Recycling spent LiFePO₄ batteries is crucial for mitigating resource shortages and lowering environmental pollution. Leaching lithium from the spent LiFePO₄ batteries using succinic acid-hydrogen peroxide system was investigated. The effects of succinic acid concentration, hydrogen peroxide volume fraction, solid mass to liquid volume ratio, leaching temperature and time on lithium leaching rate were examined. The leaching mechanism was further clarified through kinetic analysis and SEM. The results indicate that under the optimal leaching conditions of succinic acid of 0.8 mol/L, hydrogen peroxide of 2%, solid mass to liquid volume ratio of 4 mg/1 mL, leaching temperature of 80 ℃, and time of 40 min, the conditions, lithium leaching rate is more than 98%, while iron leaching rate is less than 2%. Kinetic analysis reveals that the leaching process is primarily diffusion-controlled. Overall, these findings demonstrate that the synergistic succinic acid-hydrogen peroxide system offers high efficiency and sustainability in LiFePO₄ leaching, providing a feasible route for the green recycling of spent LiFePO₄ batteries.

Germanium in lignite ash mainly exists in Ge—O—Si bonded state, vitreous encapsulated state and iron oxide adsorbed state. The traditional acid leaching method is difficult to destroy the structure of highly stable Ge—O—Si bond and dense encapsulated vitreous body, resulting in less than 50% germanium leaching rate and low resource recovery rate. Based on the comparison of three process routes of lignite ash direct acid leaching, roasting－acid leaching, alkali fusion activation－acid leaching and two leaching systems of sulfuric acid or hydrochloric acid, the process route of extracting germanium from lignite ash by high temperature alkali fusion pretreatment－acid leaching process was proposed and studied. The effects of alkali fusion temperature, mass ratio of material to alkali and alkali fusion holding time on the leaching rate of germanium in lignite ash were investigated, and the leaching effects of sulfuric acid and hydrochloric acid on alkali fusion activation products were compared. The results show that the leaching performance of germanium can be significantly improved by breaking the Ge—O—Si bond by alkali fusion and converting insoluble silicate into soluble sodium salt, and then the efficient leaching of germanium can be realized by conventional acid leaching. Under the conditions of alkali fusion temperature of 600 ℃, mass ratio of material to alkali of 1/1.8 and alkali fusion time of 1 h, the main spherical structure of lignite ash is destroyed, and the encapsulated substances in alkali fusion products are released. When hydrochloric acid or sulfuric acid leaching systems are used, the leaching rates of germanium are 86.37% and 93.98%, respectively. This technology can realize the efficient leaching of germanium in lignite ash, which can provide a new technical approach for the resource utilization of high-silicon germanium-containing secondary materials and the efficient recovery of strategic metal germanium.

In-situ uranium leaching was investigated using native acidophilic ferrous sulfate oxidizing bacillus (Acidithiobacillus ferrooxidans, L24f) and acidophilic sulfur oxidizing bacillus (Acidithiobacillus thiooxidans, L24s) from sandstone-type uranium ore. In combination with physicochemical parameter monitoring and characterization techniques such as SEM-EDS and XRD, the synergistic leaching mechanism was elucidated to determine the effectiveness of synergistic leaching and the optimal inoculation ratio. The results show that L24f and L24s strains have a significant synergistic uranium leaching effect, and the inoculation volume ratio of 1∶1 is the optimal ratio. Under this condition, the final uranium leaching rate of sandstone-type uranium ore is 86.5%, which is 7.5 percentage points higher than that of a single L24f pure bacteria system. The mixed bacterial consortium system can maintain the low pH environment of the system through complementary metabolic functions, effectively inhibit the formation of jarosite passivation layer, and significantly improve the leaching rate of uranium.

Uneven and discontinuous calcareous sandstone and mudstone interlayers are distributed in the mining area of Bayin Qinggeli uranium mine. In order to explore the influence of low-permeability interlayers on uranium leaching effect, a three-dimensional unstructured grid lithology model of ore-bearing aquifer was constructed based on borehole data in the test mining area, and the flow field and solute transport process of in-situ leaching uranium under different extraction-injection methods were simulated. By introducing a matrix calculation method based on the actual extraction-injection flow of group wells, the solute mass ratio and natural groundwater content were quantitatively compared and analyzed. The results show that compared with the original extraction-injection method, after the extraction-injection methods of SYC-1 and SYZ-1 wells are interchanged, the range of groundwater drawdown funnel is reduced, the capture ability of pumping wells to leaching solution is significantly improved, the mass ratio of extracted and injected solute is increased by 1.7 times, the natural groundwater content in pumping volume is reduced by 29.4%, the hydraulic connection between extraction-injection wells is stronger, and the leaching effect is better than that of the original extraction-injection method. Calcareous sandstone and mudstone interlayers significantly hinder the hydraulic connection between extraction-injection wells, resulting in significantly different leaching effects of different extraction-injection methods.

