Kinetics of the Thermal Decomposition of Rhodochrosite

Home , Rhodochrosite, Thermal decomposition

Article Kinetics of the Thermal Decomposition of Rhodochrosite

Iván A. Reyes 1,2 , Mizraim Flores 3,*, Elia G. Palacios 4 , Hernán Islas 1, Julio C. Juárez 5 , Martín Reyes 5, Aislinn M. Teja 5 and Cristóbal A. Pérez 1

1 Instituto de Metalurgia, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78210, Mexico; [email protected] (I.A.R.); [email protected] (H.I.); [email protected] (C.A.P.) 2 Catedrático CONACYT, Consejo Nacional de Ciencia y Tecnología, Ciudad de Mexico 03940, Mexico 3 Área Electromecánica Industrial, Universidad Tecnológica de Tulancingo, Hidalgo 43642, Mexico 4 Escuela Superior de Ingeniería Química e Industrias Extractivas, Instituto Politécnico Nacional, Ciudad de Mexico 07738, Mexico; [email protected] 5 Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo, Hidalgo 42183, Mexico; [email protected] (J.C.J.); [email protected] (M.R.); [email protected] (A.M.T.) * Correspondence: mﬂ[email protected]

Abstract: Manganese is a widely used element in the steel industry; its main source is a mineral

named rhodochrosite (MnCO3). For industrial usage, rhodochrosite is reduced to different manganese oxides by means of nodulation furnaces. In this study, rhodochrosite was thermally analyzed at temperatures ranging from 100 ◦C to 1200 ◦C. XRD (Powder X-ray diffraction), XRF (X-ray fluorescence), AAS (Atomic Absorption Spectrometry), and FESEM-EDX (Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry) were used to characterize the mineral and the residues were analyzed by XRD and FTIR (Fourier-transform infrared spectroscopy) to determine the stoichiometry of the thermal decomposition reactions. Three mass losses were observed, the first attributed to the transformation from carbonate to manganese (III) oxide, the second to the reduction to manganese tetroxide, and the third to the decomposition of calcium carbonate (CaCO ) present 3 as a contaminant in the studied mineral. Thermal decomposition kinetics shows that the first mass Citation: Reyes, I.A.; Flores, M.; loss required 17.91 kJ mol−1, indicating a control by mass transport-controlled process. For the Palacios, E.G.; Islas, H.; Juárez, J.C.; second and third mass loss, the apparent activation energy of 112.41 kJ mol−1 and 64.69 kJ mol−1 Reyes, M.; Teja, A.M.; Pérez, C.A. was obtained respectively, indicating that both mass loss events were rate-controlled. Kinetics of the Thermal Decomposition of Rhodochrosite. Keywords: kinetics; apparent activation energy; thermal decomposition; manganese carbonate Minerals 2021, 11, 34. https://doi.org/10.3390/min11010034

Received: 18 November 2020 1. Introduction Accepted: 25 December 2020 Published: 29 December 2020 Manganese occurs in natural environments in the 2+, 3+, and 4+ oxidation states. The higher the oxidation states, the stronger the tendency of this element to hydrolyze and Publisher’s Note: MDPI stays neu- precipitate. The transport of Mn in aqueous solutions is generally favored by reducing con- 2+ tral with regard to jurisdictional clai- ditions, and the Mn ion and its complexes constitute the principal transport species [1]. ms in published maps and institutio- Manganese is a relatively abundant element on the Earth’s crust and most commonly occurs nal afﬁliations. in a variety of oxides, oxyhydroxides, and carbonates such as pyrolusite (MnO2), manganite (MnO[OH]), rhodochrosite (MnCO3), and kutnahorite (CaMn[CO3]2)[2]. Manganese- based materials, especially those formed by manganese oxides, are important for their relevant physical and chemical properties, which enable their use in important technologi- Copyright: © 2020 by the authors. Li- cal applications, such as rechargeable batteries, sensors, and optical or magneto-electronic censee MDPI, Basel, Switzerland. devices. One of the main applications of manganese is in the steel industry, as manganese This article is an open access article distributed under the terms and con- imparts malleability, tenacity, and hardness to steel. Moreover, the non-ferrous applications ditions of the Creative Commons At- of manganese include the production of dry-cell batteries, plant fertilizer and animal food, tribution (CC BY) license (https:// and colorant for bricks [3–12]. Manganese-based solids with a spinel structure have also creativecommons.org/licenses/by/ attracted attention as effective catalysts in the reduction of dangerous gases, such as CO, 4.0/). NO, and N2O, and several organic compounds [3].

Minerals 2021, 11, 34. https://doi.org/10.3390/min11010034 https://www.mdpi.com/journal/minerals Minerals 2021, 11, 34 2 of 12

Depending on the Mn content, manganese ores are categorized into high grade (Mn 44%), medium grade (Mn 40–44%), low grade (Mn 35–40%), and steel-mill grade (Mn 28–35%) [13]. A giant stratiform rhodochrosite deposit is found in the town of Molango, in Hidalgo, Mexico, which is the major manganese deposit in North America. The ore horizon occurs in the Chipoco facies at the base of the Taman formation. The manganese extracted from this area is used to make ferroalloys. The rhodochrosite ore, though relatively low in manganese, is added to the blast furnace charge for the production of ferromanganese. However, during the last five years, flotation and nodulizing processes have been de- veloped, which concentrate the rhodochrosite ore into a high-grade product more suitable for manufacturing ferromanganese, reaching concentrations of 74% of Mn [14]. “Min- era Autlán” in Molango owns the world’s only nodulation rotary kiln for nodules production from manganese ore, which is used to improve the chemical and physical properties of manganese carbonates by converting them into manganese nodules. Following the concept of the cement clinker, the fine manganese ore is reacted in a refractory-lined counter-current rotary kiln with horizontal flow to produce nodules in which most of the manganese is in the divalent oxidation state. The process was first used in the USA and Norway for the treatment of manganese oxide ore fines. Since 1968, it has been used by Minera Autlan in Mexico for nodulizing carbonate ore fines. In the case of the Autlan ore, liquid formation required for nodulizing takes place at temperatures between 1145 ◦C and 1260 ◦C[15]. Nodulation is carried out to drive off volatiles (water and CO2), reducing the amount of excess oxygen (pre-reduction) and improving the size distribution (agglomeration or sintering) as well as the performance of the ore during melting in a submerged arc furnace. Previous studies have been conducted on the thermal decomposition of MnCO3. Kissinger et al. (1955) calculate the heat of reaction of each mass loss using thermodynamic data, determining that the first mass loss is an exothermic reaction, whereas the second and third mass losses are endothermic reactions [16]. Biernacki and Pokrzywnicki (1999) found that temperature accelerates the decomposition of MnCO3 to MnO2 which was faster at 691 K (418 ◦C) and calculated a value of ∆G= −17 kcal mol−1; reduction reactions occur at 703–815 K (MnO2 to Mn2O3), 815–1300 K (Mn2O3 to Mn3O4) and above 1300 K (Mn3O4 to MnO), where MnO is the most stable manganese oxide phase [17]. The Gibbs-free energy of and the enthalpy for the formation of rhodochrosite [18], have been also determined, however the kinetics of thermal decomposition of rhodochrosite have not been studied. Thermal decomposition of rhodochrosite is the main treatment process in the manganese industry; in this study, the kinetics of thermal decomposition of MnCO3 was investigated, and the apparent activation energies of the material mass losses during the process were obtained. The main contribution of this work is obtaining new kinetic parameters such as the apparent activation energy and the frequency factor for the thermal decomposition of rhodochrosite, which is a process of great importance in the production of manganese nodules by pyrometallurgy. Moreover, the stoichiometry of the decomposition reaction of manganese carbonate into different oxides is presented.

