Study on hydrometallugical reduction leaching of pyrolusite enhanced by electric field using pyrite as reductant

Study on hydrometallugical reduction leaching of pyrolusite enhanced by electric field using pyrite as reductant | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Study on hydrometallugical reduction leaching of pyrolusite enhanced by electric field using pyrite as reductant Yakun Zhao, KeFeng Pan, RuiYao Yang, ChengShuo Hou, Nan Zhang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4413889/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this paper, electric field as a chemical process intensification methods was utilized in the leaching experiment of manganese from pyrolusite using pyrite as reductant. The key leaching parameters under the action of electric field, such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H 2 SO 4 molar concentration, stirring speed, leaching temperature, direct current density, were investigated, respectively. The results suggest the optimum parameters of liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H 2 SO 4 molar concentration, stirring speed, leaching temperature, direct current density were 10ml/g, 10:3, 1.6mol/L, 250 r/min, 353K, 700 A/m 2 under the leaching time of 3h, the manganese extraction efficiency of 96.22% was obtained, the manganese extraction rate of leaching with electric field is nearly 36% higher than that of leaching without electric field, indicating that the electric field enhanced ion migration to improve manganese leaching rate. In addition, phase analysis and morphology detection revealed that leaching slag with electric field contains less elemental sulfur and unreacted pyrolusite as well as pyrite. This further showed that the introduction of electric field promoted the high valence conversion of elemental sulfur, decreased the encapsulation effect of elemental sulfur on minerals, and led to efficient leaching of manganese. Pyrolusite Pyrite Hydrometallugical reduction Electric field Manganese leaching efficiency Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction Manganese (Mn) and its related compounds such as electrolytic manganese (EM) and electrolytic manganese dioxide (EMD) are important strategic resources and play a crucial role in modern national economy[ 1 – 2 ]. In China, almost 90% of manganese resources are applied in the field of steel manufacturing, mainly because adding sufficient manganese in the steel manufacturing process can effectively improve the toughness of products[ 3 – 5 ]. At present, the main raw material for producing EM and EMD is rhodochrosite[ 4 ], [ 6 ]. However, in recent years, the manganese grade of rhodochrosite has been continuously declining, and the cost of industrial development has also increased accordingly[ 7 ]. Therefore, the application of pyrolusite to produce EM and EMD has gradually attracted more attention from the industry and experts[ 8 – 10 ]. It is worth noting that the utilization of pyrolusite is usually to select a suitable reducing agent to reduce the Mn(+ IV) to the Mn(+ II). Previous studies have shown that H 2 O 2 [ 11 – 12 ], elemental sulfur[ 13 ], SO 2 [ 14 ], waste copper[ 15 ], lignin[ 16 ], ferrous sulfate[ 17 ], corncob[ 18 ] and distiller's dried grains[ 19 ] can all promote the reduction of pyrolusite, which mainly involves pyrometallurgical reduction roasting methods and hydrometallurgical reduction leaching methods. The pyrometallurgical reduction roasting method has a series of adverse effects such as high energy consumption and high pollution, and will gradually be replaced by advanced processes in future industrial applications.[ 20 ] The hydrometallurgical reduction leaching methods, due to its low energy consumption and environmental friendliness, will become the mainstream method for the resource utilization of pyrolusite in the foreseeable future.[ 21 – 22 ] Up to now, there have been many reports on the study of hydrometallurgical reduction leaching of pyrolusite using pyrite as reducing agent. However, this reaction has adverse effects such as low manganese leaching efficiency and many by-products. This is mainly due to the encapsulation of elemental sulfur film in minerals, one of the by-products generated by the side reaction, which hinders the deep leaching of minerals[ 22 – 24 ]. To solve the above problems, many researchers have proposed using chemical process intensification techniques such as microwave[ 25 ], electric field[ 17 ], fluid field[ 26 ] to improve the Mn leaching rate of pyrolusite. As a chemical process intensification technology, electric fields have attracted the attention of researchers due to their high efficiency and environmentally friendly characteristics, and have been widely applied in various industrial fields. Li et al. achieved success in the bioremediation of polluted soil using electric field[ 27 ]. Tian et al. recovered manganese and ammonia nitrogen from electrolytic manganese residue by electric field, and obtained Mn leaching rate of 88.07% and ammonia nitrogen leaching rate of 91.5%, respectively[ 28 ]. Deng et al. systematically studied the electric field coupled sodium persulfate enhanced the leaching of vanadium from low temperature sodium roasting vanadium slag, and found synergistic effect between electric field and sodium persulfate could promote the oxidation of low valence vanadium and also catalyze the generation of persulfate from sulfates[ 29 – 30 ]. Huang et al. researched the leaching of calcium from plain and fly ash/limestone blended cement mortars under electric field, and found the use of electric fields accelerated the leaching of calcium ions, causing the leaching residue to become loose and porous[ 31 ]. Yang et al. utilized electric field to enhance the recovery of Li, Ni, Co, and Mn from waste lithium ions, with recovery rates of 98% Li, 97% Ni, 96% Co, and 93% Mn, respectively, moreover, above study further found that the introduction of electric field reduced the amount of reducing agent[ 32 ]. Yang et al. studied the enhanced extraction of valuable metal from the cathode plates of spent LIBs using electric field coupling with acetic acid and ascorbic acid, and the leaching rate of Ni, Co, Mn, and Li were 99.8%, 99.8%, 99.5%, and 99.9%, respectively, compared with leaching without electric field, the leaching rate of valuable metals was significantly improved[ 33 ]. The above researched indicated that the advantage of electric field in enhancing chemical reactions was significant. Literature research shows that there have been some studies on the leaching of pyrolusite using pyrite as a reducing agent, but these studies only focus on the leaching effect of minerals. Currently, there are relatively few reports on using electric fields as a chemical process intensification technology. In this work, the reduction leaching of pyrolusite by pyrite under electric field enhancement was studied, the leaching parameters of pyrolusite enhanced by electric field were obtained, the relational test equipment was used to characterize the leaching products and further verify the enhancement effect of electric field in the leaching reaction. Through the analysis of leaching data and products, the leaching mechanism of hydrometallugical reduction of pyrolusite with pyrite enhanced by electric field was revealed. Above these studies are beneficial for a further understanding of the hydrometallugical reduction leaching of pyrolusite-pyrite, and provided theoretical guidance for the industrial application of the reaction. 2. Materials and methods 2.1. Raw material pretreatment The pyrolusite and pyrite employed in this leaching were received from Chuxiong City, Yunnan, Province, P.R. China and Yongzhou City, Hunan, Province, P.R. China, respectively. The raw materials were first pretreated at 105℃ for 2h to remove the moisture from materials surface, then ground to a particle size of 200 mesh. Finally, phase analysis and element content detection were carried out by XRD and XRF. The analysis results were displayed in Fig. 1 , Fig. 2 , Table.1, Table.2, respectively. The chemical agents (Analytical grade) employed in this leaching were purchased from Shanghai Runjie Chemical Reagent Co., Ltd China and utilized without further purification, and all reagents or solutions were prepared with deionized water. Table 1 XRF characterization of pretreated pyrolusite. Element O Mn Fe Si Ca Mg Others Content(wt.%) 30.42 18.66 10.83 20.54 5.52 1.15 2.88 Table 2 XRF characterization of pretreated pyrite. Element Fe S Si Ca Al Mg Others Content(wt.