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Article

Peculiarities of Hematite Reduction Using Waste Activated Sludge (WAS) Carbonization Products

by
Abigail Parra Parra
*,
Marina Vlasova
,
Pedro Antonio Márquez Aguilar
,
Jorge Luis Hernández Morelos
and
Manuel Eduardo Serrano Nava
Center for Research in Engineering and Applied Sciences, Morelos State Autonomous University (CIICAp-UAEMor), Av. Universidad 1001, Cuernavaca 62209, Morelos, Mexico
*
Author to whom correspondence should be addressed.
Compounds 2024, 4(3), 548-561; https://doi.org/10.3390/compounds4030033
Submission received: 1 March 2024 / Revised: 29 August 2024 / Accepted: 5 September 2024 / Published: 10 September 2024
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Abstract

:
In the present study, XRD, SEM/EDS, Raman, EMR/EPR spectroscopy, and vibrating sample magnetometry (VSM) were used to analyze the reduction of hematite by the carbonization products of waste activated sludge (WAS) at 500–1000 °C. The reduction process includes the following steps: α-Fe2O3 → Fe2O3 + Fe3O4 (Ttr~500 °C) → Fe3O4 (Ttr~600–700 °C) → FeO → Feamorph. (Ttr~1000 °C). The prevalence of certain phase compositions at different hematite reduction temperatures makes it possible to predict the areas viable for the application of reduced oxides: adsorbents (after Ttr~500 °C) → soft ferromagnetic materials (after Ttr~600–700 °C) → electrically engineered amorphous iron (after Ttr~1000 °C).

Graphical Abstract

1. Introduction

Although the reduction of iron oxides to metallic iron has been studied in sufficient detail [1,2,3,4,5], the improvement of these technological processes continues to this day, including the use of not only coal as a reducing agent [6,7,8] but also other solid carbon-containing reducing agents [9,10,11] and various gaseous media (CO, N2, CH4, vacuum) [8,11,12,13,14,15]. Regardless of the technology chosen for obtaining metallic Fe, the general scheme for the reduction of iron oxides consists of the stages (or combination of this stages) seen in Scheme 1, which indicates the strategic direction of the reduction of hematite only down to iron.
When using coal, metallic iron is smelted at 1200 °C. However, depending on the type of reducing agent used and the composition of the gaseous medium, the transition temperatures of higher oxides to lower oxides and of lower oxides to the metal may decrease, as shown in works [16,17,18]. See Scheme 2.
From Scheme 2 it follows that, depending on the processing temperature of mixtures of waste-activated sludge (WAS) and powdered hematite (Fe2O3), samples consisting of poorly ordered carbon and various lower iron oxides can be obtained. So, from mixtures processed in the range Ttr = 800–1000 °C, it is possible to obtain specimens with a heating temperature in the range of ~100 °C to 600 °C [17]. From mixtures sintered at 1000 °C and with a subsequent slow-cooling mode, amorphous iron is synthesized in a stable state [18].
Since the reduction products of α-Fe2O3- WAS mixtures contain ferrimagnetic iron oxide (Fe3O4) and poorly ordered carbon, the aim of this work was to study the composition of the products formed in the low-sintering-temperature range of these initial mixtures (500–700 °C), in addition to the already-studied properties of their high-temperature treatment products (Ttr = 800–1000 °C) [16,17,18,19]. It was assumed that the analysis of the physicochemical properties of the new composites formed within the temperature range of 500–1000 °C would allow us not only to predict the areas of their application (electrical engineering, electronics, and chemistry) but also to illustrate the prospect of using WAS in the process of metal oxide reduction.
As noted in [19], during the low-temperature treatment of WAS, weakly ordered reactive forms of carbon are first formed. This means that it is at this stage that the Fe2O3 reduction process should proceed quickly and significantly, depending on standard technological parameters such as the component ratio (WAS/α-Fe2O3), heat treatment temperature and time, and the composition of the gaseous medium (atmosphere). However, there are no data in the literature on the use of WAS carbonization products for the reduction of iron oxides.
WAS, as a supplier of reactive carbon, was chosen for the following reasons: (a) this type of waste, which comes from wastewater treatment plants and is hazardous to the environment, occupies large areas of dumps [20]; (b) no types of WAS recycling are widely used due to their high energy costs [20]. At the same time, as established in [16,17,18,19], the temperature treatment of WAS in a reducing medium is accompanied by its carbonization. As the processing temperature increases from 400 °C to 1000 °C, various forms of carbon are formed, from slightly ordered carbon with a high content of free (dangling) carbon bonds (nanostructure) to carbon phases with an amorphous structure or a partially ordered structure [21].

