China Nonferrous Metallurgy

Abstract:The waste aluminum electrolyte contains 7% Li. The lithium recovery process includes pyrometallurgical process and wet process. The pyrometallurgical process is mainly used for the pretreatment of waste aluminum electrolyte. The wet process enriches lithium into the leaching solution by leaching and prepares lithium salt. The traditional leaching technology includes sulfuric acid leaching, nitric acid leaching, alkali leaching, etc. The main purpose of producing lithium carbonate, and part of the technical routes, realizing the comprehensive recovery of valuable components of waste aluminum electrolyte. On the basis of the traditional leaching technology route, there are also innovative technologies such as pyrometallurgical and hydrometallurgical combination, alkali-acid leaching combination, inorganic salt or organic acid leaching.Analysis of waste lithium-containing aluminum electrolyte comprehensive recovery technology research trend, it can be seen that hydrometallurgical process dominated, pyrometallurgical treatment can only be used as pretreatment to achieve further hydrometallurgical leaching, the operating environment and production conditions of hydrometallurgical leaching are more friendly, although widespread long process, process is more complex, but can realize comprehensive recovery of Li, F, Al valuable components. The advantages and disadvantages of various treatment processes and the challenges faced by engineering application are introduced. It is pointed out that the technical route based on operability, economy and maximum recovery of other valuable components in waste aluminum electrolyte has more practical significance while recovering lithium by leaching.

Abstract:To improve the utilization efficiency of electric energy and reduce the energy consumption of aluminium electrolysis,according to the real production data of an aluminium plant in Guizhou, the optimization model of aluminium electrolysis process parameters was constructed with the multi-objective of maximum current efficiency and minimum tonne of aluminium energy consumption by using the grey correlation analysis method to select the seven parameterswith significant impact, including cell voltage (U), electrolysis temperature (Tb), feed interval (tNB), aluminium level (hm), electrolyte level (hg), molecular ratio (rm) and out aluminum (q). The improved Non-dominated Sorting Genetic Algorithm (NSGA-II) was used to compare and analyse the differences between 60 sets of actual values and the theoretical values of the traditionaland improved NSGA-II algorithm, the performance of the algorithm was verified using 30 sets of actual production data, and the Pareto front was obtained by iterative calculations using MATLAB software. The results show that the optimal set of current efficiency of the improved NSGA-II algorithm is 95.66%, and the energy consumption of tonnes of aluminium is 12424.54kW·h; compared with the traditional NSGA-II algorithm, the current efficiency is improved by 0.31%, and the energy consumption of tonnes aluminium is reduced by 22.11kW·h, which achieves the effect of energy saving and consumption reduction, and verifies the effectiveness and applicability of the improved NSGA-II algorithm in improving the optimization of the process parameters of aluminium electrolysis. It verifies the effectiveness and applicability of the improved NSGA-II algorithm in improving the optimization of aluminium electrolysis process parameters, and can provide reference suggestions for the optimization of aluminium electrolysis energy saving and production design.

Abstract:Polyethylene glycol（PEG）is a commonly used wetting agent in the preparation of electrolytic copper foil, which can refine the grain, smooth the coating, and adjust the mechanical properties of the coating. There are many studies on the effect of PEG concentration on the properties of electrolytic copper foil in the existing literature, but there are few reports on the effect of PEG molecular weight on the properties of electrolytic copper foil. In this stduy, polyethylene glycol（PEG）with molecular weight of 200, 1000, 4000 and 8000 is used as the additive of electrolytic copper foil. In the presence of Cl-, electrolytic copper foil with PEG of different molecular weight is prepared by electroplating process. The effects of PEG molecular weight on copper electrodeposition behavior, surface appearance, mass weight and thickness, M-surface brightness and roughness, tensile strength and elongation were investigated. The results show that when the molecular weight of PEG is 200, the electrodeposition of copper is promoted, Compared with the electrolytic copper foil without PEG, the surface grain size is slightly larger, the roughness is increased, and the tensile strength and elongation are decreased. When the molecular weight of PEG is increased to 1000, 4000 and 8000, the electrodeposition of copper is inhibited, and the inhibition effect is 4000＞1000＞8000. At this time, the surface grain size of the prepared copper foil decreases and becomes flat and uniform, the roughness decreases, and the tensile strength and elongation also increase. Especially when the PEG molecular weight is 4000, the performance of the prepared electrolytic copper foil is the best, the M-surface roughness decreases from 3.79 to 2.79, and the tensile strength and elongation increase by 43% and 114%, respectively. PEG with different molecular weight has little effect on the mass weight, thickness and M-surface brightness of copper foil. The results of this study provide a reference for the selection of appropriate molecular weight PEG in electrolysis of copper foil.