%) 38.48 29.71 20.89 6.82 1.34 1.32 1.44 2.2. Leaching experimental steps and equipment The experimental equipment shown in Fig. 3 was used to carry out the leaching experiment of pyrolusite enhanced by electric field. First, the mixtures of pyrolusite and pyrite with a total mass of 15g was fully mixed by a certain mass ratio, and then added the mixtures to a 250ml beaker, and a certain concentration of sulfuric acid solution was added to the beaker according to a certain volume mass ratio, and finally the positive and negative electrodes are inserted on the heat-resistant gasket of the beaker, respectively. In addition, the experiment used Pb-Sb-Zn-Ag quaternary alloy (40mm×30mm) as the anode electrode and stainless steel (40 mm×32 mm ) as the cathode electrode. A direct current power supply (0–30V, 3A, made by Gwinstek Co., Ltd China) was applied to provide DC power. The reactants underwent solid-liquid separation to obtain leaching residue and leaching solution after experiments. The composition analysis of the leaching residue was carried out by XRD and SEM, and the Mn content analysis of the leaching solution was measured by Ammonium ferrous sulfate titration method (GB/T506-2002 of China)[ 20 ], and the Mn content was calculated by the following expression (1), leaching slags was dried for subsequent characterization. where ω represents calculated Mn leaching efficiency, m represents the total mass of pyrolusite. ρ represents the density of Mn in leaching solution. V represents the volume of leaching solution. w represents the mass fraction of Mn in pyrolusite. 2.3. Analysis and characterization. The raw materials and leaching slags were carried out the phase characterization by X-ray Powder diffractometer (XRD, Rigaku, SmartLab SE, Japan), the X-ray diffraction characterization of raw materials and leaching slags were handled in the range of 5° to 95° with a scanning rate of 2.2°/min, a step of 0.028°, tube current of 60 mA and tube voltage of 60kV, respectively. Furthermore, Scanning Electron Microscopy (SEM, Quanta 200, Netherlands) was mainly employed to understand the microscopic morphology of raw material mixtures and leaching slags. 3. Result and Discussion 3.1. Effect of liquid-to-solid ratio To understand the influence of liquid-to-solid ratio on the Mn leaching efficiency from pyrolusite under electric field, a series of gradient experiments with four liquid-to-solid ratios range from 6ml/g to 12ml/g were performed, and the H 2 SO 4 molar concentration, mass ratio of pyrolusite and pyrite, stirring speed, leaching temperature, direct current density was kept constant at 1.6 mol/L, 10:3, 250 r/min, and 353K, 700 A/m 2 , separately. Figure 4 directly showed that the Mn leaching rate increased with the increase of liquid-to-solid ratio from 6 ml/g to 10 ml/g, which indicated that a higher liquid-to-solid ratio was conducive to mineral dissolution and reducing the viscosity of reactants. However, when the liquid-to-solid ratio increased from 10 ml/g to 12 ml/g, the maximum Mn leaching efficiency decreased from 96.22–91.15% after leaching, the main reason for the significant decrease in Mn leaching efficiency was attributed to the dilution of reactant concentration caused by the improvement in liquid-to-solid ratio[ 34 ]. In summary, keeping the liquid-to-solid ratio at 10ml/g was considered as the optimal leaching reaction parameter. 3.2. Effect of the mass ratio of pyrolusite and pyrite To explore the influence of the mass ratio of pyrolusite and pyrite on Mn leaching rate from pyrolusite under electric field, batch leaching experiments were performed under reaction temperature of 353 K, liquid-to-solid ratio of 10ml/g, stirring speed of 250 r/min, H 2 SO 4 molar concentration of 1.6 mol/L, direct current density of 700 A/m 2 . Figure 5 directly demonstrated the Mn leaching rate improved with the change of the mass ratio of pyrolusite and pyrite. When the dosage of pyrite increased from 10:1 to 10:3, the Mn leaching rate significantly increased, mainly due to the increased in reducing agents, which led to more Mn being leached out. However, when the dosage of pyrite increased from 10:3 to 10:4, the Mn leaching rate increased slowly, which was mainly due to the increase of the dosage of pyrite, resulting in more side reactions, especially the formation of a elemental sulfur film from the side reaction, which was easy to enclose the reactants, so that the contact surface between pyrite and pyrolusite was diminished. To sum up, a mass ratio of pyrolusite and pyrite of 10:3 was considered an ideal leaching parameter for subsequent experiments. 3.3. Effect of H 2 SO 4 molar concentration To discuss the influence of the mass ratio of pyrolusite and pyrite on Mn leaching rate from pyrolusite under electric field, several repeated leaching experiments were conducted under the constant parameter of liquid-to-solid ratio of 10ml/g, mass ratio of pyrolusite and pyrite of 10:3, stirring speed of 250r/min, leaching temperature of 353 K, direct current density of 700 A/m 2 . Figure 6 directly indicated the Mn leaching rate improved with the increase of H 2 SO 4 molar concentration, mainly because the oxidation capacity of MnO 2 in pyrolusite depended on the PH value in solution. The standard electrode potential of MnO 2 /Mn 2+ and the concentration of H + ions in the solution follow an expression: φ ɵ MnO 2 /Mn 2+ = 1.224 + 0.118lg[H + ][ 17 ], [ 20 ].Therefore, it was evident that maintaining a higher concentration of H + ions in the leaching solution was beneficial for enhancing the reduction of MnO 2 . When the H 2 SO 4 molar concentration increases from 1.6 to 1.8, the increase of Mn leaching rate was not significant, which displayed that the further increase of H 2 SO 4 molar concentration had little effect on the leaching of pyrolusite. After comprehensive consideration, the H 2 SO 4 molar concentration of 1.6 mol/L was used as a leaching parameter for subsequent experiments. 3.4. Effect of stirring speed To reflect the influence of stirring speed on Mn leaching rate from pyrolusite under electric field, leaching experiments were conducted at stirring speeds of 100r/min, 150r/min, 200r/min, and 250r/min, respectively. And other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H 2 SO 4 molar concentration, leaching temperature, and direct current density were kept constant at 10ml/g, 10:3, 1.6mol/L, 353K, and 700A/m 2 , separately. Figure 7 directly revealed the Mn leaching rate improved with the increase of stirring speed, which exhibited that a higher stirring speed was conducive to the collision and reaction between molecules. Considering power consumption, a stirring speed of 250 r/min was regard as the optimal leaching parameter for the further studies. 3.5 Effect of leaching temperature To observe the influence of leaching temperature on Mn leaching rate from pyrolusite under electric field, We separately investigated the changes in Mn leaching rate when the temperature changed from 333K to 363K, and other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H 2 SO 4 molar concentration, stirring speed, direct current density were kept constant at 10ml/g, 10:3, 1.6mol/L, 250r/min, 353K, and 700A/m 2 , separately. Figure 8 directly manifested When the leaching temperature enlarged from 333K to 353K, the Mn leaching rate sharply increases. This was because the rise in leaching temperature enhanced the thermal motion between molecules, which was conducive to the progress of chemical reactions. In addition, higher leaching temperatures activated a large number of reactant molecules, which was also beneficial for reducing the energy barrier of chemical reactions. When the leaching temperature increased from 353K to 363K, it was obvious that the rise of Mn leaching rate was not significant. After leaching, it was found that the maximum Mn leaching rate was only increased by 1.2%. Therefore, considering the energy saving and experimental cost, 353K was thought as the optimal leaching parameter. 3.6 Effect of direct current density To study the influence of direct current density on Mn leaching rate from pyrolusite under electric field, We conducted a series of leaching experiments with current density changing from 0A/m 2 to 800A/m 2 and other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H 2 SO 4 molar concentration, stirring speed, leaching temperature were kept constant at 10ml/g, 10:3, 1.6mol/L, 250r/min, 353K, separately. Figure 9 manifested when the current density was 0A/m 2 (namely, leaching without electric field), the maximum manganese leaching rate was only 59.72%. However, increasing the direct current density from 500 A/m 2 to 700 A/m 2 resulted in a significant increase in Mn leaching rate. This was because the introduction of an external electric field in the leaching system promoted ions migration and conversion. Besides, when the direct current density increased from 700 A/m 2 to 800 A/m 2 , the Mn leaching rate only increased slightly, which was because the direct current density was too large, Mn 2+ on the anode electrode was easy to be oxidized to MnO 2 attached to the anode plate, prompting the Mn in the pyrolusite could not be completely leached out. After repeated weighing, the direct current density of 700 A/m 2 was regarded as the optimal leaching parameter for this batch raw ores. 3.7. Phase analysis and SEM analysis The obtained leaching slags with electric field and without electric field was respectively dried for XRD characterization after leaching experiments. The characterization results were displayed in Fig. 10 . It was obvious that the MnO 2 and FeS 2 diffraction peak of leaching slag without electric field was significantly higher than that leaching with electric field, and this further indicated the introduction of an electric field made the reaction between pyrolusite and pyrite more thorough. In addition, the diffraction peaks of elemental sulfur were found in the leaching slag without electric field, while no diffraction peaks of elemental sulfur were