Nickel, Cobalt and Manganese in the cathode materials of spent ternary lithium-ion batteries were recovered by leaching with a combination of citric acid and hydrogen peroxide. The possible reactions during the leaching process were analyzed, and the effects of factors, including citric acid concentration, mass fraction of hydrogen peroxide, leaching temperature, leaching time and liquid-to-solid ratio on the leaching rates of nickel, cobalt and manganese from cathode materials were also investigated. It is found that after 60 min leaching at 80 ℃ with citric acid at a concentration of 1.5 mol/L, hydrogen peroxide at a mass fraction of 8%, and a liquid-to-solid  ratio of 25 mL/g, the leaching rates of nickel, cobalt and manganese are 97.58%, 97.35% and 96.12%, respectively. Then, an antisolvent crystallization method is adopted with ethanol as antisolvent agent to recover metals from the obtained leach liquor, leading to the crystallization rates of nickel, cobalt and manganese at 92.34%, 93.07% and 99.69%, respectively.

A FeCoCrNiMn high-entropy alloy (HEA) coating was prepared on the 201 stainless steel surface by adopting high-speed laser cladding technology, and then the microstructure, phase distribution, microhardness of FeCoCrNiMn coating, as well as its wear properties in dry sliding condition were all investigated. It is found that such laser cladded FeCoCrNiMn HEA coating consists of a single FCC structure, with no obvious cracks observed. It also forms a good metallurgical bond with the substrate. The microhardness of the coating is around (439±2.1)HV, nearly two times that of 201 stainless steel substrate, and the strengthening mechanisms mainly include strengthening by grain refinement and solid solution strengthening. Also, the FeCoCrNiMn coating presents an obviously better wear resistance than 201 stainless steel, with an average  friction factor of 0.246 and a specific wear rate of about 2.59×10^-6 mm³/(N·m).The wear mechanisms for it include adhesive and abrasive wear. It is concluded that such FeCoCrNiMn HEA coating prepared by high-speed laser cladding technology can significantly improve the surface hardness, wear resistance and service life of machine components.

The expanded graphite (EG) derived from the graphite anodes of spent lithium-ion batteries was taken as conductive substrate, and then Sn/Co-based bimetallic sulfide was loaded by using a hydrothermal method to synthesize SnCoS₄@EG nanocomposite. And such EG presents a cross-linked porous three-dimensional lattice, and the SnCoS4 nanocrystals in the synthesized composite are uniformly dispersed in the EG, which enhances electrical conductivity of electrode material and stability of metallic sulfide, but also increases the contact area between active sites and electrolyte, leading to a higher exchange rate of Li⁺ ions at electrode/electrolyte interface. It is shown that SnCoS₄@EG electrode can exhibit a reversible specific capacity of 1195.90 mAh/g at 1.0 A/g after 500 cycles, presenting excellent durability over a large number of cycles.

Surface mechanical attrition treatment (SMAT) was adopted for low-carbon steel materials to achieve surface nanonization, and then the influence of surface nanonization on corrosion resistance of low-carbon steel was also discussed. The results show that due to surface nanonization, the low-carbon steel has a greater plastic deformation on the surface as the carbon content decreases, and the X-ray diffraction of its surface presents obviously wider peaks. It is found that after nanosizing treatment for the surface of low-carbon steel with different carbon content, the lower the carbon content, the rougher the surface and the worse the corrosion resistance.

To investigate directional independence of multistage stress memory during progressive cyclic loading of granite under compression with a series of deflection angle, experiments were conducted on cyclic loading and unloading of granite with different deflection angles by using a self-made deflection device. The Kaiser effect (KE) and the incomplete erasion phenomenon (IEP) of the maximum stress in previous multistage cycles after progressive cyclic loading with deflection angles were explored in the experiments. Results show that both KE and IEP in granite exhibit directional independence. The directional independence of KE has a critical angle of 10° and the directional independence of IEP has a critical angle of 12°. With a deflection angle of 12°, the IEP will interfere with the memory of historical maximum stress by KE. 

