Redução de minério de óxido de manganês com enxofre elementar

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The mechanism on reducing manganese oxide ore with elemental
sulfur
Zhixiong You, Guanghui Li, Jie Dang, Wenzhou Yu, Xuewei Lv
PII: S0032-5910(18)30156-6
DOI: doi:10.1016/j.powtec.2018.02.035
Reference: PTEC 13211
To appear in: Powder Technology
Received date: 18 October 2017
Revised date: 30 January 2018
Accepted date: 12 February 2018
Please cite this article as: Zhixiong You, Guanghui Li, Jie Dang, Wenzhou Yu, Xuewei
Lv , The mechanism on reducing manganese oxide ore with elemental sulfur. The address
for the corresponding author was captured as affiliation for all authors. Please check if
appropriate. Ptec(2017), doi:10.1016/j.powtec.2018.02.035
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An article submitted to Powder Technology 
The mechanism on reducing manganese oxide ore 
with elemental sulfur 
 
Zhixiong You1*, Guanghui Li2, Jie Dang1, Wenzhou Yu1, Xuewei Lv1 
 
(1-College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China. 
2-School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 
410083, China) 
 
 
 
 
*Corresponding Author: 
Dr. Zhixiong You, E-mail: youzx@cqu.edu.cn. 
Materials Building, No. 111 
College of Materials Science and Engineering, Chongqing University, 
No. 174 Shazhengjie, Shapingba District, Chongqing 400044, P.R. China 
Tel./Fax: (+86) 023 65112631 
 
 
 
 
 
 
 
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The mechanism on reducing manganese oxide ore 
with elemental sulfur 
 
Zhixiong You1*, Guanghui Li2, Jie Dang1, Wenzhou Yu1, Xuewei Lv1 
 
(1-College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China. 
2-School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, China) 
Abstract 
Extraction of Mn from manganese oxide ore via sulfur-based reduction followed 
by acid leaching has received much attention. In this study, the mechanism on 
reducing manganese oxide ore with elemental sulfur was investigated. The reduction 
of manganese dioxide by sulfur is feasible thermodynamically, and the experimental 
validation proved that manganese dioxide was reduced stepwise to low-valence state 
in the order of MnO2→Mn2O3→Mn3O4 (together with MnSO4 or SO2). Subsequently, 
Mn3O4 would be reduced to form MnS or MnO, and the tendency of forming MnO 
was enhanced with increase in the temperature. Manganese oxide (MnO) will further 
react with excessive sulfur forming MnS and MnSO4. However, the formed MnS on 
the surface of the particles would inhibit further reduction or sulfidation. During the 
reductive roasting process, MnSO4 as well as gaseous SO2 were simultaneously 
generated. The reaction between MnS and Mn3O4 occurred at temperatures over 
500 °C, which facilitated producing MnO and SO2. The roasted product contained 
MnS, MnSO4, MnO and unreacted Mn3O4 at lower temperature (<500 
oC), whereas 
the main products were MnO and MnSO4 at higher temperature (≥500 
oC). The 
content of MnO increased gradually while that of MnS was decreased by increasing 
the roasting temperature. 
 
