Leaching Of Mn Research Articles

Promotion of manganese extraction and flue gas desulfurization with manganese ore by iron in the anodic solution of electrolytic manganese

In this work, Mn ore was mixed with the wastewater anode solution of electrolytic Mn (ASEM, instead of water) and utilized as the desulfurizer for simultaneous SO2 removal from flue gas and Mn extraction. The effects of Fe2+ and Fe3+ on Mn leaching and flue gas desulfurization were investigated. For MnO2 and Mn2O3 (mixed with ASEM), the introduction of Fe2+could simultaneously increase Mn extraction efficiency and flue gas desulfurization efficiency when MnO2 and Mn2O3 mixed with ASEM was used. Fe3+ addition could improve desulfurization efficiency obviously for MnCO3. Fe2+ could react with MnO2 and H+ to form Mn2+ and Fe3+. This reaction further improved Mn extraction and simultaneously decreased the acidity of ASEM, thus promoting SO2 removal. The introduced Fe3+ could react with SO2, when MnO2 was absent from the desulfurizer slurry. The resulting Fe2+ was then oxidized by O2 to form Fe3+, which underwent a Fe3+ ↔ Fe2+ cycle to promote flue gas desulfurization. Thus, the introduction of Fe ions, especially Fe2+, could promote simultaneous Mn leaching and flue gas desulfurization with Mn ore. This work provided not only a new way for effective SO2 removal from flue gas and Mn extraction but also for recycling ASEM.

Leaching behavior and environmental risk assessment of toxic metals in municipal solid waste incineration fly ash exposed to mature landfill leachate environment

Solidification/stabilization pretreatment + landfill disposal in municipal solid waste (MSW) landfill sites is a widely accepted MSW incineration (MSWI) fly ash (FA) management strategy in China. However, in reality, the stability of FA disposed in MSW landfill sites may be affected by the organic landfill leachate environment. The purpose of this study was to explore the mobility and environmental risks of six toxic metals (Mn+, Pb/Zn/Cu/Cd/Cr/Ni), from raw and solidified/stabilized FA, by simulating a leaching environment with mature landfill leachate (MLL). The leaching of Mn+ mainly occurred in the early leaching stage, and their leaching behavior was controlled by the diffusion of surface Mn+ in the FA matrix. The destructive effect of dissolved organic matter (DOM) on the local precipitation-dissolution equilibrium of FA-leachate interface, the formation of non-adsorptive DOM-Mn+ complex (easy to migrate), and the competitive effect of DOM on the binding sites of Mn+ on the surface of the FA matrix may play an important role in increasing the leaching level of most Mn+. By contrast, the potential of solidified FA in reducing the environmental risk level of leached Mn+ was better than that of stabilized FA. However, the immobilization capability of solidification/stabilization pretreatment on various types of Mn+ in FA should be judged according to their practical disposal environment. Compared to MLL leaching tests, Acetic Acid Buffer Solution Method (HJ/T300-2007) can effectively strengthen the exposure environment and provide a reliable reference level of environmental risk for MSWI FA disposed in MSW landfill sites.

Simultaneous recovery of copper and manganese from exotic copper ore in acid chloride media using cane molasses as the reducing agent

Chile is host to one of the most considerable Cu resources in the world. The primary source of Cu is from porphyry deposits. However, associated “exotic-Cu” deposits are also significant in the Atacama Desert of northern Chile. The critical processing issue for these ores is that they are refractory to dissolution under acidic and oxidative conditions, and consequently their dissolution kinetics are relatively slow. This paper reports a study on the extraction of copper and manganese from exotic-Cu ores using cane molasses as a reducing agent in the presence of chloride ions and diluted sulfuric acid media. The effects of concentrations of cane molasses, chloride ion, and sulfuric acid are discussed. Leaching tests on ground ore in shake flasks were studied, as well as the agglomeration and curing stages of a coarse ore sample. The dissolution of the exotic copper ore is enhanced when 50 g/L of NaCl and 60 g/L of cane molasses are added to the leaching solution. The dissolution of copper associated with copper wad appears independent of the Mn dissolution. Tests with the ore agglomerated with acid, chloride ions, and cane molasses showed enhanced dissolution of manganese contained in the copper wad, but not copper. It is thus confirmed that cane molasses is a suitable reductant in the leaching of Mn, especially in the presence of chloride ions. The behavior and fate of the wad-associated copper requires further investigation.