In order to balance productivity against safety in the mining of high-level stope with gently-dipping and extra-thick orebody, an iron mine adopting sublevel open stoping with backfill was taken as an example to optimize the mining sequence. Firstly, pillars was determined to at a reasonable spacing from 14.2 m to 47.2 m based on the theory of bearing capacity of pillars. Secondly, according to stope structure parameters, the pillars were designed to be 15 m, 30 mand 45 m in thickness, respectively. An orebody model was also established with FLAC^3D and then was used to analyze the roof subsidence and pillar stability based on comparison of each mining scheme. Finally, a judgment matrix of mining sequence was constructed based on analytic hierarchy process and fuzzy comprehensive evaluation method, with both factors of safety and productivity taken into consideration in the numerical simulation. The comprehensive membership degrees of those three schemes were calculated to be 0.86, 0.79 and 0.80, respectively, and pillars in the best scheme were determined to be in the thickness of 15 m. The results of an industrial experiment have proven that this scheme can ensure stope with relative stability while achieving the maximum production capacity.

An iron concentrate obtained from magnetic separation of red mud from Shandong was used in an experimental study on the effect of titanium removal by reverse flotation. In the experiment, with sodium oleate as collector, corn starch as hematite depressant, sulfuric acid as pH regulator, pulp pH of 9, and the addition of corn starch and sodium oleate at an amount of 500 g/t and 1500 g/t, respectively, the iron concentrate was produced, with the TiO₂ grade fell down from 6.90% to 2.73%, and the TFe recovery reaching 41.80%. The results of collector adsorption and IR analysis show that sodium oleate exhibits selective adsorption characteristics, which has further confirmedthe feasibility of sodium oleate used in removing titanium by reverse flotation of iron concentrate obtained from magnetic separation of red mud.

An experimental research was performed on pre-enrichment of a weathered low-grade vanadium-bearing stone coal ore to solve the problems of complex flow and high cost for the existing direct vanadium-extraction process. The process mineralogy study shows that the predominant vanadium minerals in the stone coal ore are vanadium-bearing limonite and vanadium-bearing mica, both being weakly magnetic, and a superconducting magnetic separation (SMS) plus sedimentation process is proposed for pre-enrichment of vanadium. With magnetic field strength of 4 T and slurry flow rate of 8.0 L/min, SMS produced a pre-enriched concentrate with V₂O₅ grade of 1.44% at a recovery of 55.08%. The SMS tailings were then subjected to sedimentation and classification to further recover vanadium, leading to the final concentrate with V₂O₅ grade of 1.03% and recovery of 79.48%, presenting that 59.02% tailings were discarded. With this pre-enrichment process, vanadium in the stone coal ore can be efficiently reclaimed, which meets the requirements for subsequent metallurgical vanadium extraction.

The acid leaching solution of cathode materials from spent lithium iron phosphate batteries was taken as raw material, and iron, phosphorus and lithium elements therein were recovered by adopting an oxidation-precipitation process. The effects of factors, including endpoint pH value of reaction system, reaction temperature, concentration of sodium hydroxide, dripping rate of sodium hydroxide, and the volume ratio of hydrogen peroxide to acid leaching solution, on the precipitation rates of iron and phosphorus and the loss of lithium during the precipitation process were all investigated. Results show that with the endpoint pH value of 2.5, temperature of 75 ℃, sodium hydroxide with concentration of 1.5 mol/L, sodium hydroxide solution at a dripping rate of 7.7 mL/min, and hydrogen peroxide and acid leaching solution in a volume ratio of 1∶60, the average precipitation rates of iron and phosphorus are 99.86% and 98.23%, respectively, and the average loss of lithium is just 1.23%. Under the above-mentioned conditions, iron and phosphorus in the solution can be effectively removed and recycled in the form of iron phosphate, presenting a lower loss rate of lithium. After 5 h-heat treatment at 700 ℃, it is shown that the chemical composition of iron phosphate can meet the industrial standard.

Theoretical calculation was made for the flow field in the hydraulic transportation with deep-sea polymetallic nodule collector, and the relationship between particle size of polymetallic nodules and minimum conveying speed was obtained. The distribution of flow pattern in the conveying channel was simulated with the jet velocity of nozzle at 15 m/s, 20 m/s and 25 m/s respectively, and  rate of the flow at 30 mm away from the lower surface of the channel was measured. A laboratory test was conducted for nodules pick-up by using a collector with different jet velocities of nozzles, and it is found that the obtained results are consistent with the theoretical calculation and simulation results.

