A LA-ICP-MS sulphide calibration standard based on a chalcogenide glass

International audienceThe accurate measurement of trace element concentrations in natural sulphides by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been limited by the lack of matrix-matched calibration standards. The synthesis of a standard, IMER-1, by incorporating four minor and 34 trace elements into a chalcogenide glass matrix Ge28Sb12S60 is reported here. Chemical analysis by electron probe microanalysis (EPMA), LA-ICP-MS, solution ICP-MS, and inductively coupled plasma-optical emission spectroscopy (ICP-OES) confirmed the excellent homogeneity of major elements (1-σ relative standard deviation (RSD) <1% for S, Sb and Ge) and acceptable homogeneity of most trace elements (1-σ RSD <10%). The standard was validated by analysing trace-elements concentrations in three geological pyrite specimens using IMER-1 as the calibration standard and comparing the results to previously reported values also determined by LA-ICP-MS but using a different calibration standard, STDGL2b-2. The results suggest that IMER-1 may be an appropriate calibration standard for LA-ICP-MS analysis of trace elements in natural sulphides

A thermosyphon-driven hydrothermal flow-through cell for in situ and time-resolved neutron diffraction studies

A flow-through cell for hydrothermal phase transformation studies by in situ and time-resolved neutron diffraction has been designed and constructed. The cell has a large internal volume of 320 ml and can operate at temperatures up to 573 K under autogenous vapor pressures (ca 8.5 106 Pa). The fluid flow is driven by a thermosyphon, which is achieved by the proper design of temperature difference around the closed loop. The main body of the cell is made of stainless steel (316 type), but the sample compartment is constructed from non-scattering Ti–Zr alloy. The cell has been successfully commissioned on Australia’s new high-intensity powder diffractometer WOMBAT at the Australian Nuclear Science and Technology Organization, using two simple phase transformation reactions from KAlSi2O6 (leucite) to NaAlSi2O6H2O (analcime) and then back from NaAlSi2O6H2O to KAlSi2O6 as examples. The demonstration proved that the cell is an excellent tool for probing hydrothermal crystallization. By collecting diffraction data every 5 min, it was clearly seen that KAlSi2O6 was progressively transformed to NaAlSi2O6H2O in a sodium chloride solution, and the produced NaAlSi2O6H2O was progressively transformed back to KAlSi2O6 in a potassium carbonate solution

Formation of pyrite under hydrothermal conditions

Thesis (PhDMinerals&Materials)--University of South Australia, 2011.

Electronic environments in Ni3Pb2S2 (shandite) and its initial oxidation in air

Polycrystalline Ni3Pb2S2 (shandite) was synthesised as a non-porous ingot to enable representative surfaces prepared by fracture under UHV to be characterised by X-ray photoelectron spectroscopy (XPS) before and after exposure to air. For an unoxidised surface, the S 2p3/2 binding energy was found to be significantly lower than those reported previously for shandite itself and other sulfides having shandite structure, and consistent with the physical and chemical properties of the shandites. The core electron binding energies for the three constituent elements were in agreement with the formal oxidation state representation Ni03PbII2S−II2, analogous to that deduced previously for Ni3Sn2S2. Shandite surfaces were found to oxidise rapidly when initially exposed to air under ambient conditions, and concomitant with the formation of the Ni–O and Pb–O species, to restructure to NiS- and PbS-like surface phases having S core electron binding energies no higher than those for shandite.