2. Materials and Methods The rhodochrosite sample was obtained from the manganese ore deposit located in Molango, Hidalgo, Mexico. The sample was pulverized with an agate mortar to a size of 53 micrometers, homogenized, and analyzed using different characterization techniques such as Powder X-ray diffraction (XRD), X-ray ﬂuorescence (XRF), Atomic Absorption Spectrometry (AAS), and Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry (FESEM-EDX) a JEOL JSM-670 IF Field Emission Scanning Electron microscope was used (JEOL, Tokyo, Japan). The XRD analysis was performed using a Bruker D8 powder diffractometer (Bruker Corporation, Billerica, MA, USA), with Ni ﬁltered radiation from a Cu anode (kα1 = 1.5406 Å; 40 kV and 35 mA). Diffraction patterns were recorded in the angular range 2θ of 10–90◦, with a step size = 0.01◦ and a step time = 3 s. For the XRF analysis, an S2 PUMA equipment (Bruker) was utilized, using rhodochrosite Minerals 2021, 11, 34 3 of 12

powder less than 45 µm. For the AAS analysis, a PerkinElmer Analyst 200 (PerkinElmer Inc., Waltham, MA, USA), was utilized. The calibration of the equipment was carried out with certified standards, PerkinElmer of 1000 ppm of the element to be determined. For thermal characterization, thermogravimetric analysis was performed in a Mettler Toledo TG-DTG 851e equipment (Mettler Toledo, Greifensee, Switzerland). The experiments were carried out at a heating rate of 10 ◦C min−1 and 666 × 10−3 m3 s−1 air flow. Calcination was carried out for one hour at different temperatures (450 ◦C, 750 ◦C and 900 ◦C), subsequently the calcined solids (powder) were analyzed by FESEM−EDX to determine the elemental composition at different temperatures. The calcination residues were later analyzed by XRD and Fourier-transform infrared spectroscopy (FT-IR) in a PerkinElmer Spectrum Two with Universal ATR (PerkinElmer Inc., Waltham, MA, USA) 3000–4500 cm−1 to infer the stoichiometry of the thermal decomposition reactions. The kinetic analysis performed was based on an isothermal process using the “time to a given fraction” method [19–22]. The mass fractions for each temperature used in each mass loss ramp were determined. In the first stage, four temperatures were taken, due to the prolonged mass loss slope caused by the large amount of CO2 released; for the second and third stages, only three temperatures were considered, given that the slopes were short. Apparent activation energies accounting for the mass loss at each stage were obtained.

3. Results and Discussion 3.1. Sample Characterization Figure1 shows the XRD diffractogram of the sample used in this work, compared with the ICDD-PDF 96-900-7692, which belongs to rhodochrosite (MnCO3). In this diffractogram, a compact hexagonal structure is observed, with crystal lattice parameters of a = 4.773 Å and c = 15.642 Å, these parameters were calculated with Match! software (Version 3,

Minerals 2021, 11, 34 Crystal Impact - Dr. H. Putz & Dr. K.Brandenburg GbR, Kreuzherrenstr. 102,4 of 53227 13 Bonn, Germany). The diffractogram only shows peaks characteristic of rhodochrosite.

•

• 96-900-7692 Rhodochrosite

(MnCO3) Intensity (a.u.) Intensity

• • • • • • • •• • • •• • ••

20 30 40 50 60 70 80 90 2 theta (Cu ) kα Figure 1. 1. RhodochrositeRhodochrosite X-ray X-ray diffrac diffractiontion (XRD) (XRD) diffractogram. diffractogram.

TableTable 11 shows shows the the chemical chemical analysis analysis performed performed using XRF using and small XRF amounts and small of iron, amounts of magnesium,iron, magnesium, silicon, silicon,and calcium and were calcium found; were these found; cations these are cationspresent in are additional present incar- additional bonates species as impurities in the studied mineral. However, the high content of man- carbonates species as impurities in the studied mineral. However, the high content of ganese confirms that the mineral sample is rhodochrosite. The manganese is frequently replaced by iron, magnesium and/or calcium as shown in this formula: (Fe, Mg, Ca)CO3. These substitutions of other elements for manganese change the composition and alter the specific gravity, hardness, and color of the mineral. The bright pink color can become grayish, yellowish, or brownish in response to this chemical variability. A complete solid solution series exists between rhodochrosite and siderite (FeCO3). Likewise, quantitative elemental chemical analysis was performed by AAS, showing results similar to those obtained by XRF, manganese being the element present in major proportion in the sample.

Table 1. Rhodochrosite chemical analyses by X-ray fluorescence (XRF) and Atomic Absorption Spectrometry (AAS).

Element wt. % AAS Compound wt. % XRF Mg 5.21 MgCO3 4.91 Si without detection SiO2 2.95 Ca 1.03 CaCO3 0.53 Mn 87.92 MnCO3 86.89 Fe 5.79 FeCO3 4.72

Figure 2a shows a different particle sizes and Figure 2b shows the analysis performed by EDX on the rhodochrosite sample. The characteristic peaks of Mn, Ca, Si, Mg, Fe, and O are observed in the spectrum, which is consistent with the analysis performed by XRF. The calcium, iron and magnesium are present as carbonates species, while silicon is found as oxide.

