Leaching Of Manganese Research Articles

Mechanism of enhanced enrichment manganese from manganese ore-pyrite under microwave heating: Process optimization and kinetic studies

Realizing efficient leaching of manganese elements from low-grade manganese ore is crucial from a strategic perspective to address the insufficient supply of high-grade manganese ore resources. Meanwhile, energy and environmental issues are becoming increasingly crucial under carbon neutrality. This work introduced microwave technology into the low-grade manganese ore leaching process, and the pyrite was used as a reducing agent. The leaching behavior of manganese by microwave leaching was investigated. The results showed that 98.6% Mn were leached using the microwave leaching method under optimal conditions: 400 rpm stirring rate, 1.5 M sulfuric acid concentration, a liquid-solid ratio of 10 mL/g, low-grade manganese ore-pyrite ratio of 10/2 and leaching time of 150 min. In contrast, about 92.0% Mn was achieved using conventional leaching methods. Moreover, the kinetic behavior of manganese leaching was studied using four unreacted shrinkage core models. The kinetics result indicated that the chemical reaction control model (1-(1-X)1/3 = k1t) could be used to describe the microwave leaching process. These results have preliminary guidance for the production practice of microwave-assisted leaching of low-grade manganese ore.

In-process control of manganese dithionate in the manganese ore-based wet flue gas desulfurization coupled with efficient manganese leaching

Manganese ore-based wet flue gas desulfurization (MFGD) is a resourcing technology capable of simultaneously reutilization flue gas sulfur dioxide (SO2) and green, low-carbon manganese leaching. However, the by-product manganese dithionate (MnS2O6) greatly affects the use of desulfurization liquid. In this study, the iron introduced MFGD process to achieve the in-process control of MnS2O6 was proposed and systematically studied. The results revealed that the Fe(III) greatly enhanced the MnS2O6 degradation by manganese dioxide (MnO2), which works principally as an oxidant, and generates certain hydroxyl oxidize iron (FeOOH) to promote the MnS2O6 degradation. Kinetic studies revealed that the Fe(III) enhanced MnS2O6 degradation by manganese oxide ore (MnOO) occurred mainly on the surface of solid, and the apparent activation energy (Ea) was reduced to 43.56 kJ mol−1. The Fe(III) could be also incorporated into the MFGD process to achieve the in-process control of MnS2O6. According to the operational experiments, 5.00 g L−1 of Fe(III) in the MnOO slurry could reduce the MnS2O6 in the desulfurization liquid from 5.34 g L−1 to 1.75 g L−1 and without any noticeable negative effect. This study provides an applicable option for the low-cost and simple control of MnS2O6 of the MFGD technology, and it will also support the utilization of the low-grade manganese ore.

Bioreactor as the root cause of the "manganese effect" during Aspergillus niger citric acid fermentations.

High-yield citric acid production by the filamentous Ascomycete fungus Aspergillus niger requires a combination of extreme nutritional conditions, of which maintaining a low manganese (II) ion concentration (<5 μg L−1) is a key feature. Technical-scale production of citric acid predominantly uses stainless-steel tank fermenters, but glass bioreactors used for strain improvement and manufacturing process development also contain stainless steel components, in which manganese is an essential alloying element. We show here that during citric acid fermentations manganese (II) ions were leaching from the bioreactor into the growth media, resulting in altered fungal physiology and morphology, and significant reduction of citric acid yields. The leaching of manganese (II) ions was dependent on the fermentation time, the acidity of the culture broth and the sterilization protocol applied. Manganese (II) ion leaching was partially mitigated by electrochemical polishing of stainless steel components of the bioreactor. High concentrations of manganese (II) ions during early cultivation led to a reduction in citric acid yield. However, the effect of manganese (II) ions on the reduction of citric acid yield diminished towards the second half of the fermentation. Since maintaining low concentrations of manganese (II) ions is costly, the results of this study can potentially be used to modify protocols to reduce the cost of citric acid production.