Chalcopyrite Dissolution at 650 mV and 750 mV in the Presence of Pyrite

The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD). To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at 75 °C, pH 1.0, in the presence of quartz (as an inert mineral) and pyrite. The presence of pyrite increased the chalcopyrite dissolution rate by more than five times at Eh of 650 mV (SHE) (Cu recovery 2.5 cf. 12% over 132 days) due to galvanic interaction between chalcopyrite and pyrite. Dissolution of Cu and Fe was stoichiometric and no pyrite dissolved. Although the chalcopyrite dissolution rate at 750 mV (SHE) was approximately four-fold greater (Cu recovery of 45% within 132 days) as compared to at 650 mV in the presence of pyrite, the galvanic interaction between chalcopyrite and pyrite was negligible. Approximately all of the sulfur from the leached chalcopyrite was converted to S0 at 750 mV, regardless of the presence of pyrite. At this Eh approximately 60% of the sulfur associated with pyrite dissolution was oxidised to S0 and the remaining 40% was released in soluble forms, e.g., SO42−

Kinetics and Mechanisms of Chalcopyrite Dissolution at Controlled Redox Potential of 750 mV in Sulfuric Acid Solution

To better understand chalcopyrite leach mechanisms and kinetics, for improved Cu extraction during hydrometallurgical processing, chalcopyrite leaching has been conducted at solution redox potential 750 mV, 35–75 °C, and pH 1.0 with and without aqueous iron addition, and pH 1.5 and 2.0 without aqueous iron addition. The activation energy (Ea) values derived indicate chalcopyrite dissolution is initially surface chemical reaction controlled, which is associated with the activities of Fe3+ and H+ with reaction orders of 0.12 and −0.28, respectively. A surface diffusion controlled mechanism is proposed for the later leaching stage with correspondingly low Ea values. Surface analyses indicate surface products (predominantly Sn2− and S0) did not inhibit chalcopyrite dissolution, consistent with the increased surface area normalised leach rate during the later stage. The addition of aqueous iron plays an important role in accelerating Cu leaching rates, especially at lower temperature, primarily by reducing the length of time of the initial surface chemical reaction controlled stage

Influence of Co:Fe:Ni ratio on cobalt Pentlandite's electronic structure and surface speciation

X-ray photoemission spectroscopy (XPS) was used to investigate the electronic structure and oxidation state of transition metals in synthetic cobalt pentlandites (Fe,Co,Ni)9S8 with measured stoichiometries of Fe4.85Ni4.64S8, Co0.13Fe4.68Ni4.71S8, Co2.73Fe3.18Ni3.16S8, Co5.80Fe1.63Ni1.59S8 and Co8.70S8. The addition of cobalt was found to decrease the bond length and hence decrease the unit cell dimensions of the cobalt pentlandite crystal structure by up to 0.18 Å. High resolution XPS S 2p spectra show increases in the binding energies of bulk 5-coordinated (162.1 eV) and surface 3-coordinated (160.9 eV) sulfur (≈0.2 eV) with increasing Co concentration and decreasing bond lengths. As the Co concentration increases, variation in metal site occupation decreases, resulting in smaller S 2p FWHMs due to a dominant single Co-S state rather than mixed Fe-S, Ni-S and Co-S states with similar binding energies. The S 2p high binding energy tail, previously identified as a S 3p- Fe 3d ligand to metal transfer in Fe chalcogenides, shows a marked decrease in intensity as the concentration of Co increases, that is attributed to a decreased probability of ligand-to-metal charge transfer as the eg orbitals are filled. The transition metal XPS 2p spectra were modelled using CTM4XAS to investigate metal site occupation and ligand-to-metal charge transfer. Fe, Co, and Ni were all best simulated using a tetrahedral symmetry and 2+ oxidation state, their 2p3/2 and 2p1/2 peaks occurred at 706.9 and 719.9 eV, 778.2 and 793.1 eV, and 852.8 and 870.0 eV, respectively. A negative charge transfer energy confirms the high binding energy tail results from S3p-Fe3d ligand to metal charge transfer. This increased understanding of the pentlandite electronic structure will provide a basis for the refinement of mineral processing techniques and allow for a reduced environmental impact from limited efficiency

Effective Use of Sugarcane-Bagasse-Derived KOH-Activated Biochar for Remediating Norfloxacin-Contaminated Water

