Tao Jiang

Thiosulfate leaching is considered a promising alternative to cyanidation for gold extraction because it can be achieved at a low cost. However, existing leaching systems struggle to balance leaching efficiency with thiosulfate consumption. Herein, a novel synergistic Cu-CH₃NH₂-NH₃ leaching system was proposed, balancing thiosulfate consumption and gold leaching efficiency through a mixed-ligand strategy. Thermodynamic analysis revealed that the steric hindrance and electron-donating effects of methylamine effectively block the oxidative decomposition pathway of thiosulfate by Cu(II), significantly reducing thiosulfate consumption. However, this also reduced the dissolution rate of gold. By introducing ammonia to adjust the Cu(II) coordination environment, the system achieved a gold leaching rate of 88.6% with a thiosulfate consumption of 14.2 kg/t-ore, significantly outperforming the traditional Cu-NH₃ system. In this system, the gold leaching process mainly is catalyzed by the mixed-ligand complex Cu(NH₃)_x(CH₃NH₂)_4−x²⁺. Within the coordination sphere, the methyl group of CH₃NH₂ inhibits the axial attack of S₂O₃²⁻ on Cu(II) via electron-donating and steric hindrance effects, thereby blocking the redox pathway of S₂O₃²⁻; simultaneously, NH₃ provides active sites to promote the gold oxidation. This study provides a vital theoretical basis and technical support for developing green, low-cost, and high-efficiency gold leaching processes.

Solar-driven selective biomass conversion presents a promising pathway for green hydrogen production. However, conventional approaches are hindered by solar intermittency and the challenge of balancing conversion efficiency with over-oxidation. Here, we design photon-coupled-proton buffers (PCPBs) based on heteropolyacids, integrating photosensitivity, proton storage, and redox modulation. Under illumination, the PCPB material H₅SiVMo₂W₉O₄₀·10H₂O catalyzes glucose oxidation to formic acid while capturing protons via self-reduction to heteropolyblue. This proton-rich species can be electrolyzed at ultralow potentials (0.58/0.62 V vs. RHE at 50/100 mA cm⁻²) for on-site H₂ production alongside PCPB self-regeneration. The system achieves 56.05% formic acid conversion from 0.1 M glucose and sustains H₂ evolution (≥91 mL H₂ per mmol glucose) over 14 cycles. Notably, the PCPB prototype delivers 82.44 g H₂ per kg of glucose in aqueous solution—23.78% higher than the theoretical H₂ output from aerobic glucose-to-formic acid conversion—surpassing conventional biomass photo-reforming. Furthermore, the PCPB is also effective for fructose, maltose, starch, and cellulose. Time-resolved spectroscopy and density functional theory (DFT) calculations reveal that Mo–O_b–W sites enable photon-coupled-proton transfer under illumination, suppressing over-oxidation through dynamic proton buffering. By reshaping the photocatalytic biomass valorization pathway, this approach provides a proof-of-concept for stable, transportable, and energy-efficient solar-H₂ production.

Zinc ferrite can be found in zinc-bearing dust in ironmaking and steelmaking. It is difficult to be recovered due to its stable properties. The magnetization roasting and ammonia leaching method were used to separate iron and zinc from zinc ferrite in this study. Thermodynamic analysis showed that the key to the selective reduction of zinc ferrite to zinc oxide and ferric oxide is to control the appropriate temperature and atmosphere. The influences of the selective reduction roasting process of zinc ferrite on the conversion rate, phase change, and microevolution behavior were investigated. The microstructure analysis showed that the distribution area of iron was mainly gray, and the distribution area of zinc was mainly white grid lines. The zinc content in the white area was higher than that in the gray area. With the increase in temperature and P_CO, the white area expanded and the migration of zinc and iron was accelerated, but the iron in the white area still existed. The ammonia leaching of the magnetization-roasted product showed that a zinc leaching rate of 78.12% was achieved under the following conditions: the roasting atmosphere of P_CO/P_(CO+CO2) = 25%, the roasting temperature of 750 °C, roasting duration for 45 min, n(NH₃-H₂O):n(NH₄Cl) = 1:1, the solid–liquid ratio of 40 g/L, leachate concentration of 6 mol/L, leaching duration of 90 min, the leaching temperature of 50 °C, and the stirring rate of 200 rpm.

