Oxidative Acid Leaching Research Articles

Efficient conversion process and mechanism of bromine in bromine-rich saline wastewater

Bromine resources, widely utilized in basic chemical engineering, are considered non-renewable. A substantial amount of Bromine-Rich Saline Wastewater (BRSW), a hazardous waste, is generated during the smelting process of waste printed circuit boards (WPCBs). The efficient conversion of bromine resources is important in BRSW, which contain high concentrations of bromide ions. This study developed a synergistic treatment method utilizing electrolytic manganese anode sludge (EMAS) achieved efficient conversion of Br− to Br2 in BRSW. Optimal technical parameters are determined through single-factor experiments, and the oxidative acid leaching process was optimized using response surface methodology (RSM). The significant influencing factors for Br− conversion were ranked as acidity > anode mud addition amount > temperature > time, resulting in a bromine conversion efficiency of 96.55%. Kinetic studies of bromine conversion in BRSW during the oxidation-acid leaching process indicated a two-stage process: Stage I being a chemical reaction control model and Stage II being a diffusion control model. The reaction mechanism was elucidated, where H+ initially breaks the Mn-O bond in MnO2, exposing O vacancies and forming Mn4+, leading to a redox reaction between free Br− and Mn4+. This research embodies the concept of synergistic solid waste disposal, achieving cost-effectiveness and streamlined preparation of bromine, and providing technical and theoretical support for bromine resource recovery in BRSW.

The advances in the recovery process for precious metals from nickel slag, a review

The creation of nickel-smelting products including important metals like nickel, cobalt, and copper is a persistent issue in the nickel mining business. Another secondary source of precious metals is nickel slag. In addition, the massive amounts of nickel slag generated by the nickel smelter sector will pollute the environment, particularly the soil, since the smelting slag contains hazardous materials. This study examines techniques for recovering precious metals from nickel slag by reviewing publications from Springer Link, Google Scholar, MDPI, ScienceDirect, Membrane Journal, and other authors. The two types of metal recovery techniques from nickel slag that were examined were hydrometallurgical and pyrometallurgical techniques. This review article describes a pyrometallurgical method that involves roasting and selective reduction. In the meantime, the hydrometallurgical techniques were examined in the high-pressure oxidative acid leaching process, the atmospheric acid leaching method, and the bioleaching process. A roadmap for research designs that can be used to recover valuable metals from nickel slag sustainably has been created due to the completed literature evaluation.

Oxidative acid leaching of indium phosphide waste and recovery of indium metal by cementation with aluminum

This study presents a concise and effective method for waste indium phosphide (InP) recycling through hydrometallurgy. The waste InP was initially processed with H2SO4 in the presence of sufficient H2O2, by which phosphorus is oxidized to the valence state of +5 in the form of stable H3PO4 and indium is dissolved as soluble In3+ in the solution. As a result, efficient leaching of waste InP was achieved. Under the optimized conditions of H2SO4 concentration of 3 mol/L, H2O2/InP mole ratio of 4, liquid to solid ratio of 4, temperature of 80 °C, and reaction time of 3 h, the leaching efficiency of indium reached over 99%. Subsequently, indium was recovered from the pregnant leach solution (PLS) in the form of metallic In sponge through cementation with an aluminum plate. At the reaction temperature of 85 °C, the precipitated indium sponge could spontaneously strip from surface of aluminum plate to facilitate the cementation process, eventually achieving an overall indium recovery of over 90%. The reaction mechanisms of both the oxidative acid leaching and cementation processes are elucidated based on the thermodynamic evaluations and experimental findings.

