In the production and processing of NdFeB,more than 30% of rare earth metals will be transferred to the waste, resulting in NdFeB waste can not be effectively used. With the rapid development of new energy automobile industry,the green recycling of NdfeB waste has become a research hotspot in this field. The current research status of hydrometallurgy for recycling NdFeB waste at home and abroad, including acid leaching,precipitation, solvent extraction, alkali decomposition, ionic liquid recovery, hydrolysis and microbial decomposition, are reviewed. At the same time, the technical difficulties facing the current research are pointed out. Finally, the main research direction of NdFeB waste recycling in the future is put forward, which provides valuable reference for the secondary utilization of rare earth resources.

The process of synergistic leaching of lithium from waste lithium iron phosphate (LFP) and lithium cobalt oxide (LCO) battery cathode materials was studied, and the feasibility was analyzed by thermodynamics. The influence of various factors on synergistic leaching was investigated,and the leaching slag was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that LFP and LCO can synergistically leach lithium in an acidic system without adding any oxidant or reducing agent. The leaching rates of Li, Co, Fe and P in the cathode materials of waste batteries are 99.99%, 99.99%, 48.00% and 43.77%, respectively, under the optimal leaching conditions of sulfuric acid concentration of 0.7 mol/L, leaching temperature of 40 ℃, leaching time of 60 min, n(LCO)∶ n(LFP)=0.5 and liquid volume to solid mass ratio of 10 mL/1 g. The method can realize the purpose of recovering valuable metals from complex battery cathode materials under low acid conditions, and has certain popularization and application value.

In the process of recovering rare earth from NdFeB waste and polishing powder waste, there are problems such as large reagent consumption and high processing cost. In view of the above problems, using the reducibility of the iron in the NdFeB waste, a combined process was studied to recover rare earth from two kinds of waste. The results show that when NdFeB waste is dissolved with 6 mol/L hydrochloric acid and oxalic acid 1.2 times the mass of rare earth is added into the acid solution, the iron precipitation rate is 7.87%, and the rare earth precipitation rate can reach 96.51%. Adding 6 mol/L hydrochloric acid to the precipitated liquid is used to reduce and leach rare earth from the polishing powder waste. Under the conditions of solid mass to liquid volume ratio of 3 g/6 mL between the polishing powder waste and the precipitated liquid, the product ratio of hydrochloric acid to the precipitated liquid of 7/6, reaction temperature of 60 ℃, and reaction time of 30 min, the average leaching rate of rare earth in the polishing powder waste can reach 82.41%. The dissolved rare earth is precipitated by oxalic acid and calcined, and the total amount of rare earth oxides obtained is 98.04%. The process can realize the joint recovery of rare earth in the two kinds of waste, reduce the cost of rare earth waste treatment,and has a certain popularization and application value.

In view of the comprehensive development and utilization of rare earth as a strategic resource and its co-existing fluorine resources, in light of the urgent demand of Bayan Obo characteristic industries for high-abundance light rare earth and functional fluoride, the acid-base medium circulation-induced crystallization technology was developed with low-concentration fluorine-containing waste acid commonly found in rare earth smelting, rare earth metal electrolysis and other industries as the research object. Based on the principle of reaction kinetics and template effect, a microscopic model of induced crystalline rare earth fluoride was designed. The influence of temperature, concentration, instantaneous relative material quantity, acidity and other technological conditions on the synthesis of crystalline rare earth fluoride was investigated, and the crystallization, combination and substitution mechanisms of fluorine, inducer and rare earth were revealed. The key scientific problem of colloidal precipitation of rare earth fluoride synthesized in liquid phase is solved. The entire set of technologies can realize the high-value utilization of co-associated fluorine resources, ensure that co-associated fluorine resources as an important supplement of strategic mineral resources fluorite, and have significant economic and social benefits and broad application prospects.