Cryo-Mechanical Treatment and Hydrometallurgical Process for Recycling Li-MnO2 Primary Batteries with the Direct Production of LiMnPO4 Nanoparticles

In this work, an innovative hydrometallurgical recycling route for the recovery of all the materials composing Li-MnO2 primary batteries was proposed. End-of-life batteries were mechanically treated in an innovative pilot plant where a cryogenic crushing was performed. The mechanical treatment allowed for the release of the electrodic powder contained in the batteries with the simultaneous recovery of 44 kg of steel and 18 kg of plastics from 100 kg of batteries. Electrodic powder was employed as the raw material for the synthesis of LiMnPO4 nanoparticles. To obtain the synthesis precursors, selective sequential leaching of Li and Mn was performed. Li was extracted via water washing the electrodic powder and Li2CO3 and a purity of 99% was recovered. The black mass containing Mn oxides was leached using phosphoric acid, which gave a Mn-bearing precursor solution that was directly used for the hydrothermal synthesis of LiMnPO4 nanoparticles. A preliminary materials balance of the process was presented, indicating that the proposed process should be an easy hydrometallurgical route for the recycling of primary lithium batteries. In addition, the simultaneous production of high-value-added products that could be reintroduced into the battery manufacturing chain could ensure the economic feasibility of the process.

Reductive acid leaching of valuable metals from spent lithium-ion batteries using hydrazine sulfate as reductant

Abstract Hydrazine sulfate was used as a reducing agent for the leaching of Li, Ni, Co and Mn from spent lithium-ion batteries. The effects of the reaction conditions on the leaching mechanism and kinetics were characterized and examined. 97% of the available Li, 96% of the available Ni, 95% of the available Co, and 86% of the available Mn are extracted under the following optimized conditions: sulfuric acid concentration of 2.0 mol/L, hydrazine sulfate dosage of 30 g/L, solid-to-liquid ratio of 50 g/L, temperature of 80 °C, and leaching time of 60 min. The activation energies of the leaching are determined to be 44.32, 59.37 and 55.62 kJ/mol for Li, Ni and Co, respectively. By performing X-ray diffraction and scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy, it is confirmed that the main phase in the leaching residue is MnO2. The results show that hydrazine sulfate is an effective reducing agent in the acid leaching process for spent lithium-ion batteries.

Countercurrent leaching of Ni, Co, Mn, and Li from spent lithium-ion batteries

This study focuses on a countercurrent leaching process (CLP) for the dissolution of high-value metals from cathode active material of spent lithium-ion batteries (LIBs). Its main aim is to improve the effective utilization of acid during leaching and allow for the continuous operation of the entire CLP by adjusting the process parameters. The overall recovery of lithium (Li), cobalt (Co), nickel (Ni), and manganese (Mn) was 98%, 95%, 95%, and 92%, respectively; the acid utilization of the leaching process exceeded 95% under optimum conditions. The optimum conditions for first stage leaching were 70 g/L solid-liquid (S/L) ratio at 40°C for 30 minutes, and 2.0 M sulfuric acid, 100 g/L S/L ratio, 7 g/L starch, at 85°C for 120 minutes for second stage leaching. After five bouts of circulatory leaching, more than 98% Li, 95% Co, 95% Ni, and 92% Mn were leached under the same leaching conditions. Furthermore, we introduced the Avrami equation to describe metal leaching kinetics from spent LIBs, and determined that the second stage leaching process was controlled by the diffusion rate. In this way, Li, Ni, Co, and Mn can be recovered efficiently and the excess acid in the leachate can be reused in this hydrometallurgical process, potentially offering economic and environmental benefits.

Glucose oxidase-based biocatalytic acid-leaching process for recovering valuable metals from spent lithium-ion batteries

An environmentally benign leaching process for recovering valuable metals from the cathodes of spent lithium-ion batteries was developed. Glucose oxidase produced by Aspergillus niger can oxidize glucose to give the leaching agent gluconic acid. The presence of gluconic acid was proven by mass spectrometry. The cathode material morphology was characterized by X-ray diffractometry and scanning electron microscopy, and the efficiencies with which valuable metals were leached from the Li(NixCoyMnz)O2 material were determined by inductively coupled plasma optical emission spectroscopy. More than 95% of the Co, Li, Mn, and Ni were leached from spent lithium-ion batteries using a solid/liquid ratio of 30 g/L, 1 M gluconic acid leaching solution, a 1 vol% H2O2 reductant solution, a temperature of 70 °C, and a reaction time of 80 min. The leaching kinetics were perfectly described by the Avrami equation. The apparent activation energies for leaching of Li, Ni, Co, and Mn were determined as 41.76, 42.84, 43.59, and 45.35 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. This mild biocatalysis-aided acid leaching process is a promising method for effectively recovering valuable metals from spent lithium-ion batteries.