Thermodynamics Study for Selective Leaching of Copper and Zinc from Complex Secondary Raw Materials Using Oxidative Sulfuric Acid Leaching

This study focuses on evaluating the optimal process conditions for selectively leaching copper and zinc from complex secondary raw materials using the oxidative sulfuric acid leaching process. The research includes both physical and chemical characterization of the materials and a comprehensive thermodynamic analysis to assess the thermodynamic properties and behaviors of the system under investigation. The physical characterization involves determining parameters such as bulk density, moisture content, and granulometric composition of the samples. Elemental composition analysis is performed using X-ray fluorescence spectrometry (XRF) and energy dispersion spectroscopy (EDX), while the phase composition is determined through X-ray diffraction (XRD) analysis. Additionally, the materials' morphology is examined using scanning electron microscopy (SEM). Fraction diagrams are created using Hydra/Medusa software to assess the phase distributions of zinc and copper during the leaching process. The stability of the metals and potential chemical reactions within a defined temperature range is analyzed using Eh-pH diagrams with the HSC 9 Chemistry Software. Based on the thermodynamic analysis conducted, it is determined that effective leaching of copper and zinc from the complex secondary raw materials is achievable. Furthermore, the results indicate that the leaching process is relatively insensitive to temperature variations. The optimization of the leaching process should primarily focus on achieving optimized consumption of the oxidizing agent.

Vanadium extraction from V-bearing shale using oxidation roasting and acid leaching

Vanadium is an important rare metal element that is extensively used in various fields. Direct acid leaching with fluoride additives and salt roasting-acid leaching are common processes in vanadium production, but they have the disadvantage of high cost and serious pollution to vanadium-bearing shale ore. Therefore, it is necessary to develop an efficient and environmentally friendly process for the development of vanadium-bearing shale resources. In this study, a combination of oxidation roasting (without salt) and acid leaching was used to extract vanadium from V-bearing shale. Pilot scale testwork established the appropriate conditions as a roasting temperature of 870–900 °C, an air atmosphere (O2 concentration of 21 %), a feed rate of 15 kg/h, and a gas flow rate of 34 Nm3/h. The roasted product was leached at an acid dosage of 100 kg of sulfuric acid per ton of roasted product, a temperature of 65 °C, leach time of 4 h, and a liquid/solid ratio of 1.5:1. The pilot plant operation achieved > 85 % vanadium extraction and a vanadium content of < 0.20 % for the leach residue. The phase transformation and microstructure evolution were analyzed using X-ray diffraction, scanning electron microscopy, and surface area and pore size analyses. The results showed that V(III) transformed into V(IV) and V(V) during oxidation roasting, which were easily dissolved by acid leaching. In addition, the pore properties of the roasted products had significant effects on the subsequent leach process. This novel process of oxidation roasting and acid leaching provides an option for vanadium extraction from V-bearing shale.

Pressure Leaching of Copper Slag Flotation Tailings in Oxygenated Sulfuric Acid Media.

In this study, a hydrometallurgical method for the recovery of copper, cobalt, and zinc from copper slag flotation tailings (SFT) was investigated. SFT contains large amounts of valuable metallic compounds, such as copper, cobalt, and zinc. A representative SFT sample containing 0.50% Cu, 0.148% Co, 3.93% Zn, and 39.50% Fe was used in experimental studies. High-pressure oxidative acid leaching of SFT was carried out to assess the effects of sulfuric acid concentration, oxygen partial pressure, reaction time, solid/liquid ratio, and temperature on the extraction of copper, cobalt, zinc, and iron. The dissolution of metals from the SFT sample increased with temperature and sulfuric acid concentration. However, high acid concentrations and high solid/liquid (S/L) ratios led to gel formation that caused filtration problems and inhibited metal dissolution. The optimum leaching conditions were found to be a leaching time of 90 min, an acid concentration of 250 kg/t, a temperature of 220 °C, an S/L ratio of 1:5, and an oxygen partial pressure of 0.7 MPa. Under these conditions, 93.1 ± 1.1% Cu, 96.3 ± 1.8% Co, and 92.3 ± 1.7% Zn were extracted. Iron dissolution was only 0.5 ± 0.1%. This hydrometallurgical process almost completely recovers valuable metals. In particular, cobalt, which is of great importance in the production of lithium-ion batteries, has been declared a critical metal by the United States, Canada, and the EU and was taken into solution with very high extraction efficiency (>95%). Additionally, oxygen partial pressure enhanced copper, cobalt, and zinc dissolution. When O2 was not introduced into the leaching system, the extraction efficiencies of Co, Cu, and Zn were approximately 24.5, 5.3, and 26.3%, respectively, after 2 h of leaching treatment.