A new ionic liquid loaded resin with high selectivity for phosphate ions was synthesized and used to enrich phosphoric acid in wet process phosphoric acid. The effects of phosphoric acid mass concentration, adsorption time and temperature on phosphoric acid adsorption were investigated. The results show that the adsorption capacity of phosphoric acid can be increased to 307 mg/g under optimized adsorption conditions. The resin can effectively avoid the influence of many cations in apatite leaching solution, significantly improve the purity of wet-process phosphoric acid, and has certain environmental protection and economic benefits.

Aiming at a high iron and low grade laterite nickel ore in Indonesia, the effects of leaching conditions on the leaching of main valuable metals in the raw ore were analyzed, and the change of iron grade in the leaching residue was studied using ferrous sulfate as leaching agent. The results show that under the conditions of oxygen partial pressure of 0.4 MPa, dosage of ferrous sulfate of 280 kg/t, liquid volume to solid mass ratio of 3/1, stirring speed of 300 r/min,raw ore size of 140 ~ 200 μm and temperature of 240 ℃ for 45 min, the leaching rates of nickel and cobalt can reach 98.2% and 98.1%, respectively. The iron average grade of leaching slag can be increased to 55.8%, which is about 10% higher than that of raw ore. In the process of pressure leaching by oxygen, ferrous sulfate can be oxidized and decomposed into sulfuric acid and hematite, which is conducive to further improv the iron grade of the leaching residue.

In view of the secondary vanadium resources in high-sulfur petroleum coke gasification ash, vanadium was preenriched by oxidation roasting and then recovered by leaching with sulfuric acid. The leaching rule of vanadium from ash of oxidation roasting was investigated, the optimal leaching conditions were determined, and the leaching kinetics was discussed. The results show that under the conditions of temperature of 90 ℃, sulfuric acid concentration of 30%, liquid volume to solid mass ratio of 8∶2 and reaction time of 3 h, vanadium leaching rate in ash can reach more than 72.5% and vanadium mass fraction in acid leaching residue is 1.91%. In the test temperature range, the vanadium leaching rate conforms to the mixing control of the unreacted shrinkage core model,and the apparent reaction activation energy is 22.97 kJ/mol.

To address the problem of excessive accumulation of iron acid in bio-heap leaching of high-sulfur and low-copper ore, the regulation and mechanism of leaching of high sulfur and low copper ores by limestone were studied by bio-column leaching method and MLA detection and analysis method. The results show that the pH and Eh of the leaching solution can be significantly regulated by adding limestone with mass fraction of 2% and particle size of -10 mm+5 mm to 1.4 t ore. After 7 months of biological column leaching, the copper leaching rate can reach 71.25%, which is 52.83% higher than that of the control group without adding limestone. The distribution size of pyrite in the leaching slag of limestone addition group increases, and no xanax passivation layer is found, and the dissociation degree of fine copper minerals is positively correlated with the leaching rate. The addition of limestone can effectively enhance the copper leaching efficiency in high-sulfur and low-copper ore and reduce the burden of acid-iron wastewater treatment, which is of great significance for the sustainable development of sulfide ore mining operations.

A series of impregnated mesoporous silica SBA-15-P507 was prepared by using 2-ethylhexyl phosphate (P507) as extractor and mesoporous nano-silica material (SBA-15) as carrier. The adsorption properties of SBA-15-P507 on Co²⁺ and Ni²⁺ in wastewater were investigated. The results show that under the conditions of adsorbent dosage of 5 g/L, initial mass concentrations of Co²⁺ of 400 mg/L, initial mass concentrations of Ni²⁺ of 400 mg/L, adsorption temperature of 25 ℃, the equilibrium adsorption capacities of Co²⁺ and Ni²⁺ can reach 58.90 and 23.45 mg/g, respectively, and the adsorption equilibrium time is 40 min. The adsorption processes of Co²⁺ and Ni²⁺ conform to the quasi-second-order kinetic equation, and the adsorption isotherms of Co²⁺ and Ni²⁺ conform to the Langmuir isotherm adsorption model. The adsorption reaction of Co²⁺ is endothermic, while that of Ni²⁺ is exothermic. In the mixed simulation system containing Co²⁺ and Ni²⁺, SBA-15-P507(2.0) can selectively adsorb Co²⁺.0.1 mol/L sulfuric acid solution has significant elution effect on Co²⁺ adsorbed by SBA-15-P507(2.0). The research results can provide a new way for the purification of cobalt-nickel wastewater, which has certain theoretical guidance and practical application value.