Zinc zeolite imidazole framework material (ZIF-8) is suitable for uranium adsorption due to its high specific surface area and abundant active sites. Aiming at the problems of long time and large consumption of organic solvents in the synthesis of ZIF-8 by traditional solvent method, ZIF-8 was rapidly synthesized by green and efficient mechanochemical method using zinc hydroxide and 2-methylimidazole as raw materials and used for uranium adsorption. The results show that the ZIF-8 prepared by mechanochemical method has good crystallinity, rhombic dodecahedron morphology, specific surface area of 1 642 m²/g, and rich surface defects and active sites on the surface. Under suitable conditions, the removal rate of uranium by ZIF-8 is more than 99.99%, the maximum adsorption capacity is 476 mg/g, and the adsorption can reach equilibrium within 20 min. The process is a single-layer chemical adsorption mechanism. The cost analysis results show that the synthesis efficiency of mechanochemical method is 16 times higher than that of traditional solvent method, and former's theoretical material cost per gram of uranium is only 3.5% of that of the latter. The mechanism analysis results show that the high specific surface area of the material and the synergistic effect of hydroxyl groups and imidazole nitrogen atoms are the key to the efficient adsorption of U(Ⅵ). ZIF-8 prepared by rapid mechanochemical method has good performance and has certain application potential in the field of uranium adsorption.

Aiming at the issues of prolonged leaching cycles and low efficiency in the existing heap leaching process at a uranium mine, an on-site industrial optimization heap leaching test was conducted on fine-grained ore. The optimal process conditions and key parameters of key stages, including ore crushing, wet granulation, and spray heap leaching, on uranium extraction were systematically investigated. The results demonstrate that the closed-circuit crushing and screening process effectively regulates the feed particle size to below 4 mm. Excellent pelletisation is achieved under the conditions of drum granulator speed of 30 r/min and ore feed rate of 40 t/h. Heap leaching tests confirm that this optimised process successfully reduces the uranium from 0.158% to 0.011 5%, achieving the uranium leaching rate of 92.72%, under the conditions of liquid volume to solid mass ratio of 4.86∶1, sulfuric acid consumption of 8.56%, and spray cycle of 78 d.

For treatment of uranium-containing wastewater, a co-culture system comprising Pseudomonas cepacia and anaerobic granular sludge (PC-AnGS) was constructed, and its performance and underlying mechanisms for removing of U(Ⅵ) was systematically investigated. The results show that the removal rate of U(Ⅵ) is as high as 94.2% under the optimal conditions of initial pH=7.0, PC-AnGS dosage of 2 g/L, contact time of 10 h and temperature of 35 ℃. The results of adsorption kinetics and isotherm analysis indicate that the adsorption process conforms to the pseudo-second-order kinetics and Langmuir isothermal adsorption model, and is dominated by monolayer chemical adsorption. The control test and SEM, FT-IR, XPS and other characterization results confirm that the PC-AnGS system uses the synergistic effect of the two components to adsorb and fix U(Ⅵ) mainly through the rich functional groups on the surface, and then partial mineralization and reduction. The research results can provide certain technical reference for the bioremediation of uranium-containing wastewater.

In response to the problems of limited adsorption capacity and susceptibility to interference from ions in the existing seawater uranium extraction hydrogel materials, a novel composite hydrogel adsorbent, chitosan/imidazole crosslinked polyamidoxime hydrogel (CS/PAO@IA) was developed. This material is based on chitosan as the three-dimensional network framework and imidazole-2-formaldehyde as the chemical crosslinking agent. Through hydrogen bond effects and Schiff base reactions, a flexible and strong three-dimensional network was constructed. The correctness of the synthesized material structure was verified by systematic characterization methods, and the microscopic morphology of the material surface and the composition and valence state changes of the elements on the surface after uranium adsorption were analyzed. The uranium adsorption performance and ion selectivity of the material were tested separately. The results show that the material has good adsorption selectivity for uranyl ions in the spiked seawater with uranium mass concentration of 3.3 mg/L, and the uranium adsorption capacity is up to 18.13 mg/g. This study can provide a new idea for the development of efficient, stable and multifunctional hydrogel materials for uranium extraction from seawater.

A P204-TOPO-sulfonated kerosene synergistic extraction-Fe(Ⅱ) reduction stripping system was constructed. The effects of extraction reaction time, phosphoric acid concentration, extraction temperature, amount of iron powder and stripping temperature were investigated, and the optimal process conditions were determined. The results show that the extraction-stripping of uranium conforms to the law of diffusion control-in-phase reaction. The apparent activation energy of the extraction reaction is 34.76 kJ/mol, and that of the stripping reaction is 40.289 kJ/mol. The system is controlled by both mass transfer and chemical reaction. The optimal extraction conditions are room temperature, extraction time of 6 min, phosphoric acid concentration of 3.5 mol/L, and V_O/V_A=1/5. The optimal stripping conditions are temperature of 323.15 K, stripping time of 10 min, phosphoric acid concentration of 5 mol/L, reduced iron powder amount of 10 times the theoretical amount, and V_O/V_A=5/1. Under the optimal conditions, the uranium extraction rate is 96% and the stripping rate is 81.3%.

The leaching of manganese from low-grade manganese carbonate ore by sulfuric acid without reducing agent was studied. The effects of key parameters such as mineral particle size, sulfuric acid concentration and liquid volume to solid mass ratio on the leaching rate of manganese were investigated by single factor test, and the cyclic leaching process was optimized. The results show that under the conditions of ore particle size －300 μm－+150 μm proportion ≥ 95%, sulfuric acid concentration of 5.5 mol/L, reaction temperature of 60 ℃, each cycle leaching time of 30 min, liquid volume to solid mass ratio of 4∶1, and 4 extraction cycles of leaching, the average leaching rate of manganese is 98.35%, and the mass concentration of manganese in the leaching solution is 101.62 g/L. The proportion of manganese and impurities in the leaching solution is coordinated, and the solution composition is equivalent to the solution composition obtained by the leaching of imported manganese carbonate ore, which can provide qualified feed solution for the next step of manganese deep processing.