Copper Recovery from Chalcopyrite Concentrate by Oxidative Roasting and Acid Leaching

Copper Recovery from Chalcopyrite Concentrate by Oxidative Roasting and Acid Leaching

Leaching kinetics of copper and valuable metal extraction from copper-cadmium residues of zinc hydrometallurgy by oxidation acid leaching

Abstract Multiple purification of zinc sulfate solution is an important process for zinc hydrometallurgy, and large quantities of copper-cadmium residues are generated as byproducts in this process. Copper-cadmium residues contain a large number of valuable metals that must be recovered. A comprehensive extraction process has been proposed using sulfuric acid as the leaching reagent and hydrogen peroxide as the oxidizing reagent. The effects of acid concentration, leaching temperature, leaching time, liquid-to-solid ratio, hydrogen peroxide dosage and stirring speed on the leaching efficiency were investigated. The optimum conditions were determined as an acid concentration of 150 g/L, liquid-to-solid ratio of 4:1, hydrogen peroxide amount of 20 mL, time of 60 min, temperature of 30 °C, particle size of −d75 μm, and agitation rate of 300 r/min. It was concluded that the leaching efficiency of copper and cadmium reached 97%, but because of the existence of zinc sulfide in the residues, a lower leaching efficiency of zinc was obtained. Furthermore, the leaching kinetics of copper was also studied based on the shrinking core model. The activation energy for copper leaching was 5.06 kJ/mol, and the leaching process was controlled by the diffusion through the product layer.

A novel, clean, closed-loop process for directional recovery of rare earth elements, fluorine, and phosphorus from mixed rare earth concentrate

The recycling of Bayan Obo rare earth has attracted widespread attention due to its potential environmental risks and the importance of key metal supplies. As a traditional technology, concentrated sulfuric acid roasting has led to the continuous deterioration of the local environment because of severe fluoride and sulfur dioxide emissions. Although it is difficult to achieve efficient recovery of rare-earth elements and their associated resources with this process, it is possible to eliminate pollutant emissions, and achieve a high recovery ratio of rare-earth elements using this technique. Fluorine and phosphorus from wastewater have been well controlled. Here, a novel, clean, closed-loop process is introduced to treat rare earth concentrates, which not only does not pollute the environment, but also generate more economic values. Through the oxidative roasting-hydrochloric acid leaching step, more than 98% of fluorine and phosphorus can be stably retained in the leaching residue. The leaching residue is then converted into rare earth hydroxides, sodium fluoride, and sodium phosphate in the sodium hydroxide sub-molten salt system. Moreover, most of the concentrated lye can be reused in the sub-molten salt decomposition step by filtration. The washed filter residue is then dissolved in the hydrochloric acid leachate to produce a rare earth chloride solution. Sodium fluoride and sodium phosphate can be recovered in the washing solution. In summary, this process can realize the internal circulation of concentrated lye and water while producing a rare earth chloride solution, sodium fluoride, and sodium phosphate. Finally, the rare earth concentration in the rare earth chloride solution reached 280 g L−1, 96.40% of fluorine was converted to sodium fluoride, and 99.82% of phosphorus was converted to sodium phosphate from the washing liquid. An environmentally-friendly, easy-to-implement strategy is proposed: the entire recycling process is highly selective, closed-loop and simplified, and can be used as an alternative method to recover different resources from the current Bayan Obo concentrate.

