Low-grade Pyrolusite Research Articles

High efficiency and cost-effective innovative self-oxidation in-situ removal scheme for the preparation of battery-grade manganese sulphate

As an essential crucial intermediate in the green new energy, achieving sufficient global supply of battery-grade manganese sulfate holds significant strategic importance. However, high efficiency and cost-effective preparation of battery-grade manganese sulfate and efficiently removing impurity ions pose highly challenging. Herein, an innovative self-oxidation in-situ removal scheme successfully prepared battery-grade MnSO4 from low-grade pyrolusite. Specifically, during the purification of qualified MnSO4, abundant Fe3+ was generated in situ through the self-oxidation of pyrolusite without the need for additional oxidants. This significantly facilitated the formation of jarosite (XFe3[SO4(OH)3]2, X=K/Na), greatly enhancing the removal efficiency of K, Na, and Fe (99.69 %, 99.82 % and 99.99 %), and promoted the removal of subsequent impurity ions. Subsequently, the dissolved impurity ions were successively removed in-situ using industrial reagents, achieving technical indices (Cu 99.93 %, Co 99.73 %, Cd 93.26 %, Zn 99.50 %, Ni 98.42 %, Al 99.71 %, Si 98.67 %, Ca 99.82 %, Mg 97.90 %, and F 99.78 %) that are far superior to those of battery-grade MnSO4.This fruitful innovative scheme has promising commercia prospects and is conducive to the efficient and low-cost comprehensive utilization of global pyrolusite resource.

Remarkable enhancement of elemental mercury removal performance over natural low-grade pyrolusite through acid-etching

Using natural low-grade pyrolusite as a novel Hg0 absorbent has economic and environmental benefits, but faces the challenge of restricted adsorption and oxidation capacity. Herein, a HNO3-etching strategy is employed to modify the physicochemical property. Characterizations and relevant theoretical calculations reveal the etching’s role: (i) dissolving impurities and adjusting pore structure, which magnify pre-adsorption capacity of reactants and facilitate mutual mass transfer; (ii) creating more oxygen vacancies and promoting electron transfer, which favor the adsorption-dissociation of O2 and the migration of more O-containing species; (iii) increasing reaction rate and lowering energy barrier. The 12-hour experimental results show that the removal efficiency of Hg0 can reach 92.8 % through etching, and the increment of 30.6 % reflects the huge promotion of etching on mercury removal. Moreover, the etching also improves the stability, sulfur/water resistance and regeneration performance. Furthermore, the desorption temperature of HgO diminishes after etching, as the etching enhances the activity of Oads and Olat. By contrasting the preferential and co-adsorption pathways on pristine/defective surfaces, alterations in adsorption mechanism are revealed, further elucidating the effects of increased defects on the enhanced Hg0 oxidation activity. This work offers a practical strategy to synchronously achieve structural optimization and defect construction of pyrolusite, thereby enhancing its removal performance, which holds potential implications for industrial applications in mitigating mercury emissions.

Unrefined low-grade pyrolusite for elemental mercury removal from flue gas: Experimental and DFT insights

Dual characteristics of oxidation capacity and economic advantage endow the unrefined low-grade pyrolusite (LGP) as a potential adsorbent/catalyst. This paper successfully applied it to remove Hg0 from flue gas, by which 98.6% of removal efficiency was obtained without chemical modification or external oxidant. Effects of various flue gas components on the Hg0 removal were investigated, and the synchronous improvement in efficiency and stability by HCl was revealed. Also, its reusability was evaluated and the decrease in removal efficiency after 5th cycles is less than 6%. Product analysis indicated that over 90% of Hg0 was chemisorbed as HgO without HCl, but the presence of HCl reversed the pathway to form HgCl2 that easily escape from the surface, with a proportion of about 95%. By combing experiments, characterizations and theoretical calculations, the mechanism was preliminarily speculated: (i) without HCl, O2 and the main components of LGP (MnOx, Fe2O3, etc.) involved in the catalytic oxidation according to Mars-Maessen mechanism; (ii) HCl tended to dissociate and adsorb on the MnO2 to form the chlorinated surface, and the mercury removal followed both L-H and E-R mechanism, although E-R was dominant; (iii) the formation of HgCl lowered the energy barrier of HgCl2 desorption, thereby expediting the oxidation-removal of Hg0.

