Experimental characterization of iron mining tailings as sustainable material for thermal energy storage

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Given the importance of steel, and therefore, iron ore mining, solutions are needed to recover this waste. Despite global efforts, the current proposed solutions struggle to reach the market due to cost-effectiveness issues. This study explores a potential solution, presenting iron tailings as a viable, economical, and sustainable material for thermal energy storage systems. This technology is crucial for addressing renewable energy intermittency and capturing industrial waste heat. The experimental analysis carried out confirm the effectiveness of iron tailings in this field, with a density of up to 450 kWh/m 3 . The material stands up safety, minimal environmental impact, and favourable thermophysical properties at a low investment cost. This innovative application not only addresses energy challenges but also contributes to resolving the waste management crisis in the iron mining industry. Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Environmental social sciences/Sustainability Iron Tailings Circular Economy Thermal Energy Storage Mining industry Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction Steel is the main material used in construction, manufacturing, transportation, and many other sectors, making iron ore and iron mining a critical activity for economic, social and technological development and infrastructure projects worldwide. Iron ore accounted for 93% of the metals mined in 2021, with 2,600 million tonnes extracted (Fig. 1 b) [1]. Furthermore, iron ore is produced worldwide. The US Department of the Interior and Geological Survey 2 collect statistics for this material, listed Australia as the largest producer of iron ore (Fig. 1 a). However, mining operations result in the production of massive volumes of waste materials, including the mine tailings that result from the beneficiation of the ore 3 . The accumulation of iron mine tailing is an environmental problem that has been much discussed, mainly due to the high amount annually generated. The global production of iron ore tailings in mining industry was estimated at 1.4 billion tonnes of tailings per year (Fig. 1 c) 4 . Achieving sustainable growth while addressing environmental concerns is paramount. There are many investigations for analyse the used iron ore tailings in different applications 5 , 6 . Open literature suggest that iron ore tailings can be converted into different types of ceramics 7 – 9 : tiles, glass, bricks, etc., including structural or functional materials such as cement, concrete 10 – 13 or road materials 14 – 16 . Most studies focus on civil engineering, but despite the growing body of research, many proposed solutions fail to penetrate the market to limited low cost-effectiveness. Consequently, there is an increasing tendency to diversify and look for other environmental applications in different fields 17 – 20 . In this way, this paper proposes a novel application of iron mining tailings in the energy storage sector, to solve two major problems in two major industries. Renewable energy sources, particularly solar and wind, dace the challenge of intermittent generation, heavily reliant on resource availability 21 . Energy storage systems are thus pivotal for enabling the widespread adoption of renewable energy by mitigating supply-demand imbalances 22 . There are different types of energy storage solutions that can be classified into five main groups: electrochemical (batteries), electrical, thermal, chemical and mechanical energy storage systems 23 . High temperature thermal energy storage (TES) promising solution for large-scale energy storage, offering higher load capacity and longer storage duration compared to battery technologies 24 . TES technologies, categorized into sensible heat, latent heat or thermochemical reactions, find applications in seasonal and bulk energy storage 25 . The last two are not yet mature, compared to sensible heat storage technology that is the most widely used system in large-scale concentrated solar power plants worldwide 26 . This technology is based on the ability of materials to heat up and cool down. The thermal energy is employed to increase the temperature of a material (liquid or solid, e.g., water, sand, molten salts, rocks…) that is later cooled down to recover the energy 27 . In comparison with the other two thermal storage technologies, sensible-thermal storage systems have relatively low capital costs 28 . The quantity of energy stored is mainly determined by the specific thermal capacity of the material. According to Khare et al. 29 appropriate material requires: Thermophysical properties: small density changes versus temperature, high heat capacity and heat transport properties. Chemical properties: chemical stability, non-toxic, non-flammable, low potential reactivity. Economic properties: abundant materials with low cost of manufacturing into suitable shapes. The highest commercially viable materials for sensible heat storage applications are water and different mixtures of molten salts 30 . Nevertheless, this storage system has many drawbacks related to the use of molten salts, particularly the relatively high cost of the storage components. As fossil fuel resources diminish and environmental policies evolve, the development of innovative, cost-effective, and efficient TES systems has become imperative for achieving global energy sustainability. Thus, the search for