Leach Residue Research Articles

Study on pre-oxidation of silver concentrate and leaching behaviour of Zn, Cu and In during oxygen-pressure leaching

Given the limitations of current processing methods and the potential of high recovery of silver as a flotation concentrate, this study proposes a pre-oxidation followed by oxygen pressure sulphuric acid leaching route for zinc, copper and indium and thoroughly examines the alteration in micro-morphology of the silver concentrate of 1.22% Pb, 3010 g/t Ag and 649 g/t In. Under the optimal conditions of a sulphuric acid pre-oxidation temperature of 60 °C, and an acid-to-ore mass ratio of 0.6, over 15 h, the PO and -OH polar groups of flotation reagents on the surface of silver concentrate particles are effectively neutralized through sulphuric acid oxidation. This action prevents the formation of a hydration film and mineral inclusions, thereby facilitating the efficient leaching of valuable elements. With a set reaction temperature of 155 °C, an initial acidity of 160 g/L, a reaction time of 180 min, an oxygen partial pressure of 0.8 MPa and a liquid-to-solid ratio of 7 mL/g, the leaching efficiency of Zn, Cu and In in the silver concentrate reach 94.8%, 98.4% and 91.1%, respectively while the lead and silver grades in the leach residue increase to 2.88% and 7754 g/t, respectively.

Investigation of the effect of mechanical activation on nickel and cobalt extraction from laterite at atmospheric pressure by kinetics and leach residue analysis

ABSTRACT Nickel and cobalt extraction from laterite has been studied for years but has not been investigated enough by leach residue analysis. Also, the kinetic approach and leach residue analysis become important when mechanical activation improves nickel and cobalt extraction. Various kinetic assumptions were applied to understand the dissolution behaviour of Ni, Co, and Fe. The ore was activated mechanically in a planetary ball mill as a pre-treatment. The effects of liquid-to-solid ratio, acid ratio, leaching time, and temperature on the leaching of non-activated ore were studied to fix the parameters for the leaching of pre-treated ore. Leaching efficiencies of activated ore for 15 and 60 min exhibited better results at lower temperatures and shorter times than non-activated ore. Nickel extraction has 70% efficiency for 5 min leaching at 95°C in mechanically activated ore. Besides higher dissolution efficiency, apparent activation energy (Ea) decreased. Dissolution of metals from non-activated and activated ore was found to be mixed-controlled. Two different diffusion-controlled mechanisms that differ in the diffusion coefficient-time relationship were detected. An analysis of leach residue supported this finding.

Lithium leach residue synthesis process of high crystallinity hydroxysodalite, NaX, NaA zeolites and solidification and migration of potentially toxic elements

Converting lithium leach residue (LLR) into zeolite can reduce environmental impacts while also producing high value-added products. However, the synthesis of zeolites by LLR under alkali fusion may result in the solidification and migration of potentially toxic elements with secondary environmental impacts. Systematic research into this subject is rare in the open literature and the mobility of toxic elements from LLR derived zeolites is yet to be understood. In this paper, we have investigated the highly crystalline synthesis of hydroxy sodalite, X-type zeolite (NaX), and A-type zeolite (NaA) without stencil agent and crystal species, which can be achieved by modulating the alkali fusion temperature, all three zeolites have greater than 90 % conversion of the major elements aluminum and silicon. Meanwhile, the leachability of thallium (Tl), beryllium (Be), and potentially toxic elements (lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), arsenic (As), barium (Ba), copper (Cu), nickel (Ni), cobalt (Co), zinc (Zn)) was monitored by pH-dependent leaching test for LLR and three kinds of synthesized zeolites according to the Chinese standard and the emission of toxic elements during the synthesis process was analyzed, to investigate the migration and quantify the distribution of the toxic elements in the LLR to the product zeolites and the cleaning wastewater. The migration efficiency of potentially toxic elements from LLR to the product zeolite and cleaning wastewater was explored. It was found that most of the toxic elements Tl, Be and potentially toxic elements were solidified in the structure of the zeolites by ion exchange (solidification rate > 90 %), and a small portion flowed into the cleaning wastewater. Although there are toxic elements solidified in the structure, there is no significant leaching under various pH conditions, which is in line with the Chinese standard (GB/T 5085.3–2007). Therefore, it is considered that LLR realizes environmentally friendly zeolite production and does not cause secondary pollution to the environment. This work demonstrates great potential for green recycling of LLR from the lithium extraction process and introduces an environmentally friendly slag treatment technology.