found in the leaching slag with electric field. This might due to the introduction of an external electric field, which formed a higher potential in the leaching reaction, promoting further oxidation of elemental sulfur and allowing more minerals to be leached out. Both raw material mixtures and leaching slags were respectively determined the microscopic morphology by SEM (Scanning electron microscopy). As could be seen from Fig. 11 − 1 and Fig. 11 − 4, the surface of the raw ore samples was observed to be relatively rough, and the volume distribution of the mineral samples appeared to be very uneven. As could be seen from Fig. 11 − 2 and Fig. 11 − 5, the SEM image of leaching slag without electric field appeared to have more flocculent substances and tiny particles deposited on the surface of the residue, which further implied that it might be due to incomplete oxidation of elemental sulfur. As could be seen from Fig. 11 − 3 and Fig. 11 − 6, the SEM image of leaching slag with electric field was observed to be cleaner without flocculent substances tiny particles, indicating that the by-products produced by leaching, such as elemental sulfur, might had undergone deep transformation. Moreover, very obvious tiny micro-pores were observed on the surface of the leaching slag, which might be due to the enhanced migration ability of ions inside the mineral under the action of electric field, resulting in a higher Mn leaching efficiency. 3.7. Leaching mechanism analysis Based on the above experiments results and characterization analysis, we could further speculated the leaching reaction mechanism of pyrolusite-pyrite enhanced by electric field. As could be shown in Fig. 12 , firstly, the acidolysis of FeS 2 formed Fe 2+ and S 2 2− . Then, MnO 2 in the pyrolusite rapidly oxidized Fe 2+ to Fe 3+ . Furthermore, under the action of an electric field, Fe 3+ reacted with S 2 2− to further convert into elemental sulfur or polysulfides such as S 2 O 3 2− , S 3 O 4 2− . Finally, under the action of an electric field, MnO 2 couples with Fe 3+ to further oxidize polysulfides to sulfates. Therefore, the introduction of electric field in the leaching experiments intensified the migration ability of ions within the solution and minerals, and promoted the high valence conversion of low valence sulfur-containing compounds. Finally, introducing external electric field into the leaching reaction could strengthened the collision frequency between MnO 2 molecules and FeS 2 molecules, promoting faster and more efficient electron shuttle rates, which was beneficial for the deep leaching of pyrolusite. 4. Conclusion In this paper, the leaching experiment of reduction of pyrolusite by pyrite enhanced by electric field was investigated. The results displayed that the Mn leaching efficiency of 96.22% was obtained under the liquid-to-solid ratio of 10ml/g, mass ratio of pyrolusite and pyrite of 10:3, H 2 SO 4 molar concentration of 1.6mol/L, stirring speed of 250 r/min, leaching temperature of 353K, direct current density of 700A/m 2 , leaching time of 3h. Compared to leaching without electric field, the leaching with electric field improved the Mn leaching efficiency by nearly 36%. The phase analysis and microscopic morphology detection of the leaching products indicate that the leaching slag with electric field contained less elemental sulfur compared to the leaching slag without electric field, which was mainly attributed to the introduction of an electric field in the leaching reaction promoting the high valence state conversion of elemental sulfur, thereby reducing the encapsulation of mineral particles by the elemental sulfur film. Additionally, the introduction of electric field created a high potential in the leaching system, promoted deep oxidization of elemental sulfur, and strengthened the migration of ability of ions and the collision ability between molecules, so as to improved the Mn leaching rate of pyrolusite. Declarations Author Contribution Yakun Zhao: Experimental investigation, Data curation, Writing-original draft, Data analysis. KeFeng Pan: Methodology, Supervision, Writing-review & editing of the manuscript.RuiYao Yang: Formal AnalysisChengShuo Hou: TranslationNan Zhang: Translation Acknowledgements The authors are very grateful for the financial support from National Natural Science Foundation of China (U1802255). References Rao S, Sun J, Wang DX, Liu ZQ, Zhu W, Cao HY, Duan LJ (2023) Selective recovery of manganese and lead from electrolytic manganese residues in a sulfuric acid solution with galena as the reductant. Sep Purif Technol 308:122937 He SC, Wilson BP, Lundström M, Liu ZH (2020) Hazard-free treatment of electrolytic manganese residue and recovery of manganese using low temperature roasting-water washing process. J Hazard Mater 402:123561 Han YF, Ma XM, Zhao W, Chang YK, Zhang XX, Wang XB, Wang JJ, Huang ZY (2013) Sulfur-oxidizing bacteria dominate the microbial diversity shift during the pyrite and low-grade pyrolusite bioleaching process. J Biosci Bioeng 116–4:465–471 Ju JR, Ma RY, Li YH, Feng YL, Li HR, Wang HY, Jiang SW (2023) An efficient and clean method for the selective extraction and recovery of manganese from pyrolusite using ammonium sulfate roasting-water leaching and carbonate precipitation. Miner Eng 203:108356 Wu H, Feng YL, Li HR, Wang HJ, Ju JR (2020) Co-recovery of manganese from pyrolusite and gold from carbonaceous gold ore using fluidized roasting coupling technology. Chem Eng Process 147:107742 Ding FH, Zhang J, Wang ZJ, Chai LY, Zhang CF (2016) Simultaneous leaching of low grade bismuthinite and pyrolusite ores in hydrochloric acid medium. Hydrometallurgy 166:279–284 Wang LB, Xu YM, Tian H, Du YG (2023) Co-treatment of chromite ore processing residue and pyrolusite for simultaneous detoxification and resource utilization. Journal of Environmental Chemical Engineering. 11 – 3 109785 Liu ZW, Feng YL, Li HR, Li HS (2022) Efficient recovery of Ti, Fe and Mn based on the synergistic effect of acidic titanium dioxide wastewater and pyrolusite. J Water Process Eng 45:102484 Du JJ, Zhang YQ, Lu JJ, Gao L, Guo SH, Omran M, Chen J, Chen G (2023) Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process. Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process. 24 2041–2052 Du JJ, Gao L, Yang Y, Guo SH, Omran M, Chen J, Chen G (2021) Dielectric characterisation and reduction properties of the blending mixtures of low-grade pyrolusite and waste corn stalks in the microwave field. Fuel 305:121546 Do SH, Batchelor B, Lee HK, Kong SH (2009) Hydrogen peroxide decomposition on manganese oxide (pyrolusite): kinetics, intermediates, and mechanism. Chemosphere.75.1 8–12 Nayl AA, Ismail IM, Aly HF (2011) Recovery of pure MnSO 4 ∙H 2 O by reductive leaching of manganese from pyrolusite ore by sulfuric acid and hydrogen peroxide. Int J Mineral Process 100 3–4 116–123 You ZX, Li GH, Dang J, Yu WZ, Lv XW (2018) The mechanism on reducing manganese oxide ore with elemental sulfur. Powder Technol 330:310–316 Sun WY, Su SJ, Wang QY, Ding SL (2013) Lab-scale circulation process of electrolytic manganese production with low-grade pyrolusite leaching by SO 2 . Hydrometallurgy. 133 118–125 Yang C, Duan XX, Zhang XF, Rohani S, Wu HL, He MY, Gao YX, Liu QC, Yang J, Kong M, Liu WZ (2023) Acid-free extraction of manganese from pyrolusite tailings by in situ redox interaction with waste copperas. Process Saf Environ Prot 169:149–158 Xiong SF, Liu SXLPL, Hao SH, Hao F, Y ZL, Liu JX (2018) Recovery of manganese from low-grade pyrolusite ore by reductively acid leaching process using lignin as a low cost reductant. Miner Eng 125:126–132 Zhang XR, Liu ZH, Wu XB, Du J, Tao CY (2017) Electric field enhancement in leaching of manganese from low-grade manganese dioxide ore: Kinetics and mechanism study. Journal of Electroanalytical Chemistry. 788 165-174.7 Tian XK, Wen XX, Yang C, Liang YJ, Pi ZB, Wang YX (2010) Reductive leaching of manganese from low-grade manganese dioxide ores using corncob as reductant in sulfuric acid solution. Hydrometallurgy 96 3–4 157–160 Liu DJ, Gao L, Chen G, Zhou JW, Guo SH, Omran M, Chen J (2022) Enhancement effects of distiller's dried grains as reducing agents on the kinetics and leaching of pyrolusite from manganese ore. J Mater Res Technol 19:4270–4281 Chen G, Jiang CL, Liu RL, Xie ZM, Liu ZH, Cen SD, Tao CY, Guo SH (2021) Leaching kinetics of manganese from pyrolusite using pyrite as a reductant under microwave heating. Sep Purif Technol 277:119472 Lin SD, Gao L, Yang Y, Chen J, Guo SH, Omran M, Chen G (2020) Efficiency and sustainable leaching process of manganese from pyrolusite-pyrite mixture in sulfuric acid systems enhanced by microwave heating. Hydrometallurgy 198:105519 Lv X, Zhao HB, Zhang YS, Yan ZY, Zhao Y, Zheng H, Liu WQ, Xie JP, Qiu GZ (2021) Active destruction of pyrite passivation by ozone oxidation of a biotic leaching system. Chemosphere 277:130335 Kholmogorov AG, Zhyzhaev AM, Kononov US, Moiseeva GA, Pashkov GL (2000) The production of manganese dioxide from manganese ores of some deposits of the Siberian region of Russia. Hydrometallurgy 56(1):1–11 Nayak BB, Mishra KG, Paramguru RK (1999) Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite. J Appl Electrochem 29(2):191–200 Lin SD, Li KQ, Yang Y, Gao L, Omran M, Guo SH, Chen J, Chen G (2021) Microwave-assisted method investigation for the selective and enhanced leaching of manganese from low-grade pyrolusite using pyrite as the reducing agent. Chem Eng Process 159:108209 Xie ZM, Chen G, Liu RL, Liu ZH, Cen SD, Tao CY, Guo SH (2021) Reaction kinetics characteristics of pyrolusite leaching process enhanced by rigid-flexible combined impeller. Huagong Xuebao/CIESC Journal. 