Comprehensive extraction of valuable metals from waste ternary lithium batteries via roasting and leaching: Thermodynamic and kinetic studies

Considering the existing problems in the extraction of waste ternary materials, a method of reduction roasting - sulfuric acid leaching is proposed in this paper. The waste ternary battery material is mixed with carbon powder, reduced and roasted in an argon atmosphere to destroy the original crystal lattice of the ternary material, adjust the valuable metal ions to a valence state suitable for leaching, and reduce the difficulty of leaching. Moreover, recycling waste lithium batteries were systematically studied from the thermodynamic and kinetic aspects. Thermodynamic calculations indicate that the theoretical temperature for reduction roasting is 500–650 °C, and the roasting products are composed of lithium carbonate, nickel, cobalt, nickel oxide and manganese oxide, which has been confirmed by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy analysis. The activation energy for the reduction roasting of the cathode material was calculated as 134.7 kJ/mol by thermogravimetry–differential scanning calorimetry and Kissinger formula. The roasted electrode materials were subjected to an acid leaching process. The effects of roasting and leaching conditions on the metal extraction from waste ternary batteries were investigated based on thermodynamic calculations, and the following optimal conditions were identified: 10% carbon content, 600 °C roasting temperature, 120 min roasting time, 2 mol/L sulfuric acid concentration, 85 °C leaching temperature, 10:1 liquid-to-solid ratio and 60 min leaching time. The extraction of lithium, nickel, cobalt, and manganese reached 98.3%, 97.2%, 98.8%, 96.1%, respectively, under the optimal conditions. The kinetic analysis of the acid leaching process adopted the shrinking core model and Arrhenius formula. The activation energies of lithium, nickel, cobalt, and manganese leaching were 23.9 kJ/mol, 25.2 kJ/mol, 23.0 kJ/mol, and 27.6 kJ/mol, respectively, which indicates that acid leaching is an internal diffusion control process. This study provides an economical and efficient process route and lays a theoretical and technological foundation for the extraction of cathode materials from waste ternary batteries.

Metal leaching test of commercially available faucets in the Japanese market in 2016-2020.

In this study, metal leaching was investigated in commercially available faucets in Japan to clarify their compliance to Japanese regulations. We purchased 37 faucets from the market and analyzed the leaching of cadmium, mercury, selenium, lead (Pb), arsenic, hexavalent chromium, boron, zinc (Zn), copper, manganese, and nickel. The leaching tests were performed with and without a conditioning treatment, that simulated approximately 1-month intermittent use of faucets on weekdays, and the results were compared to estimate the changes in metal leaching during the use of faucets. The results revealed that metal leaching from most of the faucets complied with Japanese regulations. However, the levels of Pb leaching from several faucets produced by certain manufacturers exceeded the Japanese standard. The conditioning treatment was generally effective in reducing metal leaching. However, the reductions in Pb and Zn leaching tended to be lower than those of the other metals. Nickel is not legally regulated in Japan; although the number of cases where nickel concentration in leachate exceeded the water quality management target value was greater, such cases were limited to faucets primarily made of copper alloys. We believe that these results will be helpful to improve the public health associated with metal leaching from faucets.

Microwave-enhanced reduction of manganese from a low-grade pyrolusite ore using pyrite: process optimization and kinetic studies.

The inefficient leaching of manganese is the main factor hindering the commercialization of the reduction process during manganese recovery using pyrite as the reducing agent. Hence, a new method for improving recovery efficiency and reducing the cost is required. This study uses microwave heating as a strengthening method to extract Mn2+ from pyrolusite and the leaching conditions are optimized. It was found that the extraction rate of Mn2+ could reach 95.07% under microwave heating through the conditions of H2SO4 is 1.2mol/L, m(pyrolusite)/m(pyrite) equals to 10:2, leaching temperature is 90 ℃, and a liquid-solid (L/S) ratio of 10:1. The achieved extraction rate was higher than that of 75.08% under the conventional heating achieved at the same conditions. Besides, experimental studies have found that microwave heating can change the process and direction of chemical reactions, shorten the reaction time, and reduce sulfuric acid. Finally, the kinetic study indicates that the leaching process under microwave heating is controlled by surface chemical reactions. The equation of leaching kinetics is 1 - (1 - x)1/3 = 3425.32/r0·[H2SO4]1.316·[FeS2/MnO2]0.907·exp(- 45.03/(RT)·t. The activation energy is 45.03kJ/mol. Meanwhile, through a scanning electron microscope and particle size analyzer, microwave heating has a significant influence on reducing the ore diameter and increasing the specific surface area of the sample. This study aims to provide an experimental trial case for studying the mechanism of microwave-enhanced leaching process during manganese recovery using pyrite as the reducing agent. The reported kinetics research may guide the development of the industrial application for Mn recovery.