In order to simply and effectively evaluate slope stability, four machine learning models based on chaotic particle swarm optimization (CPSO) were proposed to solve the existing problems of algorithm selection and hyper-parameter optimization in traditional machine learning model, and their prediction performance were comprehensively compared among each other. A database consisting of 221 open-pit slope stability cases was established, in which 80% of the data were used for training and 20% for model testing. Based on the comparison between the prediction results of four models and the verification results of engineering practices, it is found that the support vector machine (SVM) based on CPSO is superior than other three machine learning models in terms of prediction of slope stability, presenting an accuracy up to 88%. Thus, it can provide a reliable prediction for the safety of slope in open-pit mine.

To utilize efficiently valuable metal resources containing lithium and beryllium, flotation experiments were conducted based on the study of ore properties. A lithium-beryllium bulk flotation process was used and the influences of dosages of regulator, activator and collector, and the stirring time of regulator on the flotation performance of lithium polymetallic ore were investigated. Based on the determined optimal dosages of calcium chloride and collectors of GYLZ and GYM3, a closed-circuit test produced a lithium concentrate with Li₂O grade and recovery of 6.10% and 94.01% respective, and BeO grade and recovery of 0.12% and 88.53%, respectively, achieving efficient recovery and utilization of lithium and beryllium resources in lithium polymetallic ores.

The occurrence state of iron minerals in a kind of kaolin ore in Guangdong is relatively complex. A portion of iron minerals is irremovable as they disseminate in the lattice of kaolinite, illite and other minerals in an isomorphic manner. For this reason, the calcined kaolin concentrate possesses a lower whiteness than the natural whiteness. In order to efficiently exploit and utilize the kaolin ore, a process consisting of slurry tamping, spiral classifier classification and hydrocyclone classification was adopted, resulting in a kaolin concentrate grading 30.02% Al₂O₃ at 61.70% recovery with the content of impurity Fe₂O₃ at 1.15%, which can reach grade III standard of kaolin for ceramic industry. The classification downflow was then subjected to a process consisting of grinding, magnetic separation and hydrocyclone classification, resulting in a quartz sand concentrate and a sericite concentrate. The quartz sand concentrate, containing 97.11% SiO₂ and 0.058% Fe₂O₃, can satisfy the standard for low quality quartz for glass industry, and the sericite concentrate, containing 7.07% K₂O, 31.22% Al₂O₃ and 48.32% SiO₂, with natural whiteness at 65.53%, can be used in the coating industry. The magnetic separation results in the tailings with a yield of 8.41% and SiO₂ content of 76.33%, which can be used as auxiliary materials for building sand. Through this process, different minerals can be effectively separated to achieve the purpose of comprehensive utilization of kaolin ore.

To examine the industrial feasibility of pre-discarding by using screening classification combined with gravity separation in processing of a scheelite ore from Hunan Province, industrial distributary and flotation trial tests were carried out. The results show that a process consisting of  screening and spiral chute discarding  under optimized conditions can discard tailings grading 0.034% WO₃ with a yield of 25.50% in mass, leading to tungsten loss of only 2.99%. With this pre-discarding before flotation process, both the grade and recovery of the final flotation concentrate are improved, compared to the concentrate obtained from direct flotation of overflow product.

In order to recover and utilize high value-added iron phosphate waste, an experimental study was carried out by adopting a process consisting of hydrochloric acid leaching, replacement of iron powder for copper removal, and hydrolyzation and chemical precipitation for removal of titanium and aluminum therein. The results show that after 1 h leaching at 60 ℃ with hydrochloric acid concentration of 25%, liquid-solid ratio of 6 mL/g, the leaching rate of iron can be up to 98.7%. And then after 35 min reaction at 60 ℃ with the initial pH of the solution controlled at 0.6, the addition of iron powder at an amount of 0.55 times of the molar number of iron in the leaching solution, the removal rate of copper and titanium can reach 96.2% and 83.6% respectively. By the following process of hydrolyzation and chemical precipitation with sodium fluoride 8 times of the molar number of aluminum, the removal rate of titanium and aluminum can reach 97.6% and 99.3% after 30 min reaction at 40 ℃ with pH of 1.9. It is shown that the content of impurities in the leaching solution meets the requirements for the subsequent synthesis of iron phosphate for batteries.