Keywords: Manganese dioxide, Elemental sulfur, Reductive roasting, Mechanism 
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1. Introduction 
Manganese is an important fundamental metal that has been widely applied in 
many fields, such as steel production, battery, non-ferrous metallurgy, catalyst [1], 
electrode materials [2], etc. Manganese oxide ore is the most important Mn-bearing 
resource in the world, which accounts for approximately 70% of the total manganese 
ore deposits [3]. To meet the ever-increasing demand for manganese, particularly in 
China, considerable effort has been made to recover manganese from low-grade 
pyrolusite. However, manganese dioxide must be primarily reduced into a soluble 
form before it can be extracted in dilute sulfuric acid or alkaline medium [4]. 
There are various reductants reported to have been employed for reducing 
manganese oxide ore in the processes of direct reductive leaching or pre-reduction 
followed by leaching. Manganese dioxide is likely reduced in acid solutions in the 
presence of reductants such as metallic iron or iron(II) sulfate [5, 6], pyrite [7], 
hydrogen peroxide [8], biomass [9] or oxalic acid [10], etc. Manganese is also capable 
of being extracted by SO2 leaching [11], electrolysis as well as bioleaching [12]. In 
recent years, the reductant of renewable biomass has been widely studied. A common 
problem with biomass is, however, the relatively low leaching efficiency and the 
decomposition product of biomass is adverse to the subsequent electrolysis [9]. On 
the other hand, pre-reduction of manganese oxide ore by roasting in the presence of 
reductants was expected to be employed prior to acid leaching. Carbothermal 
treatment of manganese oxide ore using coal as reducing agent is the most widely 
used approach [13]. Although this traditional method is characterized by high efficient, 
it produces a great deal of dust and SOx/NOx which pollute environment seriously. 
Worse still, roasting is generally performed at temperatures over 850 °C which 
consumes huge amounts of energy [14, 15]. Other reductants reported in the 
literatures include pyrite [16], SO2 [17, 18], ammonium salts ((NH4)2SO4 or NH4Cl) 
[19], CO/H2, CH4 [20-22] and carbohydrate [23]. 
Recently, sulfur-based reduction or sulfidation using elemental sulfur as 
reductant has received increasing attention. The sulfidation of a nickeliferous lateritic 
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ore by sulfur indicated that nickel oxide can be selectively sulfidized to a nickel–iron 
sulfide at 400-550 oC [24]. Similarly, studies on sulfidation roasting of cervantite, 
chalcopyrite, lead–zinc oxide ore, as well as zinc and lead carbonate were also 
reported [25-28]. The oxides or carbonates were likely converted to sulfides which 
can be recovered by flotation. A major problem of these technologies is the submicron 
particle size of sulfides obtained after low temperature sulfidation roasting which 
usually causes low metal recovery in flotation. 
An alternative process of reductive roasting manganese oxide ore with elemental 
sulfur prior to acid leaching has also been successfully developed and industrialized in 
China [29, 30]. This process employed a relatively lower roasting temperature which 
was considered as a cost-effective method. Fluid-bed furnace (boiling furnace) was 
the main roasting device due to the low boiling point of elemental sulfur. Sulfuric acid 
leaching was proved to be appropriate in extracting manganese as manganese sulfate 
solution was usually used for subsequent electrolysis. The generated SO2 gas during 
reductive roasting can be absorbed to prepare sulfuric acid and then used for acid 
leaching. 
In our previous work, desirable extraction ratio of manganese has been obtained 
via sulfur-based reduction followed by acid leaching [17, 30, 31]. However, the 
industrialization production indicated that the components of roasted product were 
very complicated, and the formation of manganese sulfide (MnS) was unfavorable to 
acid leaching due to the release of poisonous H2S. Thus, to better understand the 
behavior of sulfur-based reduction, in this study, the effects of S/Mn molar ratio and 
roasting temperature on the phase transformation during reductiveroasting was first 
investigated. After that, an analysis of gas composition in the outlet gas, scanning 
electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) are also 