2. Materials and Methods

2.1. Precursors and Starting Materials

In this study, samples were prepared from a homogeneous mixture of α-Fe2O3 powder (reactive, with 99.99% purity, from “Reactivos Química Meyer”, Mexico city, Mexico) and waste-activated sludge (WAS) at a humidity of ~40%. As shown in Table 1, clay and sand are present in the WAS, along with organic components. Therefore, low-temperature iron oxide reduction products are “contaminated” by these components. After the temperature treatment (Ttr = 600 °C, ttr = 30 min, in conditions of oxygen deficit) of WAS, the waste’s composition includes a number of elements absorbed from wastewater (see Table 2). The data from Table 1 and Table 2 indicate that the “resulting material” can be used in technical but not medical applications.

2.2. Preparation Method

Homogenous mixtures were prepared from WAS and α-Fe2O3. The α-Fe2O3 content varied in the range of 40–60 wt.%, and the WAS content changed in the range of 60–40 wt%. The obtained slimy mixtures were dried for 3 days and then placed in a vacuum chamber with a pressure of 1.3 Pa. The chamber was purged with argon for 10 min. Then, the powder mixtures were placed in steel capsules with covers. The volume of the steel capsules was 34.55 cm3. The volume of dried mixture inside the capsules was 15.00 cm3. After that, the capsules were transferred to a muffle furnace. The heat treatment of the mixtures was carried out at 500, 600, and 700 °C for 30 min and 800, 900, and 1000 °C for 60 min. Three series of samples were prepared to obtain reliable measurements.

2.3. Characterization

The obtained specimens were investigated via X-ray diffraction (XRD) using Cu Kα radiation (Siemens D-500 diffractometer, Bruker, Karlsruhe, Germany). For a semi-quantitative assessment of the crystalline phases’ content, the following formula was used: I = A100·B, where I is the peak intensity in arbitrary units, A100 is the amplitude of the strongest line, and B is the peak width at half maximum. The contents of oxides and carbon in the pure WAS after treatment at 600 °C for 30 min were determined with the use of an X-ray Fluorescence S8TIGER spectrometer (Bruker, Karlsruhe, Germany). Electron microscopy studies and Energy Dispersive X-ray spectroscopy (EDS) were performed using a Schottky FE-SEM (SU5000 HITACHI,(Tokyo, Japan)) with Detector XFlash (6–60 Bruker, Karlsruhe, Germany). A Raman spectroscopy study was performed using a Raman microscope Senterra 2, at 785 nm. The WAS’s magnetic properties were analyzed using a VSM in a Quantum Design PPMS Versalab system. A JEOL JES TE-300 instrument (JEOL, Inadaira, Tokyo), was used for the electron magnetic resonance (EMR) studies. The adsorption properties of the synthesized mixtures were evaluated by the UV–vis method using an USB4000-XR1 Ocean Optics spectrometer (Ocean Optics, Orlando, FL, USA). In this work, a 40 ppm aqueous solution of MB was used. The MB content was evaluated from changes in the intensity of the band in the UV–vis spectra at λ~665 nm and preliminarily prepared calibration graphs of C = f(I), where C is the dye concentration, and I is the intensity of the band in the UV–vis spectra.