A kind of contaminated paddy soil was taken for pot experiment by adding FeSO₄ to investigate the impact of FeSO₄ on the formation of iron plaques on the root surface and the migration of the Cd from Cd-contaminated paddy soil. Results show that with the addition of FeSO₄ increased from 0 to 320 mg/kg, the pH value of the paddy soil tends to decline, maximally by 0.70. The TCLP-Cd content in the potting soil rises to a certain extent compared to the control group. The addition of FeSO₄ significantly reduces the Cd content in leaves, husks, and brown rice, as well as effectively increases the amount of root iron plaque, thus the absorption of Cd in the soil by rice is moderately controlled. However, the addition of external iron resource can bring impact to the pH of soil and bioavailability of Cd, so it is recommended that in practical operation, FeSO₄ should be added with some alkaline restorative materials such as lime to contaminated paddy fields for enhancing the control.

Methylene blue was degraded by adopting a heterogeneous Fenton system composed of manganese residue and H₂O₂, and the effects of initial pH value, H₂O₂ concentration, dosage of manganese residue and reaction temperature on the degradation performance were studied. The reusability of manganese residue was investigated, and the removal mechanism of methylene blue in the manganese residue/H₂O₂ system was also discussed. The results show that the removal rate of methylene blue can exceed 98.1% after 120 min reaction at temperature of 25 ℃, with methylene blue concentration of 20 mg/L, H₂O₂ concentration of 10 mmol/L, manganese residue dosage of 2 g/L, and initial pH value of 2.5. After the manganese residue is recycled for 5 times, the removal rate of methylene blue can be still up to 95.5% by 300 min reaction. In the manganese residue/H₂O₂ heterogeneous Fenton system, ·OH plays a leading role in the degradation of methylene blue.

With micron silicon powder as matrix, phosphorus-doped silicon-carbon composite material (Si-P@C) was synthesized by solid-state thermal diffusion and high-temperature pyrolysis, and then used as anode material of lithium-ion batteries. The results show that Si-P@C anode material demonstrates an initial discharge specific capacity up to 2 164 mAh/g  at a current density of 0.2 A/g. Compared with pure silicon, Si-P@C anode material presents greatly improved cycling performance. After 50 cycles at a current density of 0.5 A/g, it demonstrates a high reversible specific capacity of 1 176 mAh/g, with the capacity retention ratio of 73.5%. It is concluded that phosphorus-doping and carbon coating can effectively improve the electron transfer ability and reaction kinetics of silicon anode.

To solve the problem of structural instability of cathode material (LiNi_0.8Co_0.1Mn_0.1O₂) (NCM)) during cycling, a strategy of  co-doping of Rb⁺ and Cl^- was proposed for NCM materials. The synergistic effect of  co-doping of Rb⁺ and Cl^- in the NCM lattice can increase the diffusion rate of Li⁺ and relieve the internal strain, thus hindering the mixing of Li⁺/Ni²⁺ during high cut-off voltage cycling. Electrochemical test results show that Li_0.99Rb_0.01(Ni_0.8Co_0.1Mn_0.1)O_1.99Cl_0.01 (RbCl-NCM) has a discharge capacity up to 176.9 mAh/g at a current density of 10C. The initial discharge capacity at  1C is 203.5 mAh/g.  After 200 cycles, its capacity retention ratio is as high as 87.8%,  showing an excellent cycling performance, while the capacity retention ratio of NCM material is only 57.3%.

The comprehensive recycling ways for tailings after vanadium extraction, including recovery of valuable components, synthesis of new functional materials and preparation of multi-purpose building materials, were explained, which can provide a reference for application of technologies in comprehensive recycling of tailings after vanadium extraction.

Based on the experimental study on fragmentation and pulverization characteristics of polymetallic nodules in the process of ore lifting, it is found that there is obvious fragmentation of nodules during lifting process. With the volume concentration of 6.5%, the mass percent of polymetallic nodules with particle size larger than 50 mm decreases from 75.58% to 23.78%; with the volume concentration of 15%, the mass percent decreases from 51.51% to 10.08%.Pulverization of nodules was observed in the experiment. With the volume concentration of 6.5%, the mass percent of the polymetallic nodules powder with particle size less than 0.1 mm is 1.79%, and the median particle size is 10.07 μm; with the volume concentration of 15%, the mass percent of polymetallic nodule powder with particle size less than 0.1 mm is 1.99%, and the median particle size of the powder is 9.47 μm. Based on the experimental data, it is estimated that as per mining of 10 million tons of polymetallic nodules, the powder discharge will cause tens of thousands of tons of Fe and Mn losses, as well as hundreds of tons of Co, Ni and Cu losses. Besides, the maximum redeposition thickness of the sediment plume induced by mining is more than 3 mm after diffusion and settlement, which will bring a significant impact to environment.

