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ABSTRACTThis study introduces a novel synergistic leaching process for ferronickel powder and high nickel matte, enabling the atmospheric leaching and the hematite precipitation process to mitigate carbon emissions associated with the treatment of Ni laterite. The results indicated that following seven cycles of synergistic leaching, the Ni2+concentration in the solution exceeded 80 g/L, compared with the 15 cycles required for non-synergistic leaching. Optimal leaching conditions included a temperature range of 80°C−95°C, a stirring speed of 300 rpm, an initial H2SO4concentration of 100 g/L, and a reaction time of 8 h, maintaining a final pH of 3.5−4.5, and an excess of ferronickel powder. Leaching successfully extracted Ni and Fe from ferronickel powder, with Cu2+in the solution being reduced and enriched in the leaching residue. For the hematite precipitation process, optimal conditions involved a temperature of 200°C, a stirring speed of 500 rpm, a reaction time of 3 h, and an addition of 20 g/L of high Ni matte. The Fe removal efficiency exceeded 86%, resulting in hematite products that contained 61.15% Fe, 0.60% Ni and 1.48% S. These products can be commercially utilised, either sold to cement plants or utilized as raw materials for ironmaking.

ABSTRACTSolid–liquid equilibrium solubility of magnesium sulphate (MgSO4) is essential for designing and optimising the removal and recovery of magnesium (Mg) from standard zinc (Zn) hydrometallurgy systems via freeze crystallization. In this study, the solubility data of MgSO4in ternary system MgSO4-H2SO4-H2O and quaternary system MgSO4-ZnSO4-H2SO4-H2O were determined in different zinc sulphate (ZnSO4) concentrations and sulphuric acid (H2SO4) concentrations through the isothermal equilibrium method within the temperature range from 263.15–293.15 K. The results indicated that the solubility of MgSO4decreased with decreasing temperature and increasing concentrations of H2SO4and ZnSO4. Furthermore, the modified Apelblat equation was applied to correlate the experimental solubility data, yielding results consistent with the experimental findings. Furthermore, X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy SEM-EDS analysis results indicated that the main phases of the equilibrium solid consist of mixed crystallization products of Zn sulphate heptahydrate (MgSO4·7H2O) and Mg sulphate heptahydrate (ZnSO4·7H2O). The microstructure of the equilibrium solid was affected by the sulphate concentration.

ABSTRACTThe separation of Zn and Fe, K, and Na ions remains a challenge in the recovery process of Zn-containing secondary resources. A hydrothermal process without adding neutralizer was developed to remove Fe, K, and Na ions from the leaching solution of zinc oxide dust. Results showed that Fe and K ions were synchronously eliminated, yielding low-contaminant jarosite products with excellent crystallinity and rosette-like morphology under the following conditions: gas pressure = 1.6 × 106Pa, agitation speed = 600 rpm, reaction time = 3 h, and temperature ranges at 368.15 K−423.15 K. The removal efficiency of Fe and K ions reached 99.8% and 97.7%, respectively. The obtained low-contaminant jarosite contained Fe 31.09%−31.98%, Zn 1.05%−1.24%, S 12.33%−12.71%, K 6.12%−6.46%, and Na 0.44%−0.87%. Additionally, the Na ions in the leaching solution precipitated can also along with Fe ions, forming low-contaminant natrojarosite products containing Fe 31.36%−35.66%, Zn 1.60%−1.88%, S 10.66%−12.56%, Na 2.85%−3.26% and K 0.74%−0.85%. The optimal hydrothermal temperature for the removal of Fe, K, and Na ions while minimising energy consumption was determined to be 393.15 K. The low-contaminant jarosite and natrojarosite products possess potential applications in the field of yellow pigments, building materials, iron and arsenic removal, adsorption materials, catalytic materials, etc.

Examination of the original types and abundant topotype specimens from the Emanuel Formation (Early Ordovician) and the correlative subsurface Nambeet Formation of the Canning Basin in Western Australia confirms a septimembrate species apparatus for Protoprioniodus simplicissimus, the type species of the genus. Species of Protoprioniodusare characterized by having a seximembrate or septimembrate protoramiform–protopectiniform apparatus with a distinctive basal surface well-developed between the basal margin and the basal flange in the constituent elements. The generic concept of Protoprioniodusis re-defined based on its type species and reassessment of all the species previously assigned to this genus. Protoprioniodusmight be evolved in late Tremadocian (Early Ordovician) possibly from an unknown species of basal Oistodus. With five species confirmatively assigned to, Protoprioniodusis recognized as a morphologically distinctive conodont clade within family Oistodontidae and biostratigraphically useful for correlation of the uppermost Tremadocian to Middle Ordovician rocks. Protoprioniodus simplicissimuswas cosmopolitan while other species seem variably restricted in palaeogeographic distribution.