3. Results and Discussion

3.1. X-ray Data

The low-temperature treatment of the Fe2O3-WAS mixtures is accompanied by the reduction of hematite to magnetite (Figure 1a,b and Figure 2a–c). At Ttr > 700 °C and over increasing heat treatment times, Fe oxide was gradually reduced to amorphous iron (Figure 1c and Figure 2d–f) [17]. This means that to obtain ferrimagnetic iron oxide (Fe3O4), it is necessary to carry out a heat treatment of the initial mixtures in the range Ttr = 600–700 °C for 30 min. After processing the mixtures in the region of 800–1000 °C for 60 min, in addition to amorphous iron, a small amount of Fe3O4 was present. This means that these samples must also have magnetic properties.

3.2. SEM/EDS Data

The hematite reduction process was accompanied by significant morphological transformations. If, during the low-temperature treatment of Fe2O3-WAS mixtures, powders with a particle size of ~0.1–0.2 μm are formed, then, as Ttr increases, their agglomeration, coarsening, and merging are noted (Figure 3). At Ttr = 1000 °C, the reduction product, that is, amorphous iron, is a 3D sample of the Fe plates with inorganic inclusions captured by the activated sludge during the process of water purification [17,18].
The EDS analysis shows that there are inhomogeneously distributed elements across the sample volume (Figure 4). After both low- and high-temperature treatments of the initial mixtures, the obtained specimens contain not only elements such as Fe, O, and C but also Al and Si. The last elements are “contamination traces” from WAS mixed with clay and sand. So, after Ttr = 500 °C, among the main components of the powder mixtures (carbon and iron oxides), one can detect “islands” of dehydrated clay and an accumulation of silica (sand) particles (see Figure 4). With a decrease in WAS content, the contents of Al and Si decreased (Table 3). A decrease in the carbon content with an increase in the Fe2O3 content in the initial mixtures corresponds to the participation of the carbon formed from WAS in the reduction of iron oxides (Table 3).

3.3. Raman Study

The Raman study of the samples after the low-temperature treatment (see Figure 5a) revealed the presence of Fe3O4 and disordered carbon. Changes in the intensity of the peak at 288 cm−1 (for Fe3O4) (Figure 5b) and the peak at 1315 cm−1 (Figure 5c), corresponding to disordered (amorphous) carbon, correlated with the reduction of Fe2O3 to Fe3O4 by disordered carbon [24,25,26]. These results are consistent with the XRD data and EDS data (see Figure 2b,c and Figure 5a,b and Table 3).

3.4. Electron Magnetic Resonance Study

Note that when studying both paramagnetic and ferromagnetic resonant centers, the term electron magnetic resonance (EMR) is used as a more general term than the terms electron paramagnetic resonance (EPR), ferromagnetic resonance (FMR), etc. [27].
Because the processing of Fe2O3-WAS mixtures was conducted in the range of 500–1000 °C, the hematite reduction products changed their magnetic properties from antiferromagnetic to ferrimagnetic (Fe3O4, Fe) [27,28,29]. Accordingly, their magnetic resonance spectra changed significantly (Figure 6). The interpretation of these spectra is complicated by the fact that the Fe2O3 reduction products are not nanoparticles, but a collection of powder agglomerates of diverse sizes and are even solid. The spectra observed in the low-temperature samples can be attributed to the ferrimagnetic resonance spectra of aggregated Fe3O4 particles. As the processing temperature of the mixtures increases, the change in the view of spectra increasingly corresponds to the EMR of the metal. This indicates the completion of the reduction process of iron oxides to Fe at Ttr = 1000 °C [30].