Recovery of Cobalt, Copper and Zinc from Küre-Kastamonu Historical Copper Slag by High Pressure Oxidative Acid Leaching

Recovery of Cobalt, Copper and Zinc from Küre-Kastamonu Historical Copper Slag by High Pressure Oxidative Acid Leaching

Separation and recovery of copper in Cu−As-bearing copper electrorefining black slime by oxidation acid leaching and sulfide precipitation

Abstract A new hydrometallurgical route for separation and recovery of Cu from Cu−As-bearing copper electro- refining black slime was developed. The proposed process comprised oxidation acid leaching of Cu−As-bearing slime and selective sulfide precipitation of Cu from the leachate. The effects of various process parameters on the leaching and precipitation of Cu and As were investigated. At the first stage, Cu extraction of 95.2% and As extraction of 97.6% were obtained at 80 °C after 4 h with initial H2SO4 concentration of 1.0 mol/L and liquid-to-solid ratio of 10 mL/g. In addition, the leaching kinetics of Cu and As was successfully reproduced by the Avrami model, and the apparent activation energies were found to be 33.6 and 35.1 kJ/mol for the Cu and As leaching reaction, respectively, suggesting a combination of chemical reaction and diffusion control. During the selective sulfide precipitation, about 99.4% Cu was recovered as CuS, while only 0.1% As was precipitated under the optimal conditions using sulfide-to-copper ratio of 2.4:1, time of 1.5 h and temperature of 25 °C.

Study on thermodynamic model of arsenic removal from oxidative acid leaching

In this paper, we propose a new strategy to remove arsenic from arsenic-containing waste residues by oxidation-acid leaching. The experimental results show the example is effective for different types of arsenic-containing waste residues. Chemical thermodynamic calculations provide guidance for leaching of oxidizing acids, while theoretical calculations and experimental data have successfully proven the shielding layer of AsH3. The acid leaching characteristics of different types of arsenate were analyzed, a multi-metal ion equilibrium system in acid leaching was established, and a model of arsenic removal by oxidizing acid was established. An in-depth understanding of the relationship between the amount of acid required to leaching different arsenic-containing waste residues and the pH of the leachate provides new perspectives on how to efficiently collect hazardous materials from industrial waste residues.

Environmental impact of spent lithium ion batteries and green recycling perspectives by organic acids - A review.

The huge usage of rechargeable batteries in electronics has added to a recurrent problem worldwide in generating tonnage of spent lithium-ion batteries (LIBs). The inadequacy of the resources of the depleting critical metals has also been described in vogue. The environmental assessment of the life cycle of the LIBs has been elucidated vis-a-vis the effects of raw material supply, transportation, and recycling. Based on the available work for recycling technologies, this review also attempts to elicit the various methods practiced in discharging/dismantling, classification, and separation of components followed by metal recovery. The authors have reviewed the major developments in the area of recycling of cathode material by using various acids for extraction of metals from spent LIBs, compared the merits and demerits of acids used and presented a comprehensive outlook to the processes formulated vis-à-vis imperative need for using green techniques. The necessity for benign recycling methods is stressed upon to alleviate the need for high temperature and oxidative acid leaching conditions. The various green lixiviants (organic acids) attempted to extract metals from spent LIBs have been discussed in detail with respect to the mechanism, efficacies as well as the various factors (selectivity, cost, etc.) that govern the use of organic acids in battery recycling. It was ascertained that the GHG emissions to extract Co using organic acids stand 1/8 of that using an inorganic acid leaching process. Efforts need to be envisaged in separating the leached metals from these lixiviants ensuring economics and environmental benefits.

