gray powders (Ln=Sm, Ho). They crystallize in a fluorite type crystal structure with disordered anion distribution (Fm3̅m; SmHO: a=5.46953(6) Å, V=163.625(5) Å3; HoHO: a=5.27782(3) Å, V=147.016(2) Å3, based on powder X-ray diffraction) and show stability towards air. Lanthanide-oxygen and -hydrogen distances are 2.36838(3) Å in SmHO and 2.28536(1) Å in HoHO and comparable to those in binary lanthanide oxides and hydrides. Elemental analyses confirm the composition LnHO. Quantum-mechanical calculations show a negative enthalpy for the reaction RE2O3+REH3→3 REHO for all lanthanides and Y, with increasing values for decreasing ionic radii.

Express-Method for the Study of Electrolyte Anion Profiles in the Bulk of Dense Anodic Alumina Films

ABSTRACTThe procedure proposed is the express method for the study of anion distribution profiles in the anodic aluminum oxide film. The method consists in measuring the variation of the steady-state electrode potential during the oxide etching. It allows the influence of the initial aluminum composition, the electrolyte composition, anodization regimes, etc. on the characteristics of dense anodic alumina films to be studied. The method developed can be used to study a chemical evolution in anodic alumina formed to correlate with modelling and simulations across materials science disciplines.