The stability of slope with fault under the impact of  blast-induced seismic wave was analyzed by using simulation to study the dynamic response of slope with different fault thickness under the impact of explosive vibration. The results show that there exists elevation amplification effect when blast-induced seismic wave propagates along slope surface and fault area. The thicker the fault, the faster the attenuation of blast-induced seismic wave. As the fault becomes thicker, the displacement of slope under the action of blast-induced vibration gradually increases, and the overall deformation resistance becomes smaller. Under the action of blast vibration, the fault with different thickness obviously brings different influence to slope stability. With the fault thickness of 2-8 m, the slope stability decreases continuously and rapidly, and tends to be stable as the fault thickness exceeds 8 m.

The single application of analytical hierarchy process (AHP) and grey relational analysis (GRA) algorithm is always affected by some subjective factors, leading to great deviation between the obtained evaluation result and the actual result. In view of this problem, a composite algorithm based on an integrated range analysis with GRA and AHP was proposed. Then, a phosphate mine in the southwest China was taken as an example, and this algorithm was adopted  to analyze the sensitivity of factors, including gravity, internal friction angle, cohesive force, elastic modulus and Poisson'sratio, to the stability of slope in the Area A. The results show that the sensitivity of those influencing factors to the slope stability in Area A is in the following descending order: internal friction angle, cohesive force, gravity, elastic modulus, Poisson's ratio. It is found that the analysis result is consistent with the actual situation of the mine.

Mineral processing tests were carried out for a low-grade copper ore from South America containing 0.027% Mo and 0.45% Cu. After optimization of the reagent regime, a close-circuit test by adopting a flowsheet of Cu-Mo bulk flotation plus Cu/Mo separation resulted in a copper concentrate grading 26.93% Cu at 81.96% recovery, and a molybdenum concentrate grading 25.32% Mo at 76.24% recovery. Therewith, copper and molybdenum resources in the lean ore can be effectively recovered.

The kinetics and thermodynamics of oleate ion adsorption on the surface of fluorapatite and dolomite were studied by adopting TOC measurement and molecular simulation. The study on kinetics of adsorption shows that with HEDP as the depressant, the adsorption rate of oleate ions on fluorapatite is greater than on dolomite, and the adsorption on both minerals conforms to the quasi-second-order kinetic model. Furthermore, according to the study on adsorption thermodynamics, the characteristics of oleate ion adsorption on the inner pore surface of both fluorapatite and dolomite, on (001) surface of fluorapatite and (104) surface of dolomite nearly conform to Langmuir model. For identical specific surface area, the adsorption amount of oleate ions on dolomite is higher than that on fluorapatite, indicating that there are more active sites per unit surface area on dolomite than on fluorapatite.

The crystal structure and surface properties of minerals and the mechanism of interaction between minerals and flotation agents were systematically analyzed by means of quantum chemical calculation and molecular dynamics simulation. Meanwhile, the flotation mechanism of kyanite minerals and quartz was discussed. The results show that the differences in the surface properties of kyanite, andalusite, sillimanite and quartz determine the differences in floatability, and citric acid can increase the floatability difference between kyanite minerals and quartz. The simulation result of computational chemistry  is consistent with the experimental result of flotation.

With orange residue extract and tetrasodium glutamate diacetate (GLDA) as raw materials, a green activator was prepared. Then, the effects of phosphate-solubilizing bacteria (PSB) combined with green activator on the enrichment, translocation and accumulation of cadmium from soil by ryegrass were studied. The results show that PSB can significantly promote the growth of ryegrass in cadmium-contaminated soil. However, the growth of ryegrass is inhibited by only using green activator, with the dry weight of ryegrass at the end of experiment decreased by 27.37%; while a combination of PSB and green activator can make the final dry weight of ryegrass become 1.29 times that in the blank group, indicating that the addition of PSB can alleviate the negative effect of green activator on the growth of ryegrass. A combination of both can increase the content of phytoavailable cadmium in soil, while decrease the total cadmium concentration in soil. It is shown that the enrichment coefficient of Cd in stem and root parts of ryegrass increases by 35.37% and 10.23%, respectively, and the translocation factor of cadmium by ryegrass increases by 22.58%. In addition, the total accumulation of cadmium in the stem and root parts of ryegrass is up by 87.90% and 32.69%, respectively. It is found that the total accumulation of cadmium in the stem is all greater than that in the root whether by using PSB and green activator separately, or by a combination of both, indicating that PSB combined with green activator can promote the phytoextraction efficiency of cadmium from soil by ryegrass.