Leaching of Co, Mn and Ni Using H2O2 in Sulfuric Acid Medium from Mobile Phone LIBs

From the economic point of view, spent lithium-ion batteries (LIBs) are a precious resource that contains metals such as Co, Mn and Ni. On the other hand, environmental considerations and repetitious exploitation of natural resources, the so-called primary resource, have drawn significant attention to recycling resources. Regarding the special properties of Co, Mn and Ni, the leaching method was used to recover these metals from LIBs. For this purpose, sulfuric acid due to appropriate efficiency in the presence of H2O2 as a reducing agnet was chosen. To obtain optimum conditions of Co, Mn and Ni leaching, effective parameters on leaching steps such as sulfuric acid concentration, pulp density and H2O2 vol% were investigated. The results of ICP analysis showed that leaching of Co, Mn and Ni in the presence of 1 M sulfuric acid and 15% H2O2 (v/v) at a pulp density of 50 g/L had high efficiency, and more than 99 wt% of metals was simultaneously leached. In the absence of H2O2, leaching percent of Co, Mn and Ni was not significant and it was attributed to various oxides present in LIBs that include different valances.

High Performance FeNC and Mn-oxide/FeNC Layers for AEMFC Cathodes

While the Anion Exchange Membrane Fuel Cell (AEMFC) is gaining interest due to high power performance recently achieved with platinum-group-metal (PGM) catalysts, its implementation will require high-performing PGM-free cathodes. FeNC catalysts have shown high activity and stability for the Oxygen Reduction Reaction (ORR) in alkaline electrolyte; however, the production of hydrogen peroxide during ORR can lead to premature degradation of FeNC and ionomer. In order to minimize the amount of peroxide formed on FeNC, α-MnO2, β-MnO2, δ-MnO2 and α-Mn2O3 were investigated as co-catalysts, with the aim of increasing the apparent activity of FeNC-based cathodes for the hydrogen peroxide reduction reaction (HPRR). The specific activity of α-Mn2O3 for the HPRR was distinctly superior to the other Mn-oxides. The four Mn-oxides were mixed with a FeNC catalyst comprising atomically-dispersed FeNx sites, showing higher HPRR activity and higher four-electron ORR selectivity than FeNC alone. The stability of α-Mn2O3/FeNC was studied operando by on-line inductively-coupled plasma mass spectrometry, to evaluate the potential and time dependent leaching of Mn and Fe. Finally, FeNC and α-Mn2O3/FeNC were applied at the cathode of AEMFCs, both achieving similar or higher current density at 0.9 V than a Pt/C commercial cathode, and peak power densities of ca. 1 W·cm−2.

Catalytic ozonation of an azo-dye using a natural aluminosilicate

Catalytic ozonation of Orange II (100 mg/L) was studied using aluminosilicate Montanit300® (M) modified with H2SO4 (MS) and HCl (MH). Characterization of these samples was performed through several techniques: SEM/EDX, FTIR, XRD, FRX, TPD pyridine, surface area, pHPZC. Acid treatment increased surface area, Si:Al ratio and quantity of acid sites, but reduced pHPZC and Fe and Mn content.Ozonation experiments achieved complete decoloration and remarkable TOC conversions of 66, 65, 88 and 91 % by single ozonation and catalytic ozonation with MH, MS and M, respectively. Higher M and MS activity under acidic pH was attributed to Mn leaching. Decreased mineralization efficiency in the presence of tert-butanol suggested a radical mechanism. At neutral pH, M showed no activity, while MS presented mild activity owing to its enlarged hydrophobicity.The M sample sustained mineralization levels over 20 h. Lower O3 dose caused quick MS deactivation. However, it was reversed through calcination and prevented with a higher oxidant dose.Mn is naturally found in Montanit300®, thus making it an inexpensive catalyst. The development of a dynamic cycle combining reduced and oxidized forms of Mn was key to the outstanding activity observed.