3.5. Study of Magnetic Properties

A study of the ferromagnetic properties of the Fe2O3 reduction products is shown (Figure 7, Table 4), which indicates that these are soft ferromagnets. So, “pure” magnetite is a ferrimagnetic phase with high magnetization (92 emu/g) and low coercivity (100–400 Oe) [31]. For pure iron, the saturation magnetization is 217 emu/g, and its Hc changes from 0.5 to 1.20 Oe [32]. Amorphous iron-based alloys’ magnetization reaches 1.7 T and their coercivity Hc changes from 0.03 to 0.075 Oe [33,34].
From the data obtained, it can be concluded that the magnetic properties of the material depend on the composition of the initial mixtures and the heat treatment regimes used. This is due to the fact that, in the samples, after Ttr = 600–800 °C, the Fe3O4 phase is predominantly present; after Ttr = 900 °C, FeO is fixed; and, after Ttr = 1000 °C, the Fe amorphous phase is present [16,17,18]. The overestimated values of Hc were due to the inclusion of SiO2, Al2O3, and C between the Fe3O4 crystallites or Fe lamellae.
Soft magnetic materials are used as magnetic cores in transformers, motor stators, radio engineering, etc. In this study, ferromagnetic powders were used to purify water of oil pollution. Figure 8 shows that after the Fe3O4 powder is applied to the surface of an oil slick, follicles that sink to the bottom are formed. Follicles are easily removed from the water using magnetic cleaning (with a neodymium magnet covered with film for the easy removal of powder + oil). The degree of the surface and water volume’s purification from oil products by the adsorbent depends on the volume of the spilled oil and the amount of adsorbent used. Therefore, for a single cleaning of 30 mL of water containing 3 mL of crude oil, 3 g of adsorbent is required. In these conditions, up to 95.5% of the pollutant was removed. For the 100% removal of hazardous impurities, secondary cleaning is required.
So, our studies have shown that the temperature treatment of WAS-Fe2O3 mixtures within the range of 500–1000 °C under conditions of oxygen deficiency leads to the formation of composite powders consisting of poorly/lowly ordered carbon and lower iron oxides up to amorphous iron (see Scheme 2). Depending on the composition of the initial mixtures and the heat treatment mode, it is possible to obtain materials with different electrical and magnetic properties. At the same time, the products of the low-temperature treatment of mixtures of WAS-Fe2O3, in the region of 500–700 °C, with a high content of active carbon and ferromagnetic iron oxides may be of interest as adsorbents.

3.6. Adsorption Properties

Currently, the wastewater treatment (in both domestic and industrial enterprises) of organic pollutants is an extremely pressing task. There are various methods of water purification, but the most widely used are activated carbon and clay purification and magnetic purification. Due to the large number of published works on this topic, we have highlighted several review works [35,36,37,38,39,40] and point out that technologies for producing inexpensive adsorbents are constantly being developed [41,42,43,44,45,46,47,48]. Recently, a new class of magnetically sensitive adsorbents has been presented, consisting of Fe3O4 and a second non-magnetic component (SiO2, C, Clinoptilolite, and others) [49,50,51,52,53,54]. Of great interest are the composite magnetic adsorbents Fe3O4-C [40,55], for which carbon is obtained in various ways: both via the activation of coals [56] and carbonization of organic components and wastes [50,51,57,58,59,60].
In this work, studies of the adsorption of methylene blue (MB) from an aqueous solution by Fe2O3-WAS samples subjected to Ttr from 500 °C up to 800 °C showed that “low-temperature” composite C-Fe3O4 powders (even with Fe2O3 additives) are effective adsorbents (Figure 9 and Figure 10). The presence of magnetic iron oxides in the resulting precipitate makes it easy to extract the precipitate from the purified solution via magnetic separation.
Thus, studies have shown that when temperature-treating Fe2O3-WAS mixtures in the range of 500–1000 °C and under conditions of oxygen deficiency, various sets of carbon and iron oxides are obtained, up to amorphous iron (see Scheme 2). Depending on the predominance of one or another type of iron oxide and the carbon content, within the use of the same technology it is possible to obtain composite materials with different properties and, therefore, uses in different engineering applications.