Minerals 2021, 11, 34 4 of 12

manganese conﬁrms that the mineral sample is rhodochrosite. The manganese is frequently replaced by iron, magnesium and/or calcium as shown in this formula: (Fe, Mg, Ca)CO3. These substitutions of other elements for manganese change the composition and alter the speciﬁc gravity, hardness, and color of the mineral. The bright pink color can become grayish, yellowish, or brownish in response to this chemical variability. A complete solid solution series exists between rhodochrosite and siderite (FeCO3). Likewise, quantitative elemental chemical analysis was performed by AAS, showing results similar to those obtained by XRF, manganese being the element present in major proportion in the sample.

Table 1. Rhodochrosite chemical analyses by X-ray ﬂuorescence (XRF) and Atomic Absorption Spectrometry (AAS).

Element wt. % AAS Compound wt. % XRF

Mg 5.21 MgCO3 4.91 Si without detection SiO2 2.95 Ca 1.03 CaCO3 0.53 Mn 87.92 MnCO3 86.89 Fe 5.79 FeCO3 4.72

Figure2a shows a different particle sizes and Figure2b shows the analysis performed by EDX on the rhodochrosite sample. The characteristic peaks of Mn, Ca, Si, Mg, Fe, and O are observed in the spectrum, which is consistent with the analysis performed by XRF. Minerals 2021, 11, 34 The calcium, iron and magnesium are present as carbonates species, while silicon5 of is13 found

as oxide.

FigureFigure 2. Imagen 2. Imagen of rhodochrosite of rhodochrosite by by Field Field Emission Emission Scanning Scanning Electron Microscopy Microscopy (FESEM) (FESEM) (a) and (a) andEnergy Energy Dispersive Dispersive X-ray SpectrometryX-ray Spectrometry (EDX) (EDX) spectrum spectrum (b). (b).

FigureFigure3 shows 3 shows the the results results ofof the thermogr thermogravimetricavimetric and and differential differential thermal thermal analysis analysis (TG-DTG)(TG-DTG) of of the the rhodochrosite rhodochrosite sample, whic whichh was was carried carried out outat temperatures at temperatures ranging ranging fromfrom 100 100◦C °C to to 1200 1200◦ C.°C.The The samplesample undergoe undergoess three three mass mass losses losses during during the thermal the thermal anal- analy- sis.ysis. The The first first mass mass loss loss is is 27.5%, 27.5%, whichwhich starts starts at at 350 350 °C◦ andC and ends ends at approximately at approximately 660 °C. 660 ◦C. It is attributed to the transformation of manganese carbonate (MnCO3) into manganese III It is attributed to the transformation of manganese carbonate (MnCO3) into manganese III oxideoxide (Mn (MnO2O);3); this this isis confirmedconfirmed by by the the XRD XRD analysis analysis (Figure (Figure 4), 4which), which matches matches the oxide the oxide reference2 data3 ICDD-PDF 96-900-752. In this first mass loss, the carbonate dissociation reference data ICDD-PDF 96-900-752. In this first mass loss, the carbonate dissociation results in the emission of CO2. The second mass loss starts at approximately 660 °C and◦ results in the emission of CO2. The second mass loss starts at approximately 660 C and ends at 800◦ °C and is attributed to the conversion of manganese (III) oxide to manganese ends(II, at III) 800 oxide;C andthis is attributedconfirmed again to the by conversion XRD, where of Mn manganese3O4 was identified (III) oxide according to manganese to (II,the III) ICDD-PDF oxide; this 96-900-1964 is confirmed pattern again (Figure by XRD, 4) [23,24]. where Finally, Mn3O the4 was third identified mass loss accordingof 1.4% to thewhich ICDD-PDF begins 96-900-1964at 800 °C and patternends at 910 (Figure °C, is4 )[attributed23,24]. to Finally, the decomposition the third mass of calcium loss of 1.4% whichcarbonate; begins this at 800can be◦C verified and ends by FESEM-ED at 910 ◦C,X is analysis, attributed made to theto calcined decomposition powders at of 900 calcium carbonate;°C which thisshows can all be the verified elements by detected FESEM-EDX in the initial analysis, sample made (Figure to 5), calcined except for powders cal- at 900cium◦Cwhich and carbon. shows Calcium all theelements carbonate detected is transformed in the initialinto oxide, sample however, (Figure the5), exceptsmall for amount of calcium in the residues was not detected by the EDX. The decomposition of iron and magnesium carbonates occurs at 350 and 600 °C respectively, remaining as oxides in the sample. The conversion of carbonate to manganese oxide occurs quickly and has been reported to be due to an endothermic reaction [16]. The product is α−Mn2O3, the stable manganese oxide species at temperatures up to 970 °C. In the second stage, the specimen releases oxygen, transforming into Mn3O4. Manganese carbonate is decomposed to MnO by heating under vacuum conditions or high temperatures (more than 1200 °C). Supplying oxygen to a sample of MnO formed by heating MnCO3 under vacuum results in Mn2O3 or Mn3O4, depending on the temperature, but not in MnO2, in this case, our sample present only 3 transformations, but the third mass loss is not attributed to manganese transformation [16]. Heating MnCO3 in air, however, yields α-MnO2 in a poorly crystallized form (Figure 4). Although the most stable form of manganese oxide is MnO, this species is formed at temperatures above 1200 °C in the heat treatment of MnCO3 in the presence of oxygen [15–18,23].

Minerals 2021, 11, 34 5 of 12

calcium and carbon. Calcium carbonate is transformed into oxide, however, the small amount of calcium in the residues was not detected by the EDX. The decomposition of iron and magnesium carbonates occurs at 350 and 600 ◦C respectively, remaining as oxides in the sample. The conversion of carbonate to manganese oxide occurs quickly and has been reported to be due to an endothermic reaction [16]. The product is α-Mn2O3, the stable manganese oxide species at temperatures up to 970 ◦C. In the second stage, the specimen releases oxygen, transforming into Mn3O4. Manganese carbonate is decomposed to MnO by heating under vacuum conditions or high temperatures (more than 1200 ◦C). Supplying oxygen to a sample of MnO formed by heating MnCO3 under vacuum results in Mn2O3 or Mn3O4, depending on the temperature, but not in MnO2, in this case, our sample present only 3 transformations, but the third mass loss is not attributed to manganese transformation [16]. Heating MnCO3 in air, however, yields α-MnO2 in a poorly crystallized form (Figure4) . Although the most stable form of manganese oxide is MnO, this species is ◦ Minerals 2021, 11, 34 formed at temperatures above 1200 C in the heat treatment of MnCO3 in6 of the 13 presence of Minerals 2021, 11, 34 6 of 13 oxygen [15–18,23].

