China Nonferrous Metallurgy

Abstract:Oxalic acid was used as a leaching agent to extract vanadium from spent FCC catalysts. The impacts of the main leaching conditions on extraction rates of vanadium, silicon and aluminum were examined. With a leaching time of 240min, a leaching temperature of 95℃, and an oxalic acid concentration of 2.0mol/L, the vanadium extraction rate exceeded 70%. The residue of the spent FCC catalysts after leaching and the steel slag were coupled as raw materials to prepare geopolymers, and the leaching concentration of vanadium toxicity was tested. The results showed that the leaching concentration of vanadium toxicity increased after the residue of the spent FCC catalysts was used to prepare the geopolymers, and the fixation rate decreased. The existence form of vanadium in the spent FCC catalysts and its changes during the reaction process were analyzed by XPS. During the geopolymer preparation process, V₂O₅ in the spent FCC catalysts was transformed into NaVO₃, causing the vanadium in the geopolymers to exist mainly in the form of VO^-₃ anions. Therefore, the vanadium in the spent FCC catalysts can only be immobilized by the geopolymers through physical encapsulation, and the immobilization rate is positively correlated with compressive strength of the geopolymers. The leaching of silicon and aluminum should be controlled simultaneously during the leaching process, so that the geopolymer products prepared have better mechanical properties, thus improving the fixation rate of residual vanadium and meeting the standard of vanadium toxicity leaching.

Abstract:As a large-scale energy storage technology, all-vanadium redox flow batteries (vanadium batteries) have received widespread attention because of their high safety, stability, long service life, design flexibility and low environmental impact. However, vanadium batteries are limited in their development and commercial application because of solubility of vanadium compounds and stability of vanadium ions. In this paper, to improve the capacity, energy density and high-temperature stability of vanadium batteries, the main components of the vanadium electrolyte of the sulfuric-phosphoric mixed acid system and their performance effects were investigated. Through stability, electrochemical performance and battery performance of the electrolyte testing and analysis, the study shows that the sulfuric-phosphoric mixed acid system significantly improves the high-temperature stability of V(V) electrolyte, and the stabilization time is extended by 68h at 50℃. However, when the phosphoric acid concentration exceeds 0.2mol/L, a new precipitate of VOPO4 is formed, and the original V2O5 gradually disappears. When the sulfuric-phosphoric mixed acid electrolyte concentration composition is vanadium ion concentration of 2.0mol/L, sulfuric acid concentration of 3.0mol/L, phosphoric acid concentration of 0.15mol/L keeping stable after 100 times charge and discharge at 50℃, and without any precipitation, its capacity is 16.9Ah/L, energy density is 21.5Wh/L, coulomb efficiency is 94.0%.

Abstract:High nickel matte is an important intermediate product in the nickel metallurgical process. By using nickel matte, nickel products such as ferronickel, electrolytic nickel and nickel sulfate can be mutually transformed and balanced in the market, which is of great significance for the steady development of nickel industry. A large number of leaching residues containing nickel, copper, cobalt, gold, silver, platinum, palladium and other precious metals are produced from high matte nickel after nickel hydrometallurgical extraction, which has great comprehensive utilization value. Researchers have solved the key technologies of separation and extraction of valuable components of high nickel matte leaching residue, and realized the development of the enterprise from the original single electrolytic nickel production workshop to an industrial park for comprehensive recovery of nickel, copper, cobalt and precious metals such as gold, silver, platinum and palladium. In recent years, driven by the increasingly strict environmental protection policies and the low-carbon transformation of metallurgical process, technologies such as hot acid pressure leaching for nickel reduction in residues, oxygen pressure leaching instead of rotary kiln roasting to treat the residues after copper extraction, and resource utilization of sodium sulfate wastewater are further proposed to optimize and upgrade the existing process and improve the quality and efficiency. This paper mainly introduces the current situation of the metallurgical process of high nickel matte leaching residue, analyzes the existing problems, expounds the latest progress of the improved process, metallurgical principle and industrial practice, and provides reference for relevant enterprises.