Abstract:Molybdenum recovery ratecanbeover 95% in the treatment of molybdeniteby oxygenpressure and water leaching process. Subsequently, ammonia leachingofoxygen pressure and water leaching residue will lead to the presence of some insoluble molybdate in the ammonia leaching residue, which decrease the recovery of molybdenum. Oxygen pressure and water leaching residue of molybdenum concentrate as raw material with NaOH and Na₂CO₃ as leaching agents, the effects of leaching agent dosage, temperature, liquid-solid ratio, and leaching time on molybdenum leaching rate were investigated in this paper.The chemical composition analysis of oxygen pressure and water leaching residue and alkaline leaching residue were analysed to reveal the mechanism of alkaline leaching of oxygen pressure and water leaching residue.Results show thatthe oxygen pressure and water leaching residue contains CaMoO₄, which cannot be effectively leached by NaOH. In case of using Na₂CO₃ as leaching agent, spontaneous decomposition of CaMoO₄ occurs at temperature above 20℃, and the higher the temperatureis, the easier the decomposition is. The optimum conditions for using Na₂CO₃ as leaching agent are temperature of 90℃, Na₂CO₃ consumption coefficient of 1.2, liquid-solid ratio of 4∶1, time of 90 minutes, and stirring speed of 400 rpm, in which, the molybdenum leaching rate can reach 97.15%.Under the optimum conditions for using NaOHas leaching agent, themolybdenum leaching rateis 93.98%。Results indicatethat the leaching rate of Mo canbe effectively increased by using Na₂CO₃ as leaching agent.

Abstract:Zinc electrolysis anode slime contains a large amount of manganese. At present, the commonly treatment method in enterprises is to return to the leaching process for reuse, but this method will lead to a high concentration of manganese ions in the system solution, which will affect electrolysis. In this study, the reduction leaching behavior of manganese in zinc electrolytic anode slime in SO₂-H₂O system was investigated by using the reduction characteristics of SO₂, and the effects of process conditions on the leaching rate of manganese and the dissolution rate of potassium and calcium were investigated. The results show that under the conditions of initial acidity of 0g/L, liquid-solid ratio of 4.0, SO₂ dosage of 3.5mol, reaction temperature of 40℃, reaction time of 1.5h and stirring speed of 400r/min, the leaching rate of Mn reaches 99.7%, and the dissolution rates of K and Ca are 89.7% and 28.6%, respectively. The impurities such as K and Ca in the manganese-rich solution can be removed by chemical precipitation method and used to prepare industrial grade manganese sulfate. The main chemical components of the leaching residue are Pb 37.79%, Ag 1480g/t, Sr 12.49% and Si 6.07%, which exist in the forms of PbSO₄, SrSO₄ and SiO₂, respectively. Pb, Ag and Sr in the volatile residue can be reduced to dust by pyrometallurgical process, and then further separated. The method avoids the problem that the concentration of manganese ions in the electrolytic system is too high, and realizes the enrichment of valuable metal elements lead, silver and strontium in the leaching residue. The enrichment factor is about 9, which improves the added value of the leaching residue.