Freezing/thawing effects on geochemical behavior of residues from acid mine drainage passive treatment systems

Passive systems are promising for the treatment of acid mine drainage (AMD) but generate metal-rich solids or residues. In subarctic climate, freezing/thawing (F/T) cycles may influence the chemical stability of waste, including residues from AMD passive treatment. The objective of this study was to assess and better understand the effect of F/T cycles on contaminants (metal and sulfates) leaching from AMD post-treatment residues. To do so, samples of residues WA50 (50 % wood ash and 50 % wood chips), PBR (30 % inorganic materials and 70 % organic substrate) and C50 (50 % calcite and 50 % wood chips) were collected from a laboratory tri-unit passive treatment system for iron-rich AMD (Fe-AMD) operated for over 1-year. To better understand the effect of freezing upon contaminant leaching, kinetic tests in weathering cells under wetting/drying (W/D) and F/T cycles were performed. Results showed that F/T cycles are likely to enhance the potential of metal leaching from post-treatment residues. The Fe leaching was 1.6-(for WA50), 3.2-(for C50) and 5.2-(for PBR) times higher under F/T cycles relative to the W/D cycles. Similarly, Zn leaching was 2.4-(for WA50), 4.9-(for PBR) and 5-(for C50) times higher under F/T cycles compared to the W/D cycles. Finally, Mn leaching was 2.4-(for WA50) and 5.2-(for PBR) times higher under F/T cycles relative to the W/D cycles but no difference in Mn concentration was observed for C50 residues. These findings suggest that during snow melt or early spring significant metal concentrations could be released while disposing AMD passive treatment residues.

Transport and transformation of uranium and heavy metals from uranium tailings under simulated rain at different pH

Uranium tailings are radioactive and toxic solid wastes that could contaminate waters, soils and sediments. Actually the risk of contamination is poorly known due to the lack of knowledge on the mobility of contaminants, especially the influence of acid rain on leaching, transformation and speciation of contaminants. Here, we studied the effect of simulated rain at different pH on the transport and transformation of Mn, Sr, Pb and U from uranium tailings. Semi-dynamic leaching tests and sequential extraction were conducted for Mn, Sr, Pb and U to determine their leaching patterns and to determine their speciation in uranium tailings. Results show that Mn, Sr, Pb and U become more leachable with decreasing rain pH. The release of these metals is initially rapid and then reaches a near steady state. After leaching with simulated rain, concentrations of metal-exchangeable and metal-carbonate fractions in tailings are highly reduced. The process governing the leaching of Mn and U is mainly wash-off, whereas the leached Sr and Pb are dissolution-controlled.

An improved process methodology for extracting cobalt from zinc plant residues

Zinc plant residue contains valuable metals that can be reused as a source for obtaining these metals. This paper describes the use of sodium thiosulfate (Na2S2O3) in leaching of Co and Mn from zinc plant residue, and purifying the leach solution in order to obtain a pure solution of Co(II). After dissolution of zinc using sulfuric acid, Co and Mn were dissolved in H2SO4 in the presence of a reducing agent. The effects of temperature, acid percentage, type and concentration of reducing agent on dissolution were studied. The results for sodium thiosulfate showed the dissolution of 90.7% and 87.6% Co and Mn, respectively at 65 °C, with an acid concentration of 5% and sodium thiosulfate concentration of 6 g/L. The corresponding results in the presence of H2O2 as a reducing agent are 94.7% Co, 96.3% Mn at 50 °C with the same acid and reagent concentration. An analysis of variation (ANOVA) on the corresponding data was performed. A new correlation as a function of reducing agent yielding the recovery for Co and Mn was derived. Moreover, the purification process of metals was investigated which was a combination of the precipitation method for removing iron, and the solvent extraction for separating Co(II) and Mn(II). The factors influencing solvent extraction i.e., pH, organic concentration, and organic/aqueous ratio were optimized. Finally, two processes for extracting Co and Mn from the hot filter cake (HFC) were proposed and compared.

Reduction-ammoniacal leaching to recycle lithium, cobalt, and nickel from spent lithium-ion batteries with a hydrothermal method: Effect of reductants and ammonium salts