used to characterize the reduced solid samples so as to identify the reduction 
mechanism. 
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2. Experimental 
2.1. Materials 
The manganese ore sample was obtained from a mine located in China. The 
as-received ore was crushed by hammer, and high purity pyrolusite was manually 
separated under an optical microscope. The pyrolusite sample was used as the raw 
material after being ground to 100 wt.% of the particles passing 0.074 mm. The main 
chemical composition of the sample is shown in Table 1. The Mn content was 59.6 
wt.% which is equivalent to 94.3 wt.% MnO2. The XRD pattern in Fig. 1 indicates 
manganese mainly existed in the form of pyrolusite (MnO2). The gangue mineral was 
a small amount of quartz (SiO2) whose effect was ignored during the reductive 
roasting process. 
Element sulfur (powder) was used as the reducing agent, whose purity was above 
99.99%. 
2.2. Experimental procedure 
Ten grams of ground pyrolusite sample was mixed with elemental sulfur in 
various ratios, and charged into a tightly sealed stainless steel reactor (cylindric, 
volume: 50 ml) [30]. The reactor was then put into an electric resistance muffle 
furnace which was preheated at a rate of 10 oC/min to a desired temperature. After 
roasting for 30 min, the roasted product staying in the sealed reactor was taken out 
and cooled to room temperature. Finally, the cooled product was discharged from the 
reactor and collected for analysis. 
2.3. Analytical method 
The X-ray Diffraction analysis was conducted using a diffractometer (RIGAKU 
D/Max 2500, Japan) under the conditions as follows: Cu Kα, tube current and voltage: 
250 mA, 40 kV, scanning range: 10o-80o (2θ), step size: 0.02o (2θ) and scanning speed: 
8o/min. 
The microstructure of roasted samples was observed by using environmental 
scanning electron microscope which was equipped with an energy dispersive 
spectrometer (ESEM, FEI QUANTA 200, Holland). ESEM images were recorded in 
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backscatter electron mode operating in a low vacuum of 0.5 Torr and 20 keV. 
The thermo-gravimetric (TG) experiments were conducted using a Setaram Evo 
TG-DTA 1750 thermal analyzer. The tests were carried out under the following 
conditions: temperature range of 30-1000 oC, heating rate of 20 K/min, argon 
atmosphere and the total flow rate of 20 mL/min. The evolved gas was detected in 
real time by TILON LC-D200 mass spectrograph. 
3. Thermodynamic analysis of reductive roasting 
The main possible chemical reactions between manganese oxides and sulfur are 
listed in Table 2. Their 
PlogK
 values based on free energies calculated (by Factsage 
7.0) under a total pressure of 1 atm at specified temperatures are also presented in 
Table 2. It can be observed that the reactions of Eqs. 1-6 are predicted to occur 
spontaneously at temperatures less than 900 K. Manganese oxides are likely reduced 
by sulfur forming low-valence compounds due to their negative free energies. It is 
noteworthy that manganese oxide (MnO) and manganese sulfate (MnSO4) are able to 
further react with sulfur to form different products depended on the roasting 
conditions. 
In order to predict the theoretical products between manganese dioxide and 
sulfur, the software Factsage 7.0 was also used to calculate the equilibrium 
composition of roasted products, as shown in Fig. 2. Figures 2(A) and (B) show the 
equilibrium amounts of roasted products for 1 mol manganese dioxide as functions of 
S/Mn molar ratio and roasting temperature, respectively. 
From Fig. 2(A), it reveals that MnO2 is firstly reduced to Mn2O3 and MnSO4 at 
350 oC (Eq. 1). The stoichiometric S/Mn molar ratio is 0.20 at which MnO2 
disappears while 0.4 mol Mn2O3 together with 0.2 mol MnSO4 are formed. As the 
S/Mn ratio is increased, Mn2O3 will be reduced forming Mn3O4 and MnSO4 (Eq. 2). It 
can be seen that the amount of Mn2O3 is decreased while that of Mn3O4 and MnSO4 
increases correspondingly within the S/Mn molar ratio range of 0.20-0.25. Similarly, 
Mn3O4 will further be reduced to MnO as well as MnSO4 (Eq. 4) by increasing S/Mn 
from 0.25 to 1/3. The formation of MnO is easier than MnS at the calculated 
temperature (Eq. 4 > 3). Manganese sulfide (MnS) is not formed until the S/Mn molar 
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ratio is over 1/3 (Eqs. 6 and 7). With higher sulfur addition (S/Mn>1.00), MnSO4 
begins to be reduced resulting in continuous increase in MnS. The results in Fig. 2(A) 