A cost-effective method for enhancing manganese leaching from rhodochrosite caused by surfactant-regulated crystal growth of CaSO4·2H2O

The cost-effective leaching of manganese (Mn2+) from rhodochrosite is critical for achieving energy saving, curtailing pollutants, and cleaner production of electrolytic metallic manganese (EMM). In this work, different surfactants were used to enhance Mn2+ leaching from rhodochrosite. The effects of the surfactants: trisodium citrate (TC), sodium oleate (SOL), ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), and tetradecyltrimethyl ammonium bromide (TTAB) on the Mn2+ leaching efficiency were evaluated. The enhanced mechanism of Mn2+ leaching is discussed, and an economic evaluation is presented. The leaching efficiency of Mn2+ reached 91.8% in the presence of 5 mg/L TC, which is 13.8% higher than that in the absence of TC using a temperature of 50 °C, a solid-liquid ratio of 1:5, an acid-to-ore ratio of 0.58:1, and reaction time of 3.5 h. In the leaching mechanism, TC inhibited the growth of the 020, 040, and 041 crystal planes of CaSO4·2H2O; thus, CaSO4·2H2O crystals with a shortened columnar morphology and smaller sheet shapes were obtained. The grain refinement of CaSO4·2H2O did not readily wrap on the surface of rhodochrosite, consequently increasing the probability for rhodochrosite to react with H+, and improving the leaching efficiency of Mn2+. Moreover, TC did not remain in the leachate to impact the subsequent electrolytic deposition. This study provides a cost-effective method for leaching Mn2+ from rhodochrosite.

Sulfur and lime affect soil pH and nutrients in a sandy Pinus taeda nursery

Two pH experiments were conducted at a sandy, bareroot loblolly pine (Pinus taeda L.) nursery in Texas. A sulfur trial (0, 813, 1626, 2439 kg ha-1 of elemental sulfur) was installed to determine if lowering soil pH would result in nutrient toxicity symptoms and affect seedling morphology. Although soil acidity in the sulfur study ranged from pH 3.9 to pH 5.0, none of the treatments resulted in micronutrient toxicity and none affected height growth, root-collar diameter, root mass, shoot mass or the root-mass ratio (root dry mass/total dry mass). Acidifying soil with sulfur increased leaching of calcium, potassium, magnesium, manganese and zinc but there was no effect on seedling morphology. The objective of the liming trial (0, 813, 1626, 3252 kg ha-1 of dolomitic lime) was to determine if increasing alkalinity would result in an iron deficiency and reduce seedling growth. As expected, applying lime increased the calcium and magnesium levels but had no effect on soil levels of iron, phosphorus, potassium, sulfur, zinc and sodium. However, the root-mass ratio was reduced by applications of dolomitic lime (pH ranged from 5.3 to 6.0). Differences in soil properties (i.e. plot location) had a greater effect on seedling morphology than lime applications. Foliage levels of manganese and boron were reduced by the highest rate of lime and sulfur, respectively.

A stepwise processing strategy for treating manganese residue and the remediation of hexavalent chromium in water and soil by manganese residue-derived (Fe,Mn)C2O4

This work provides a new approach for effective treatment and utilization of manganese residue (MR), including leaching, desulfurization, and recycling of iron and manganese. The secondary residue and the acidic filtrate (pH = 0.94) composed of H2SO4 and H2C2O4 could be used as a cement material and the medium and reductant for manganese sulfate production system, respectively. Approximately 94.5% of Fe and 97.5% of Mn were recovered to produce (Fe,Mn)C2O4 composite, which had a capacity of 122.7 mg g−1 for removing Cr(VI) and a good performance in a wide pH range of 2–9. The removal of Cr(VI) by (Fe,Mn)C2O4 was attributed to adsorption, reduction, and co-precipitation. What's more, the control experiment of FeC2O4 and MnC2O4 affirmed the synergism between Mn and Fe in (Fe,Mn)C2O4 composite, attributed to that the accelerated reduction of Mn(III) by Fe(Ⅱ) and the co-reduction effect of Fe with Mn on Cr(VI) synergistically promoted the reduction of Cr(VI). Furthermore, the ability of (Fe,Mn)C2O4 for immobilizing Cr(VI) in the soil was investigated, and the result proved that (Fe,Mn)C2O4 significantly reduced the leaching and releasing risk of Cr(VI). This strategy for treating and utilization of MR has great economic and ecological benefits.