Investigation of Phosphate Removal from Aqueous Solutions Using Zinc Extraction Waste

It is important for waste management to economically evaluate the solid leach residues released in zinc production facilities and classified as hazardous waste due to the metals they contain, without harming the environment and human health. Although the disposal of these residues often requires special technologies, hazardous wastes are left to the environment or landfills due to the expense of these technologies and the inadequacy of legal sanctions in some cases. For this reason, it is important from an economic and environmental perspective to evaluate these residues and bring them into the industry. In this study, lead cake formed during zinc extraction production, brought from Kayseri Çinkur enterprises, was used. Since this waste contains high amounts of lead as well as zinc and iron, the conditions for removing phosphate from aqueous solutions were investigated. Phosphate removal adsorption isotherms were obtained using the obtained batch test results. Additionally, some thermodynamic quantities regarding phosphate removal were calculated. As a result of the experiment, it was determined that the P removal efficiency from aqueous solutions significantly depends on the solution pH and the dose of waste lead cake. It was also determined that phosphate removal from aqueous solutions obeyed the Langmuir and Freundlich isotherm. Additionally, it was observed that phosphate adsorption equilibrium was established after a period of 120 min. By mixing 100 mg/L phosphate solution with pH 7.69 with 20 g/L lead cake without any addition and contacting for 120 minutes, approximately 74% of the phosphate can be effectively removed by adsorption.

Efficient mechanochemical leaching of zinc from zinc oxide ores

A basket grinder was used as mechanochemical activation equipment to study low-grade lead–zinc oxide ores in the Lanping area, China and a mechanochemical leaching (MCL) process combining grinding with NaOH solution leaching was proposed for zinc leaching. The effects of leaching temperature, NaOH concentration, leaching time, liquid–solid ratio, and stirring speed on zinc leaching rate were investigated. Experimental results show that under the optimal conditions, the zinc leaching rate of MCL reaches 92.3%, which is 7.2% higher than that of conventional stirring leaching (CSL). And small difference in energy consumption is observed between the two processes, indicating the superiority of MCL. The strengthening mechanism of mechanochemical activation was investigated by analyzing the zinc phase of raw ore, and XRD, SEM−EDS, EPMA and particle size analyses were conducted on leaching residues from different processes under the optimal conditions.

A mild and efficient closed-loop recycling strategy for spent lithium-ion battery

As lithium metal resource supply and demand stabilize and prices decrease, the efficient recovery of valuable metals other than lithium from spent lithium-ion batteries is receiving increasing attention. Currently, challenges remain in the selective lithium recovery efficiency and the high cost of regenerating valuable metal slag after lithium extraction, particularly for spent ternary cathode materials. To address these challenges, this study introduces a closed-loop recovery process for spent ternary cathode materials, employing sulfur-assisted roasting to achieve efficient lithium extraction and high-value direct regeneration of ternary leaching residues. At moderate temperatures (500 ℃), LiNixCoyMn1−x-yO2 (NCM) materials undergo a directional transformation of lithium to Li2SO4 in synergy with sulfur and oxygen, achieving a lithium leaching extraction rate of 98.91 %. Additionally, the relatively mild reaction conditions preserve the secondary spherical morphology and uniform distribution of NiCoMn-based oxide residue without introducing adverse impurities, ensuring the successful regeneration of high-value NCM cathode materials (R-NCM). The R-NCM material exhibits good discharge capacity (144.3 mA·h/g at 1 C) and relatively stable cycling performance, with a capacity retention rate of 80 % after 150 cycles. This work provides a viable pathway for the efficient and environmental-friendly pyrometallurgical closed-loop recovery of spent lithium-ion batteries.