indicate that the reduction of manganese oxides by sulfur proceeds stepwise from 
high-valence to low-valence states during the reductive roasting process. 
The effect of roasting temperature on the equilibrium composition of reducing 1 
mol MnO2 by 0.5 mol sulfur (S/Mn=0.50) was also calculated and the results are 
plotted in Fig. 2(B). MnO2 is expected to be reduced in the order of MnO2→Mn2O3→
Mn3O4 at all the calculated temperatures. However, the reduction procedure of Mn3O4 
as well as the final products largely depend on the roasting temperature. There are 
three temperature intervals plotted in Fig. 2(B). The temperature of about 285 oC 
represents the change of reducing Mn3O4 between Eqs. 3 and 4. Manganese sulfide 
(MnS) and MnSO4 (Eq. 3) are favored below 285 
oC, whereas Mn3O4 is more likely 
reduced to MnO and MnSO4 above 285 
oC (Eq. 4). The theoretical S/Mn molar ratio 
for thoroughly converting 1 mol MnO2 to MnO is 1/3, the rest of sulfur will keep on 
reacting with MnO. As a result, the final products include MnO, MnS and MnSO4 
under the conditions of S/Mn=0.50 and temperature of 285-585 oC. By increasing the 
roasting temperature up to 585 oC, the reaction of Eq. 9 occurs preferentially which 
results in the formation of MnO and SO2. 
4. Results and discussion 
4.1. Phase transformation 
4.1.1 Effect of S/Mn molar ratio 
To identify the phase transformation of manganese dioxide during reductive 
roasting, XRD analysis was performed for determining the phase composition of 
roasted products. The effect of S/Mn molar ratio was investigated by keeping roasting 
temperature at 350 °C and roasting time of 30 min, and the results are compared in 
Fig. 3. 
It can be observed that the products were very complicated. The patterns of roasted 
products are different from that of the pyrolusite sample. Manganese dioxide was 
already reduced even at 350 °C. Manganese dioxide (MnO2) in the raw material 
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disappeared, whereas Mn2O3 and MnSO4 were formed according to the reaction of Eq. 
1. Mn2O3 was almost not reduced with S/Mn molar ratio of 0.20 due to the lower 
sulfur addition. By increasing the S/Mn molar ratio to 0.33, part of Mn2O3 was 
reduced to form Mn3O4 whose diffraction was obviously observed (Eq. 2). It is 
evident that the diffractions of Mn2O3 were not observed when the S/Mn molar ratio 
was increased to 0.50. Instead, MnS was generated and its diffraction was intensified 
with increasing S/Mn ratio to 1.00 (Eq. 3). Meanwhile, the amount of MnSO4 
increased gradually as the S/Mn molar ratio was increased from 0.2 to 2.0. The results 
of XRD patterns are generally in accordance with the thermodynamic analysis except 
for the inconspicuous appearance of MnO. Although the thermodynamic analysis in 
Fig. 2 revealed that the formation of MnO is easier than MnS at 350 oC. Mn3O4 may be 
reduced directly to MnS instead of MnO at the experimental conditions. An 
alternative possibility is that MnO further reacted with the excessive sulfur. According 
to the previous study of sulfur-based roasting, sulfur must diffuse throughthe product 
phase for further reaction [24]. Thus, the formation of MnS was inevitable once sulfur 
contacted with MnO. In addition, the diffraction of quartz was not obviously observed 
in the XRD patterns due to its low content. 
4.1.2 Effect of roasting temperature 
By fixing the S/Mn molar ratio at 0.50 and roasting time of 30 min, the phase 
transformation at different temperatures was also examined and the XRD patterns of 
roasted products are plotted in Fig. 4. 
It can be seen that the main phases were MnS, MnSO4 as well as unreduced 
Mn3O4 at 350 
oC. As the roasting temperature was increased to 400 oC, the diffraction 
of MnO was obviously observed and its diffractions were intensified greatly until 500 
oC. The diffraction pattern of product prepared at 450 oC was almost the same as that of 
400 oC. Upon increasing the temperature to 600 oC, more MnO was generated and the 
contents of Mn3O4 and MnS are reduced correspondingly. Higher roasting temperature 
was beneficial to the formation of MnO which can be explained from the view of 
thermodynamics. The dramatic increase of MnO from 450 oC to 600 oC was also caused 
by the reaction between Mn3O4 and MnS (Eq. 10), because MnS would react with 
Mn3O4 to form MnO and SO2 at temperatures above about 500 
oC (proved by the 
evolved gas analysis in Sec. 4.3). As expected thermodynamically (in Sec.3), the final 