4. Conclusions

The temperature treatment of Fe2O3-WAS mixtures within the range of 500–1000 °C under conditions of oxygen deficiency made it possible to identify three important regions, which are characterized by distinct sets of Fe2O3 reduction products and by the low-ordered carbon formed during the thermodestruction of WAS.
In the low-temperature processing region (Ttr~500 °C), Fe2O3, Fe3O4, and C were formed. These powders have adsorption properties.
In the region of medium-temperature treatment (Ttr~600–700 °C), Fe3O4, and C are predominantly formed. These powders have magnetic properties and can be used to remove viscous films from the surface of less viscous liquids.
During high-temperature treatments (Ttr~1000 °C), amorphous iron is formed. This 3D material can be used in electrical engineering.

5. Patents

The authors declare that patents exist that are derived from this work in progress.

Author Contributions

Conceptualization, M.V. and P.A.M.A.; Formal analysis, M.V. and P.A.M.A.; Methodology, A.P.P., J.L.H.M. and M.E.S.N.; Writing—review and editing, A.P.P. and J.L.H.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Compounds 04 00033 sch001
Scheme 1. Stages of the iron oxides reduction process.
Scheme 1. Stages of the iron oxides reduction process.
Compounds 04 00033 sch001
Compounds 04 00033 sch002
Scheme 2. Iron oxide reduction process using WAS from 500°C to 1000°C.
Scheme 2. Iron oxide reduction process using WAS from 500°C to 1000°C.
Compounds 04 00033 sch002
Compounds 04 00033 g001
Figure 1. X-ray diffraction patterns of WAS-Fe2O3 mixtures treated at different temperatures (a–c). For γ-Fe2O3 (RRUFF ID: R140712.9); Fe3O4 (RRUFF ID: R080025.1); FexO [22]; Fe (JCPDS#6-0696); and Feamorph see [23].
Figure 1. X-ray diffraction patterns of WAS-Fe2O3 mixtures treated at different temperatures (a–c). For γ-Fe2O3 (RRUFF ID: R140712.9); Fe3O4 (RRUFF ID: R080025.1); FexO [22]; Fe (JCPDS#6-0696); and Feamorph see [23].
Compounds 04 00033 g001
Compounds 04 00033 g002
Figure 2. Change in intensity of diffraction peaks of Fe3O4 (for 2θ = 36.12°), FexO (for 2θ = 60.84°), and Fe (for 2θ = 45°) depending on WAS content in Fe2O3-WAS mixtures. In (a) samples Ttr = 500 °C, ttr = 30 min, (b) samples Ttr = 600 °C, ttr = 30 min, (c) samples Ttr = 700 °C, ttr =30 min, (d) samples Ttr = 800 °C, ttr = 60 min, (e) samples Ttr = 900 °C, ttr = 60 min and (f) samples Ttr = 1000 °C, ttr = 60 min.
Figure 2. Change in intensity of diffraction peaks of Fe3O4 (for 2θ = 36.12°), FexO (for 2θ = 60.84°), and Fe (for 2θ = 45°) depending on WAS content in Fe2O3-WAS mixtures. In (a) samples Ttr = 500 °C, ttr = 30 min, (b) samples Ttr = 600 °C, ttr = 30 min, (c) samples Ttr = 700 °C, ttr =30 min, (d) samples Ttr = 800 °C, ttr = 60 min, (e) samples Ttr = 900 °C, ttr = 60 min and (f) samples Ttr = 1000 °C, ttr = 60 min.
Compounds 04 00033 g002
Compounds 04 00033 g003
Figure 3. Micrographs of specimens obtained from mixture 60 wt.% WAS-40 wt.% Fe2O3 after temperature treatment at 500 °C, t = 30 min (a,a′); 800 °C, 60 min (b,b′); and 1000 °C, 60 min (c,c′).
Figure 3. Micrographs of specimens obtained from mixture 60 wt.% WAS-40 wt.% Fe2O3 after temperature treatment at 500 °C, t = 30 min (a,a′); 800 °C, 60 min (b,b′); and 1000 °C, 60 min (c,c′).