Optimisation of hybrid process to recover zinc from electric arc furnace dust using design of experiment approach

ABSTRACT Recoverable metals like zinc and iron are present in the dust from electric arc furnaces (EAF), a byproduct of the steelmaking process. These metals are mainly present as zinc ferrite (ZnFe2O4), magnetite (Fe3O4), and zinc oxide (ZnO) compounds. ZnO is easily dissolved in either an acidic or an alkaline solution; however, ZnFe2O4 is more difficult to dissolve. Therefore, our earlier paper suggested the thermodynamic analysis of a preliminary caustic-roasting treatment to transform the ZnFe2O4 from EAF dust into more soluble products of ZnO and NaFeO2. Finally, the present study carried out a hybrid process that involved the caustic roasting of EAF dust and a caustic leaching of the roasted product. At first, the effects of caustic-roasting process parameters on zinc-ferrite conversion were studied using the Taguchi method. The implication of Design of Experiment (DoE)-Taguchi analysis and the analysis of variance (ANOVA) shows the optimum caustic-roasting conditions are: roasting temperature of 350 oC, NaOH/ EAF dust molar ratio of 4, and roasting time of 60 minutes. The effect of temperature, reaction time, NaOH concentration, and solid/liquid (S/L) ratio was also examined using the same method in the subsequent caustic-leaching process. Similarly, the analysis shows that maximum Zn dissolution is possible at a NaOH concentration of 6M, a leaching temperature of 40 oC, a liquid-to-solid ratio of 60 ml/g, and a leaching time of 60 minutes. After the hybrid process, the zinc recovery was 83%, while most iron oxides remained in the leach residue.

The stepwise extraction strategy for selective recovery of scandium from hydrochloric acid leachate of bauxite residue based on reactivity of metal ions

The recovery of Sc from secondary resources such as bauxite residue has received considerable interest. As the main elements in bauxite residue, Fe and Al exhibit significant interference in the selective separation of Sc. Herein this work, a stepwise extraction strategy of Sc from the hydrochloric acid leachate of bauxite residue was proposed based on the differences in reactivity of metal ions. The results show that Fe(III) and Sc(III) can be extracted sequentially with Aliquat 336 and Cyanex 272 from hydrochloric leachate. The separation factors of Fe/Sc, Fe/Al and Sc/Al were up to 4.3 × 104, 4.1 × 104 and 2.6 × 103, respectively. The results of spectroscopic characterization indicate that a cation exchange and coordination occur during the extraction of Sc(III) with Cyanex 272. The Sc(III) complex with Cyanex 272 (H2A2) is presented as ScClA2(HA)2¯. The loaded Aliquat 336 and Cyanex 272 can be stripped with acidified sodium sulfite and oxalic acid, respectively. The extraction-stripping performance of the stepwise separation route was investigated and the extraction efficiency of Fe(III) and Sc(III) can be remained above 97 % after 5 cycles. The proposed strategy has the potential to be considered industrially for the recovery of Sc from bauxite residue and other secondary resources.