A Green Cyclic Leaching Process for Low-Grade Pyrolusite via a Recyclable Fe(II) Reductant

The low-cost Fe(II) reductants used in the leaching of pyrolusite usually cause high concentrations of iron ions in the leaching solution, which are difficult to treat and recover. Herein, a green cyclic leaching process for pyrolusite with recycling and reusing of Fe(II) reductants was developed. Sodium sulfide was introduced to reduce and precipitate iron ions in the leaching solution. Ep-H diagrams show that Fe3+ can be reduced to Fe2+ by S2− and form a precipitate with the high efficiency of 93.09%. Since the main component of the precipitate was ferrous disulfide with reducibility, it was used as a reducing agent for low-grade manganese oxide ores. A total of 97.96% of the manganese was highly reductively leached by the obtained precipitate of 0.28 g·g−1 ore. Furthermore, the leaching efficiency was almost unchanged after five iterations of cyclic experiments. The cyclic leaching process enables the efficient leaching of manganese and the recycling of iron, which provides a green and economic method for the efficient utilization of low-grade pyrolusite resources.

Reductive Leaching and Recovery of Nano-crystalline MnO2 from Low-Grade Pyrolusite Ore

Reductive Leaching and Recovery of Nano-crystalline MnO2 from Low-Grade Pyrolusite Ore

Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process

With the continuous economic and social development of China, the demand for pyrolusite has increased tremendously, accompanied by a decrease in high-grade pyrolusite (HGP). Thus, it is urgent to find viable alternatives, such as low-grade pyrolusite (LGP). Currently, a relatively mature process technology is a one-step acid leaching of manganese (Mn) from pyrolusite using pyrite (PY) as a reducing agent. While the method can achieve a relatively high leaching efficiency of Mn at atmospheric pressure, it requires a significant amount of time. To pursue maximum effectiveness and efficiency, here we applied microwave leaching technology to the one-step acid leaching process to the extraction of Mn from LGP, and PY as a reducing agent. The results showed that the leaching efficiency of Mn reached 96.2% at time = 150 min, agitation speed = 400 rpm, temperature = 363 K, acid concentration = 1.5 M, liquid-solid ratio = 10: 1 (mL: g), and SLGP-SPY mass ratio = 10: 2. Furthermore, the kinetic analysis showed that the chemical reaction control model (1-(1-X)1/3 = kt) can be used to explain the mechanism of the microwave leaching process. Finally, according to the Arrhenius equation, the apparent activation energy (Ea) for the microwave leaching process was calculated as 44.8 kJ/mol. This work provides the preliminary theoretical and technical basis for recovering Mn from LGP. In summary, these results imply that LGP could be effectively utilized and developed by microwave heating technology in the future.

Oxidative Leaching of Low-Grade Pyrolusite in Alkaline Solutions to Produce Potassium Manganate

Oxidative Leaching of Low-Grade Pyrolusite in Alkaline Solutions to Produce Potassium Manganate