Zinc-containing dust can be found in ironmaking and steelmaking, and it is an important secondary resource of zinc. Zinc-containing dust from an electric furnace was used as a raw material to study the phase transformation behavior of the dust using a calcification roasting process and the zinc–iron separation behavior by using ammonia leaching. The zinc-bearing dust was mixed with CaO and roasted to transform the zinc ferrite into zinc oxide. The results showed that increasing the calcium oxide to dust ratio could promote the conversion of zinc ferrite to zinc oxide. When the calcium oxide ratio reached 60%, the peak of zinc ferrite in the calcined-roasted product in the zinc-containing dust basically disappeared. As the temperature increased, the zinc oxide grains increased but were still smaller than 10 µm. The calcined-roasted product was crushed and ground, and the zinc was leached by ammonia. A zinc–iron recovery rate of 86.12% was achieved by the ammonia leaching. The leachate could be used for zinc extraction by electrolysis. The leaching residue was mainly calcium ferrate, which could be used in sintering production. The proposed process may achieve on-site recovery of zinc-containing dust in steel-making plants.

May Concentrate Iron ore, as a refractory iron concentrate, deteriorates the permeability of the sintered layer during the sintering process due to its fine particle size and poor granulating performance. Therefore, it cannot be widely used in iron ore sintering. In this study, the strengthening granulation of May Concentrate Iron ore using pre-pelletizing to expand its utilization ratio was proposed. The experiments of conventional granulation, pre-pelletizing granulation and sinter pot test were carried out. Increasing May Concentrate Iron ore (a refractory iron concentrate) proportion was detrimental to conventional granulation, reducing the quasi-particle particle size and strength. May Concentrate Iron granulating and sintering performances were improved by pre-pelletizing. The quasi-particle average size at 36% May Concentrate Iron proportion jumped to 4.92 mm of pre-pelletizing granulation from 3.22 mm of conventional granulation. Meanwhile, the permeability index rose to 0.33 from 0.11, while the falling and drying pulverization ratio fell to 7.05% and 6.11% from 22.59% and 15.88%, respectively. The consolidation mode of matrix materials was liquid phase consolidation, while that of May Concentrate Iron pellets was solid phase consolidation, forming the structure of the pellets embedded in the matrix materials. Furthermore, the partial alkalinity of the matrix materials was increased because of the separation of May Concentrate Iron, generating a large amount of acicular calcium ferrite with better consolidation strength than conventional granulation sintering.

In this study, the manganese (Mn) was doped in the MnFe₂O₄ crystal by the solid-phase synthesis method. Under the optimum conditions (pH = 3), the max removal rate and adsorption quantity of Cr(VI) on MnFe₂O₄ adsorbent obtain under pH = 3 were 92.54% and 5.813 mg/g, respectively. The DFT calculation results indicated that the adsorption energy (E_ads) between HCrO₄⁻ and MnFe₂O₄ is −215.2 KJ/mol. The Cr(VI) is mainly adsorbed on the Mn atoms via chemical bonds in the form of HCrO₄⁻. The adsorption of Mn on the MnFe₂O₄ surface belonged to chemisorption and conformed to the Pseudo-second-order equation. The mechanism investigation indicated that the Mn in MnFe₂O₄ has an excellent enhancement effect on the Cr(VI) removal process. The roles of Mn in the Cr(VI) removal process included two parts, providing adsorbing sites and being reductant. Firstly, the Cr(VI) is adsorbed onto the MnFe₂O₄ via chemisorption. The Mn in MnFe₂O₄ can form ionic bonds with the O atoms of HCrO₄⁻/CrO₄²⁻, thus providing the firm adsorbing sites for the Cr(VI). Subsequently, the dissolved Mn(II) can reduce Cr(VI) to Cr(III). The disproportionation of oxidized Mn(III) produced Mn(II), causing Mn(II) to continue to participate in the Cr(VI) reduction. Finally, the reduced Cr(III) is deposited on the MnFe₂O₄ surface in the form of Cr(OH)₃ colloids, which can be separated by magnetic separation.