Selective extraction of molybdenum from an industrial powdery tungsten-molybdenum mixture scraps through ultrasonic-assisted electrochemical dissolution mechanism

Extraction and recovery of W and Mo from waste scraps hold significant importance for sustainable resource utilization and environmental protection. Ultrasonic-assisted leaching was demonstrated to be a clean and efficient method for metal dissolution and separation, and the research emphasis of this work was focused on ultrasonic electrochemical behaviors. The HNO3 leaching behaviors of W and Mo under conventional and ultrasonic-assisted processes from powdery W-Mo mixture scraps generated in the powder metallurgy process were investigated. It’s demonstrated that Mo and W can be selectively separated by the regulation of lixiviant concentration and temperature, in which the Mo is converted into the soluble ions (MoO22+) while the W particle is kept in original metallic state and covered with insoluble WO3·H2O. Experiment results indicated that 96.38 % Mo and 8.03 % W were rapidly leached in 2 mol/L HNO3 within ultrasonic-assisted leaching for 10 min at 25 °C, showing a favorable pre-separation effect. Phase transformation and microstructure evolution of the leaching residues under conventional and ultrasonic-assisted leaching processes were analyzed. It’s suggested that Mo can precipitate in the form of molybdenum oxide hydrates, covering the unreacted particle surfaces and further hindering the Mo leaching, especially at higher temperature. This unfavorable situation can be relieved by the introduction of ultrasonic cavitation effect. Importantly, the electrochemical dissolution behaviors of pure W, pure Mo, and W-Mo alloy sheets in HNO3 solution were compared employing the potentiodynamic polarization and electrochemical impedance spectroscopy testing to reveal the ultrasonic intensifying mechanism in this study. Eventually, the ultrasonic electrochemical intensifying mechanism can be referential for the efficient dissolution of metal-based scraps for resource recycling.

Simultaneous removal of ammonia nitrogen and manganese by anoxic/oxic (A/O) process from electrolytic manganese residue leachate

Ammonia nitrogen and manganese contained in the leachate of electrolytic manganese residue are causing serious damage to the ecological environment. In this study, anaerobic/oxic (A/O) process as a biological method to achieve simultaneous removal of nitrogen and manganese produced during the actual production of manganese. Results indicated that after 137 d of operation, the system achieved 96.73 ± 1.25%, 98.42 ± 0.60%, 96.97 ± 0.19%, and 100% removal of Mn(II), NH4+-N, TN, and chemical oxygen demand (COD), respectively. Extracellular polymeric substances (EPS) secreted by microorganisms was converted to carbon source to promote denitrification. Scanning electron microscopy (SEM) showed that Mn(II) formed manganese crystals in the process of complete reflection with sludge, acting as electron donor to achieve simultaneous removal of nitrogen and manganese, and removal of Mn(II) was found by X-ray photoelectron spectroscopy (XPS) through redox and valence changes. 16S rRNA indicated that Proteobacteria, Deinococcus-Thermus, Bacteroidete, and Firmicutes were involved in the process of removal nitrogen and manganese. The presence of Limnobacter allowed a more stable accumulation of NO2−-N in reactor, thus achieving shortcut nitrification-denitrification, and Flavihumibacter promoted the secretion of EPS. Collectively, the study reveals that the interaction of autotrophic denitrifying bacteria (Chryseolinea), heterotrophic denitrifying bacteria (Fusibacter, Thauera), and manganese-oxidizing bacteria (Pseudaminobacter, Bacillus, Pedomicrobium, Aeromonasr) achieved simultaneously removal of nitrogen and manganese from the reactor shortcut nitrification-denitrification. This study provides a new insight for the treatment of electrolytic manganese residue leachate produced in the process of manganese production.

The fractional extraction for sustainable recovery of rare earth and thorium in radioactive waste with oxoacetate functionalized ionic liquid