Aluminium and manganese leaching and retention in two contrasting soils treated with aluminium-based sludge water in a column experiment

Liquid waste (sludge water (SW)) from treatment of drinking water contains impurities which pose disposal challenges. Irrigation with SW could be a solution for the Morton Jaffray Water Works. This study was conducted to determine the effects of SW dilution on aluminium (Al) and manganese (Mn) concentrations in (a) leachates from columns with either clay or a sandy loam soil and (b) different depths in the columns. The columns were leached with tap water (control) and 25, 50, 75 and 100% of the original SW concentration and the leachates were analysed for pH, electrical conductivity (EC), Al, and Mn. The sectioned soils (0–5, 5–10, 10–15 cm depths) were analysed for pH, exchangeable acidity, extractable Mn and total Al and Mn. Leaching with undiluted SW significantly increased EC and Al and Mn concentrations and lowered pH in leachates of the first four and two leaching events in the clay and sandy loam soils, respectively. The last two to four leaching events released additional Mn. Higher SW concentrations significantly increased retention of Mn, Al, extractable Mn and acidity, and lowered pH in the soils. In practice, irrigation with SW may retain the pollutants and acidify the soil, increasing Mn mobility, potentially causing leaching and phytotoxicity.

Leaching kinetics of manganese from pyrolusite using pyrite as a reductant under microwave heating

• Microwave heating was applied to the hydrometallurgical reduction leaching of pyrolusite. • Compared with conventional heating, microwave heating could improve manganese leaching rate and save energy. • The reduction leaching kinetics behavior of pyrolusite by microwave heating was studied. Microwave heating was applied to leaching of manganese from pyrolusite using pyrite as reductant. The leaching parameters on manganese extraction, such as mass ratio of pyrite and pyrolusite, H 2 SO 4 concentration, liquid to solid ratio, reaction temperature, were investigated. The results displayed that under the optimum parameters of mass ratio of pyrite and pyrolusite of 0.25, H 2 SO 4 concentration of 1.6 mol/L, liquid to solid ratio of 10 ml/g, reaction temperature of 353 K, the leaching time of 3 h, Mn extraction rate reached 93.03%. Under the same conditions, Mn extraction rate was only 75.84% by conventional heating, The Mn leaching rate obtained by microwave heating was 17.19% higher than that obtained by conventional heating. Moreover, the leaching data was successfully verified based on unreacted shrinking core model. A shift in the rate control step was found. The leaching rate control step was determined by surface chemical reaction within 0 ~ 100 min and by diffusion through product layer within 100 ~ 180 min, respectively, the apparent activation energy was 30.95 kJ/mol and 53.03 kJ/mol, separationly, and the apparent rate equation was respectively expressed as: 1 - 1 - r 1 / 3 = 46.71 m F e S 2 / m M n O 2 0.7154 H 2 S O 4 0.3042 V L / M S 0.7821 e x p - 30950 / R T t 1 - 3 1 - r 1 - r 1 2 / 3 + 2 1 - 1 - r r - r 1 1 / 3 = 387000 m F e S 2 / m M n O 2 1.4498 H 2 S O 4 0.6093 V L / M S 1.2043 e x p - 53030 / R T t

Study on Adding Ammonium Hydrogen Fluoride to Improve Manganese Leaching Efficiency of Ammonia Leaching Low-Grade Rhodochrosite

The ammonia leaching method for treating low-grade rhodochrosite has the advantages of a good impurity removal effect and low environmental pollution. In this paper, aiming at the low leaching efficiency of low-grade rhodochrosite treated by the ammonia leaching method, studies on enhancing the leaching efficiency of manganese by using ammonium hydrogen fluoride as an additive are carried out. The effects of different ammonia concentrations, leaching temperatures, leaching times, liquid-solid ratios, stirring rates, and the addition of ammonium hydrogen fluoride on the leaching efficiency of manganese with and without ammonium hydrogen fluoride as an additive were comparatively studied, and the parameters of ammonia concentration, ammonia leaching temperature, and ammonium hydrogen fluoride dosage were optimized in the experimental study. The results indicated that ammonium hydrogen fluoride as an additive in the treatment of low-grade rhodochrosite by the ammonia leaching method could effectively increase the leaching efficiency of manganese, and the optimal process parameters were obtained. Meanwhile, the addition of ammonium hydrogen fluoride didn’t affect the quality of the steamed ammonia product.