products remained consistent between 350-550 oC. The difference in the composition 
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of diverse temperatures may be ascribed to the kinetic factors. In addition, increasing 
roasting temperature also resulted in greater sublimation of sulfur (the boiling point of 
sulfur is about 450 oC). 
MnS+3Mn3O4=10MnO+SO2(g) ΔG
θ=224.085-0.292T (kJ/mol) (Eq. 10) 
4.2. Microstructure analysis 
In order to further understand the characteristics of the reduced product, the 
microstructure was examined by using SEM-EDS. Figures 5 and 6 show the SEM-EDS 
results of the products treated at 350 oC and 550 oC, respectively. From the EDS results and 
surface scanning images in Fig. 5, it can be observed that small particles were more easily 
reduced or sulfided. However, the interior part of larger particles was scarcely reduced, as 
observed from the EDS of spot 1. Manganese distributes almost uniformly in the particles, 
whereas sulfur is more distinct within the near-surface parts. It proves that reduction 
reaction takes place from periphery to the interior of the particles. The sulfidation of 
manganese on the surface of the particles would inhibit further reduction or sulfidation, 
which suggests the manganese sulfide generated restrains the mass transfer of sulfur. 
Compared with the microstructure obtained at 550 oC with S/Mn molar ratio of 0.5, 
the most distinct difference was the distribution of sulfur (Fig. 6). This is because the main 
Mn-bearing phases under the current conditions were MnO as well as MnSO4. Only a 
small number of manganese sulfide existed within the near-surface parts. There are several 
reasons for this: 1) Manganese dioxide would decompose to form Mn2O3 and O2 at 550 
oC, 
which destroys the original compact structure and facilitates the reduction process. 2) 
According to the thermodynamic analysis, Mn3O4 is more likely reduced to MnO rather 
than MnS with increase in the roasting temperature. 3) Manganese sulfide would not 
coexist with the high-valence manganese oxides, which promotes the formation of MnO. 
The EDS analysis were consistent with the phase composition and XRD patterns 
determined in Figs. 3 and 4. The results also indicate that although increasing temperature 
can reduce the content of MnS, it was difficult to be eliminated thoroughly, especially on 
the surface of the particles. 
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4.3 TG and evolved gas analysis 
The reaction of manganese oxide ore with sulfur was also studied by 
thermo-gravimetric (TG) with evolved gas analysis using premixed ore and sulfur 
additions. The results are shown in Fig. 7. Regarding the TG curve in the absence of 
sulfur, there are two distinct weight losses within the temperature range. The weight 
loss at about 550 oC was attributed to the decomposition of MnO2 to Mn2O3, and 
followed by the decomposition of Mn2O3 with increase in the temperature. Oxygen 
was released during the decomposition which was proved by the ion current of 32 
A.M.U. (Fig. 7(B)). 
For samples of ore mixed with varying amounts of sulfur, the TG and ion current 
results provide evidence of several separate reactions. It can be observed that the 
reduction of manganese dioxide with sulfur began at a relatively low temperature in 
comparison to the as-received ore. The weight loss at approximately 300 oC was 
ascribed to the reaction of the samples by elemental sulfur as well as sulfur 
evaporation. It is difficult to distinguish between the reaction and sulfur evaporation 
even from the results of 64 A.M.U. peaks, which corresponds to the atomic mass of 
both S2 and SO2. It is interesting to note that the decomposition of MnO2 appears to 
occur at higher temperatures when sulfur was added to the raw material since the 32 
A.M.U. peak was shifted to higher temperatures. However, the shifted temperature 
may be due to that the oxygen formed from the core of the particles would further 
react with the intermediate products, which lead to the oxygen being detected later. 
The peak of A.M.U. 32 in the presence of sulfur was obviously lower than that of the 
raw sample. The second peak of A.M.U. 64, suggesting the formation of SO2 as sulfur 
was already sublimated, was mainly derived from the reaction between manganese 
sulfide and manganese oxides (Eq. 10). There is a third, higher temperature reaction 
generating SO2 observed, for both samples with sulfur additions. This reaction was 
