Transactions of Nonferrous Metals Society of China (中国有色金属学报)•2026•DOI: 10.1016/S1003-6326(26)67067-7
Conventional ammonium sulfate leaching of ionic rare earth ores generates 4–6 t of ammonia-nitrogen wastewater per ton of rare earth and drives mining-area soil pH to 3.5–4.0, creating an acute environmental compliance risk. This study evaluates a low-ammonium synergistic lixiviant comprising 0.020 mol/L (NH4)2SO4 and 0.010 mol/L acetic acid (HAc) at pH 4–5, 30 °C, and 1 h contact time. Comparative leaching experiments establish a rare earth element (REE) leaching efficiency of 88.92%, a 13.36% absolute increase over single 0.020 mol/L (NH4)2SO4 leaching. To achieve the same ~90% efficiency benchmark, the conventional single-salt system requires 0.030 mol/L (NH4)2SO4; the synergistic system therefore reduces ammonium consumption by 33.3%. Surface characterization indicates a dual mechanism: H+ attenuates electrostatic interactions between RE3+ and silicate surfaces, enhancing NH4+–RE3+ exchange, while CH3COO− forms soluble RE3+/Al3+ complexes that prevent Al(OH)3 passivation and sustain surface reactivity. The protocol offers a directly deployable route to cut reagent cost and ammonia-nitrogen load without sacrificing recovery, addressing the principal bottleneck restraining sustainable ionic rare earth ore exploitation under China's dual-carbon and rare earth total-amount control policies.
Transactions of Nonferrous Metals Society of China (中国有色金属学报)•2025•DOI: 10.1016/S1003-6326(25)67033-6
The phase composition at the slag−iron interface and the distribution behavior of titanium, vanadium, chromium and silicon between hot metal and Ti-bearing electric furnace slag were thoroughly explored. The basicity range for the anosovite phase region was defined by using a phase diagram and a minimum smelting temperature was set at 1540 °C. Thermodynamic calculations demonstrate that the activities of TiO2 and SiO2 in the slag decrease with increasing basicity, while those of V2O3 and Cr2O3 increase. Similarly, the activities of [Ti] and [Si] in the molten metal decrease, while those of [V] and [Cr] rise with increasing basicity. As basicity increases, the distribution ratios, LTi and LSi decrease, whereas LV and LCr increase. Significantly, the recovery efficiencies of vanadium and titanium are improved with higher basicity. The primary phases identified in the slag include anosovite, diopside, and titanium spinel. However, when the basicity exceeds 0.8, the formation of the perovskite phase becomes less favorable, suggesting that basicity should be maintained at or below 0.8.
Journal of Central South University•2025•DOI: 10.1007/s11771-025-6071-7
Mechanical activation (MA) is a significant pretreatment technique for enhancing the dissolution of mineral; however, its promotion effect on the role of pyrite during chalcopyrite bioleaching has not been elucidated up to now. In this study, the effect of MA on the role of pyrite on chalcopyrite bioleaching mediated by Acidithiobacillus ferroxidans was investigated by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, and electrochemical measurement. The results showed MA could significantly reduce the minerals particle size, and increase the specific surface area and surface energy of minerals. For example, the d50 of chalcopyrite reduced from 13.40 to 0.31 μm after MA. The copper extraction of mixed MA-chalcopyrite and MA-pyrite system was 63.4%, which exhibited a 51.8% enhancement compared to the non-activated mixed system. Electrochemical experiments identified that the strengthening effect of pyrite on chalcopyrite dissolution was negligible before MA. After MA, the dissolution mechanism of chalcopyrite was not changed, and pyrite could not only provide additional oxidants (acids and iron) but also act as the cathode in the galvanic couple. In this case, the bioleaching of chalcopyrite was accelerated. Therefore, a model of the promotion effect of mechanical activation on the role of pyrite on chalcopyrite bioleaching was proposed.