Abstract:In this study, “sulfide leaching-selective reduction” process was proposed for tellurium recovery. The copper telluride slag and refining slag from the silver separation furnace in the process of anode slime treatment process was used as the raw materials in this study. In the sulfide leaching process, the sodium sulfide excess coefficient was 10 and 6 times, the solid to liquid ratio was 10∶1, the rotation speed was 400r/min, the temperature was 90℃ and 40℃, and the time was 3h. Under these conditions, the tellurium leaching efficiencies of the two were 97.00% and 99.75%, respectively. In the directed reduction process, the sodium sulfite excess coefficient was 5 times, the rotation speed was 400r/min, the temperature was 70℃, and the time was 3h. Under these conditions, the tellurium reduction ratios of the two were 99.75% and 91.49%, respectively. The total tellurium recoveries of the two were 96.76% and 91.26%, respectively. The purity of coarse tellurium powder was higher than 99%. The selenium in the waste liquid after selective reduction was further recovered. The excessive sodium and sulfur in the waste liquid can be recovered by evaporation and crystallization after oxidation. Generally, the total process performed good adaptability, high recovery, high product purity, low cost and short process flow in tellurium recovery.

Abstract:In this paper, the reaction behavior of Fe of jamesonite in the process of low temperature molten salt smelting is studied. By simulating the reaction process of Fe of the jamesonite in the Na₂CO₃-NaCl molten salt system, XRD was used to analyze the reaction behavior of Fe in the smelting process of FeS, FeS₂, ZnO and carbon powder in the same system.and the Fe distribution on the surface and cross section of the lead-antimony alloy obtained from the smelting of jamesonite was characterized by SEM-EDS.The results show that FeS reacts with ZnO to form FeO, and FeS₂ reacts with Na₂CO₃ to form FeS and Na₂S at 973K. At 1073K, FeS and FeS₂ are reduced with ZnO and carbon powder to form Fe, Fe₃O₄ and ZnS. At 1173K, the reaction products of FeS and FeS2 with ZnO and carbon powder mainly include ZnS, Fe, Fe₃O₄ and Fe₂O₃. Fe elements in FeS and FeS₂ are gradually oxidized to Fe, Fe₃O₄ and Fe₂O₃ with the increase of temperature or the extension of reaction time.Fe is eventually expelled from the reaction system mainly in the form of slag.The study can provide scientific basis for studying the reaction behavior of Fe of jamesonite in low temperature melting of Na₂CO₃-NaCl system.

Abstract:At present, the production of Be(OH)₂ by leaching neutralization liquid of beryllium ore is generally added to ammonia water for stirring and precipitation under boiling conditions, resulting in increased energy consumption and a large amount of ammonia volatilization, volatile ammonia has a strong pungent odor and carries toxic beryllium substances that seriously affect the working environment of workers.In order to reduce energy consumption and reduce the volatilization of ammonia, the neutralization liquid circulating precipitation test was carried out under room temperature conditions.The test results show that the volume fluctuation of suspension precipitatant increases when the 5th cycle precipitation is carried out, and after the 10th cycle, the volume of suspension precipitatant remains stable and fluctuate, and the phenomenon of stratification is obvious, the ammonia consumption of each precipitation is 55~65mL, and the volume of suspension precipitated is stable in the range of 2500~2800mL. Compared with the existing process, ammonia consumption is reduced by nearly 70%, and the BeO content and impurity content in Be(OH)₂ are comparable to the existing production methods.The process greatly saves amount of ammonia water, reduces investment of heating equipment, reduces energy consumption, and reduces safety risk of the operation position, which provides some feasible references for the improvement of beryllium neutralization and liquid precipitation process in the future.

Abstract:With the increasing current intensity, the thermal field and flow field generated by the aluminum reduction cell are more complex. Based on the COMSOL Multiphysics 3D simulation software, the thermal field slice model and the flow field full cell model are established. The thermal field and flow field of a 400kA aluminum reduction cell of a manufacturer are studied. The accuracy of the simulation and the rationality of the manufacturers design are verified by comparing the test results and simulation results with the field test data. On the basis of numerical simulation, it is verified that nano materials are added to the side and bottom of the aluminum reduction cell, and the maximum temperature of the aluminum reduction cell is from 978℃ to 985℃, which shows that the aluminum reduction cell has a good thermal insulation effect. The flow field of the aluminum reduction cell with a height of 260~310mm aluminum liquid layer is studied, and it is found that the aluminum level is relatively stable within the range of 270~280mm.

Abstract:Phosphogypsum (PG) is a waste product containing rare earth elements from the phosphate fertilizer industry,with low levels of rare earth elements, but have large reserve quantity, and the recycling of rare earth elements from it has large economic value. The study focuses on the in-depth characterization of phosphogypsum and the study of the leaching process. Microwave assisted acid leaching of phosphogypsum was proposed to acid leaching of the rare earth elements. The results show that under the conditions of nitric acid concentration of 2.0mol/L, solid/liquid ratio of 6∶100，leaching temperature of 80℃ and leaching time of 30min, the leaching rate of total rare earth elements in phosphogypsum was 96.52% under the microwave reactor. The mechanism of microwave acid leaching was investigated with the characterization of SEM and XRD, which further showed that the interaction of microwave and high temperature in the process of microwave acid leaching would destroy the crystal structure to refine the particles, thus promoting the effect of microwave leaching 12.3% higher than that of water bath leaching.