Rare earth (RE) are critical elements in many technologies, their clean production has attracted widespread attentions. To develop clean separation technology for RE, a novel oxoacetate ionic liquid (IL) extractant was developed to recovery RE elements and Thorium (Th) in the radioactive waste residue from ion-absorbed RE separation industry. The IL [N-methyl-N,N-dioctyloctan-1-aminium][2-(bis(2-ethylhexyl)amino)-2-oxoacetate] ([N1888][DEAO]) had good selectivity to RE and Th, which helps to remove radioactive Th and recover RE from waste residue leachate. RE and Th could be effectively separated with 0.02 mol/L [N1888][DEAO]. Maximum extraction capacity of Th reached 1.02 g/L, which could meet the needs of Th removal in the waste residue. A combination of saturated NaC2O4 solution and NaOH solution was used for the stripping of Th. After five cycles, the extraction efficiency of Th remained above 90 %. After four-stage extraction with [N1888][DEAO] and three-stage scrubbing, a RE solution with Th content less than 0.6 mg/L was obtained. It is fully achieved that there is no excess wastewater and waste salt in the fractional process. The RE elements in the waste residue can be effectively recycled, also the collection of the radioactive element Th can be realized.

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Separation and recovery of sulfur from direct leach residue of zinc oxygen pressure leaching by dissolution in n-decane and recrystallization

The effective recovery and utilization of elemental sulfur in the direct leach residue (DLR) from zinc oxygen pressure leaching poses a significant challenge. This study analyzes the distribution characteristics of sulfur in DLR and determines its solubility in n-decane at various temperatures. Results indicate a gradual increase in sulfur solubility with temperature, reaching a maximum of 6.84 g/100 mL at 150 °C Utilizing the Apelblat model, a fitting equation of lnX = 88.3–7155.9/T − 12.0lnT is derived. Under conditions of 130 °C, a liquid–solid ratio of 8:1, a reaction time of 3 min, and a stirring speed of 300 rpm, 99.2% of sulfur in the residue can be dissolved in n-decane. Additionally, this separation process naturally enriches other valuable elements in the residue. The cooling rate significantly influences sulfur purity, with elemental sulfur forming high-quality crystals exhibiting a positive octahedral rhombic morphology at a cooling rate of 0.018 °C/s. Finally, the dissolution mechanism of sulfur in n-decane involves sulfur complexation, and the reliability of the sulfur solubility model is verified.

Enrichment of valuable metals from silver tailings using the alkali roasting-leaching method

To solve the tailings accumulation and mineral resource scarcity issues, this study uses silver tailings as a raw material and sodium carbonate roasting followed by water and acid two-step leaching process to investigate the enrichment of copper, cobalt, and lead. Based on the identification of occurrence forms of copper, cobalt, and lead in the silver tailings, the process parameters of the Na2CO3 roasting and acid leaching were optimized. The silver tailings were mixed with sodium carbonate at a mass ratio of 1:1.3 and roasted at 750 °C for 30 min, and the roasted clinker was leached using water at 80 °C for 15 min. The water leaching residue was then leached using H2SO4 acid at a concentration of 3 mol/L, a liquid–solid ratio of 10 mL/g, and at room temperature for 3 min. We finally obtained leaching efficiencies of 97.02 % and 86.45 % for copper and cobalt, respectively; 79.17 % of lead went into the acid leaching residue. The copper and cobalt were significantly enriched in the polymetallic enriched ore powder at 10.76 and 7.12 times the content in the tailings, respectively, reaching industrial grade that could be used as a new type of ore raw material for the extraction of copper and cobalt. Lead was enriched in the acid leaching residue at a content of 7.61 times that of the tailings and was mixed with the tailings to be further roasted and leached to enrich the lead. These results provide a theoretical foundation for the full resource utilization of metallic tailings.

Study on the treatment of pyrolysis products from the nitric acid pressure leach liquor of laterite