Preliminary Study on the Reductive Leaching of Manganese Ores using FeSO?/Iron Powder as Reducing Agents under Room Temperature

The leaching of manganese (Mn) ore in sulphuric acid (H2SO4) under reductive conditions has been studied. The effects of leaching parameters such as ore/reductant mass ratio, acid concentration, ore particle size, solid/liquid ratio, leaching time and different reductant potential on the maximum recovery of manganese have been investigated. The optimal leaching conditions were ore/reductant mass ratio of 1:3.4, acid concentration of 10% v/v H2SO4, ore particle size of 63-200 µm, particle size of iron powder of –150 µm, solid/liquid ratio of 1:20, and leaching time of 1.5 hours at room temperature. A comparative analysis on the recovery of manganese ore was also investigated under the optimal leaching conditions for two different reductants, iron sulphate (FeSO4) and iron powder. The maximum manganese recoveries at the optimal leaching conditions in the presence of FeSO4 and iron powder are 80.6% and 95%, respectively. The results indicate that manganese can readily be leached during short time at room temperature. Furthermore, iron powder has a stronger reducing power compared to FeSO4 with respect to manganese ore recovery.

Preliminary Study on the Reductive Leaching of Manganese Ores using FeSO₄/Iron Powder as Reducing Agents under Room Temperature

The leaching of manganese (Mn) ore in sulphuric acid (H2SO4) under reductive conditions has been studied. The effects of leaching parameters such as ore/reductant mass ratio, acid concentration, ore particle size, solid/liquid ratio, leaching time and different reductant potential on the maximum recovery of manganese have been investigated. The optimal leaching conditions were ore/reductant mass ratio of 1:3.4, acid concentration of 10% v/v H2SO4, ore particle size of 63-200 µm, particle size of iron powder of –150 µm, solid/liquid ratio of 1:20, and leaching time of 1.5 hours at room temperature. A comparative analysis on the recovery of manganese ore was also investigated under the optimal leaching conditions for two different reductants, iron sulphate (FeSO4) and iron powder. The maximum manganese recoveries at the optimal leaching conditions in the presence of FeSO4 and iron powder are 80.6% and 95%, respectively. The results indicate that manganese can readily be leached during short time at room temperature. Furthermore, iron powder has a stronger reducing power compared to FeSO4 with respect to manganese ore recovery.

Acid-assisted leaching of iron and manganese from Sri Lankan laterite: a potential source of alumina production

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2020 Impact Factor: 0.515The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Release of Cadmium, Lead and Manganese from Unglazed Ceramic Food Containers to Pickled Mustard Greens Juice and Soy Sauce

Leaching of toxic elements from containers to food can be a direct threat to human health, especially when they are used to hold highly corrosive foods over a long time. The concern of this study is the leaching of cadmium, lead and manganese from unglazed ceramic containers when holding two leachates, including pickled mustard greens juice and a soy sauce. The containers were randomly collected from four ceramic production facilities in Bat Trang - Hanoi, Nam Sach - Hai Duong, Tien Hai - Thai Binh and Thuan An - Binh Duong, where no standard was employed to control heavy metal contents in raw materials and products. The release of cadmium, lead and manganese from the containers to the leachates were analyzed at 24-hour intervals for six days for pickle juice and at two-month intervals for a year for soy sauce. The results showed that the concentrations of those elements increased non-linearly during the course of the study and increased more rapidly in the more acidic medium. The concentrations of cadmium, lead and manganese in the pickle juice (pH reduced from 4.1 to 2.9) after six days were 80.78, 140.10, and 150.11 ppb, and in the soy sauce (pH stable at 6.1) after twelve months were 11.32, 11.86 and 13.87 ppb, respectively. It suggests that further research on the long-term leaching of toxic elements from containers to highly acidic foods is needed to protect the health of consumers.

Enabling Aqueous Processing for LiNi0.5Mn1.5O4‐Based Positive Electrodes in Lithium‐Ion Batteries by Applying Lithium‐Based Processing Additives

Aqueous processing of positive electrode active materials (AMs) could enable a more economical and environmentally friendly production of lithium‐ion batteries. Intrinsically, aqueous processing of positive AMs is hampered by lithium‐proton exchange in the AM surface, leading to a poor electrochemical performance and a resulting strong increase in the pH value in the electrode paste, thereby corroding the aluminum current collector. Herein, the influence of different lithium salts as processing additive to tailor the pH value of the electrode paste, the manganese dissolution during processing, and the electrochemical performance is described for aqueous processing of LiNi0.5Mn1.5O4‐based positive electrodes. Positive electrodes, based on an aqueous LiNi0.5Mn1.5O4‐based electrode paste which is mixed with LiN(SO2CF3)2 (LiTFSI), achieve a comparable electrochemical performance to state‐of‐the‐art nonaqueous‐processed electrodes. Manganese dissolution into the electrode paste is examined by inductively coupled plasma‐mass spectrometry (ICP‐MS), showing that the addition of lithium salts to the electrode paste substantially decreases manganese leaching during processing. Furthermore, postmortem analysis shows that the addition of LiTFSI to the electrode paste has a positive effect not only during processing but also on charge/discharge cycling performance.