Microwave-boosted elemental mercury removal using natural low-grade pyrolusite

Utilizing natural minerals to remove Hg0 from flue gas was regarded as a preferable route to control mercury pollution. This paper purposed a novel microwave (MW)-boosted removal method using natural low-grade pyrolusite (NLP), by which over 85 % of Hg0 was removed and approximately 10–20 % of the increment of efficiency was obtained. Compared with thermo-catalysis, MW also empowered NLP with a wider active-temperature range (100–250 °C) and better H2O and SO2 resistances. Kinetic analysis showed that MW increased the rate constant and reduced the activation energy, Hg-TPD and material balance analyses demonstrated that major Hg0 was chemisorbed as HgO. Via the thermal treatment experiments, the regeneration performance of NLP was confirmed to be good. From the experiments and characterizations, the mechanism was preliminarily speculated: (i) the contribution order of the active components was MnO2 > Mn3O4 > Fe2O3; (ii) the redox pairs of Fe(II)/Fe(III) and Mn(III)/Mn(IV), as well as the O-species, involved in the conversion from Hg0 to HgO. Density functional theory calculations revealed the pathway and mechanism: (i) MnO2 exhibited higher oxidation activity, whereas Mn3O4 showed higher adsorption activity; (ii) Odis derived from Oads enhanced the removal of Hg0 by increasing the adsorption energies and amounts of transferred electron; (iii) Oads had advantages over Olat in term of desorbing HgO, which was the rate-determining step.

Study on Microwave-assisted Reduction of Pyrolusite

Abstract: Manganese is a vital metal resource, and increased consumption of manganese is leading to the shortage of high-grade manganese ore resources. However, a large number of low-grade manganese ore resources ((Mn<30%) accounts for about 60% of the total manganese resources) have not been effectively utilized because of the lack of efficient industrial utilization methods. Researching new technologies for reducing low-grade pyrolusite is an urgent problem to be solved. Microwave is an effective and environmentally friendly heat source widely used in mining, metallurgy, and chemistry. Different substances have different dielectric constants. The difference in dielectric constant affects the absorption rate of substances, resulting in different heating rates for different substances when heated by microwaves. Microwave is widely used in the metal smelting process because of its unique heating method. So far, few works have been done to verify that microwave heating can effectively promote the reduction of pyrolusite. This article summarizes some current methods of reducing low-grade pyrolusite and compares them with the method of reducing pyrolusite by microwave heating. In addition, this article introduces the principle of microwave- enhanced reduction of pyrolusite and discusses the opportunities and challenges faced by microwave heating technology in its subsequent development. The aim is to analyze and study the promoting effect of microwave heating technology on the reduction of pyrolusite, further improve the utilization of low-grade pyrolusite, and provide new methods and approaches for the comprehensive utilization of mineral resources and provide assistance in industrial production.

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.

Efficient Extraction of Manganese from Low-Grade Pyrolusite by a Sawdust Pyrolysis Reduction Roasting-Acid Leaching Process

Efficient Extraction of Manganese from Low-Grade Pyrolusite by a Sawdust Pyrolysis Reduction Roasting-Acid Leaching Process

Rapid Preparation of Manganese Monoxide by Microwave-Enhanced Selective Carbothermal Reduction

Most of the manganese resources in China have existed in the form of low-grade pyrolusite which is not utilized efficiently because of the high energy consumption and environmental pollution during the reduction process. Applying microwave heating to minerals reduction endows improved production efficiency and reduced production costs. In the present work, rapid preparation of manganese monoxide (MnO) was attempted through reducing low-grade pyrolusite with coal reducing agent by microwave heating, with the samples characterized by XRD, scanning electron microscopy, XPS as well as TG/DSC. The influences of the reduction reaction parameters on the reduction process of Mn in pyrolusite were comprehensively studied. The results indicated that higher temperatures and longer holding times facilitated the reduction roasting of pyrolusite, and manganese monoxide can be fabricated with a reduction ratio of 97.7% obtained at 650°C for 50 min. The mechanism of the gradual transformation of MnO2 to MnO from the macroscopic to the molecular level was also revealed in the order of MnO2 → Mn2O3 → Mn3O4 → MnO. Compared to traditional roasting, the proposed microwave-enhanced roasting process benefits from the superior kinetic conditions provided by the synergy between microwave enhancement and compact pellets, and thus reduced the roasting temperature and roasting time.