Simulation of precious metals recovery from nickel smelter slag under high-pressure oxidative acid leaching (HPOXAL)

The nickel smelter slag as a solid waste of pyrometallurgical operations can be harmful to the environment especially against the ground that will be contaminated by hazardous components contained the smelter slag. Nickel smelter slag has the content of valuable metals as the following: Nickel (Ni), Cobalt (Co), Copper (Cu), Iron (Fe) and Zinc (Zn). Those valuable metals were carried out by high-pressure oxidative acid leaching to recover all the valuable metals suitable with the high measures of recovery. High-pressure oxidative acid leaching (HPOXAL) is a suitable process for the nickel smelter slag with the parameters of the leaching process as the following: the particle size about – 150 + 74 μm, sulfuric acid solution with the concentration of 0.3 mol in 1 liter solution, Ratio of Liquid to Solid (L/S) with 7 ml of liquid to 1 gram of solid components, oxygen overpressure at 600 kPa, operating temperature about 180 - 200 °C and the retention time of 80 minutes. The measures recovery of this leaching process for each valuable metal in percent of initial weight such as nickel and cobalt about 97%, copper about 95%, 94% of zinc and all iron can be separated, respectively. At the separation section, LIX 984N as extractant extracts copper from the product (leaching solution) of the reactor, limestone was used to capture iron in the leaching solution, versatic 10 and decyl-4PC were conducted to remove undesirable mineral that was generated from the leaching process, and cyanex 272 extractants to extract such as nickel, cobalt, and zinc, respectively. This simulation used the feed flowrate with 150 tons per day. The results of the precious metals product were generated each the mass rate such as copper, nickel, cobalt, zinc, and iron with 927 kg/day, 2147 kg/day, 875 kg/day, 199 kg/day and 71,000 kg/day, respectively.

Behaviour of Si, Al, Fe and Mg during oxidative sulfuric acid leaching of low grade uranium ore: A kinetic approach

This paper deals with the behavior of reactive micaceous gangue minerals like chlorite and biotite during the oxidative sulfuric acid leaching of uranium ores taking case study of a typical low grade Indian uranium ore hosted by chlorite-biotite-muscovite-quartzo-feldspathic schist. The progress of the gangue minerals chemical reactivity was monitored kinetically by analyzing the concentration of Si, Al, Fe and Mg ions in the leach liquor and through SEM-EDS analysis of feed and leach residue. The kinetic plots were analysed using shrinking core model and the rate equations deduced for all the aforementioned four elements constituting the gangue indicated significant role played by concentration of sulfuric acid, redox potential, temperature of reaction and particle size in the diffusion controlled process, which is also substantiated from the thermodynamic parameters computed. The results indicated decreased particle size, increased sulfuric acid concentration, longer contact time, higher rate of agitation and increased redox potential results in higher concentration of Si, Al, Fe, Mg and U.

Controlling the Composition and Magnetic Properties of Nano-SrFe12O19 Powder Synthesized from Oily Cold Mill Sludge by the Citrate Precursor Method.

This paper proposes a new method for producing nano-SrFe12O19 powder by the citrate precursor route using solid waste as a source of iron. This solid iron-containing waste, which exists in the form of an oily sludge, is produced by a cold rolling mill. This sludge was first subjected to a process, including sulfuric acid leaching, oxidation, precipitation, and nitric acid leaching, to obtain an iron nitrate (Fe(NO3)3) solution. Next, the Fe(NO3)3 solution was mixed with a strontium nitrate (Sr(NO3)2) solution obtained by subjecting strontium carbonate to nitric acid leaching. Subsequently, citric acid, as chelating agent, and ammonia water, as precipitating agent, were added to the mixed solution to form a gel. The gel was dried and spontaneously combusted, then annealed at different temperatures for 2 h in flowing air. The effects of the Fe3+/Sr2+ molar ratio and annealing temperature on the formation, morphology, and magnetic properties of SrFe12O19 were investigated. The results showed that single-phase SrFe12O19 powder was obtained by decreasing the Fe3+/Sr2+ molar ratio from the stoichiometric value of 12 to 11.6 and increasing the annealing temperature to 1000 °C for 2 h. Adjustment of the Fe/Sr molar ratio to 12 and the annealing temperature to 900 °C enabled the magnetic properties to be optimized, including saturation magnetization (Ms) 80.2 emu/g, remanence magnetization (Mr) 39.8 emu/g, and coercive force (Hc) 6318 Oe.