Abstract:K_xV₂O₅ with excellent electrochemical properties can be used as an excellent cathode material for aqueous zinc-ion batteries, and its controllable synthesisis especially important.In this study,the effects of the molar ratio of oxalic acid (C₂H₂O₄·₂H₂O) to vanadium pentoxide (V₂O₅) on the structure, morphology and electrochemical properties of potassium vanadate (K_0.486V₂O₅) cathodes were investigated. The controllable preparation of K_0.486V₂O₅ was achieved.The results show that when the molar ratio of C₂H₂O₄·₂H₂O/V₂O₅ is about 5∶2, potassium vanadate has higher crystallinityandmore regularnanorod-likemorphology. The distinct pseudocapacitive effect endows it with excellent rate performance and outstanding kinetic characteristics, showing high capacity and good cycling stability. At current densities of 0.1,0.2,0.5, 1,2,5 and 10A·g^-1, the discharge specific capacities are 395.3,366.9,323.4,283.5,247.7,181.8 and 127.3mAh·g^-1, respectively. At a high current density of 5A·g^-1, it still delivers a reversible capacity of 196.5mAh·g^-1 after 2000 cycles with an ultrahigh capacity retention rate of 127.9%.The energy storage process of K_0.486V₂O₅ is controlled by ion diffusion process and surface capacitance behavior. With the increase of the scanning rate, the storage of Zn²⁺ is mainly controlled by the capacitive behavior. The significant pseudocapacitance effect is the key factor to obtaining excellent rate performance and eminentkinetic behavior.

Abstract:In the analysis of high purity rare earth element, C272 microcolumn separation or TODGA separation matrix is usually used to enrich the element to be measured, but this method is inefficiency and difficult to operate, and it is easy to introduce external impurities and incomplete elution, leading to deviations in results. In this paper, a test method for rare earth elements in high purity cerium trioxide (Ce₂O₃) by inductively coupled plasma mass spectrometry (ICP-MS/MS) was established. The collision mode was used to determine Y、La、Nd、Sm、Eu、Dy、Ho、Er、Tm、Yb、Lu and the mass shift mode was used to determine Pr、Gd and Tb in the Ce₂O₃ The test used 0.1% matrix injection in the MS/MS mode, and nitrous oxide (N₂O) was used as the reaction gas through mass shift reaction of O and N atoms. It can effectively overcome the mass spectrum interference caused by high matrix and achieve accurate determination of 14 impurity rare earth elements in high purity Ce₂O₃ Under optimized experimental conditions, the detection limits of fourteen elements were in the range of 0.001~0.020mg/kg, the recoveries were in the range of 81.2%-105.3%. The developed method can determine impurity elements in high purity rare earth oxides quickly and accurately, and provide a way for the analysis of impurities in high purity rare earth oxides.

Abstract:Due to the large amount of sulfur and silicon elements in bismuth concentrate, the silver content in bismuth concentrate can not be completely dissolved by aqua regis, resulting in incomplete sample dissolution, which may result in low measurement results. In this study, perchloric acid and ammonium bifluoride were added in sample pretreatment to dissolve sulfur and silicate compounds, and then the content of silver in bismuth concentrate was determined by flame atomic absorption spectrometer (AAS), which effectively solved the influence of high sulfur and silicon content in bismuth concentrate on sample dissolution and determination. During the test, bismuth concentrate was dissolved with 2.0mL perchloric acid, 0.2g ammonium bifluoride and aqua regis system. Under the condition of 20% HCl medium, the silver content of bismuth concentrate samples was measured by flame atomic absorption spectrometer. The results showed that the detection limit of this test method was 0.0066μg/mL. It is lower than the lower limit of 0.022μg/mL, which indicates that this test method is feasible and can meet the determination requirements of silver content in bismuth concentrate. The relative standard deviation (RSD, n=7) was 0.20% to 1.95%, and the recoveries were 97.7% to 105.0%. There is no obvious matrix effect interference in the synthetic element interference determination. The method is suitable for the determination of 50.0g/t~10000.0g/t silver in bismuth concentrate, which provides a more simple and practical method for enterprises and testing institutions to determine the silver content in bismuth concentrate.