most likely the decomposition of MnSO4. 
4.4 Discussion on the mechanism of reductive roasting 
According to the discussion mentioned above, the reaction procedure of MnO2 
was very complex. The mechanism of reducing manganese dioxide with elemental 
sulfur is described in Fig. 8. As elucidated in Fig. 8, MnO2 is reduced to low-valence 
state according to the following steps: MnO2→Mn2O3→Mn3O4. Simultaneously, both 
manganese sulfate and gaseous SO2 were generated during the reductive roasting 
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process. The reduction of Mn3O4 was largely related to the roasting temperature. 
Mn3O4 was expected to be reduced to form MnS or MnO at different temperatures, 
and the tendency of generating MnO was enhanced with increase in the roasting 
temperature. Moreover, MnS will react with Mn3O4 producing MnO if the roasting 
temperature is above 500 °C. Manganese oxide (MnO) will further react with 
excessive sulfur to form MnS and MnSO4. Lower temperature as well as higher sulfur 
addition are beneficial to the formation of MnS and MnSO4. 
The phase composition revealed that MnSO4 was generated under all the 
experimental conditions. Although it was able to be formed through the reaction 
between SO2 and MnO2, MnSO4 was mainly derived from the reduction of 
manganese oxides by sulfur. This is because MnO2 was easily reduced to low-valence 
compounds which inhibited the reaction between SO2 and MnO2. According to the 
results of TG-MS analysis, part of sulfur was also converted to gaseous SO2. At lower 
roasting temperature, SO2 was mainly generated by reducing manganese oxides with 
sulfur, while the reaction between MnS and Mn3O4 would promote its amount at 
higher temperature. 
The roasted products were also extremely complex which contained MnS, 
MnSO4 and unreacted Mn3O4 at lower temperature, whereas the main products were 
MnO and MnSO4 at higher temperature. The content of MnO increased gradually 
while that of MnS and MnxOy were decreasedby increasing the roasting temperature. 
5. Conclusions 
In this study, the mechanism on reducing manganese oxide ore with elemental 
sulfur was investigated. The conclusions can be summarized as follows: 
(1) The reduction of manganese dioxide by sulfur is feasible. Manganese dioxide was 
reduced stepwise to low-valence state in the order of MnO2→Mn2O3→Mn3O4. 
Subsequently, Mn3O4 would be reduced to form MnS or MnO (together with 
MnSO4 or SO2), and the tendency of forming MnO was enhanced with increase in 
the roasting temperature. Manganese oxide (MnO) will further react with 
redundant sulfur to form MnS and MnSO4. 
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(2) During the reductive roasting process, MnSO4 as well as gaseous SO2 were 
simultaneously generated. Manganese sulfate was mainly derived from the 
reduction of manganese oxides by sulfur. The reaction between MnS and Mn3O4 
would occur at temperatures over 500 °C, which facilitated producing MnO and 
SO2. 
(3) The roasted products contained MnS, MnSO4, MnO and unreacted Mn3O4 at lower 
temperature (<500 oC), whereas the main products were MnO and MnSO4 at 
higher temperature (≥500 oC). The content of MnO increased gradually while that 
of MnS was decreased by increasing the roasting temperature. 
(4) The reduction reactions take place from periphery to the interior of the particles. 
Manganese sulfide formed on the surface of the particles would inhibit further 
reduction or sulfidation. 
Acknowledgements 
The authors wish to express their thanks to the National Natural Science 
Foundation of China (Grant No. 51234010) and the Fundamental Research Funds for 
the Central Universities (Project No. 106112017CDJXY130001) for the financial 
support of this research. 
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Figure captions 
Fig. 1. XRD pattern of the pyrolusite sample. 
Fig. 2. Equilibrium composition of roasted products as functions of S/Mn molar ratio and roasting 
temperature. 
Fig. 3. XRD patterns of roasted products at different S/Mn molar ratios. (350 oC, 30 min) 
Fig. 4. XRD patterns of roasted products at different temperatures. (S/Mn=0.50, 30 min) 
Fig. 5. SEM-EDS analysis and main elements distribution in the roasted product. (T=350 oC, 
S/Mn=1.0) 
Fig. 6. SEM-EDS analysis and main elements distribution in the roasted product. (T=550 oC, 
S/Mn=0.5) 
Fig. 7. TG-MS analysis of MnO2 and sulfur mixtureat different molar ratios. 
Fig. 8. The mechanism of reducing MnO2 with elemental sulfur. 
 