Some inevitable issues of the acid leaching method used to recycle spent lithium-ion batteries (LIBs), such as toxic gas emission, excessive acid-base consumption, inferior metal selectivity and equipment corrosion, have gradually emerged and restricted the promotion and development of this method. It is therefore essential to develop a sustainable closed-loop recycling technology (reduction-ammoniacal method) for spent LIBs. In this study, the effects of various species of ammonia, ammonium salts and reductants on the leaching of Li, Co, Ni, Mn and Al from spent LIBs were investigated with a hydrothermal method. An increase of the electrode potential of the reductant greatly accelerated the selective leaching of Li, Co and Ni, which agreed with the thermodynamic analysis results. The standard electrode potentials of the LiNixCoyMn1−x−yO2 (NCM) materials were also determined by using approximate calculations. When using (NH4)2SO3 as a reductant in a one-step leaching process, 100% Co, 98.3% Ni and 90.3% Li were extracted into the ammonia-ammonium chloride solutions. From the kinetics analysis, the surface chemical reaction shrinking core model was found to control the leaching behavior of Li, Co, and Ni in the reduction-ammoniacal leaching process. A shell-core structure was composed of a product layer, a diffusion layer of the solid core and an unreacted core. Species in the product layer reduced the leaching efficiencies of Li, Co, and Ni. The results obtained for this hydrothermal reduction-ammoniacal method applied to recycle spent LIBs provide insights for the design of a high-speed, exceptionally selective, closed-loop recycling technique.

Selective recovery of valuable metals from industrial waste lithium-ion batteries using citric acid under reductive conditions: Leaching optimization and kinetic analysis

Recycling of valuable metals from waste lithium-ion batteries (LIBs) has recently attracted significant attention due to the environmental and economical concerns. In this paper, a simple and economical leaching process based on citric acid system was developed for the leaching of metals from the industrial waste LIBs without the manual separation of current collectors, i.e. copper and aluminum foils. The results showed significantly higher leaching efficiencies of metals due to the presence of copper and aluminum. About 91% Li, 90% Co, 94% Ni and 89% Mn were leached under the optimum leaching conditions of 0.5 mol/L citric acid, solid to liquid (S/L) ratio of 80 g/L at 90 °C for 80 min. Furthermore, the effects of the addition time and species of reductant on the leaching of Li, Co, Ni, and Mn were investigated, and the selectivity over Cu and Al as well. The kinetics data revealed that the leaching of Li, Co, Ni and Mn fitted best to the Avrami equation controlled by the surface chemical reaction, whilst the leaching of Cu and Al corresponded to the surface chemical-controlled reaction based on shrinking core model. The leaching feed before and after leaching were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Effect of cement incorporation on the leaching characteristics of elements from fly ash and slag treated soils

Inclusion of cement in fly ash and slag mixed soils could potentially alter the leaching behavior of elements. This study investigated the leaching characteristics of calcium (Ca), magnesium (Mg), sulfur (S), manganese (Mn), barium (Ba) and chromium (Cr) from cement activated soil-fly ash, soil-slag mixtures and soil, fly ash, steel slag and cement alone. Batch water leach tests, acid neutralization capacity and pH-dependent leach tests were performed. Test results indicated that, effluent concentrations of Ca and Ba increased, while Mg concentrations decreased with cement additions. No consistent trend was observed between S concentrations and cement content. The leaching of Cr and Mn remained unaffected by cement incorporation. Results of this study showed that the solution pH had the greatest influence on the leaching behaviors of the elements. Ca, Mg, S and Mn followed cationic leaching patterns, whereas Ba showed both cationic and amphoteric leaching patterns. The highest concentrations of Cr were observed at extreme acidic conditions, followed by a concentration plateau at the pH range of 5.5–10, and subsequent decrease and increase in concentrations at pH of 11.5 and 13, respectively. Geochemical modeling results suggested that except for Cr, the leaching mechanisms of the elements were controlled by their sulfate and (hydr)oxide minerals. The leaching of Cr was possibly controlled by BaCrO4 and CaCrO4. It was observed that the presence of carbonate minerals did not play a significant role on the leaching mechanisms of the elements, when cement was used as an activator.

Facile synthesis of three-dimensional Mn3O4 hierarchical microstructures for efficient catalytic phenol oxidation with peroxymonosulfate

Hierarchical porous materials have a wide application prospect in heterogeneous catalysis because they can provide plentiful surface active sites and well-developed mass transfer channels while being easily separable, as compared with their nanosized counterparts. In this study, three-dimensional hausmannite (Mn3O4) hierarchical micron-sized materials (Mn3O4-H) were synthesized by a simple room-temperature aqueous solution route. The catalytic performance was evaluated by activation of peroxymonosulfate (PMS) to oxidize phenol, a model organic pollutant, in aqueous solution. The Mn3O4-H showed a higher efficiency in activating PMS for phenol oxidation than two Mn3O4 nanomaterials, i.e., nanoparticles and nanorods, attributed to the higher specific surface area and more surface reactive sites arising from the hierarchical structure. The Mn3O4-H also showed high catalytic stability, with low Mn leaching during phenol degradation tests. Phenol degradation reaction kinetics followed the pseudo-first-order rate laws, and the reaction was accelerated at higher temperature. In addition, the effects of important operation parameters such as catalyst loading and PMS concentration on catalytic performance of Mn3O4-H were evaluated. The present research provides a facile approach for synthesis of green and effective catalytic materials to be used in PMS-based advanced oxidation processes for environmental remediation.