72 – 5 2586–2595 Li JM, Li FM, Tong MH, Zhao Z, Xi KL, Guo SH (2024) Construction of an effective method combining in situ capping with electric field-enhanced biodegradation for treating PAH-contaminated soil at abandoned coking sites. Sci Total Environ 922:171209 Tian Y, Shu JC, Chen MJ, Wang JY, Wang Y, Luo ZG, Wang R, Yang FH, Xiu FR, Sun Z (2019) Manganese and ammonia nitrogen recovery from electrolytic manganese residue by electric field enhanced leaching. J Clean Prod 236:117708 Deng RR, Xie ZM, Liu ZH, Tao CY (2019) Leaching kinetics of vanadium catalyzed by electric field coupling with sodium persulfate. J Electroanal Chem 854:113542 Deng RR, Xie ZM, Liu ZH, Deng L, Tao CY (2019) Enhancement of vanadium extraction at low temperature sodium roasting by electric field and sodium persulfate. Hydrometallurgy 189:105110 Huang Q, Liu HM, Wang Q, Shan YW, Tang DS, Zhang Z, Zhu XH (2024) Electric field-induced deterioration of cement mortars owing to calcium leaching. Developments Built Environ 17:100303 Yang J, Zhou Y, Zhang ZL, Xu KH, Zhang K, Lai YQ, Jiang LX (2023) Effect of electric field on leaching valuable metals from spent lithium-ion batteries. Transactions of Nonferrous Metals Society of China, 33 – 2, pp 632–641 Yang K, Zhu CP, Li J, Meng BC, Zhong KN, Huang WL, Yu J, Fang Z (2023) Electric field-assisted leaching of valuable metals from spent lithium-ion batteries in a mixture of acetic acid and ascorbic acid. Hydrometallurgy 221:106152 Luo ZG, Shu JC, Chen MJ, Wang R, Zeng XF, Yang Y, Wang R, Chen SY, Liu RL, Liu ZH, Sun Z, Yu KL, Deng Y (2021) Enhanced leaching of manganese from low-grade pyrolusite using ball milling and electric field. Ecotoxicol Environ Saf 211:111893 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4413889","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":304053053,"identity":"3ab62623-e128-4ed5-8683-580550ae9a52","order_by":0,"name":"Yakun Zhao","email":"","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yakun","middleName":"","lastName":"Zhao","suffix":""},{"id":304053054,"identity":"441712b5-dd50-4130-8a38-380d36ddf787","order_by":1,"name":"KeFeng Pan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0UlEQVRIiWNgGAWjYDACZgjF2MDe2PjgA2laeA43G84gxTLGBon0NmkOYpQaHGd++Lig5o7shpsPG6QZGOzkdBsIaJFsZjM2nnHsmfGG24kNxgUMycZmBwho4WdmMJPmYTucCNKSPIPhQOI2QlrYmNm/SfP8A2q5ebDhMA8xWviZecykeduAWm4wNjYTpUWymafYeGbfYeOZZxKbGWcYEOEXg/PHNz4u+HZYtu/48ec/PlTYyRHUAgLg2FQAqzQgQjlci3wDkapHwSgYBaNg5AEALyVG8N1WWBIAAAAASUVORK5CYII=","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"KeFeng","middleName":"","lastName":"Pan","suffix":""},{"id":304053055,"identity":"dc8b607b-4f4d-4b98-a672-a1c72bd952df","order_by":2,"name":"RuiYao Yang","email":"","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"RuiYao","middleName":"","lastName":"Yang","suffix":""},{"id":304053056,"identity":"0f3b56af-016f-49bd-a535-f54ec24cc12d","order_by":3,"name":"ChengShuo Hou","email":"","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"ChengShuo","middleName":"","lastName":"Hou","suffix":""},{"id":304053057,"identity":"091122d7-5525-4aab-899a-0f16933c0bf0","order_by":4,"name":"Nan Zhang","email":"","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Nan","middleName":"","lastName":"Zhang","suffix":""},{"id":304053058,"identity":"4cb27812-6f9c-4b17-9575-6a8134a18668","order_by":5,"name":"Geng Chen","email":"","orcid":"","institution":"","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Geng","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2024-05-13 14:30:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4413889/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4413889/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":56990982,"identity":"8c2f4db8-3fdc-4781-8e28-ebcb374b8958","added_by":"auto","created_at":"2024-05-23 06:22:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":21558,"visible":true,"origin":"","legend":"\u003cp\u003eXRD characterization of pretreated pyrolusite.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/95605e257cb158e56fb9ca99.png"},{"id":56990985,"identity":"ffecf862-fbfa-4210-9b79-591320fe1ffb","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":19188,"visible":true,"origin":"","legend":"\u003cp\u003eXRD characterization of pretreated pyrite.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/f87c7b1991e75a108cdf06ca.png"},{"id":56991507,"identity":"2e4f8896-2a19-49c0-8a21-06c25a49ec50","added_by":"auto","created_at":"2024-05-23 06:30:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":78266,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental equipment of pyrolusite leaching enhanced by electric field.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/9943c6e3393699966c3af048.png"},{"id":56990983,"identity":"514fa2fc-edb3-4c99-9b13-53a84feaecff","added_by":"auto","created_at":"2024-05-23 06:22:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":38907,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of liquid-to-solid ratio on Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/2bde25868819ce52ea4aba10.png"},{"id":56990990,"identity":"d7c792d4-40c5-4b15-b181-93ee64aeb35f","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":32453,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of mass ratio of pyrolusite and pyrite on Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/f71ad3418a3dfdf2c36459c3.png"},{"id":56990988,"identity":"3669274f-5b54-4483-a288-9c431e337c38","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":27651,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e concentration on Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/be0e07c9d9418558d790578f.png"},{"id":56991508,"identity":"fe05d25a-7fbc-41bd-9d3d-f383128b4668","added_by":"auto","created_at":"2024-05-23 06:30:58","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":43527,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of stirring speed on the Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/01341dcac416e5c82e5b3b3f.png"},{"id":56990986,"identity":"826e9ee6-d094-4fbe-87ac-408a008c3a42","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":25706,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of leaching temperature on the Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/c72b41413ce68b3b69c16892.png"},{"id":56990989,"identity":"68be74af-d0fd-465d-a486-8e471246ee1d","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":44635,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of direct current density on the Mn leaching efficiency under electric field\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/4de635a57029cf92071da934.png"},{"id":56990991,"identity":"1a528fa2-b372-48d7-8850-939017809cb7","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":167338,"visible":true,"origin":"","legend":"\u003cp\u003eXRD comparison of leaching slag with electric field and without electric field\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/1f8e54ae4be7cb78de29056b.png"},{"id":56990994,"identity":"83c17064-6f43-49f5-8069-d4937fa908f0","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1019746,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images: (1), (4) raw ore mixture; (2), (5) leaching slag without electric field; (3), (6) leaching slag with electric field\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/d6b70e8e7ac1f4ebc3004cf4.png"},{"id":56990993,"identity":"bc31f36a-e1d2-40da-9167-12b89362869e","added_by":"auto","created_at":"2024-05-23 06:22:58","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":118704,"visible":true,"origin":"","legend":"\u003cp\u003eleaching mechanism diagram of pyrolusite enhanced by electric field\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/6aafbb5350ec1d175eff3656.png"},{"id":58453359,"identity":"c7bc7a1e-2054-46f6-9245-749b7cf2ae9c","added_by":"auto","created_at":"2024-06-16 21:31:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2755140,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4413889/v1/2f486261-3329-494c-a93e-4858d63ed4e3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on hydrometallugical reduction leaching of pyrolusite enhanced by electric field using pyrite as reductant","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eManganese (Mn) and its related compounds such as electrolytic manganese (EM) and electrolytic manganese dioxide (EMD) are important strategic resources and play a crucial role in modern national economy[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In China, almost 90% of manganese resources are applied in the field of steel manufacturing, mainly because adding sufficient manganese in the steel manufacturing process can effectively improve the toughness of products[\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. At present, the main raw material for producing EM and EMD is rhodochrosite[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, in recent years, the manganese