Abstract:Red mud is a strong alkaline solid residue produced in the process of alumina production, which limits its large-scale application in cement and other fields. It is urgent to develop efficient alkali removal technology of red mud and support sodium content analysis and detection technology. In this paper, sodium in Bayer red mud was measured by flame atomic absorption spectrophotometry. The existing method was improved. The red mud sample was digested by hydrochloric acid (1+1) without using precious metal crucible. The digestion time of the sample was optimized. The ionization interference of sodium was effectively eliminated by KCl, and the effective concentration range of KCl in the literature was corrected. Under the optimized measurement conditions, the recovery rate of standard addition was 99.17 %~105.00%, and the relative error of red mud standard sample was -0.22%~0.29%. The relative standard deviation (n=10) of red mud was 1.28%, and the relative standard deviation (n=3) of red mud standard sample was 0.85%~2.72%. The method has high sensitivity, good accuracy and precision, and the conventional laboratory can meet the analysis and detection conditions, which can provide reliable analysis and detection support for the development of efficient alkali removal and comprehensive utilization technology of red mud.

Abstract:The magnetic walnut shell biochar was prepared by using walnut shell powder as biomass raw material and H₂O₂ and FeCl₃ as modifiers in turn under oxygen-limited conditions, and then the chitosan/magnetic walnut shell biochar composite (CS/MWSB) was prepared by using chitosan as modifier and polyethylene glycol as cross linking agent, and SEM, FT-IR, N₂ desorption, XRD, XPS, and VSM techniques were used to characterize the morphological and physicochemical properties, and the adsorption performance of CS/MWSB on Pb(Ⅱ) in simulated wastewater was investigated by static tests. The results showed that: the surface of CS/MWSB had a large number of microporous structures, and the active groups and the aromatic group of CS/MWSB increased when the surface was loaded with spherical Fe3O4 particles and chitosan; the CS/MWSB with 30% chitosan loading had the strongest adsorption capacity for Pb(Ⅱ); for the Pb(Ⅱ) solution with the initial concentration of 400mg/L, when the adsorbent was dosed at 4g/L, the adsorption capacity of CS/MWSB was increased by the adsorption of Pb(Ⅱ). The adsorption rate of CS/MWSB for Pb(Ⅱ) was 90.86% and the adsorption capacity was 89.86mg/g at pH 5.0 and temperature 40℃ for 3h. The adsorption of Pb(Ⅱ) by CS/MWSB was in accordance with the quasi-secondary kinetic equation and the adsorption process was mainly chemisorption.

Abstract:Based on the carbon emission reduction needs of the lead recovery industry in the production process, this article uses the life cycle assessment method to study the carbon footprint of three typical recycled lead processes: sodium method lead paste pre-desulfurization and low-temperature melting, ammonium bicarbonate pre-desulfurization and low-temperature melting, and high-temperature melting. The results indicate that the carbon emissions during the lead paste recovery process mainly come from the use of energy and reducing agents; the carbon footprint of the lead paste high-temperature melting process is 876kg/t of lead; compared with high-temperature melting, low-temperature melting process has lower environmental impact and less pollution; the carbon footprint of lead paste sodium method pre-desulfurization low-temperature melting and ammonium bicarbonate method pre-desulfurization low-temperature melting have been reduced by 38.9% and 25.6%, respectively, with high carbon emission reduction benefits. The research results point out the direction for carbon abatement in the recovery process of waste lead paste, and have important guiding significance for promoting low-carbon development in the recycled lead industry.

Abstract:As a cutting-edge material for photocatalysis, TiO₂ has received extensive attention. The performance of TiO₂ as a photocatalyst depends on various parameters, including morphology, surface area, and crystallinity. Although TiO₂ exhibits good catalytic activity in various catalytic systems, its performance as a photocatalyst is generally limited due to its low electrical conductivity and wide band gap. Many different studies have been devoted to overcoming these problems, resulting in significant improvements in photocatalytic performance. In this paper, the research progress of TiO₂ photocatalytic hydrogen evolution reaction in recent years is reviewed, and the adjustment and improvement of the photocatalytic activity of TiO₂ by the change of catalyst components, doping and photosensitization are discussed. The advantages and limitations of each modification method are reviewed. Finally, the main obstacles and development prospects of TiO₂ as a photocatalyst in the future development are pointed out.