105 105 100 0.08 100 0.08

95 580 °C

95 580 °C 90 0.06 90 27.5 wt. % 0.06 85 27.5 wt. % 85 80 80 0.04 0.04 75 665 °C 75 665 °C Mass Mass (%)

Mass Mass (%) 70 70 0.02

6.7 wt. % Derivative (%/°C) 0.02

6.7 wt. % Derivative (%/°C) 65 1.4 wt. % 65 1.4 wt. % 60 60 0.00 55 0.00

55 900 °C 50 900 °C 50 200 400 600 800 1000 1200 200 400 600 800 1000 1200 Temperature (°C) Temperature (°C) Figure 3. Thermogravimetric and derivative thermal analysis of rhodochrosite (TG-DTG). Figure 3. 3. ThermogravimetricThermogravimetric and derivative and derivative thermal thermal analysis of analysis rhodochrosite of rhodochrosite (TG-DTG). (TG-DTG).

3000 Mn3O4, 96-900-1964 3000 Mn3O4, 96-900-1964 Rhodochrosite calcined at 900 °C Rhodochrosite calcined at 900 °C

Mn2O3, 96-900-7521 2000 Mn2O3, 96-900-7521 2000 Rhodochrosite calcined at 750 °C Rhodochrosite calcined at 750 °C Intesity (a.u) Intesity Intesity (a.u) Intesity

1000 Rhodochrosite calcined at 450 °C 1000 RhodochrositeICDD-PDF 96-900-7692 calcined at 450 °C ICDD-PDF 96-900-7692

0 0 20 30 40 50 60 70 80 90 20 30 40 50 60 70 80 90 2 theta (degrees) 2 theta (degrees) Figure 4. XRD diffractogram of calcined powders of rhodochrosite at different temperatures. Figure 4. XRD diffractogram of calcined powders of rhodochrosite at different temperatures. Figure 4. XRD diffractogram of calcined powders of rhodochrosite at different temperatures.

Minerals 2021, 11, 34 6 of 12 Minerals 2021, 11, 34 7 of 13

Minerals 2021, 11, 34 7 of 13

Figure 5. (a) FESEM image of rhodochrosite calcinationcalcination residuesresidues (900(900 ◦°C)C) and (b)) EDXEDX analysis.analysis.

Figure 5. (a) FESEM image of rhodochrosite calcination residues (900 °C) and (b) EDX analysis. As shown in Figure6 6,, thethe FTIRFTIR analysisanalysis confirmsconfirms that that the the MnCO MnCO33 is decomposed toto α α ◦ α−-MnMn22O3 andand α−-MnMn2OO33 isis transformed transformed to to Mn Mn3O3O4. 4At. At 25 25 °C,C, three three intense intense bands bands appear appear at As shown in Figure 6,− the1 FTIR analysis confirms that the MnCO3 is decomposed to at 1404, 862 and 727 cm−1 , corresponding to the asymmetric stretching (ν ), in-plane (ν ) 1404, 862 and 727 cm , corresponding to the asymmetric stretching (ν3), in-plane3 (ν2) and2 α−Mn2O3 and α−Mn2νO3 is transformed to Mn3O4. At 25 °C,2 three− intense bands appear at and out-of-planeν4 ( 4) bending vibrations of the32− CO3 group respectively [25–30]; a very 1404,out-of-plane 862 and 727 ( )cm bending−1, corresponding vibrations to theof the asymmetric CO group stretching respectively (ν3), in-plane [25–30]; (ν2) and a very weak weak band appearing around 1080 cm−1 can be assigned to the ν symmetric stretching band appearingν around 1080 cm−1 can be assigned2− to the ν1 symmetric1 stretching vibration out-of-plane ( 4) bending vibrations of the CO3 group respectively [25–30]; a very weak −1 vibration [25,29], while those appearing at higher wavenumbers (2493 and− 18001 cm ) are band[25,29], appearing while thosearound appearing 1080 cm−1 can at higherbe assigned wavenumbers to the ν1 symmetric (2493 and stretching 1800 cm vibration) are probably [25,29],probablydue to while overtones due those to overtonesappearingor combination at or higher combination bands, wavenumbers freque bands,ntly (2493 frequentlyfound and 1800in carbonate foundcm−1) are in probably carbonateminerals [25]. miner- As dueals [to25 overtones]. As the calcinationor combination temperature bands, freque is increased,ntly found MnCOin carbonate3 is first minerals converted α[25]. toAsα -Mn2O3, the calcination temperature is increased, MnCO−3 1is first converted to− 1-Mn2O3, as evi-◦ theas evidencedcalcination bytemperature both the emergingis increased, sharp MnCO (603−31 is cm first )converted and broad to (500−α1-Mn cm2O3, )as peaks evi- (450 C) denced by both the emerging sharp (603 cm ) and broad (500 cm −) peaks1 (450 °C)2− and the dencedand the by diminishing both the emerging intensity sharp of(603 the cm bands−1) and1404, broad 862(500 and cm−1 727) peaks cm (450due °C) and to CO the3 of the diminishing intensity of the bands 1404, 862 and 727 cm−1 due to CO32− of the rhodochro- diminishingrhodochrosite. intensity Further of the increases bands 1404, in the862 calcinationand 727 cm−1 temperaturedue to CO32− of resulted the rhodochro- in the complete site. Further increases in the calcination temperature resulted in the complete decomposi- site.decomposition Further increases of the in carbonatethe calcination material temperature into a mixture resulted ofinα oxidesthe complete (α-Mn decomposi-2O3 and Mn3O4) at tion◦ of the carbonate material into a mixture◦ of oxidesα ( -Mn2O3 and Mn◦3O4) at 750°C and tion750 ofC the and carbonate finally purematerial Mn into3O4 aphase mixture at 950of oxidesC. As ( can-Mn be2O3 observed and Mn3O at4) 750at 750°CC no and evidence of 3 4 finallyfinally pure pure Mn Mn3O2−4 Ophase phase at 950 at 950°C. As°C. can As be can observed be observed at 750 °Cat 750no evidence °C no evidence of any of of any−1 of any of the CO3 characteristic vibration bands were found. The sharp peak at 564 cm is the CO2−32− characteristic vibration bands were found. The sharp peak at−1 564 cm−1 is due to thedue CO to3 α characteristic-Mn O and vibration the bands bands appearing were found. at 655, The 475 sharp cm− 1peakare attributedat 564 cm tois due Mn toO [30–32]. 2 3 −1 3 4 αα-Mn2 2O3 3 and the bands appearing at 655, 475−1 cm are attributed3 to4 Mn3O4 [30–32]. The The-Mn latterO and two the bands, bands togetherappearing with at 655, a weak, 475 cm rounded are attributed band observed to Mn O around [30–32].972 The cm −1 and −1 −1 latterlatter two two bands, bands, together together with with a weak, a weak, rounded rounded− band1 observedband◦ observed around around972 cm 972and cmthe and the the strong, sharp peak appearing at 606−1 cm at 900 C, are all assigned to Mn3O4 [30–33] strong,strong, sharp sharp peak peak appearing appearing at 606 at cm606 cmat 900−1 at °C, 900 are °C, all areassigned all assigned to Mn3O to4 [30–33] Mn3O 4 [30–33] stretching vibrations. stretchingstretching vibrations. vibrations. -1 900 °C -1