grade of rhodochrosite has been continuously declining, and the cost of industrial development has also increased accordingly[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Therefore, the application of pyrolusite to produce EM and EMD has gradually attracted more attention from the industry and experts[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is worth noting that the utilization of pyrolusite is usually to select a suitable reducing agent to reduce the Mn(+\u0026thinsp;IV) to the Mn(+\u0026thinsp;II). Previous studies have shown that H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], elemental sulfur[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], SO\u003csub\u003e2\u003c/sub\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], waste copper[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], lignin[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], ferrous sulfate[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], corncob[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and distiller's dried grains[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] can all promote the reduction of pyrolusite, which mainly involves pyrometallurgical reduction roasting methods and hydrometallurgical reduction leaching methods. The pyrometallurgical reduction roasting method has a series of adverse effects such as high energy consumption and high pollution, and will gradually be replaced by advanced processes in future industrial applications.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] The hydrometallurgical reduction leaching methods, due to its low energy consumption and environmental friendliness, will become the mainstream method for the resource utilization of pyrolusite in the foreseeable future.[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eUp to now, there have been many reports on the study of hydrometallurgical reduction leaching of pyrolusite using pyrite as reducing agent. However, this reaction has adverse effects such as low manganese leaching efficiency and many by-products. This is mainly due to the encapsulation of elemental sulfur film in minerals, one of the by-products generated by the side reaction, which hinders the deep leaching of minerals[\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. To solve the above problems, many researchers have proposed using chemical process intensification techniques such as microwave[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], electric field[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], fluid field[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] to improve the Mn leaching rate of pyrolusite.\u003c/p\u003e \u003cp\u003eAs a chemical process intensification technology, electric fields have attracted the attention of researchers due to their high efficiency and environmentally friendly characteristics, and have been widely applied in various industrial fields. Li et al. achieved success in the bioremediation of polluted soil using electric field[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Tian et al. recovered manganese and ammonia nitrogen from electrolytic manganese residue by electric field, and obtained Mn leaching rate of 88.07% and ammonia nitrogen leaching rate of 91.5%, respectively[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Deng et al. systematically studied the electric field coupled sodium persulfate enhanced the leaching of vanadium from low temperature sodium roasting vanadium slag, and found synergistic effect between electric field and sodium persulfate could promote the oxidation of low valence vanadium and also catalyze the generation of persulfate from sulfates[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Huang et al. researched the leaching of calcium from plain and fly ash/limestone blended cement mortars under electric field, and found the use of electric fields accelerated the leaching of calcium ions, causing the leaching residue to become loose and porous[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Yang et al. utilized electric field to enhance the recovery of Li, Ni, Co, and Mn from waste lithium ions, with recovery rates of 98% Li, 97% Ni, 96% Co, and 93% Mn, respectively, moreover, above study further found that the introduction of electric field reduced the amount of reducing agent[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Yang et al. studied the enhanced extraction of valuable metal from the cathode plates of spent LIBs using electric field coupling with acetic acid and ascorbic acid, and the leaching rate of Ni, Co, Mn, and Li were 99.8%, 99.8%, 99.5%, and 99.9%, respectively, compared with leaching without electric field, the leaching rate of valuable metals was significantly improved[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The above researched indicated that the advantage of electric field in enhancing chemical reactions was significant.\u003c/p\u003e \u003cp\u003eLiterature research shows that there have been some studies on the leaching of pyrolusite using pyrite as a reducing agent, but these studies only focus on the leaching effect of minerals. Currently, there are relatively few reports on using electric fields as a chemical process intensification technology. In this work, the reduction leaching of pyrolusite by pyrite under electric field enhancement was studied, the leaching parameters of pyrolusite enhanced by electric field were obtained, the relational test equipment was used to characterize the leaching products and further verify the enhancement effect of electric field in the leaching reaction. Through the analysis of leaching data and products, the leaching mechanism of hydrometallugical reduction of pyrolusite with pyrite enhanced by electric field was revealed. Above these studies are beneficial for a further understanding of the hydrometallugical reduction leaching of pyrolusite-pyrite, and provided theoretical guidance for the industrial application of the reaction.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. \u003cem\u003eRaw material pretreatment\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe pyrolusite and pyrite employed in this leaching were received from Chuxiong City, Yunnan, Province, P.R. China and Yongzhou City, Hunan, Province, P.R. China, respectively. The raw materials were first pretreated at 105℃ for 2h to remove the moisture from materials surface, then ground to a particle size of 200 mesh. Finally, phase analysis and element content detection were carried out by XRD and XRF. The analysis results were displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Table.1, Table.2, respectively.\u003c/p\u003e \u003cp\u003eThe chemical agents (Analytical grade) employed in this leaching were purchased from Shanghai Runjie Chemical Reagent Co., Ltd China and utilized without further purification, and all reagents or solutions were prepared with deionized water.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eXRF characterization of pretreated pyrolusite.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eOthers\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eContent(wt.%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eXRF characterization of pretreated pyrite.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eOthers\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eContent(wt.%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. \u003cem\u003eLeaching experimental steps and equipment\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe experimental equipment shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e was used to carry out the leaching experiment of pyrolusite enhanced by electric field. First, the mixtures of pyrolusite and pyrite with a total mass of 15g was fully mixed by a certain mass ratio, and then added the mixtures to a 250ml beaker, and a certain concentration of sulfuric acid solution was added to the beaker according to a certain volume mass ratio, and finally the positive and negative electrodes are inserted on the heat-resistant gasket of the beaker, respectively. In addition, the experiment used Pb-Sb-Zn-Ag quaternary alloy (40mm\u0026times;30mm) as the anode electrode and stainless steel (40 mm\u0026times;32 mm ) as the cathode electrode. A direct current power supply (0\u0026ndash;30V, 3A, made by Gwinstek Co., Ltd China) was applied to provide DC power.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe reactants underwent solid-liquid separation to obtain leaching residue and leaching solution after experiments. The composition analysis of the leaching residue was carried out by XRD and SEM, and the Mn content analysis of the leaching solution was measured by Ammonium ferrous sulfate titration method (GB/T506-2002 of China)[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], and the Mn content was calculated by the following expression (1), leaching slags was dried for subsequent characterization.\u003c/p\u003e\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"398\" height=\"64\"\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cb\u003eω\u003c/b\u003e represents calculated Mn leaching efficiency, \u003cb\u003em\u003c/b\u003e represents the total mass of pyrolusite. \u003cb\u003eρ\u003c/b\u003e represents the density of Mn in leaching solution. \u003cb\u003eV\u003c/b\u003e represents the volume of leaching solution. \u003cb\u003ew\u003c/b\u003e represents the mass fraction of Mn in pyrolusite.