Compounds 04 00033 g003
Compounds 04 00033 g004
Figure 4. A map of the elemental distribution of the powder particles, obtained after their treatment with a 60 wt.% WAS-40 wt.% Fe2O3 mixture at 500 °C for 30 min.
Figure 4. A map of the elemental distribution of the powder particles, obtained after their treatment with a 60 wt.% WAS-40 wt.% Fe2O3 mixture at 500 °C for 30 min.
Compounds 04 00033 g004
Compounds 04 00033 g005
Figure 5. View of Raman shift (a) and change in peak intensity of Fe3O4 at 288 cm−1 (b) and of disordered carbon at 1315 cm−1 (c), depending on the mixture’s composition.
Figure 5. View of Raman shift (a) and change in peak intensity of Fe3O4 at 288 cm−1 (b) and of disordered carbon at 1315 cm−1 (c), depending on the mixture’s composition.
Compounds 04 00033 g005
Compounds 04 00033 g006
Figure 6. Types of resonance spectra of samples from various mixtures.
Figure 6. Types of resonance spectra of samples from various mixtures.
Compounds 04 00033 g006
Compounds 04 00033 g007
Figure 7. Magnetic hysteresis loops for the specimens obtained from a mixture of 50 wt.% WAS-50 wt.% Fe2O3 after treatment at 800, 900, and 1000 °C and for t = 60 min.
Figure 7. Magnetic hysteresis loops for the specimens obtained from a mixture of 50 wt.% WAS-50 wt.% Fe2O3 after treatment at 800, 900, and 1000 °C and for t = 60 min.
Compounds 04 00033 g007
Compounds 04 00033 g008
Figure 8. Removal of crude oil from water. In (a) water volume with oil film); (b) formed follicles after introduction of F3O4 powder on oil film; (c,d) extraction of follicles using a magnet; (e) water volume after removing the oil.
Figure 8. Removal of crude oil from water. In (a) water volume with oil film); (b) formed follicles after introduction of F3O4 powder on oil film; (c,d) extraction of follicles using a magnet; (e) water volume after removing the oil.
Compounds 04 00033 g008
Compounds 04 00033 g009
Figure 9. Adsorption of MB depending on the length of exposure (a), and view of water decolorization (b). In (a), 1 is the concentration of MB in ppm; 2 is the percentage of MB adsorption. The adsorbent was obtained using a mixture of 60 wt.% Fe2O3-40 wt.% WAS at Ttr = 500 °C, ttr = 30 min. The initial MB concentration in the water (10 mL) was 40 ppm. The weight of the powdered adsorbent was 0.7 g.
Figure 9. Adsorption of MB depending on the length of exposure (a), and view of water decolorization (b). In (a), 1 is the concentration of MB in ppm; 2 is the percentage of MB adsorption. The adsorbent was obtained using a mixture of 60 wt.% Fe2O3-40 wt.% WAS at Ttr = 500 °C, ttr = 30 min. The initial MB concentration in the water (10 mL) was 40 ppm. The weight of the powdered adsorbent was 0.7 g.
Compounds 04 00033 g009
Compounds 04 00033 g010
Figure 10. Adsorption of MB depending on the length of exposure (a), concentration of MB in water (b), and weight of the adsorbent (c). View of water decolorization (d). In (a–c), 1 is the concentration MB in ppm; 2 is the percentage of MB adsorption. The adsorbent was obtained using a mixture of 50 wt.% Fe2O3-50 wt.% WAS at Ttr = 700 °C, ttr = 30 min. The initial MB concentration in water (10 mL) was 40 ppm. For (a,b), the weight of the powdered adsorbent was 0.7 g.