Abstract:The content of sulfuric acid and zinc ion in zinc electrolyte directly affects the purity and product quality of zinc. At present, the detection of sulfuric acid and zinc ion content in electrolyte depends on offline detection, the degree of automation is low, and the research and application of combined determination device is less. In this paper, the photometric titration on-line analysis system is introduced, and the content of sulfuric acid and zinc ion is determined by optimizing the detection parameters and the absorbance mutation.Under the conditions of sampling speed of 30mL/min and waiting time of 2s after liquid extraction, the sampling accuracy of the sample can be guaranteed. Zinc ion was determined by EDTA complexometric titration, with xylenol orange as the indicator, the amount of 0.2mL, the amount of hexamethylenetetramine buffer solution was 50mL, and the zinc ion was determined at the wavelength of 525nm. Sulfuric acid was determined by acid-base titration with methyl red-methylene blue indicator at a dosage of 0.2mL, and the wavelength was controlled at 420nm. The titration end point was determined by the color change of the indicator. The results showed that it was feasible to determine the titration end point according to the absorbance mutation by using the photometric sensor to collect the signal under the optimized experimental conditions. The stability test of the standard sample was carried out in the experiment, and the actual value was basically consistent with the identified value, indicating that the device and method were accurate and reliable. According to the method, the precision of the actual sample (n=7) and the recovery rate of the standard addition were tested and compared with the manual off-line detection. The overall RSD of the precision was less than 1.2%, and the recovery rate of the standard addition was 98.4%~101% and 99.1%~99.8%, respectively. The t test proves that there is no difference between the instrument test results and the manual test. The device can realize automatic analysis, simple operation, and the analysis items are carried out at the same time, which can meet the needs of online continuous production detection.

Abstract:During pyrometallurgical processes, thallium is easily volatilized and entered into flue gas scrubbing operations, resulting in a large amount of thallium-containing wastewater and posing environmental pollution risks. Additionally, millions of tons of leaching residue waste, mainly composed of ZnFe2O4, are generated in the lead-zinc industry. Therefore, this study proposes the Preparation of high-efficiency thallium adsorption materials from zinc leaching residues. Initially, the zinc and iron are extracted from the residues using an acid leaching method. Thereafter, iron is separated from the leachate through a selective precipitation process. Ultimately, the iron precipitate is subjected to freeze-drying to produce thallium adsorbent. The counter-current leaching method achieves high leaching efficiencies of zinc and iron(Zn: 97.05% and Fe: 99.31%). The concentrations of zinc and iron in the leachate are 86.54g/L and 77.86g/L, respectively. The selective iron precipitation process is capable of precipitating 99.78% of the iron from the leachate, with the zinc loss controlled to below 0.5% concurrently. Upon treatment with the freeze-drying process, the iron precipitate exhibits exceptional performance in the adsorption of thallium, achieving a removal rate of 98.9% in an aqueous solution with a concentration of 3g/L thallium. A dilute hydrochloric acid solution with a pH value of 1.5 can desorb 95% of the adsorbed thallium, providing favorable conditions for the further recovery and resource utilization of thallium. This process not only achieves green and high-value recovery of zinc leaching slag but also successfully prepares an iron-based thallium adsorbent with competitive performance.

Abstract:The efficient removal of chloride ion (Cl-) is a bottleneck problem in the field of the recycling of waste acid generated from the nonferrous metallurgy. In recent years, advanced oxidation process has shown great application potential in removal of Cl-. In this paper, the dechlorination efficiency, mechanism, cost and operation management of lead dioxide (PbO₂), sodium bismuthate (NaBiO₃) and potassium peroxymonosulfate (PMS) were compared and analyzed. In order to achieve the residual Cl- concentration of less than 200mg/L for the requirements of waste acid reuse, the dosage of PbO₂ NaBiO₃ and PMS were 4, 1.5 and 1.5 times of the theoretical value, while the required reaction temperature were 50, 20 and 60℃, respectively. The regeneration of PbO₂ and NaBiO₃ were realized by mixing the dechlorination solid products with chlorine gas absorption solution, and the dechlorination efficiency of the regenerated reagents were higher than 90% in five cycles. Highly active intermediate species such as hydroxyl radical (·OH), sulfate radical (·SO^-₄) and chlorine radical (·Cl) were involved in the dechlorination processes of PbO₂ NaBiO₃ and PMS. The contribution of direct oxidation, indirect oxidation of ·OH and indirect oxidation of ·SO^-₄ for dechlorination process of PMS were about 84%, 9% and 7%, respectively. In terms of practical application value, NaBiO₃ has more advantages in cost and energy consumption due to its renewability, high by-product recovery value and low reaction temperature, while PMS is simpler in terms of operation and management because it does not introduce impurities.