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Analysis and characterization.\u003c/h2\u003e \u003cp\u003eThe raw materials and leaching slags were carried out the phase characterization by X-ray Powder diffractometer (XRD, Rigaku, SmartLab SE, Japan), the X-ray diffraction characterization of raw materials and leaching slags were handled in the range of 5\u0026deg; to 95\u0026deg; with a scanning rate of 2.2\u0026deg;/min, a step of 0.028\u0026deg;, tube current of 60 mA and tube voltage of 60kV, respectively. Furthermore, Scanning Electron Microscopy (SEM, Quanta 200, Netherlands) was mainly employed to understand the microscopic morphology of raw material mixtures and leaching slags.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Result and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1. \u003cem\u003eEffect of liquid-to-solid ratio\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo understand the influence of liquid-to-solid ratio on the Mn leaching efficiency from pyrolusite under electric field, a series of gradient experiments with four liquid-to-solid ratios range from 6ml/g to 12ml/g were performed, and the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, mass ratio of pyrolusite and pyrite, stirring speed, leaching temperature, direct current density was kept constant at 1.6 mol/L, 10:3, 250 r/min, and 353K, 700 A/m\u003csup\u003e2\u003c/sup\u003e, separately. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e directly showed that the Mn leaching rate increased with the increase of liquid-to-solid ratio from 6 ml/g to 10 ml/g, which indicated that a higher liquid-to-solid ratio was conducive to mineral dissolution and reducing the viscosity of reactants. However, when the liquid-to-solid ratio increased from 10 ml/g to 12 ml/g, the maximum Mn leaching efficiency decreased from 96.22\u0026ndash;91.15% after leaching, the main reason for the significant decrease in Mn leaching efficiency was attributed to the dilution of reactant concentration caused by the improvement in liquid-to-solid ratio[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. In summary, keeping the liquid-to-solid ratio at 10ml/g was considered as the optimal leaching reaction parameter.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2. \u003cem\u003eEffect of the mass ratio of pyrolusite and pyrite\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo explore the influence of the mass ratio of pyrolusite and pyrite on Mn leaching rate from pyrolusite under electric field, batch leaching experiments were performed under reaction temperature of 353 K, liquid-to-solid ratio of 10ml/g, stirring speed of 250 r/min, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration of 1.6 mol/L, direct current density of 700 A/m\u003csup\u003e2\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e directly demonstrated the Mn leaching rate improved with the change of the mass ratio of pyrolusite and pyrite. When the dosage of pyrite increased from 10:1 to 10:3, the Mn leaching rate significantly increased, mainly due to the increased in reducing agents, which led to more Mn being leached out. However, when the dosage of pyrite increased from 10:3 to 10:4, the Mn leaching rate increased slowly, which was mainly due to the increase of the dosage of pyrite, resulting in more side reactions, especially the formation of a elemental sulfur film from the side reaction, which was easy to enclose the reactants, so that the contact surface between pyrite and pyrolusite was diminished. To sum up, a mass ratio of pyrolusite and pyrite of 10:3 was considered an ideal leaching parameter for subsequent experiments.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Effect of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration\u003c/h2\u003e \u003cp\u003eTo discuss the influence of the mass ratio of pyrolusite and pyrite on Mn leaching rate from pyrolusite under electric field, several repeated leaching experiments were conducted under the constant parameter of liquid-to-solid ratio of 10ml/g, mass ratio of pyrolusite and pyrite of 10:3, stirring speed of 250r/min, leaching temperature of 353 K, direct current density of 700 A/m\u003csup\u003e2\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e directly indicated the Mn leaching rate improved with the increase of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, mainly because the oxidation capacity of MnO\u003csub\u003e2\u003c/sub\u003e in pyrolusite depended on the PH value in solution. The standard electrode potential of MnO\u003csub\u003e2\u003c/sub\u003e/Mn\u003csup\u003e2+\u003c/sup\u003eand the concentration of H\u003csup\u003e+\u003c/sup\u003e ions in the solution follow an expression: φ\u003csup\u003eɵ\u003c/sup\u003e MnO\u003csub\u003e2\u003c/sub\u003e/Mn\u003csup\u003e2+\u003c/sup\u003e = 1.224\u0026thinsp;+\u0026thinsp;0.118lg[H\u003csup\u003e+\u003c/sup\u003e][\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].Therefore, it was evident that maintaining a higher concentration of H\u003csup\u003e+\u003c/sup\u003e ions in the leaching solution was beneficial for enhancing the reduction of MnO\u003csub\u003e2\u003c/sub\u003e. When the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration increases from 1.6 to 1.8, the increase of Mn leaching rate was not significant, which displayed that the further increase of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration had little effect on the leaching of pyrolusite. After comprehensive consideration, the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration of 1.6 mol/L was used as a leaching parameter for subsequent experiments.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.4. \u003cem\u003eEffect of stirring speed\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo reflect the influence of stirring speed on Mn leaching rate from pyrolusite under electric field, leaching experiments were conducted at stirring speeds of 100r/min, 150r/min, 200r/min, and 250r/min, respectively. And other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, leaching temperature, and direct current density were kept constant at 10ml/g, 10:3, 1.6mol/L, 353K, and 700A/m\u003csup\u003e2\u003c/sup\u003e, separately. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e directly revealed the Mn leaching rate improved with the increase of stirring speed, which exhibited that a higher stirring speed was conducive to the collision and reaction between molecules. Considering power consumption, a stirring speed of 250 r/min was regard as the optimal leaching parameter for the further studies.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Effect of leaching temperature\u003c/h2\u003e \u003cp\u003eTo observe the influence of leaching temperature on Mn leaching rate from pyrolusite under electric field, We separately investigated the changes in Mn leaching rate when the temperature changed from 333K to 363K, and other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, stirring speed, direct current density were kept constant at 10ml/g, 10:3, 1.6mol/L, 250r/min, 353K, and 700A/m\u003csup\u003e2\u003c/sup\u003e, separately. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e directly manifested When the leaching temperature enlarged from 333K to 353K, the Mn leaching rate sharply increases. This was because the rise in leaching temperature enhanced the thermal motion between molecules, which was conducive to the progress of chemical reactions. In addition, higher leaching temperatures activated a large number of reactant molecules, which was also beneficial for reducing the energy barrier of chemical reactions. When the leaching temperature increased from 353K to 363K, it was obvious that the rise of Mn leaching rate was not significant. After leaching, it was found that the maximum Mn leaching rate was only increased by 1.2%. Therefore, considering the energy saving and experimental cost, 353K was thought as the optimal leaching parameter.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.6 \u003cem\u003eEffect of direct current density\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo study the influence of direct current density on Mn leaching rate from pyrolusite under electric field, We conducted a series of leaching experiments with current density changing from 0A/m\u003csup\u003e2\u003c/sup\u003e to 800A/m\u003csup\u003e2\u003c/sup\u003e and other leaching parameters such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, stirring speed, leaching temperature were kept constant at 10ml/g, 10:3, 1.6mol/L, 250r/min, 353K, separately. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e manifested when the current density was 0A/m\u003csup\u003e2\u003c/sup\u003e (namely, leaching without electric field), the maximum manganese leaching rate was only 59.72%. However, increasing the direct current density from 500 A/m\u003csup\u003e2\u003c/sup\u003e to 700 A/m\u003csup\u003e2\u003c/sup\u003e resulted in a significant increase in Mn leaching rate. This was because the introduction of an external electric field in the leaching system promoted ions migration and conversion. Besides, when the direct current density increased from 700 A/m\u003csup\u003e2\u003c/sup\u003e to 800 A/m\u003csup\u003e2\u003c/sup\u003e, the Mn leaching rate only increased slightly, which was because the direct current density was too large, Mn\u003csup\u003e2+\u003c/sup\u003e on the anode electrode was easy to be oxidized to MnO\u003csub\u003e2\u003c/sub\u003e attached to the anode plate, prompting the Mn in the pyrolusite could not be completely leached out. After repeated weighing, the direct current density of 700 A/m\u003csup\u003e2\u003c/sup\u003e was regarded as the optimal leaching parameter for this batch raw ores.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.7. \u003cem\u003ePhase analysis and SEM analysis\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe obtained leaching slags with electric field and without electric field was respectively dried for XRD characterization after leaching experiments. The characterization results were displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. It was obvious that the MnO\u003csub\u003e2\u003c/sub\u003e and FeS\u003csub\u003e2\u003c/sub\u003e diffraction peak of leaching slag without electric field was significantly higher than that leaching with electric field, and this further indicated the introduction of an electric field made the reaction between pyrolusite and pyrite more thorough. In addition, the diffraction peaks of elemental sulfur were found in the leaching slag without electric field, while no diffraction peaks of elemental sulfur were found in the leaching slag with electric field. This might due to the introduction of an external electric field, which formed a higher potential in the leaching reaction, promoting further oxidation of elemental sulfur and allowing more minerals to be leached out.\u003c/p\u003e \u003cp\u003eBoth raw material mixtures and leaching slags were respectively determined the microscopic morphology by SEM (Scanning electron microscopy). As could be seen from Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;1 and Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;4, the surface of the raw ore samples was observed to be relatively rough, and the volume distribution of the mineral samples appeared to be very uneven. As could be seen from Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;2 and Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;5, the SEM image of leaching slag without electric field appeared to have more flocculent substances and tiny particles deposited on the surface of the residue, which further implied that it might be due to incomplete oxidation of elemental sulfur. As could be seen from Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;3 and Fig.\u0026nbsp;11\u0026thinsp;\u0026minus;\u0026thinsp;6, the SEM image of leaching slag with electric field was observed to be cleaner without flocculent substances tiny particles, indicating that the by-products produced by leaching, such as elemental sulfur, might had undergone deep transformation. Moreover, very obvious tiny micro-pores were observed on the surface of the leaching slag, which might be due to the enhanced migration ability of ions inside the mineral under the action of electric field, resulting in a higher Mn leaching efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.7. \u003cem\u003eLeaching mechanism analysis\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eBased on the above experiments results and characterization analysis, we could further speculated the leaching reaction mechanism of pyrolusite-pyrite enhanced by electric field. As could be shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e, firstly, the acidolysis of FeS\u003csub\u003e2\u003c/sub\u003e formed Fe\u003csup\u003e2+\u003c/sup\u003eand S\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e. Then, MnO\u003csub\u003e2\u003c/sub\u003e in the pyrolusite rapidly oxidized Fe\u003csup\u003e2+\u003c/sup\u003e to Fe\u003csup\u003e3+\u003c/sup\u003e. Furthermore, under the action of an electric field, Fe\u003csup\u003e3+\u003c/sup\u003e reacted with S\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e to further convert into elemental sulfur or polysulfides such as S\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, S\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e. Finally, under the action of an electric field, MnO\u003csub\u003e2\u003c/sub\u003e couples with Fe\u003csup\u003e3+\u003c/sup\u003e to further oxidize polysulfides to sulfates. Therefore, the introduction of electric field in the leaching experiments intensified the migration ability of ions within the solution and minerals, and promoted the high valence conversion of low valence sulfur-containing compounds. Finally, introducing external electric field into the leaching reaction could strengthened the collision frequency between MnO\u003csub\u003e2\u003c/sub\u003e molecules and FeS\u003csub\u003e2\u003c/sub\u003e molecules, promoting faster and more efficient electron shuttle rates, which was beneficial for the deep leaching of pyrolusite.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this paper, the leaching experiment of reduction of pyrolusite by pyrite enhanced by electric field was investigated. The results displayed that the Mn leaching efficiency of 96.22% was obtained under the liquid-to-solid ratio of 10ml/g, mass ratio of pyrolusite and pyrite of 10:3, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration of 1.6mol/L, stirring speed of 250 r/min, leaching temperature of 353K, direct current density of 700A/m\u003csup\u003e2\u003c/sup\u003e, leaching time of 3h. Compared to leaching without electric field, the leaching with electric field improved the Mn leaching efficiency by nearly 36%.\u003c/p\u003e \u003cp\u003eThe phase analysis and microscopic morphology detection of the leaching products indicate that the leaching slag with electric field contained less elemental sulfur compared to the leaching slag without electric field, which was mainly attributed to the introduction of an electric field in the leaching reaction promoting the high valence state conversion of elemental sulfur, thereby reducing the encapsulation of mineral particles by the elemental sulfur film. Additionally, the introduction of electric field created a high potential in the leaching system, promoted deep oxidization of elemental sulfur, and strengthened the migration of ability of ions and the collision ability between molecules, so as to improved the Mn leaching rate of pyrolusite.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYakun Zhao: Experimental investigation, Data curation, Writing-original draft, Data analysis. KeFeng Pan: Methodology, Supervision, Writing-review \u0026amp; editing of the manuscript.RuiYao Yang: Formal AnalysisChengShuo Hou: TranslationNan Zhang: Translation\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors are very grateful for the financial support from National Natural Science Foundation of China (U1802255).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRao S, Sun J, Wang DX, Liu ZQ, Zhu W, Cao HY, Duan LJ (2023) Selective recovery of manganese and lead from electrolytic manganese residues in a sulfuric acid solution with galena as the reductant. Sep Purif Technol 308:122937\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe SC, Wilson BP, Lundstr\u0026ouml;m M, Liu ZH (2020) Hazard-free treatment of electrolytic manganese residue and recovery of manganese using low temperature roasting-water washing process. J Hazard Mater 402:123561\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan YF, Ma XM, Zhao W, Chang YK, Zhang XX, Wang XB, Wang JJ, Huang ZY (2013) Sulfur-oxidizing bacteria dominate the microbial diversity shift during the pyrite and low-grade pyrolusite bioleaching process. J Biosci Bioeng 116\u0026ndash;4:465\u0026ndash;471\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJu JR, Ma RY, Li YH, Feng YL, Li HR, Wang HY, Jiang SW (2023) An efficient and clean method for the selective extraction and recovery of manganese from pyrolusite using ammonium sulfate roasting-water leaching and carbonate precipitation. Miner Eng 203:108356\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu H, Feng YL, Li HR, Wang HJ, Ju JR (2020) Co-recovery of manganese from pyrolusite and gold from carbonaceous gold ore using fluidized roasting coupling technology. Chem Eng Process 147:107742\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDing FH, Zhang J, Wang ZJ, Chai LY, Zhang CF (2016) Simultaneous leaching of low grade bismuthinite and pyrolusite ores in hydrochloric acid medium. Hydrometallurgy 166:279\u0026ndash;284\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang LB, Xu YM, Tian H, Du YG (2023) Co-treatment of chromite ore processing residue and pyrolusite for simultaneous detoxification and resource utilization. Journal of Environmental Chemical Engineering. 11\u0026thinsp;\u0026ndash;\u0026thinsp;3 109785\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu ZW, Feng YL, Li HR, Li HS (2022) Efficient recovery of Ti, Fe and Mn based on the synergistic effect of acidic titanium dioxide wastewater and pyrolusite. J Water Process Eng 45:102484\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDu JJ, Zhang YQ, Lu JJ, Gao L, Guo SH, Omran M, Chen J, Chen G (2023) Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process. Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process. 24 2041\u0026ndash;2052\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDu JJ, Gao L, Yang Y, Guo SH, Omran M, Chen J, Chen G (2021) Dielectric characterisation and reduction properties of the blending mixtures of low-grade pyrolusite and waste corn stalks in the microwave field. Fuel 305:121546\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDo SH, Batchelor B, Lee HK, Kong SH (2009) Hydrogen peroxide decomposition on manganese oxide (pyrolusite): kinetics, intermediates, and mechanism. Chemosphere.75.1 8\u0026ndash;12\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNayl AA, Ismail IM, Aly HF (2011) Recovery of pure MnSO\u003csub\u003e4\u003c/sub\u003e∙H\u003csub\u003e2\u003c/sub\u003eO by reductive leaching of manganese from pyrolusite ore by sulfuric acid and hydrogen peroxide. Int J Mineral Process 100 3\u0026ndash;4 116\u0026ndash;123\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYou ZX, Li GH, Dang J, Yu WZ, Lv XW (2018) The mechanism on reducing manganese oxide ore with elemental sulfur. Powder Technol 330:310\u0026ndash;316\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun WY, Su SJ, Wang QY, Ding SL (2013) Lab-scale circulation process of electrolytic manganese production with low-grade pyrolusite leaching by SO\u003csub\u003e2\u003c/sub\u003e. Hydrometallurgy. 133 118\u0026ndash;125\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang C, Duan XX, Zhang XF, Rohani S, Wu HL, He MY, Gao YX, Liu QC, Yang J, Kong M, Liu WZ (2023) Acid-free extraction of manganese from pyrolusite tailings by in situ redox interaction with waste copperas. Process Saf Environ Prot 169:149\u0026ndash;158\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiong SF, Liu SXLPL, Hao SH, Hao F, Y ZL, Liu JX (2018) Recovery of manganese from low-grade pyrolusite ore by reductively acid leaching process using lignin as a low cost reductant. Miner Eng 125:126\u0026ndash;132\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang XR, Liu ZH, Wu XB, Du J, Tao CY (2017) Electric field enhancement in leaching of manganese from low-grade manganese dioxide ore: Kinetics and mechanism study. Journal of Electroanalytical Chemistry. 788 165-174.7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTian XK, Wen XX, Yang C, Liang YJ, Pi ZB, Wang YX (2010) Reductive leaching of manganese from low-grade manganese dioxide ores using corncob as reductant in sulfuric acid solution. Hydrometallurgy 96 3\u0026ndash;4 157\u0026ndash;160\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu DJ, Gao L, Chen G, Zhou JW, Guo SH, Omran M, Chen J (2022) Enhancement effects of distiller's dried grains as reducing agents on the kinetics and leaching of pyrolusite from manganese ore. J Mater Res Technol 19:4270\u0026ndash;4281\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen G, Jiang CL, Liu RL, Xie ZM, Liu ZH, Cen SD, Tao CY, Guo SH (2021) Leaching kinetics of manganese from pyrolusite using pyrite as a reductant under microwave heating. Sep Purif Technol 277:119472\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin SD, Gao L, Yang Y, Chen J, Guo SH, Omran M, Chen G (2020) Efficiency and sustainable leaching process of manganese from pyrolusite-pyrite mixture in sulfuric acid systems enhanced by microwave heating. Hydrometallurgy 198:105519\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLv X, Zhao HB, Zhang YS, Yan ZY, Zhao Y, Zheng H, Liu WQ, Xie JP, Qiu GZ (2021) Active destruction of pyrite passivation by ozone oxidation of a biotic leaching system. Chemosphere 277:130335\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKholmogorov AG, Zhyzhaev AM, Kononov US, Moiseeva GA, Pashkov GL (2000) The production of manganese dioxide from manganese ores of some deposits of the Siberian region of Russia. Hydrometallurgy 56(1):1\u0026ndash;11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNayak BB, Mishra KG, Paramguru RK (1999) Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite. J Appl Electrochem 29(2):191\u0026ndash;200\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin SD, Li KQ, Yang Y, Gao L, Omran M, Guo SH, Chen J, Chen G (2021) Microwave-assisted method investigation for the selective and enhanced leaching of manganese from low-grade pyrolusite using pyrite as the reducing agent. Chem Eng Process 159:108209\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie ZM, Chen G, Liu RL, Liu ZH, Cen SD, Tao CY, Guo SH (2021) Reaction kinetics characteristics of pyrolusite leaching process enhanced by rigid-flexible combined impeller. Huagong Xuebao/CIESC Journal. 72\u0026thinsp;\u0026ndash;\u0026thinsp;5 2586\u0026ndash;2595\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi JM, Li FM, Tong MH, Zhao Z, Xi KL, Guo SH (2024) Construction of an effective method combining in situ capping with electric field-enhanced biodegradation for treating PAH-contaminated soil at abandoned coking sites. Sci Total Environ 922:171209\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTian Y, Shu JC, Chen MJ, Wang JY, Wang Y, Luo ZG, Wang R, Yang FH, Xiu FR, Sun Z (2019) Manganese and ammonia nitrogen recovery from electrolytic manganese residue by electric field enhanced leaching. J Clean Prod 236:117708\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeng RR, Xie ZM, Liu ZH, Tao CY (2019) Leaching kinetics of vanadium catalyzed by electric field coupling with sodium persulfate. J Electroanal Chem 854:113542\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeng RR, Xie ZM, Liu ZH, Deng L, Tao CY (2019) Enhancement of vanadium extraction at low temperature sodium roasting by electric field and sodium persulfate. Hydrometallurgy 189:105110\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang Q, Liu HM, Wang Q, Shan YW, Tang DS, Zhang Z, Zhu XH (2024) Electric field-induced deterioration of cement mortars owing to calcium leaching. Developments Built Environ 17:100303\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang J, Zhou Y, Zhang ZL, Xu KH, Zhang K, Lai YQ, Jiang LX (2023) Effect of electric field on leaching valuable metals from spent lithium-ion batteries. Transactions of Nonferrous Metals Society of China, 33\u0026thinsp;\u0026ndash;\u0026thinsp;2, pp 632\u0026ndash;641\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang K, Zhu CP, Li J, Meng BC, Zhong KN, Huang WL, Yu J, Fang Z (2023) Electric field-assisted leaching of valuable metals from spent lithium-ion batteries in a mixture of acetic acid and ascorbic acid. Hydrometallurgy 221:106152\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuo ZG, Shu JC, Chen MJ, Wang R, Zeng XF, Yang Y, Wang R, Chen SY, Liu RL, Liu ZH, Sun Z, Yu KL, Deng Y (2021) Enhanced leaching of manganese from low-grade pyrolusite using ball milling and electric field. Ecotoxicol Environ Saf 211:111893\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Pyrolusite, Pyrite, Hydrometallugical reduction, Electric field, Manganese leaching efficiency","lastPublishedDoi":"10.21203/rs.3.rs-4413889/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4413889/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this paper, electric field as a chemical process intensification methods was utilized in the leaching experiment of manganese from pyrolusite using pyrite as reductant. The key leaching parameters under the action of electric field, such as liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, stirring speed, leaching temperature, direct current density, were investigated, respectively. The results suggest the optimum parameters of liquid-to-solid ratio, mass ratio of pyrolusite and pyrite, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e molar concentration, stirring speed, leaching temperature, direct current density were 10ml/g, 10:3, 1.6mol/L, 250 r/min, 353K, 700 A/m\u003csub\u003e2\u003c/sub\u003e under the leaching time of 3h, the manganese extraction efficiency of 96.22% was obtained, the manganese extraction rate of leaching with electric field is nearly 36% higher than that of leaching without electric field, indicating that the electric field enhanced ion migration to improve manganese leaching rate. In addition, phase analysis and morphology detection revealed that leaching slag with electric field contains less elemental sulfur and unreacted pyrolusite as well as pyrite. This further showed that the introduction of electric field promoted the high valence conversion of elemental sulfur, decreased the encapsulation effect of elemental sulfur on minerals, and led to efficient leaching of manganese.\u003c/p\u003e","manuscriptTitle":"Study on hydrometallugical reduction leaching of pyrolusite enhanced by electric field using pyrite as reductant","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-23 06:22:53","doi":"10.21203/rs.3.rs-4413889/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"82e3d9da-c70e-4b08-9ac6-18099b556def","owner":[],"postedDate":"May 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-06-16T21:23:22+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-23 06:22:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4413889","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4413889","identity":"rs-4413889","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}