Acting as a raw material, mangosteen peel  was subjected to decolorization with isopropanol and activation with alkaline reagent for preparing a kind of adsorbent, which was then used to adsorb copper ions in solution. The result from an adsorption experiment shows that increasing pH value can be beneficial to the adsorption of copper ions onto mangosteen peel, with the maximum adsorption capacity up to 1.5 molCu²⁺/kg. The adsorption can reach equilibrium within 30 min. The amount of loaded copper ions has a significant effect on the characteristic temperature of thermal decomposition of adsorbents during combustion. When the concentration of copper ions is lower than 2 mmol/L, there are higher number of loaded copper ions, and the temperature at which thermal decomposition begins and violent combustion decomposition ends becomes lower. When the concentration of copper ion is higher than 2 mmol/L, the characteristic value of thermal decomposition temperature no longer changes significantly. Copper ion plays a role of catalyst in the combustion process, which can effectively promote the combustion reaction.

A side blowing furnace was adopted to treat the leaching residue of copper anode slime and recover valuable metals therein comprehensively. The effects of soda dosage, granular coal dosage, precipitation time and top flue gas temperature on the recovery rates of main metals Pb, Sb, Bi, Au and Ag were investigated. The results show that with soda at an amount of 2.5%, granular coal at an amount of 3%, the precipitation time of 1.5 h, and the top flue gas temperature of 750 ℃, the precious lead product is obtained after processing, grading 1 544 g/t Au (1.84 times enrichment), 10.37% Ag (1.4 times enrichment), 22.89% Pb (2.1 times enrichment), and 27.45% Bi (2.2 times enrichment).

In order to study the effects of pores in surface-coated carbon layer on the rate performance of graphite cathode materials, a small amount of boric acid was added to generate gasification and effusion effect of boric acid during the softening stage of the coated asphalt. Then, a carbon layer with certain pores was formed on the surface of natural graphite tailings through carbonization, and graphite cathode materials with various proportions of pores were obtained. The results show that boric acid forms a carbon layer on the surface of particles containing mesoporous and macroporous pores. A higher proportion of mesopores in the surface carbon layer leads to more  diffusion channels for Li⁺ in the carbon layer L_C, and lower diffusion impedance of Li⁺. In that case, the rate performance and cycling performance of the material are enhanced.

The influence of Mg and Si content on the types and properties of actual precipitates in Al-Cu-Mg-Ag-Si alloy was investigated. The results show that a large amount of S phase and coarse second phases exist in the Al-Cu-Mg-Ag-Sialloy with high Mg content and regular Si content; the common θ phase and Ω phase are precipitated in the low-Mg and low-Si alloy; the common second phases in 6xxx aluminum alloys, such as σ and β″ phases, appear in the alloy with low Mg content and regular Si content, and also fine and dispersed θ phases are precipitated in the alloy, which results in excellent strengthening effect of the alloy. Both Si and Mg greatly alter the precipitation sequence of the alloy, and the effect of Si cannot be offset by increasing Mg content. The addition of Si significantly inhibits the precipitation of  Ω  phase, while a considerable increase of Mg content can promote the precipitation of S phase.

In order to study the corrosion mechanism of welded material of Q370qENH weathering steel by submerged arc welding (SAW) , experiments were conducted on immersion corrosion and electrochemical corrosion of Q370qENH substrate samples and weld seam samples after SAW process, and the morphology and composition of the surface rust formed after immersion corrosion were characterized. The results indicate that the corrosion resistance of the weld seam of Q370qENH by SAW process is lower than the substrate, and its electrochemical impedance is 38% of the substrate. The reason for the lower corrosion resistance of weld seam than the substrate and the formation mechanism of surface rust were all analyzed. The research results can provide scientific and theoretical basis for the safety assessment for the service of weathering steel in engineering projects of steel bridges for high-speed railway, as well as its following maintenance.