Figure 10. Adsorption of MB depending on the length of exposure (a), concentration of MB in water (b), and weight of the adsorbent (c). View of water decolorization (d). In (a–c), 1 is the concentration MB in ppm; 2 is the percentage of MB adsorption. The adsorbent was obtained using a mixture of 50 wt.% Fe2O3-50 wt.% WAS at Ttr = 700 °C, ttr = 30 min. The initial MB concentration in water (10 mL) was 40 ppm. For (a,b), the weight of the powdered adsorbent was 0.7 g.
Compounds 04 00033 g010
Table 1. Composition and type of WAS.
Table 1. Composition and type of WAS.
ElementsContent, %
Organic material80.20
clay + sand19.80
type of WASorganic sludge in wastewater
texturesteaming slimy sand
Note: These data were presented by the ECCACIV (Morelos, Mexico).
Table 2. The content of compounds in waste-activated sludge (wt.%) treated at 600 °C for 30 min.
Table 2. The content of compounds in waste-activated sludge (wt.%) treated at 600 °C for 30 min.
FormulaCSiO2CaOAl2O3Fe2O3ZnOK2OTiO2CuOΣ
WAS after treatment98.65%0.66%0.12%0.17%0.15%0.035%0.02%0.02%0.06%0.115
Table 3. Content of elements in specimens after temperature treatment of WAS-Fe2O3 mixtures.
Table 3. Content of elements in specimens after temperature treatment of WAS-Fe2O3 mixtures.
Type of Mixture, wt.%Ttr, °C; ttr, Min.Content of Elements, wt.%
FeCOSiAl
40 WAS-60 Fe2O3500; 30
600; 30
800; 60
1000; 60		46.51
44.00
66.22
91.64		21.64
20.00
6.09
2.63		31.00
30.05
27.07
4.97		0.23
0.13
0.2
0.14		0.62
0.39
0.41
0.61
50 WAS-50 Fe2O3500; 30
600; 30
800; 60
1000; 60		48.43
37.00
58.02
92.9		17.57
28.00
19.82
2.65		33.33
28.80
20.18
1.61		0.59
1.99
1.02
1.31		0.12
0.58
0.96
2.34
60 WAS-40 Fe2O3500; 30
600; 30
800; 60
1000; 60		55.61
34.99
49.14
86.11		14.37
32.00
15.00
3.08		29.23
25.50
30.95
9.70		0.09
0.72
3.76
0.35		0.7
1.28
1.15
0.86
Table 4. Magnetic properties of specimens.
Table 4. Magnetic properties of specimens.
Reduction
Conditions		Composition of Mixtures, wt.%
60 Fe2O3-40 WAS50 Fe2O3-50 WAS40 Fe2O3-60 WAS
Ms,
emu/g		Hc, OeMs,
emu/g		Hc, OeMs, emu/gHc, Oe
600 °C, 30 min76.1740.878.210777.380.4
700 °C, 30 min74.329576.9812574.15105
800 °C, 60 min 3525
900 °C, 60 min 4424
1000 °C, 60 min 40150
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Parra Parra, A.; Vlasova, M.; Aguilar, P.A.M.; Morelos, J.L.H.; Nava, M.E.S. Peculiarities of Hematite Reduction Using Waste Activated Sludge (WAS) Carbonization Products. Compounds 2024, 4, 548-561. https://doi.org/10.3390/compounds4030033

AMA Style

Parra Parra A, Vlasova M, Aguilar PAM, Morelos JLH, Nava MES. Peculiarities of Hematite Reduction Using Waste Activated Sludge (WAS) Carbonization Products. Compounds. 2024; 4(3):548-561. https://doi.org/10.3390/compounds4030033

Chicago/Turabian Style

Parra Parra, Abigail, Marina Vlasova, Pedro Antonio Márquez Aguilar, Jorge Luis Hernández Morelos, and Manuel Eduardo Serrano Nava. 2024. "Peculiarities of Hematite Reduction Using Waste Activated Sludge (WAS) Carbonization Products" Compounds 4, no. 3: 548-561. https://doi.org/10.3390/compounds4030033

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