Contrastive nutrient leaching from two differently textured paddy soils as influenced by biochar addition

The aims of the current study were to (1) examine the interactive effects of biochar addition and differently textured soils (clayey and sandy soils) on nutrient leaching and (2) identify potential mechanisms related to the leaching. A repacked soil column experiment was set up to test the effects of five biochar rates added to clayey and sandy soils grown with rice (Oryza sativa L. ssp. japonica) for 3 months. Four leaching events were conducted to measure concentrations of ten elements in the leachate, including calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), aluminum (Al), iron (Fe), manganese (Mn), ammonium nitrogen (NH4+), nitrate nitrogen (NO3−), and phosphorus (P). On the sandy soil, biochar addition linearly and significantly reduced Ca concentration (by 38%), but increased Na (by 92%), K (by 292%), and P (by 411%) concentrations in the leachate, compared to the non-biochar-added soil. In contrast, on the clayey soil, biochar addition showed no obvious effect on the leaching of these elements. Biochar addition significantly reduced leaching of Al, Fe, Mn, and NH4−, but increased leaching of Mg. Mechanisms related to the reduced leaching of NH4−, Ca, Al, Fe, and Mn could be involved in the liming effect and increased nutrient holding capacity by biochar addition, and those responsible for increased leaching of Na, K, and P could be involved in co-addition of these elements with the added biochar. Biochar addition had contrastive effects on nutrient leaching, which was more profound on sandy soil than on clayey soil grown with rice crop.

PH-Dependent Leaching Characteristics of Major and Toxic Elements from Red Mud

This study analyzes the leaching behavior of elements from red mud (bauxite residue) at pH values ranging from 2 to 13. The leaching characteristics of metals and contaminated anions in five red mud samples produced by Bayer and combined processes were analyzed using the batch leaching technique following the US Environmental Protection Agency (USEPA) Method 1313. In addition, the geochemical model of MINTEQ 3.1 was used to identify the leaching mechanisms of metals. The results showed that Ca, Mg, and Ba follow the cationic leaching pattern. Al, As, and Cr show an amphoteric leaching pattern. The leaching of Cl− is unaffected by the pH. The maximum leaching concentration of the proprietary elements occurs under extremely acidic conditions (pH = 2), except for As. The leaching concentration of F− reaches 1.4–27.0 mg/L in natural pH conditions (i.e., no acid or base addition). At the same pH level, the leaching concentrations of Pb, As, Cr, and Cu are generally higher from red mud produced by the combined process than that those of red mud from the Bayer process. The leaching concentration of these elements is not strongly related to the total elemental concentration in the red mud. Geochemical modeling analysis indicates that the leaching of metal elements, including Al, Ca, Fe, Cr, Cu, Pb, Mg, Ba, and Mn, in red mud are controlled by solubility. The leaching of these elements depended on the dissolution/precipitation of their (hydr)oxides, carbonate, or sulfate solids.

Direct Leaching of Low-Grade Zinc Oxide Ore Containing High Amounts of Iron and Manganese

Consumption of zinc metal has been rapidly increased in the world. Zinc metal exists as oxide, sulfide, carbonate and silicate ores, among which zinc oxide ores have not been mined because it is very difficult to separate zinc from gangue or to concentrate using the conventional flotation processes. In the current study, a low-grade zinc oxide ore containing 5.9% Zn, 33.4% Fe and 13.7% Mn was selected to investigate direct leaching. Results of the direct leaching at conventional conditions showed that the Zn leaching efficiency was improved at high acidity, high temperature and grinding conditions and reached about 60% at temperature of 50 °C, d80 of 110 microns, leaching time of 120 min and sulfuric acid consumption of 3.3 kg/kg Zn. Results showed that between 20 and 30% of zinc is associated with other species containing manganese IV. In the reductive leaching experiments by using Na2SO3 as reductant, the maximum Zn and Mn leaching efficiencies are about 82.7% and 96.2%. Dissolving high manganese as impurity in the pregnant solution is a potential concern with the reductive leaching process that needs further investigation.