An indium-nitrogen-carbon electrode material (PAO/In-N-C) modified with amidoxime was prepared using graphite felt as matrix material by chemical modification and coating, and uranium was extracted from seawater by electrochemical workstation. The effects of the PAO/In-N-C electrode material dosage, applied voltage, pH of spiked seawater and adsorption time on the extraction of uranium from low-concentration spiked seawater were investigated. The ion selectivity and recycling performance of the electrode material were tested, and the interaction mechanism between the electrode and uranyl ions was discussed. The results show that the extraction rate of uranium is 71.16% under the conditions of applied voltage of -3~0 V, PAO/In-N-C electrode material dosage of 7 mg, adsorption time of 400 min, and seawater pH=8.10.PAO/IN-N-C electrode material reduction of uranium in seawater is divided into two steps: electroadsorption and electrodeposition. Firstly, the electromagnetic field is used to accelerate the migration of $\mathrm{UO}_{2}^{2+}$ to the electrode surface, and then the electroneutral compound UO₂ is formed and deposited on the electrode surface. The material has remarkable adsorption kinetics, good ion selectivity and reusability,and is expected to be used for uranium extraction from seawater.

Aiming at the problems such as relatively simple control and intelligent detection model of hydrometallurgical equipment and weak generalization ability,an algorithm model for intelligent control and fault detection of hydrometallurgical equipment based on deep learning was proposed. Firstly, SAC deep reinforcement learning algorithm was used to perform intelligent control of hydrometallurgical equipment. The improved ARIMA algorithm is used to detect the fault of the equipment. In order to further improve the real-time performance of the algorithm, LoRA fine-tuning network is introduced to fine-tune and accelerate the model with low parameters, and LoRA fine-tuning network to fine-tune and accelerate the model with low parameters. The accuracy of the model is 93.24% and the accuracy of fault detection is 91.34%. The practical application effect is good.

The extraction of iron from fly ash by HCl leaching and electrochemical deposition was studied. The micro-morphology and elemental composition of fly ash were systematically analyzed by SEM-EDS,XRF, ICP and XRD, and the key factors in the leaching process and their effects were investigated. The dynamic changes of pH, current density and Fe ion concentration during electrochemical deposition were also discussed. The results show that the iron leaching rate increased with the increase of HCl concentration, liquid volume to solid mass ratio, leaching temperature and leaching time. In the electrochemical deposition stage, pH increases gradually, while current density and Fe ion concentration decrease. The optimal leaching parameters are HCl concentration of 6 mol/L, liquid volume to solid mass ratio (HCl solution to fly ash) of 8∶1, reaction temperature of 90 ℃, reaction time of 90 min. For the electrochemical deposition process, the voltage is 3 V, the optimal pH range is between 0.5 and 1.9, and the final sediment is pure iron.

Removal of iron from high silicon-aluminum ratio and high iron coal gangue using thermally activated enhanced—hydrochloric acid leaching process was studied. The effects of calcination temperature, calcination time, hydrochloric acid concentration, leaching temperature, liquid-to-solid mass ratio, and leaching time on the iron leaching rate were examined, and the process conditions were optimized through orthogonal experiments. The results show that under the optimized conditions of calcination temperature of 500 ℃, calcination time of 1 h, hydrochloric acid concentration of 20%, leaching time of 3 h, leaching temperature of 90 ℃, and liquid-to-solid mass ratio of 4/1, leaching rate of Fe can reach 94.25%. The method can efficiently remove iron from coal gangue while effectively enriching Si and Al elements, providing technical reference for the resource utilization of coal gangue.