900 °C 606 cm -1 606 cm -1 475 cm

750 °C -1 475 cm

750 °C -1 -1 655 cm -1 -1 -1 -1

450 °C 655 cm 603 cm -1 -1 862 cm -1 1404 cm -1 -1

450 °C 475 cm 603 cm 862 cm 1404 cm -1 -1 727 cm Transmittance (%) Transmittance 603 cm -1 -1 475 cm -1 727 cm Transmittance (%) Transmittance -1 603 cm -1 -1 500 cm -1 1800 cm 2493 cm -1 -1 727 cm -1 500 cm 1800 cm MnCO3 25 °C2493 cm 862 cm -1 1404 cm -1

3000 2500 2000 1500 1000 500 727 cm MnCO3 25 °C 862 cm Wavenumber (cm-11404 cm ) 3000 2500 2000 1500 1000 500 FigureFigure 6. 6.FTIRFTIR spectra spectra of calcined of calcined powders powders of rhodochrosite of rhodochrosite at different at different temperatures. temperatures. Wavenumber (cm-1)

Figure 6. FTIR spectra of calcined powders of rhodochrosite at different temperatures.

Minerals 2021, 11, 34 7 of 12

Table2 shows the proposed reduction process taking place in the thermal treatment of rhodochrosite, specifying the initial and ﬁnal temperatures for the reactions that occur. These reactions are similar to those proposed by different authors, coinciding in the different thermal decomposition products and in the temperature ranges in which they are carried out [15,16,23].

Table 2. Proposed reactions occurring in the thermal decomposition of rhodochrosite.

Stage T0 Tf Reaction ◦ ◦ 1 1 350 C 660 C 2MnCO3 + 2 O2 → Mn2O3 + 2CO2 ◦ ◦ 1 2 660 C 780 C 3Mn2O3 → 2Mn3O4 + 2 O2 ◦ ◦ 3 780 C 900 C Mn3O4

3.2. Kinetics of Thermal Decomposition The kinetics of thermal decomposition was investigated considering the three mass losses experienced by the rhodochrosite. The method called “time to a given fraction” was used to determine the apparent activation energy for each of the stages [19–22]. By this method, it is possible to determine the apparent activation energy, Ea, in- dependent of the function f(y) in the rate equation; it is also possible to determine if Ea varies during the course of a transformation. The method is based on the fact that the fraction-transformed “y” and time “t” are functionally related, therefore it is possible to consider t as the dependent variable (see Equations (1)–(4))

dy = k· f (y) (1) dt

dt = k−1 f −1(y)dy (2) The time ty to transform a given fraction y = Y is then

Z y=Y −1 −1 ty = k f (y)dy (3) y=0

where ty is the time at a given transformation stage, k is the rate constant, y is the material transformed fraction, and f(y) is a function of y.

E 1 ln t = const − ln A + a (4) y R T

where A is the Arrhenius constant (frequency factor), Ea is the apparent activation energy, R is the ideal gases constant (8.3144 J mol−1 K−1), and T is the temperature in Kelvin (K). The rate constant can be estimated by the Arrhenius law. The time ty to the chosen value of the fraction transformed Y is determined from a series of isothermal experiments carried out at several temperatures. The integrated equation, where Ea represents the apparent activation energy for the time required to reach certain reaction progress, is given by Equation (6). The slope of the plot of ln ty versus 1000/T is then used to calculate Ea (Equation (6)) [19–22], which represents the apparent activation energy for the time required to reach certain reaction progress. The transformed fraction for the temperatures of each of the three stages was calculated using Equation (5), to determine the thermal decomposition kinetics and obtain the transformation at a given time [19,34,35].

(m0 − mt) y = (5) m0 − m f Minerals 2021, 11, 34 8 of 12

Minerals 2021, 11, 34 9 of 13 where y is the mass fraction reacted, m0 is the mass at the beginning of the experiment, mt is the mass at a given time t, and mf is the mass at the end of the experiment [36–38]. Figure7 shows the proﬁle of reacted fractions for each stage. The ﬁrst mass loss Figure 7 shows the profile of reacted fractions for each stage. The first mass loss (Fig- (Figure7a) has four temperatures, since it presents a long slope with a wide range of tem- ure 7a) has four temperatures, since it presents a long slope with a wide range of temper- peraturesatures and and isotherms isotherms of of different different temperatures temperatures can can be obtained. be obtained. These These four fourtemperatures temperatures showshow similar similar behavior. behavior. The The nextnext two mass mass losse lossess (Figure (Figure 7b,c)7b,c) exhibit exhibit non-linear non-linear behavior. behavior. Here,Here, only only three three temperatures temperatures werewere considered for for each each loss loss in the in thelast lasttwo twostages. stages.

1.2 1 a) b) 1 0.8 0.8 600 °C 0.6 550 °C 0.6 800 °C 500 °C 750 °C 0.4 0.4 450 °C 700 °C Transformed fraction (y) Transormed fraction0.2 (y) 0.2