Abstract:Spent lithium-ion batteries are not only rich in lithium, cobalt, nickel and other important metal resources, but also contain heavy metals, organic pollutants, etc. The synergistic leaching scheme of the existing literature usually introduces impurity elements such as phosphorus and rare earth, which makes the metal separation process more complicated. In this study, lithium cobalt oxide waste with oxidability and cobalt white alloy waste with reducibility were taken as the research objects, and the experimental study on the synergistic leaching of lithium cobalt oxide waste-cobalt white alloy was carried out. The effects of mass ratio of cobalt white alloy and lithium cobalt oxide waste, sulfuric acid concentration, leaching temperature, leaching time and other factors on the synergistic leaching were investigated, and the mechanism of leaching process was discussed. The results show that under the conditions of mass ratio 0.25, sulfuric acid concentration 1mol/L, leaching temperature 60℃, leaching time 1h, solid-liquid ratio 50g/L and stirring rate 375r/min, the leaching efficiencies of Li, Co, Cu and Fe can reach 99.83%, 97.51%, 95.36% and 75.6%, respectively. The 2+ produced by the dissolution of cobalt white alloy in the synergistic leaching process plays a reducing role, which promotes the dissolution of LiCoO₂, and the generated Fe³⁺ form FeOOH precipitation. This method not only achieves synergistic leaching, but also reduces the introduction of chemical reagents, which provides theoretical and technical support for the clean and efficient utilization of waste lithium ion batteries and cobalt white alloys.

Abstract:During the sulfuric acid roasting process of copper anode mud with high selenium and tellurium content, the roasted sand was sintered into large blocks, resulting in a low evaporation ratio of selenium. In response to this issue, this study utilized the high content of elemental copper in high copper slag to explore the synergistic sulfuric acid roasting process of copper anode mud and high copper slag, and conducted conditional experiments. The experimental results indicate that it is feasible to use high copper slag synergistic sulfation roasting process to treat copper anode mud, and under the condition of a mass ratio of copper anode slime to high copper slag (measured by dry weight) of 1∶0.1, the mass ratio of sulfuric acid to the mixture of 0.85∶1, the slurry time of 60 minutes, and the four zones of roasting temperature of 300℃, 480℃, 570℃, 610℃, and 120 minutes, respectively. The selenium content in the roasted sand could be reduced to below 0.1%. Industrial tests have shown that the produced roasted sand particles are small and honeycomb shaped internally. The selenium in the copper anode mud is effectively evaporated, and the average selenium content in the roasted sand is reduced from 6.67% to 0.09%, with a removal rate of 98.65%. The crude selenium generated during the sulfation roasting process has a purity greater than 96% and can be used to produce high-purity selenium or directly sold externally; The copper in the generated roasted sand can be separated by ball milling water leaching, gold can be recovered by chlorination, silver can be recovered by ammonia leaching of gold slag, and finally valuable metals can be further recovered by pyrometallurgical melting of silver slag. Compared with the conventional copper anode mud sulfuric acid roasting method, this process achieves deep evaporation of selenium from copper anode mud and effective treatment of high copper slag, which has promotional value.

Abstract:The rational treatment of spent electroless nickel plating bath is a subject of environmental protection and resource utilization owing to its large emission and complex composition. The recycling of sulphur, sodium, phosphorous and carbon elements in the spent bath is seldom investigated. BaSO4 powders were prepared by a co-precipitation method from the spent bath where nickel ions were removed, using the complexation of citrate anions for barium ions. It was investigated that the effects of the molar ratio of citrate ions and barium ions, pH value, temperature and time on the removal rate of sulfate ions, barium sulfate’s productivity, morphology and particle size distribution. The results show that under the condition of the ions ratio of 1∶3, the pH value of 9, the temperature of 55℃ and the time of 10h, the removal rate of sulfate ions and the productivity of barium sulfate reach 99.7% and 98.9%, respectively. The obtained barium sulfate consists of narrow-distribution uniform-sized high-purity spherical-like particles. This route achieves the high-value resource utilization of sulfate anions in the spent electroless nickel plating bath, which conforms to the concept of green circular economy.