Fe₃O₄@SiO₂@IL was prepared by immobilizing imidazole based ionic liquids on the surface of magnetic nanoparticles with impregnation method, and  was then used to remove Hg²⁺ in the water. The effects of pH value, adsorption time, and adsorbent dosage on the Hg2+ removal rate were investigated. The results show that Fe₃O₄@SiO₂@ILcan have a wide application, and Hg²⁺ removal rate can exceed 99.1% with pH of 7.2-9.5. Fe₃O₄@SiO₂@IL presents a high rate of Hg²⁺ adsorption, and the adsorption can reach equilibrium within 90 minutes. For 25 mL Hg²⁺ solution with a concentration of 2 μg/mL, Hg²⁺ can be completely removed by adding 20 mg of adsorbent. The adsorption isotherms of Fe₃O₄@SiO₂@IL indicate that the saturated adsorption capacity of the adsorbent for Hg²⁺ is 548.37 mg/g.

Rare earth elements are important resources for national development and industrial upgrading, and it is critical to establish an improved rare earth policy system. Based on the constructed analysis framework of rare earth policies, 48 rare earth policies issued from 1985 to 2022 in China were evaluated by using text data mining, social network and policy modeling consistency (PMC)-index model from three aspects, including the evolution process of rare earth policies, policy network and quantitative policy analysis. It is found  that the evolution of China's rare earth policies can be divided into four stages, among which standardizing the exploitation procedure for rare earth resources and rectifying the order of rare earth market have always been the focus of China's rare earth policies. A policy network has been initially constructed, but there is poor correlation among policies and there are many isolated policies, which indicates that the correlation among policies needs to be strengthened. The overall design of the polices is reasonable, but there are some deficiencies in incentive measures and effectiveness. Finally, some suggestions are put forward to optimize and improve China's rare earth policies based on the features and shortcomings.

Based on the relevant patents of layered cathode materials for sodium-ion batteries in China, a review of patent applications (authorization) is presented in terms of annual trend and main applicants. Also, some representative patents on precursors, structure, chemical washing and coating of layered cathode materials for sodium-ion batteries are chosen for analysis. Finally, the industry development trend, as well as technical difficulties and hotspot in this industry are summarized.

The advantages and disadvantages of several technologies for recycling spent LiFePO₄ batteries, including pre-treatment, hydrometallurgical process, and direct regeneration and repairing, were presented in terms of recovery efficiency, economic and environmental benefits, and commercial feasibility. The development trend of each technology is also analyzed. All these can serve as reference for optimizing and improving the technologies to recycle spent LiFePO₄ batteries in the future.

In an experiment, with hydrochloric acid as leaching agent and NaClO₃ as oxidizing agent, lithium was selectively leached from cathode material of spent lithium iron phosphate battery, and the effects of factors, including dosage of hydrochloric acid, solid-liquid ratio and reaction time, on the lithium leaching rate were investigated. It is shown that with an addition of hydrochloric acid at an amount of 1.0 time theoretical value, solid-liquid ratio of 1∶3 and reaction time of 3 h, the average lithium leaching rate can reach 99.33% by using this process. After that, magnesium hydroxide and sodium hydroxide were added into the raffinate in turn to remove impurities of P, Al and Fe. And then, the obtained solution was used to prepare Li₂CO₃ at 95 ℃ by adding anhydrous sodium carbonate. After water washing to remove NaCl, a high purity Li₂CO₃ (99.62%) can be obtained, which meets the industrial standard for industrial-grade lithium carbonate.

The problems of oxidation and corrosion of LIBs copper foil in its production and application have restricted its service life and battery safety. Based on the research status of anti-oxidation technologies for LIBs copper foil in recent years, the mechanism of different passivation methods is summarized. After an introduction of the corrosion mechanism of copper foil fluid in Li-ion battery electrolyte, the research progress in improving corrosion resistance by modification of copper foil surface is reviewed. On this basis, the prospects of chromium-free passivation technology and surface modification technologies for copper foil are presented. At last, a clean, eco-friendly and efficient anti-oxidation and anti-corrosion concept is proposed.

The progress in the research of micro-fine mineral flotation process is reviewed in terms of grinding, pulping, separation, and finally a prospect for the research direction of micro-fine mineral flotation process is presented.

An introduction of preparation method of Fe/Al₂O₃ ceramet composites is presented. The combination mechanism of Fe-base and ceramic phase in the preparation process of Fe/Al₂O₃ cermet composites, as well as the optimization of preparation technique and material properties are all expounded based on the principle of powder metallurgy. Finally, the future direction for Fe/Al₂O₃ cermet composites research is also predicted.