IMPROVEMENT OF THE TECHNO¬LOGY FOR OBTAINING MANGANESE(IV) OXIDE FROM SECONDARY RAW MATERIALS

Today's level of integrated use of minerals and beneficiation wastes in Ukraine, in particular, at the Kryvbas GOK, is unsatisfactory, as it is generally allowing the production of additional types of construction products. The volume of mining is growing, but only a small percentage of the extracted volume is transferred to the finished product. The residue in the form of waste is returned to the environment, polluting it. The reason for this is the lack of technology for integrated mineral processing and waste disposal.&#x0D; The article presents the results of industrial tests of off-balance manganese ore processing technology of Ordzhonikidze GOK with a manganese content of 15–30%. It is shown that nitric acid leaching of manganese with subsequent precipitation of impurities with soda or alkali allows you to consistently purify manganese from transition and alkaline earth metals. The obtained manganese oxide has a high degree of purity, which allows obtaining pure compounds Mn (NO3)2∙6H2O, MnO2 and metallic manganese for chemical current sources. The use of columnar clarifiers with a fluidized bed with the application of pulsations allowed to eliminate time-consuming filtration processes. Concomitantly formed sodium nitrate serves as a raw material for mineral fertilizers. Experimental studies on the beneficiation of off-balance manganese ores allowed us to determine the main technological parameters of the extraction of components and to develop a technological scheme of beneficiation.&#x0D; According to the proposed technological scheme, it is possible to obtain high-quality concentrates of manganese (IV) oxide. The use of optimal technological parameters of enrichment allows up to 95% of Mn to be extracted from off-balance manganese raw materials. In the long run, this will reduce dependence on imports of manganese raw materials and significantly reduce the cost of domestic manganese products.

Hydrometallurgical leaching and kinetic modeling of low-grade manganese ore with banana peel in sulfuric acid

Manganese was leached from a low-grade manganese ore (LGMO) using banana peel as the reductant in a dilute sulfuric acid medium. The effects of banana peel amount, H2SO4 concentration, reaction temperature, and time on Mn leaching from the complex LGMO were studied. A leaching efficiency of ∼98% was achieved at a leaching time of 2 h, banana peel amount of 4 g, leaching temperature of 120°C, manganese ore amount of 5 g, and sulfuric acid concentration of 15vol%. The phase, microstructural, and chemical analyses of LGMO samples before and after the leaching process confirmed the successful leaching of manganese. Furthermore, the leaching process followed the shrinking core model and the leaching rate was controlled by a surface chemical reaction (1 − (1 − x)1/3 = kt) mechanism with an apparent activation energy of 40.19 kJ·mol−1.

Enhanced leaching of manganese from low-grade pyrolusite using ball milling and electric field

In this study, electric field and ball milling were used to leach Mn2+ from low-grade pyrolusite (LGP). The effects of current density, reaction time, reaction temperature, ball-to-powder weight ratio, and ball milling time on the leaching efficiency of Mn2+ from LGP as well as the leaching mechanism were systematically studied. The results showed that the combined use of electric field and ball milling enhanced the leaching of Mn2+ from LGP. The leaching efficiency of Mn2+ reached 97.79% under the optimum conditions of LGP-to-pyrite mass ratio of 1:0.18, current density of 30 mA/cm2, LGP-to-H2SO4 mass ratio of 1:0.4, liquid-to-solid ratio of 5:1, ball-to-powder weight ratio of 1:1, ball milling time of 2 h, temperature of 80 °C, and leaching duration of 120 min. This value was 25.95% higher than that attained without ball milling and 41.45% higher than that attained when neither ball milling nor electric field was employed. Pyrite was fully oxidized to generate additional SO42− and Fe3+, and was further hydrolyzed to form jarosite (KFe3(SO4)2(OH)6) and hydronium jarosite (Fe3(SO4)2(OH)5·2H2O) via ball milling and electric field application. Moreover, the electric field changed the surface charge distribution of the mineral particles and promoted collisions between them as well as the collapse of the crystal lattice, further improving the leaching efficiency of Mn2+ from LGP. This study provided a new method for leaching Mn from LGP.