0 0 024681012 024681012 Time (min) Time (min) 1.2 c) 1

0.8

0.6 1000 °C 900 °C 0.4 850 °C

Transformed fraction (y) 0.2

0 024681012 Time (min) FigureFigure 7. Transformed 7. Transformed fraction fraction of rhodochrosite of rhodochrosite thermal thermal decomposition: decomposition: (a )(a ﬁrst) first mass mass loss, loss, ( b(b)) second second massmass loss,loss, andand ( c)) third third mass loss. mass loss. Table 3 summarizes the temperatures of each stage of thermal decomposition, the Table3 summarizes the temperatures of each stage of thermal decomposition, the time time taken to reach 50% transformation (ty, y = 0.50), and the apparent activation energy takenvalues to reach obtained 50% from transformation Figures 8 to (t10.y, “y” y = could 0.50), have and theany apparenttransformation activation value, energy thus ob- values obtainedtaining fromsimilar Figures apparent8– 10activation. “y” could energy have values. any transformation value, thus obtaining similar apparent activation energy values. Table 3. Time taken to reach 50% of conversion (y = 0.5) from the data obtained in Figure 7. Table 3. Time taken to reach 50% of conversion (y = 0.5) from the data obtained in Figure7. Time to 50%, Temperature Ea Stage ln (tY) 1000/T (K−1) tY (min) (°C) −1 Time to 50%, (kJ∙mol E) a ◦ − Stage 5.181 ln (1.644tY) Temperature 450 ( C) 1000/T 1.383 (K 1) tY (min) (kJ·mol−1) 4.766 1.561 500 1.293 17.91 First 5.1814.029 1.6441.393 450 550 1.215 1.383 4.766 1.561 500 1.293 First 3.075 1.123 600 1.145 17.91 4.029 1.393 550 1.215 3.0755.240 1.1231.656 600 700 1.027 1.145 Second 2.976 1.089 750 0.977 112.41 5.240 1.656 700 1.027 1.430 0.357 800 0.931 Second 2.976 1.089 750 0.977 112.41 1.4302.275 0.3570.819 800 850 0.890 0.931 Third 1.470 0.385 900 0.852 64.69 2.275 0.819 850 0.890 0.982 −0.020 1000 0.785 Third 1.470 0.385 900 0.852 64.69 0.982 −0.020 1000 0.785 From Figure 8, the apparent activation energy of the first mass loss (27.5%) can be calculated. It results in an apparent activation energy of 17.91 kJ mol−1, with a frequency

Minerals 2021, 11, 34 10 of 13

factor of 3.607; thus, it is a process controlled by mass transfer (diffusion-controlled process) [20,22,34,35]. This is because the thermal stability of the carbonates increases with the size of the cations that compose them; in this way, for a given period, the stability grows with the group of alkaline earth towards alkali. The manganese carbonate does not have high thermal stability, hence, a slow mass transfer is sufficient for the transformation to manganese (III) oxide (Mn2O3), where manganese atoms are found at two different octahedral sites. Additionally, Mn2O3 has four short Mn−O bonds and two longer ones. Minerals 2021, 11, 34 This oxide (Mn2O3) has a greater capacity of oxygen adsorption providing more sta- 9 of 12 bility than MnCO3, since it is a type-p semiconductor, which leads to an increase in the catalytic performance of this species with respect to type-n semiconductors or insulators.

1.8 y = 2.15x - 1.28 R² = 0.91

1.6 (Y 0.5) = (Y

y 1.4 ln t ln

1.2 Minerals 2021, 11, 34 11 of 13

1 1 1.1 1.2 1.3 1.4 1.5 2 1000/T

Minerals 2021, 11, 34 Figure1.6 8. Determination of the apparent activation energy required for the conversion11 of of13 MnCO to Figure 8. Determinationy of= the13.52x apparent - 12.20 activation energy required for the conversion of MnCO3 3 toMn Mn22OO33. R² = 0.98 1.2 −1 The2 apparent activation energy for the second mass loss (6.7%) was 112.41 kJ mol , with a frequency factor of 199,386 (Figure 9), indicating a rate-controlling process (Y 0.5) = (Y

[20,22,34,35];Y 0.8 therefore, a greater amount of thermal energy is required to reduce manga- 1.6 2 3 3 4 neseln t (III) oxide (MnyO =) 13.52xand convert - 12.20 it to manganese tetroxide (Mn O ), also known as +2 +3 +2 hausmannite.0.4 This oxide hasR² a= distorted 0.98 spinel structure, (Mn [Mn2 ]O4), where Mn cat- +3 ions occupy1.2 tetrahedral sites and Mn cations occupy octahedral sites.

(Y 0.5) = (Y 0

Y 0.80.92 0.94 0.96 0.98 1 1.02 1.04

ln t 1000/T 0.4

Figure 9. Determination of the apparent activation energy required for the conversion of Mn2O3 to Mn3O4. 0 Finally,0.92 the apparent 0.94 activation 0.96 energy 0.98 (Figure 10) 1 corresponding 1.02 to the 1.04 third mass loss was found to be 64.69 kJ mol−1, with1000/T a frequency factor of 475,230; this indicates that the transformation is also conducted by a rate-controlling process [20,22,34,35]. The third Figure 9. Determination of the apparent activation energy required for the conversion of Mn2O3 to massFigure loss 9. Determination is only 1.4%, of and the itapparent can be attribactivationuted energy to the requireddecomposition for the conversion of calcium of carbonate Mn2O3 to (CaCOMnMn3O34O. 34),. which is present as an impurity in the mineral [39,40].

Finally,1 the apparent activation energy (Figure 10) corresponding to the third mass loss was found to be 64.69 kJ mol−1, with a frequency factor of 475,230; this indicates that the transformation0.8 is also conducted by a rate-controlling process [20,22,34,35]. The third mass loss is only 1.4%, and it can be attributed to the decomposition of calcium carbonate (CaCO0.63), which is presenty = 7.78x as an -impurity 6.16 in the mineral [39,40]. R² = 0.96 0.41 (Y 0.5) = (Y Y 0.20.8 ln t ln 0.6 y = 7.78x - 6.16 0 R² = 0.96 0.4

(Y 0.5) = (Y -0.2

Y 0.78 0.8 0.82 0.84 0.86 0.88 0.9 0.2 ln t ln 1000/T 0 Figure 10. Determination of the energy required for the decomposition of CaCO3. Figure 10. Determination of the energy required for the decomposition of CaCO3. -0.2 4. Conclusions0.78 0.8 0.82 0.84 0.86 0.88 0.9 An XRF analysis of the rhodochrosite1000/T sample obtained from the mining district of Molango, Hidalgo, Mexico, indicates the presence of 86.89% manganese carbonate

(MnCO3); this was verified with the XRD analysis. According to the thermogravimetric analysis,Figure 10. threeDetermination mass losses of the of energythe mineral required rhodoc for thehrosite decomposition were found. of CaCO The first3. loss of 27.5% is attributed to the conversion of the carbonate to manganese (III) oxide with an activation energy4. Conclusions of 17.91 kJ mol−1. The second loss is attributed to the conversion of manganese (III) An XRF analysis of the rhodochrosite sample obtained from the mining district of Molango, Hidalgo, Mexico, indicates the presence of 86.89% manganese carbonate (MnCO3); this was verified with the XRD analysis. According to the thermogravimetric analysis, three mass losses of the mineral rhodochrosite were found. The first loss of 27.5% is attributed to the conversion of the carbonate to manganese (III) oxide with an activation energy of 17.91 kJ mol−1. The second loss is attributed to the conversion of manganese (III)