Bagasse-derived biochar (SCB750) was prepared at 750 °C using Chinese sugarcane bagasse as a carbon source and then modified with KOH for the removal of the antibiotic norfloxacin (NOR) from aqueous solutions. 3K-SCB750, prepared using a solid-to-liquid mass ratio of bagasse:KOH = 1:3, was found to have the best adsorption performance for NOR. Under the conditions of pH 5, 25 °C, 2.4 g L−1 adsorbent, and 300 mg L−1 NOR, its adsorption of NOR reached equilibrium (97.5% removal) after 60 min. The adsorption behaviours were in line with the quasi-second-order kinetic and Langmuir isotherm models, respectively. The maximum theoretical adsorption capacity reached up to 157.4 mg·g−1 at 40 °C. The thermodynamic parameters showed that the adsorption of NOR onto 3K-SCB750 was a spontaneous, endothermic, and physical process. In addition, Brunauer−Emmett−Teller analysis (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy were conducted to investigate the structural and adsorption properties of 3K-SCB750. Fourier transform infrared spectroscopy (FTIR) was also applied to understand the mechanism of adsorption of NOR onto 3K-SCB750. All of the results indicated that 3K-SCB750 had a large specific surface area of 1038.8 m2·g−1, an average pore size of 1.9 nm, and hierarchical structures with random pores and cracks for efficient removal of NOR. NOR adsorption mechanisms on 3K-SCB750 were related to the pore-filling effect and electrostatic attraction. Therefore, 3K-SCB750 biochar may be used as a promising adsorbent of antibiotics in wastewaters

Mechanistic insight into the non-hydrolytic sol–gel process of tellurite glass films to attain a high transmission

The development of amorphous films with a wide transmission window and high refractive index is of growing significance due to the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films. High-index TeO2-based glass films made via the sol-gel process are particularly suitable as their low temperature preparation process promises high compatibility with a large variety of nanoparticles and substrates that suffer from low thermal stability. However, due to the lack of in-depth understanding of the mechanisms of the formation of undesired metallic-Te (highly absorbing species) in the films, the preparation of high-transmission TeO2-based sol-gel films has been severely hampered. Here, by gaining insight into the mechanistic chemistry of metallic-Te formation at different stages during the non-hydrolytic sol-gel process, we identify the chemical route to prevent the generation of metallic-Te in a TeO2-based film. The as-prepared TeO2-based film exhibits a high transmission that is close to the theoretical limit. This opens up a new avenue for advancing the performance of hybrid optoelectronic films via incorporating a large variety of unique nanoparticles. © 2020 The Royal Society of Chemistry

Sawdust-Derived Activated Carbon with Hierarchical Pores for High-Performance Symmetric Supercapacitors

The recyclable utilization of waste biomass is increasingly important for the development of a sustainable society. Here, the sawdust-derived activated carbon (SD-AC) has been prepared via a convenient H3PO4-based activation method and further trialed as an electrode for use as a high-performance symmetric supercapacitor. The as-prepared SD-AC possesses a hierarchically porous structure with micropores (0.55 nm) and mesopores (2.58 nm), accounting for its high specific surface area of 621 m2 g&minus;1, with a pore volume of 0.35 cm3 g&minus;1. Such a hierarchically porous structure can offer a favorable pathway for fast ion penetration and transportation, enhancing its electrochemical performance. As a result, the SD-AC electrode exhibits a maximum specific capacitance of up to 244.1 F g&minus;1 at 1.0 A g&minus;1, a high rate capability (129.06 F g&minus;1 at 20 A g&minus;1), and an excellent cycling performance, with 87% retention over 10,000 cycles at 10 A g&minus;1. Of particular note is that the SD-AC-based symmetric supercapacitor achieves a maximum energy density of 19.9 Wh kg&minus;1 at the power density of 650 W kg&minus;1, with a long-term cycle lifespan. This work showcases the recyclable utilization of waste biomass for the preparation of high-value activated carbon for efficient energy storage