Abstract:The study of solid-liquid mixing characteristics is of great significance to the optimization of production efficiency, energy consumption and other indicators, and the vertical mixing kettle is more often used in actual production. In this paper, we use the CFD method and the DEM method to carry out numerical simulation research on the particle mixing characteristics of the vertical mixing kettle in terms of the particle density, particle size, mixing speed and the initial liquid level height, etc., and evaluate the particle mixing characteristics in terms of three dimensions, namely the velocity field, turbulent kinetic energy distribution and the degree of mixing of the particles. The mixing characteristics of particles were judged from three dimensions: velocity field, turbulence energy distribution and particle mixing degree. The results show that, among these factors, the particle density and stirring speed have the greatest influence on the mixing characteristics, especially when the particle density is 1200kg/m³, the relative standard deviation value reaches about 0.5, which indicates that the mixing degree is better; the larger the stirring speed is, the better the mixing performance is; the particle size has less influence on the mixing performance, but the smaller the particle size is, the more easy it is to be suspended, and the increase of the particle size decreases the mixing degree; the change of initial liquid surface height leads to the change of solid content rate, but it has no effect on the solid-liquid mixing performance.

Abstract:between the two phases. Taking into account surface tension and gravity, the equations for the conservation of mass and momentum are calculated in real time. The pressure-velocity coupling is realized by the SIMPLE scheme, and the interface reconstruction is achieved by the geometric reconstruction PLIC scheme. The effects of stirring speed, bubble size, surface tension, density ratio and initial position of bubbles on the motion and deformation of bubbles in the stirring tank were analyzed. The results show that the stirring speed can change the shape of the bubble, and the surface tension can maintain the shape of the bubble and prevent the deformation of the bubble. The bubble size and density ratio affect the velocity of the bubble, which further affects the deformation behavior of the bubble, and the difference of the initial position of the bubble has a significant impact on the movement and deformation of the bubble. The results of this paper can provide a theoretical reference for optimizing the flotation process parameters and improving the flotation efficiency of minerals.

Abstract:Given the current lack of a mature system and conclusions regarding the pneumatic conveying of wet granular materials in dense phase, this paper explores the flow mechanisms and flow patterns of wet granular dense phase pneumatic conveying, providing theoretical support for the optimization design of pneumatic conveying systems. The study employs a bidirectional coupling numerical simulation method using computational fluid dynamics (CFD) and discrete element method (DEM) to analyze the motion forms of dry and wet granular plugs in horizontal pipelines and the trajectories of particle movement. It further investigates the impact of moisture content on the conveying flow pattern, conveying efficiency, and pressure drop during conveying.The results indicate that under the same gas velocity, wet particles can form plug flow, while dry particles initially exhibit plug flow, which then evolves into dune flow as the plug is penetrated by the gas, ultimately becoming bottom flow. As the gas velocity increases, the pressure drop per unit length of the horizontal pipeline shows a trend of first decreasing and then increasing.Under the condition of mass flow rate of 0.5kg/s and water content of 5%, the pipeline pressure drop is the lowest when the conveying speed is 9m/s, which is the best economic speed value.The pressure curve of wet particles remains in a highly fluctuating unstable state; when two monitoring points are located outside the plug, the axial pressure difference is nearly zero, while when the monitoring points are inside the plug, the axial pressure difference can reach -600Pa. By analyzing and monitoring the pressure drop changes during the conveying of wet particles, signs of equipment failure can be detected in a timely manner, allowing for early warnings of potential issues and the implementation of preventive measures to avoid equipment damage and production interruptions.

Abstract:The rotating chute is an important component of the blast furnace burden distribution system. It can affect the speed and distribution of burden materials at the chute tip by changing chute angle and rotating speed, hence further impact the falling trajectory. In this work, we use the discrete element method to study the behavior of burden materials under different conditions including varying the chute structure, chute angle, and particle shape. The results demonstrate that the segregation can occur during the chute distribution process, and the chute angle of the chute has a great influence on the burden distribution. The larger the angle, the more stable the material flow; the larger the particle size, the greater the influence of the particle shape. The square shaped chute can effectively decease the width of the material flow, thereby achieving the effect of precise distribution. The addition of wear-resistant lining plates can also achieve the precise distribution to a certain extent.