Table captions 
Table 1 Main chemical composition of the pyrolusite sample. 
Table 2 Main reactions between manganese oxides and elemental sulfur. 
 
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Tables 
Table 1 Main chemical composition of the pyrolusite sample. 
Component TMn* TFe* SiO2 Al2O3 CaO MgO S P 
Wt.% 59.6 0.55 3.76 0.93 0.16 0.13 0.01 0.019 
*TMn/TFe: total Mn/Fe grade. 
 
 
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Table 2 Main reactions between manganese oxides and elemental sulfur. 
Eq. Possible reactions 

TΔG =A+BT, kJ/mol PlogK

 
A B 600K 700K 800K 900K 
1 S + 5MnO2 = 2Mn2O3 + MnSO4 -365.259 -0.052 34.52 29.97 26.57 23.92 
2 S + 8Mn2O3 = 5Mn3O4 + MnSO4 -405.425 0.135 28.24 23.20 19.42 16.48 
3 S+1/3Mn3O4=2/3MnS+1/3MnSO4 -50.218 0.027 3.27 2.74 2.34 2.03 
4 S + 3Mn3O4 = 8MnO + MnSO4 3.621 -0.069 3.62 3.75 3.84 3.91 
5 S + 2Mn3O4 = 6MnO + SO2 150.621 -0.237 -0.73 1.14 2.55 3.64 
6 S+2/3MnO=2/3MnS+1/3SO2(g) 3.970 -0.042 1.83 1.88 1.92 1.95 
7 S + MnO = 3/4MnS + 1/4MnSO4 -49.263 0.020 3.24 2.63 2.17 1.81 
8 S + 1/2MnSO4 = 1/2MnS +SO2(g) 113.081 -0.169 -1.02 0.39 1.44 2.26 
9 S + 2MnSO4 = 2MnO +3SO2(g) 447.126 -0.556 -9.63 -4.03 0.12 3.30 
 
 
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Highlights 
(1) The mechanism on reducing manganese oxide ore with elemental sulfur is 
revealed. 
(2) MnO2 is reduced stepwise in the order of MnO2→Mn2O3→Mn3O4→MnS/MnO, 
together with MnSO4 or SO2. 
(3) Higher temperature is beneficial to the formation of MnO. 
(4) The phase composition of the roasted product under different conditions is 
confirmed. 
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