The design and optimization of extraction mixing tank is one of the key factors affecting the extraction efficiency of rare earth. The mixing performance of semi-open curved-blade disc-type stirring impeller(semi-open BWY), semi-open straight-blade disc-type stirring impeller(semi-open BPY), closed curved-blade disc-type stirring impeller (closed BWY) and closed straight-blade disc-type stirring impeller(closed BPY) paddle in the mixing tank was studied by experiment and numerical simulation. The negative pressure, power, discharge flow rate and flow field distribution generated by the four types of impellers at different rotational speeds were investigated. Taking closed BPY as an example, the six parameters of blade diameter, blade width, blade arc length, inner ring diameter, suction port diameter of the mixing tank, and the height between the blade and the suction port were analyzed in detail. The correlation equations of negative pressure, power number, turbulent kinetic energy dissipation rate and displacement number were established. The results show that under the same power conditions, reducing the blade diameter, inner ring diameter, suction port diameter, height between the blade and the suction port and blade width, as well as increasing the blade arc length, can enhance the mixing suction capacity, but it can reduce the blade displacement.

To address the issue of low ion exchange adsorption performance of natural zeolite caused by the presence of impurities, which makes it ineffective in adsorbing ammonia nitrogen in wastewater, the modification of natural zeolite using inorganic acids, inorganic bases, and inorganic salts was studied. The effects of different initial ammonia nitrogen mass concentration, zeolite particle size, zeolite dosage and reaction time on ammonia nitrogen adsorption performance of natural zeolite were investigated. The adsorption effects of zeolite under different modification conditions on ammonia nitrogen were compared. The results indicate that the ammonia nitrogen adsorption rate of natural zeolite gradually decreases with the increase of zeolite particle size and initial ammonia nitrogen mass concentration, and gradually increases with the increase of zeolite dosage and reaction time. The ammonia nitrogen adsorption effect of zeolite modified by sodium chloride is significantly better than that of zeolite modified by inorganic acids and inorganic bases, as well as other inorganic salts. When the sodium chloride concentration is 0.8 mol/L, the ammonia nitrogen adsorption rate can reach 78.0%, which is 1.64 times that of natural zeolite.

In order to reduce the content of impurities such as Cu, Fe, Zn and reduce the loss of Ni in crude nickel sulfate solution of copper electrolysis by-products, the process of selective precipitation of copper by Na₂S₂O₃—deep extraction of zinc removal iron—evaporation crystallization was studied for deep purification of the solution, and the key process parameters were optimized. The results show that the precipitation rate of Cu can reach 99.89% and the loss rate of Ni is only 1.22% using Na₂S₂O₃ as precipitator under the optimum conditions of Na₂S₂O₃ excess coefficient of 2.0, solution pH of 5.0, reaction temperature of 85 ℃ and reaction time of 2 h. Using P204 as extracant, the extraction rates of Zn and Fe can reach 99.87% and 99.98%, respectively, and the loss rate of Ni is 2.24% under the optimal conditions of pH=3.0, P204 volume fraction of 25%, saponification rate of 50%, V_O/V_A=1.5/1, extraction temperature of 25 ℃ and extraction time of 10 min. Electroplating grade nickel sulfate crystal products are obtained by evaporation and crystallization of the deeply purified nickel sulfate solution. The quality can meet the national standard GB/T 26524—2023 Class Ⅱ indicators, and can be used as high-quality raw materials for electroplating and other industrial uses.

Rare earth resources are easy to produce low concentration rare earth solution or very low concentration rare earth wastewater in the process of development and extraction, which causes problems such as enrichment difficulties, environmental pollution and resource waste. The sources and characteristics of common low concentration rare earth solutions are introduced, and the principles and research progress of enrichment and recovery technologies of low concentration rare earth solutions in recent years are reviewed, including precipitation, solvent extraction, membrane separation and adsorption separation. The advantages and disadvantages of various enrichment and recovery methods are analyzed, future direction for technological development are also outlined.

In order to accurately simulate the variation process of gold leaching rate, a multistage leaching model was designed, and the reaction rate prediction model based on the Forward Neural Network (FNN) and Radial Basis Function (RBF) was constructed.The validity of the model was verified by numerical simulation and comparative test. The results show that the error between the predicted value and the actual value of the gold leaching rate is between 2.1% and 2.6%, which is effective and accurate.

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.

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.

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.

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.

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.