The removal method of superstandard components of uranium acid seepage water from sulphur-containing uranium waste rock in a mining area was studied. Firstly, 1 g/L mineral powder was added to the wastewater exceeding the standard to remove Cd, Cu and part U, and then the pH of seepage water from the waste rock landfill on the south and north sides was adjusted from 2.78 and 2.66 to 4.70 and 4.30, respectively, and the optimal contact reaction time was 30 min. The effects of Mg(OH)₂, Ca(OH)₂, Na₂CO₃ and NaOH on the further treatment of U, Mn and Zn in the effluent treated by ore powder were compared. The results show that Ca(OH)₂ has the best removal effects on U, Mn and Zn.Under the conditions of 0.32 and 0.96 g/L of Ca(OH)₂ and pH of 7 ~ 8, the removal rate of U, Cu, Cd, Zn and Mn can reach over 99.8%, over 90%, over 90%, over 95% and over 75.5%, respectively. And the settling speed is fast, and the suspended liquid volume can be reduced by about 70% after standing for 60 min. The precise calculation of the change of ion concentration during the addition of Ca(OH)₂. The results of sediment characterization show that hydrotaltale-like substances are formed during the purification process,Mn²⁺ and Zn²⁺ ions entered the hydrotalc structure and are removed,and uranyl ions may be removed by electrostatic adsorption with hydrotalc, surface complexation or interlayer anion exchange.

The effects of the changes of speed (N), distance (C₁) from the bottom and pitch (C₂) of the double-layer baffle three-arc blade composite paddle on the flow field in the stirring tank using particle image velocimetry (PIV) were studied. The flow field characteristics of the double-layer baffle three-arc blade propeller and the double-layer baffle-free three-arc blade propeller were simulated and compared. The results show that when the rotation speed N=110 r/min, the velocity distribution of the flow field in the kettle is relatively uniform, and the high-speed zone in the kettle is concentrated near the propellers. When C₂=0.27h(h is the liquid level height of the stirred tank), the connection flow between the propellers is stable, and the overall mixing capacity in the kettle is significantly enhanced. When C₁=0.29h, the area of the low-velocity zone in the kettle is greatly reduced. The baffle of the double-layer baffle three-arc blade propeller limits its radial pushing capacity, but the axial pushing capacity is significantly enhanced. The research results can provide a reference for the application of double-layer baffle three-arc blade propeller in practical industry.

Aiming at the issues of low computational efficiency and insufficient intelligence in predicting hydrometallurgical process parameters, a process optimization control model that utilizes 1D-CNN for predicting copper ion concentration and Seq2Seq for predicting mass transfer rate, with the objective of maximizing economic benefits was proposed. The optimization problem is solved using the DDPG algorithm. The results of numerical simulation and empirical study show that the model can predict the parameters of copper extraction process with high accuracy, realize the effective optimization and adjustment of parameters, and promote the improvement of economic benefits.

Aiming at the problems of low pre-treatment efficiency and significant mass spectrometry interference in the determination of rare earth elements in coal-related samples, a method for the determination of rare earth elements in coal and fly ash samples by high-temperature and high-pressure microwave digestion-ICP-MS in a mixed acid system of HNO₃-HF-HClO₄-H₂SO₄ was established. The effects of pre-treatment methods, sample weight, digestion system and mass spectrometry interference on the determination results were investigated. The results show that the linear correlation coefficients of the calibration curves are all greater than 0.999 6, the detection limits are 0.003 7~0.042 μg/g, the relative standard deviations (RSD, n=11) of the determination results of each element are all within 5.85%, the recoveries of standard addition are 95.0%~107.2%, and the relative errors are all less than 6.95%. The method has high accuracy and good stability, which greatly improves the determination efficiency.