As the demand for nickel increases sharply, it is of great significance to extract valuable metals such as nickel and cobalt from lateritic nickel ore with huge reserves. Based on the nitric acid pressure leaching process (NAPL) of laterite nickel ore, a clean process of laterite nickel ore treatment is proposed. The process includes concentration and crystallization of pressure leaching solution of nitric acid, pyrolysis of mixed nitrate crystal, alkaline leaching of mixed oxides and acid leaching of alkaline leaching residue. Based on previous work, the high-pressure alkaline leaching process of pyrolysis products (mixed oxides) and atmospheric pressure sulfuric acid leaching process of alkaline leaching residue were studied in this paper. First, the Eh-pH diagrams of metal-water system of common elements in laterite nickel ore was summarized according to the reaction equations of different substances in aqueous solution, and the subsequent wet leaching process was guided. The following alkaline leaching experiments showed that under the conditions of 300 g/L NaOH concentration, 3.5 mL/g liquid–solid ratio, 160 °C leaching temperature and 1 h leaching temperature, 85.0 % of aluminum in mixed oxides can be leached and scandium can be enriched by 13 times. Finally, under the conditions of initial sulfuric acid concentration of 4 M, temperature of 100 °C, leaching time of 30 min and liquid–solid ratio of 4 mL/g, the leaching rates of Al, Ni, Mg, Co, Mn, Fe and Sc in alkaline leaching residue were 92.0 %, 97.5 %, 98.4 %, 92.3 %, 62.7 % and 68, respectively. A new procedure for treating lateritic nickel ore is proposed, allowing for thorough recovery and usage of important components. The technique is green and environmentally benign, resulting in closed-loop production of laterite-nickel ore treatment with numerous application possibilities.

High efficiency separation of bastnaesite (REFCO3) and monazite (REPO4) in mixed rare earth concentrate by heating under N2 and leaching with HCl/AlCl3

Bayan Obo mixed rare earth (RE) concentrate is one of the most significant rare earth mineral resources worldwide. However, the concentrated sulfuric acid roasting method, which is commonly used to treat ores, generates pollutants such as waste gas, wastewater, and leach residue, resulting in the squandering of the associated resources. This paper introduces a green process involving selective mineral phase transformation (MPT) by heating, followed by leaching to separate bastnaesite and monazite in a mixed RE concentrate to facilitate their subsequent decomposition or extraction. The effects of the MPT conditions on rare earth extraction were investigated. During the MPT process, bastnasite decomposed into REOF, which is more easily leached, whereas monazite remained unchanged. Under suitable conditions, the leaching efficiency of REOF reached 93.7%, while that of monazite (REPO4) was only 3.2%. Furthermore, the content of monazite in the leach residue was 91.2%. Compared to the mixed RE concentrate, numerous cracks and pores were generated on the surface and inside the MPT products. Furthermore, the total pore volume and specific surface area significantly increased, which made the reaction between the MPT products and hydrochloric acid more efficient. Thus, the MPT process facilitated the leaching of bastnasite and its separation from monazite.

Making waste profitable: Efficient recovery of metallic iron from jarosite residues

To address the hazardous by-product of zinc smelting and resource utilization of jarosite residue, this study applies an electric field-assisted hot acid treatment to completely recycle Iron (Fe). This innovative approach aims to enhance the leaching efficiency of Fe from jarosite residue. The introduction of electric field changes the charge distribution on the surface of the particles to enhanced ions and electrons exchange and promotes the collision between particles to strengthen reaction kinetics. Based on the above, the leaching efficiency of Fe in jarosite under sulfuric acid attack is improved observably. The result shows that Fe leaching efficiency reaches 98.83%, which is increased by 28% under the optimal experimental conditions: current density of 30 mA/cm2, H2SO4 concentration of 1.5 mol/L, solid-liquid ratio of 70 g/L, temperature of 80 °C and time of 12 h. Leaching kinetics calculations shows that the apparent activation energy is 16.97 kJ/mol and leaching of jarosite residue is controlled by a mixture of chemical reaction and diffusion, temperature and concentration of leaching solution have influence on leaching. This work provides a feasible idea for the efficient leaching Fe from jarosite residue.