Crystalline Manganese Dioxide Recovery from Low-Grade Pyrolusite Ore Using Tartaric Acid as Reductant

Crystalline Manganese Dioxide Recovery from Low-Grade Pyrolusite Ore Using Tartaric Acid as Reductant

Comparative investigation on removal of thallium(Ⅰ) from wastewater using low-grade pyrolusite and pyrolysis residue derived from oily sludge: performance, mechanism and application

The pyrolysis residue (PR) and low-grade pyrolusite (LGP) were developed as adsorbents for Tl(I) removal from aqueous solution. The Tl(Ⅰ) removal performance and mechanisms of PR and LGP were investigated. At initial solution pH of 4, Tl(Ⅰ) concentration of 1.6 mg⋅L−1 and adsorbent dosage of 3 g⋅L−1, the Tl(Ⅰ) removal efficiency achieved 93.44% for PR and 98.25% for LGP. Both the adsorption of PR and LGP for Tl(I) follow the pseudo‒second‒order kinetic model. The fitting results of intraparticle diffusion model show that the rate‒controlling step of Tl(Ⅰ) adsorption on PR and LGP include film diffusion and intraparticle diffusion. The adsorption isotherm data for PR are fitting better by Temkin model, while the adsorption of Tl(Ⅰ) on LGP is described well by the Freundlich model. The XRD and XPS analysis reveal that the Tl(Ⅰ) removal by PR is achieved via surface complexation and chemical precipitation in the form of TlFe2S3 and Tl2S, while oxidation-induced surface precipitation of Tl2O3 and the enhanced surface complexation are deduced as the main mechanisms for Tl(Ⅰ) removal by LGP. The treatment of real industrial wastewater implies that PR has a comprehensive removal capacity to heavy metals (Zn, Cd, Tl) and adding LGP after the adsorption by PR could remarkably reduce Tl concentration up to the emission standards of pollution for inorganic chemical industry.

Study on the high-efficiency separation of Fe and Mn from low-grade pyrolusite and the preparation of LiMn2O4 materials for lithium-ion batteries

• No any reducing agent is used in whole recovery process. • The separation effect of pyrolusite by sulfidation roasting is satisfactory. • The conversion process of manganese oxide is studied in detail. There is a serious shortage of high-grade manganese ore resources, so the development and utilization of low-grade manganese ore are of great significance. In this paper, the mixed roasting/water leaching method of sulfuric acid and pyrolusite is used to efficiently recover Mn and Fe elements. Under the optimal process conditions, acid/ore ratio of 2:1, water/acid ratio of 1:5, the roasting temperature of 650 °C, and holding time of 4 h, the leaching rates of Mn and Fe are 99.10% and 0.67%, respectively. Additionally, the conversion process between manganese-containing precipitate and manganese oxide is studied, and high-purity Mn 3 O 4 is obtained. LiMn 2 O 4 , an electrode material for lithium-ion batteries, is successfully prepared by solid-phase synthesis with Mn 3 O 4 as a manganese source. The initial charge specific capacity of the LiMn 2 O 4 is 115.7 mAh·g −1 at 0.1C. Additionally, the charge specific capacity of the LiMn 2 O 4 is still 78.64 mAh·g −1 after 100 cycles at 1C. The process does not use any reducing agents, surfactants, etc., and has the characteristics of short, simple, easy-to-operate, economical, and reasonable process, which is helpful to realize the efficient recovery and reuse of manganese and iron resources in the pyrolusite.

An eco-friendly approach for NaCl recovery from organic pollutants-containing waste salt by roasting together with low-grade pyrolusite

A large amount of organic pollutants-containing waste salt is produced in chemical production process, which is usually filled or deposited without treatment, causing serious environmental pollution and a waste of salt resource. In this work, in order to reduce the emission of toxic and harmful gasses and make full use of the organic matter component in waste salt, pyrolusite was used as an absorbent in the process of high-temperature pyrolysis of waste salt, of which MnO 2 was reduced to MnO while absorbing harmful gasses. The dual effects of roasting to remove organic pollutants from the waste salt and increase manganese leaching efficiency were systematically investigated, and the roasting mechanism and process were explored. Co-recovery of NaCl from organic pollutants-containing waste salt and manganese from pyrolusite ore was achieved. The results indicated that the optimum the removal efficiency of organic matter in the waste salt could be reached 99.45%, the purity of recovered NaCl products was 99.83% and leaching efficiency of 99.62% for manganese under the mass ratio of waste salt to pyrolusite of 8:5, the co-roasting temperature of 650 °C, and the roasting time of 40 min. • Co-recovery of NaCl from waste salt and Mn from low-grade pyrolusite was realized. • Pyrolusite was used as an adsorbent to absorb toxic gasses reducing pollution. • The mechanism and process of co-recovery were investigated.