Minerals 2021, 11, 34 10 of 12

From Figure8, the apparent activation energy of the ﬁrst mass loss (27.5%) can be calculated. It results in an apparent activation energy of 17.91 kJ mol−1, with a frequency factor of 3.607; thus, it is a process controlled by mass transfer (diffusion-controlled process) [20,22,34,35]. This is because the thermal stability of the carbonates increases with the size of the cations that compose them; in this way, for a given period, the stability grows with the group of alkaline earth towards alkali. The manganese carbonate does not have high thermal stability, hence, a slow mass transfer is sufﬁcient for the transformation to manganese (III) oxide (Mn2O3), where manganese atoms are found at two different octahedral sites. Additionally, Mn2O3 has four short Mn−O bonds and two longer ones. This oxide (Mn2O3) has a greater capacity of oxygen adsorption providing more stability than MnCO3, since it is a type-p semiconductor, which leads to an increase in the catalytic performance of this species with respect to type-n semiconductors or insulators. The apparent activation energy for the second mass loss (6.7%) was 112.41 kJ mol−1, with a frequency factor of 199,386 (Figure9), indicating a rate-controlling process [20,22,34,35]; therefore, a greater amount of thermal energy is required to reduce manganese (III) oxide (Mn2O3) and convert it to manganese tetroxide (Mn3O4), also known as hausmannite. +2 +3 +2 This oxide has a distorted spinel structure, (Mn [Mn2 ]O4), where Mn cations occupy tetrahedral sites and Mn+3 cations occupy octahedral sites. Finally, the apparent activation energy (Figure 10) corresponding to the third mass loss was found to be 64.69 kJ mol−1, with a frequency factor of 475,230; this indicates that the transformation is also conducted by a rate-controlling process [20,22,34,35]. The third mass loss is only 1.4%, and it can be attributed to the decomposition of calcium carbonate (CaCO3), which is present as an impurity in the mineral [39,40].

4. Conclusions An XRF analysis of the rhodochrosite sample obtained from the mining district of Molango, Hidalgo, Mexico, indicates the presence of 86.89% manganese carbonate (MnCO3); this was verified with the XRD analysis. According to the thermogravimetric analysis, three mass losses of the mineral rhodochrosite were found. The first loss of 27.5% is attributed to the conversion of the carbonate to manganese (III) oxide with an activation energy of 17.91 kJ mol−1. The second loss is attributed to the conversion of manganese (III) oxide into manganese (II,III) tetroxide (Mn3O4). In this oxide reduction, an apparent activation energy of 112.41 kJ mol−1, was calculated, indicating that the conversion depends entirely on the temperature. XRD and FTIR analysis were used to identify the residues after each of the mass losses, which confirming the observed material composition changes. Kinetic parameters show that not much energy is required to convert manganese carbonate into its different oxides; however, high temperatures are required to decontami- nate rhodochrosite due to the thermal stability of the different carbonates contained in the mineral. With the kinetic parameters obtained (activation energy and the frequency factor), the fuel required to feed the nodulation furnaces can be calculated.

Author Contributions: Formal analysis, J.C.J.; Investigation, I.A.R., M.F. and C.A.P.; Methodology, H.I. and A.M.T.; Supervision, E.G.P. and M.R. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: All data presented is original. Conﬂicts of Interest: The authors declare no conﬂict of interest.

References 1. Wolfram, O.; Krupp, R.E. Hydrothermal solubility of rhodochrosite, Mn (II) speciation, and equilibrium constants. Geochim. Cosmochim. Acta 1996, 60, 3983–3994. [CrossRef] Minerals 2021, 11, 34 11 of 12