Copper heap leach residue aggregates in concrete: Properties and performance

This study assesses the feasibility of using copper heap leach residue (CHLR) as a sustainable alternative to natural aggregates in concrete production. The CHLR possesses flaky-angular shape grains with rough surface texture and microcracks, crystalline silica of 51.6 %, 6.1 mg/g silt-clay with a median particle size of 4.3 mm, and it becomes suitable for the partial replacement of natural fine and coarse aggregates after removing 4.2 mg/g fines through 60-minute wash. Concrete containing 25–75 % CHLR aggregates met design slump and air content of 125±25 mm and 2±0.5 %, respectively, while also demonstrating a negligible 2.9 % reduction in fresh density and 2.8 % increase in compaction factor. Concrete containing 50 % CHLR as a partial replacement of natural coarse and fine aggregates achieved compressive strengths of 47.3 MPa and 45.1 MPa at 28 days, while the compressive strength of control mix was 46.7 MPa. The mechanical properties significantly declined at 75 % CHLR incorporated concretes. The BSE-EDS analysis highlighted improved interfacial transition zone for CHLR aggregates with minimal microcracks at early age compared to the natural aggregates but developed interfacial transition zone microcracks with prolonged curing leading to a decline in mechanical strength development.

Rapid iron extraction from nickel leaching residue by a hydrogen plasma smelting reduction

The processing of limonite-type lateritic nickel ore through sulfuric acid leaching generates leaching residue that requires careful handling and treatment. This residue, which contains over 38% iron, has the potential to be an alternative raw material for the iron and steel industry. However, the direct use of this residue as a burden material in the steel industry faces challenges due to the substantial presence of sulfur, which exceeds 1%. In the pursuit of sustainability within the iron and steel sector, researchers have increasingly focused on advancing hydrogen plasma technology. Laboratory tests were conducted on the treatment of the leaching residue exposed to hydrogen plasma smelting reduction. The results revealed that within just 5 s of exposure to hydrogen plasma, the transformation of the residue into metal was initiated. After 30 s of exposure, the formation of metal had already occurred, but the sulfur content remained above 0.5%. However, when the residue was exposed to hydrogen plasma for 180 s, the sulfur content in the metal decreased to less than 0.1%. The presence of nickel and chromium in the resulting metal products should be taken into consideration, especially when special steels or stainless steel are being produced.

Efficient and clean treatment of indium-bearing zinc ferrite: A new approach using a water-regulated deep eutectic solvent

Indium, a strategic key metal, is mainly recovered from zinc leaching residue. However, a challenging problem in the treatment of zinc leaching residue is how to efficiently and cleanly treat the poorly soluble phase, the indium-bearing zinc ferrite (IBZF). Here, we propose a novel strategy for the selective extraction of indium, zinc and iron from IBZF. By introducing water to regulate the coordination environment of a choline chloride-anhydrous oxalic acid based deep eutectic solvent (ChCl-Oxa based DES), efficient leaching and deep separation of indium, zinc and iron were achieved. Water, acting as both co-solvent and diluent, played a critical role in the whole process. The addition of a little water reduces the viscosity of the DES, thereby improving the leaching of indium, zinc and iron. Under specific leaching conditions (leaching temperature of 90 °C, liquid/solid ratio of 20:1 ml/g, molar ratio of ChCl:Oxa = 1:1, molar ratio of DES:H2O = 1:3 and reaction time of 3.5 h), the leaching efficiencies of indium, zinc and iron were 96.27 %, 95.55 % and 96.33 %, respectively. The subsequent addition of large amounts of water dilutes and dissociates the structure of the DES, facilitating the stepwise precipitation and deep separation of metal ions. The precipitation efficiency of zinc and iron reached 93.06 % and 98.07 %, respectively. Residual indium ions in the solution were effectively adsorbed by activated carbon, with a recovery efficiency of 75.7 % after five cycles of adsorption. The solution separated from the metal ions was well regenerated by evaporation and addition of Oxa. Our work represents a novel approach for the recycling and clean utilization of zinc leaching residue. And the regulation of the coordination environment of metal ions in DES is proved to have great potential in metal recycling.