The comprehensive utilization of oxidative hydrochloric acid leaching of anode slime bearing fluorine, arsenic and antimony

This work presented a new strategy to comprehensive utilization of hydrochloric acid leaching solution of anode slime bearing fluorine, arsenic, and antimony. Firstly, the fluorosilicic acid and fluorosilicates in the leaching solution were removed by barium chloride. Then the arsenic and antimony in the defluorinated leaching solution were separated by distillation. Finally, AsSb alloy was electrodeposited from the electrolyte prepared with the distillates. Results show that the defluorination efficiency is 97.81% under optimum condition and the residual fluorine concentration decreases from 21.46 to 0.47 g/L. The distillation recovery of As(III) is 97.44% in the defluorinated leaching solution. AsSb alloy can be electrodeposited from the electrolyte containing 5 g/L As(III), 1 g/L Sb(III) and 4 mol/L HCl. The obtained AsSb alloy shows an amorphous structure with a composition of 84.48 wt% As and 15.52 wt% Sb. Moreover, after electrodeposition of AsSb alloy, the electrolyte can be returned to the leaching process and a closed loop for the solution treatment is achieved.

Extraction of copper from copper and cadmium residues of zinc hydrometallurgy by oxidation acid leaching and cyclone electrowinning

Copper and cadmium residue (CCR) is a hazardous solid waste generated in the process of zinc hydrometallurgy, and contains large amounts of Cu, Zn, Cd and Pb. Recovery of Cu from this material was investigated in the present study. CCR containing 30–40 wt.% Cu was leached in an oxidizing atmosphere with H2SO4 and the optimum leaching conditions were determined as follows: H2SO4 concentration of 180 g/L, L:S ratio of 3:1 (mL/g), H2O2 excess coefficient of 7.0, leaching temperature of 80 °C, and leaching time of 3 h. The leach solution was then subjected to cyclone electrowinning without purification or concentration, for recovery of Cu. The leaching step showed over 95% extraction of Cu under the optimized conditions. The cyclone electrowinning yielded Cu of >99.5% purity with current efficiencies exceeding 97%.

Oxidative acid leaching of mechanically activated sphalerite

ABSTRACTThe pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44 kJ mol−1 as the activation time increased from 0 to 30, 60, and 120 min, respectively. The reaction orders for the H2SO4 solutions of the sphalerite samples activated for 0, 30, 60, and 120 min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H2SO4 could be reduced by means of mechanical activation.

Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition

Recycling of Nd-Fe-B magnets is one of the few solutions to alleviate the supply risks of certain rare earth elements (REE) such as Nd and Dy. One of the most promising solutions with regards to extraction of end-of-life (EOL) magnets is to apply hydrogen decrepitation and to physically separate the Nd-Fe-B as a demagnetized hydrogenated powder. Such a powder can be directly recycled into new sintered magnets, or indirectly recycled by a conventional oxidation roasting and acid leaching flowsheet. The oxidation stability of powders, the microstructure after oxidation and the role of compositional variations can be of importance for the success of such subsequent direct or indirect recycling routes. In this study, magnets with varying compositions were subjected to different hydrogen treatments (e.g. hydrogenation, partial or full degassing and vacuum or conventional disproportionation) and subsequently studied for their comparative oxidation behavior and microstructural changes. While initial magnet composition was found to have little or no effect on oxidation behavior, the treatment type was found to have a direct impact on both the particle size distribution and the oxidation mechanism. The general oxidation rate was found to be the equally highest for hydrogenated and partially degassed samples followed by fully degassed and then disproportionated samples. After complete oxidation, complex REE-Fe-O compounds were formed more extensively in hydrogenated and fully degassed NdFeB samples than in the disproportionated samples.