A novel leaching process with highly-low residual organics from pyrolusite ore and its kinetics

This study focused on the exploration of a novel reductive leaching method from pyrolusite ore which can effectively reduce residual organics in leaching solution. Formaldehyde was used as a reductant to extract manganese from low-grade pyrolusite. Organic residue in the leaching solution was analyzed via HPLC. Kinetics model was also exposed. The optimized leaching conditions were as follows: H2SO4 concentration 2.21 mol/L, liquid-to-solid ratio 8:1, 2.5 ml formaldehydel/10g low-grade pyrolusite, stirring rate 200 r/min, leaching temperature 353 K and leaching time 120 min. The extraction ratios of Mn, Al, Fe, Mg, and Ca were 90.24%, 22.78%, 61.61%, 53.38%, and 84.2%, receptively under the optimized conditions. Formic acid was the main residual organic from the oxidized production of formaldehyde; its concentration was only 2.24 g/L. The kinetic data for leaching process obeyed a mix-controlled kinetic model. The apparent activation energy of leaching reaction was 34.81 kJ/mol for 0-30min, 30.1 kJ/mol for 30–150min, respectively.

Dielectric characterisation and reduction properties of the blending mixtures of low-grade pyrolusite and waste corn stalks in the microwave field

Recently, pyrometallurgical reduction of low-grade pyrolusite is one of the potential techniques for expanding the resources for manganese. However, the process has a high cost on fossil energy and produces a large amount of greenhouse gases. This work proposed a novel method of using biomass, namely corn stalks, to reduce and roast low-grade pyrolusite under microwave field to provide positive alternatives for fossil energy. The microwave-assisted reduction was studied systematically, and the corresponding mechanism was also studied by thermodynamic analysis and dielectric properties analysis. Results indicated that co-pyrolysis reduction characteristics of the mixtures were mainly divided into three stages: the pre-reaction stage (25 °C–196 °C), activated pyrolysis reduction stage (196 °C–480 °C), and carbonisation stage (>430 °C). The mechanism of MnO2 reduction is attributed to reductive volatiles (H2, CO, CH4) and the fixed carbon (C) produced by biomass pyrolysis. Meanwhile, the reduction efficiency of Mn can achieve 97.2% at 650 °C for 60 min with 25% corn stalks, indicating efficient pyrolusite reduction by microwave heating. These results enrich the fundamental knowledge on the corresponding industrial technology development.

Bioleaching of manganese from a low-grade pyrolusite ore using Aspergillus niger: Process optimization and kinetic studies

Low-grade metal resources generated during different mineral processing activities are increasing while there are not many economic and environmentally friendly techniques to manage them. There is no viable technique for the manganese extraction from low-grade ores as the conventional procedures are costly and environmentally unfriendly. In this research, the D-optimal response surface methodology has been used to optimize the bioleaching parameters. Varied contact methods (one-step, two-step, and spent medium), nutrition sources (sucrose and glucose), and pulp densities (1 g.L−1 to 10 g.L−1) were used in different experiments having been done in 30 days using Aspergillus niger. A maximum recovery of over 80% of Mn was achieved based on the acidolysis, complexolysis, and redoxolysis leaching of the organic acids produced by the fungi under the optimum condition; a two-step approach, in a glucose medium, and with a pulp density of 1 g.L−1. A kinetic study was also performed and revealed that the leaching mechanism was a mixed one which consisted of two stages (diffusion through the liquid film and a chemical reaction) for the first 12 day period, and a mechanism of diffusion through the product layer for the rest of the experiment.

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.