2. Kim, S.T.; Kang, J.O.; Yun, S.T.; O’Neil, J.R.; Mucci, A. Experimental studies of oxygen isotope fractionation between rhodochrosite (MnCO3) and water at low temperatures. Geochim. Cosmochim. Acta 2009, 73, 4400–4408. [CrossRef] 3. Casaletto, M.P.; Fierro, G. Surprising formation of a rhodochrosite-like (MnCO3) phase on Co-Zn-Mn sintered spinels upon storage at room temperature and ambient air. Appl. Surf. Sci. 2017, 421, 97–108. [CrossRef] 4. Thackeray, M.M.; Johnson, C.S.; Vaughey, J.T.; Li, N.; Hackney, S.A. Advances in manganese-oxide composite electrodes for lithium-ion batteries. J. Mater. Chem. 2005, 15, 2257–2267. [CrossRef] 5. Yabuuchi, N.; Kajiyama, M.; Iwatate, J.; Nishikawa, H.; Hitomi, S.; Okuyama, R.; Usui, R.; Yamada, Y.; Komaba, S. P2-type Na(x)[Fe(1/2)Mn(1/2)]O2 made from earth-abundant elements for rechargeable Na batteries. Nat. Mater. 2012, 11, 512–517. [CrossRef][PubMed] 6. Venkatesan, T.; Rajeswari, M.; Dong, Z.W.; Ogale, S.B.; Ramesh, R. Manganite-Based Devices: Opportunities, Bottlenecks and Challenges. Philos. Trans. R. Soc. Lond. Ser. A 1998, 356, 1661–1680. [CrossRef] 7. Edwin Suresh Raj, A.M.; Mallika, C.; Sreedharan, O.M.; Nagaraja, K.S. Manganese oxide–manganese tungstate composite humidity sensors. Mater. Lett. 2002, 53, 316–320. [CrossRef] 8. Cui, X.; Liu, G.; Lin, Y. Amperometric biosensors based on carbon paste electrodes modified with nanostructured mixed-valence manganese oxides and glucose oxidase. Nanomed. Nanotechnol. 2005, 1, 130–135. [CrossRef][PubMed] 9. Kim, K.J.; Park, Y.R. Sol–gel growth and structural and optical investigation of manganese-oxide thin films: Structural transformation by Zn doping. J. Cryst. Growth 2004, 270, 162–167. [CrossRef] 10. Nakamura, H.; Kohn, K. Magnetoelectric effect of rare earth manganese oxide RMn2O5. Ferroelectrics 1997, 204, 107–114. [CrossRef] 11. Wang, C.; Guo, G.C.; He, L. Ferroelectricity Driven by the Noncentrosymmetric Magnetic Ordering in Multiferroic TbMn2O5: A First-Principles Study. Phys. Rev. Lett. 2007, 99, 1–4. [CrossRef][PubMed] 12. Pereira, M.J.; Lima, M.M.F.; Lima, R.M.F. Calcination and characterization studies of a Brazilian manganese ore tailing. Int. J. Miner. Process. 2014, 131, 26–30. [CrossRef] 13. Gao, Y.; Olivas-Martinez, M.; Sohn, H.Y.; Kim, H.G.; Kim, C.W. Upgrading of low grade manganese ore by selective reduction of iron oxide and magnetic separation. Metall. Mater. Trans. B 2012, 43, 1465–1475. [CrossRef] 14. Loofbourow, R.L. Mining Methods and Costs at Granada Gold Mines, Ltd. Rouyn, Quebec; University of Michigan Library: Quebec, QC, Canada, 1933. 15. Available online: https://www.autlan.com.mx/en/business-units/autlan-manganese/molango-unit/ (accessed on 31 Au- gust 2020). 16. Kissinger, H.G.; McMurdie, H.F.; Simpson, B.S. Thermal Decomposition of Manganous and Ferrous Carbonates. J. Am. Ceram. Soc. 1955, 24, 168–172. [CrossRef] 17. Biernacki, L.; Pokrzywnicki, S. The thermal decomposition of manganese carbonate. J. Therm. Anal. Calorim. 1999, 55, 227–232. [CrossRef] 18. Fazeli, A.R.; Taren, J.; Basavalingu, B.; Bhandage, G.T. Standard thermodynamic data for Rhodochrosite from equilibrium decomposition curve. Proc. Indian Acad. Sci. (Earth Planet. Sci.) 1991, 100, 37–40. 19. Putnis, A. Introduction to Mineral Sciences; Cambridge University Press: Cambridge, UK, 1992. 20. Hidalgo, T.; Kuhar, L.; Beinlich, A.; Putnis, A. Kinetics and mineralogical analysis of copper dissolution from a bor- nite/chalcopyrite composite sample in ferric-chloride and methanesulfonic-acid solutions. Hydrometallurgy 2019, 188, 140–156. [CrossRef] 21. Jiménez, A.; Prieto, M. Thermal Stability of Ettringite Exposed to Atmosphere: Implications for the Uptake of Harmful Ions by Cement. Environ. Sci. Technol. 2015, 49, 7957–7964. [CrossRef] 22. Redfern, S.A.T. The kinetics of dehydroxylation of kaolinite. Clay Miner. 1987, 22, 447–456. [CrossRef] 23. Available online: https://www.netzsch-thermal-analysis.com/en/materials-applications/batteries/manganese-oxide- reduction/ (accessed on 28 August 2020). 24. Zhao, Y.; Zhu, G.; Cheng, Z. Thermal analysis and kinetic modeling of manganese oxide ore reduction using biomass straw as reductant. Hydrometallurgy 2010, 105, 96–102. [CrossRef] 25. Ray, L.F.; Jiˇrí, C.; Godwin, A.A.; Marilla, J.D. Raman spectroscopic study of the uranyl carbonate mineral voglite. J. Raman. Spectrosc. 2008, 39, 374–379. 26. Zhang, R.H.; Zhao, D.; Huang, M.; Yang, R.J.; Ma, F.X.; Fan, Y.C. Synthesis, crystal structure and photoluminescence properties of a new rare-earth carbonate Na3Eu(CO3)3·6H2O. J. Chil. Chem. Soc. 2017, 62, 3403–3406. [CrossRef] 27. Grunenwald, A.; Keyser, C.; Sautereau, A.M.; Crubézy, E.; Ludes, B.; Drouet, C. Revisiting carbonate quantification in apatite (bio) minerals: A validated FTIR methodology. J. Archaeol. Sci. 2014, 49, 134–141. [CrossRef] 28. Hu, H.; Xu, J.Y.; Yang, H.; Liang, J.; Yang, S.; Wu, H. Morphology-controlled hydrothermal synthesis of MnCO3 hierarchical superstructures with Schiff base as stabilizer. Mater. Res. Bull. 2011, 46, 1908–1915. [CrossRef] 29. Menezes, P.A.; Indra, A.; Bergmann, A.; Chernev, P.; Walter, C.; Dau, H.; Strasser, P.; Driess, M. Uncovering the prominent role of metal ions in octahedral versus tetrahedral sites of cobalt-zinc oxide catalysts for efficient oxidation of water. J. Mater. Chem. 2016, 1, 1–25. [CrossRef] 30. Ashoka, S.; Chithaiah, P.; Tharamani, C.N.; Chandrappa, G.T. Synthesis and characterisation of microstructural α-Mn2O3 materials. J. Exp. Nanosci. 2010, 5, 285–293. [CrossRef] Minerals 2021, 11, 34 12 of 12

31. Finocchio, E.; Busca, G. Characterization and hydrocarbon oxidation activity of coprecipitated mixed oxides Mn3O4/Al2O3. Catal. Today 2001, 70, 213–225. [CrossRef] 32. Julien, C.M.; Massot, M.; Poinsignon, C. Lattice vibrations of manganese oxides: Part I. Periodic structures. Spect. Acta A 2004, 60, 689–700. [CrossRef] 33. Lakshmi, S.V.; Pauline, S.; Vinosel, V.M. Microstructural Characteriztion of Trimanganese Tetra Oxide (Mn3O4) Nanoparticle by Solvothermal Method and Its Dielectric Studies. Int. J. Eng. Sci. Technol. 2014, 3, 123–131. 34. Ballester, A.; Verdeja, L.F.; Sancho, J. Metalurgia Extractiva, 2nd ed.; Síntesis: Barcelona, Spain, 2000; Volume I. 35. Levenspiel, O. Ingeniería de las Reacciones Químicas, 2nd ed.; Reverté: Barcelona, Spain, 2002. 36. Flores, M.U.; Reyes, I.A.; Palacios, E.G.; Patiño, F.; Juárez, J.C.; Reyes, M.; Teja, A.M.; Islas, H.; Gutiérrez, E.J. Kinetic analysis of the thermal decomposition of a synthetic mercury jarosite. Minerals 2019, 9, 200. [CrossRef] 37. Torrente, M.C.; Galán, M.A. Kinetics of the thermal decomposition of oil shale from Puertollano (Spain). Fuel 2001, 80, 327–334. [CrossRef] 38. Khachani, M.; Hamidi, A.E.; Kacimi, M.; Halim, M.; Arsalane, S. Kinetic approach of multi-step thermal decomposition processes of iron (III) phosphate dihydrate FePO4·2H2O. Thermochim. Acta 2015, 610, 29–36. [CrossRef] 39. Ingraham, T.R.; Marier, P. Kinetic studies on the thermal decomposition of calcium carbonate. Can. J. Chem. Eng. 1963, 41, 170–173. [CrossRef] 40. Kohobhange, S.P.K.; Manoratnea, C.H.; Pitawalab, H.M.T.G.A.; Rajapaksec, R.M.G. Thermal decomposition of calcium carbonate (calcite polymorph) as examined by in-situ high-temperature X-ray powder diffraction. J. Phys. Chem. Solids 2019, 134, 21–28.