new low-cost storage materials is pivotal in attaining cost-effective thermal storage alternatives. Furthermore, the availability of storage material in sufficient quantity is a key factor. Lack of availability or even a conflict over the end use of the TES material can lead to price fluctuations and puts the development of storage systems at risk. The characteristics of the materials to be used have been extensively studied, but environmental aspects are often given less consideration in the selection of a storage material. Leveraging various industrial by-products as heat storage materials presents a viable with a dual objective: obtaining a viable and cost-effective TES material while reducing mining environmental impact. Several solutions have been proposed in this filed such as inert ceramics obtained from the treatment of the asbestos waste (Cofalit) 31 , fly ashes from the incineration of municipal solid waste 32 or ashes from coal-fired thermal power plants 33 . This study proposes iron tailings, which is one of the main wastes of the mining industry as a heat storage material. Introducing iron tailings into the energy recovery or production sectors opens new avenues for valorising this waste material while addressing pressing environmental and energy challenges. 2 Materials and methods The iron ore tailings samples were collected from an iron mine in Canada. An experimental design program for this research project was developed to achieve the presented objectives (Fig. 2 ). First, a comprehensive analysis of the physicochemical properties was performed according to international regulations. Then, different specific tests were carried out to analyse the thermal properties of the material. 2.1 Physicochemical analysis Iron tailings were characterized in terms of chemical composition (X-ray fluorescence, XRF) and physical properties (permeability, particle size distribution and density). XRF is an elemental, semi-quantitative analysis technique based on the ability of atoms to absorb energy from a source of X-ray radiation. As a consequence, secondary X-rays are emitted, which will have an intensity proportional to the concentration of the X-rays in the sample. an intensity proportional to the concentration of each element. The equipment used in this case is the ARL-ADVANT-XP. The permeability coefficient of iron tailings was determined using a constant load perimeter in which the vertical flow of water through a test tube is laminar according to ISO 17892-11:2019. Particle size distribution was obtained by sieving iron tailings (ISO 17892-4:2016) and density and porosity was determined according to ISO 17892-3:2015. 2.2 Thermal properties For thermal properties, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were performed using a simultaneous TGA/DTA and TGA/DSC thermal analyser (SETARAM TG-DSC Setsys). Thermogravimetry is based on the measurement of the change in mass of a sample when subjected to a change in temperature in a controlled atmosphere. In a DTA, both the sample and a reference material, which is thermally, physically and chemically inert, are subjected to a temperature variation. Thermogravimetry and calorimetry analysis are thermal analytical techniques in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature. TGA was performed from room temperature to 1000°C at a heating rate of 10°C/min, in an air atmosphere. DSC was conducted from room temperature up to 1000°C, heating speed of 10°C/min and in argon atmosphere to avoid reactive effects such as oxidation or combustion when using air. 3 Results and discussion 3.1 Physicochemical analysis The influence factors of chemical composition of iron tailings mainly depend on the local iron ore resources. Variety is mainly caused by the great difference of physical and chemical properties of iron ore resources in different parts of the world. The chemical composition of materials from different mines is showed in Fig. 3 . The tailings are mainly composed of SiO 2 but also have significant percentages of Fe 2 O 3 and Al 2 O 3 . Depending on the type of ore, appreciable amounts of CaO and MgO may be present. In the case of the iron tailings analysed in this work, they have a lower silica content which is compensated by a higher iron content. Tailings analysed have very fine size and 44.9% of void content. The particle–size distribution curve of tailings as received is shown in Fig. 4 . The density obtained for iron tailings are in consonance with different materials reported in literature which are used/studied as high temperature sensible TES materials such as high temperature concretes (2,250 kg/m 3 ) 34 , Cofalit (3,120 kg/m 3 ) 35 or castable ceramics (3,500 kg/m 3 ) 36 . High density improves energy storage density which reduces the volume of the thermal energy storage system 37 . Regarding the mean flow (0.0138 mL/s), hydraulic gradient (6.90 m/m) and permeability coefficient (5.04 x10 − 7 m/s) obtained, they report slightly lower values than conventional materials. 3.2 Thermal properties In order to determine the thermal stability of the iron tailings in the complete operation temperature range, thermalgravimetric analysis were carried out. Figure 5 a shows the measured mass difference obtained from the experiments as a function of temperature. The TGA results are usually presented as ‘mass loss’ (TG%) since, at the beginning of the test, the balance is tared to 0 and the losses of mass are represented by negative values from this initial point with a minimum value of -100% which would correspond to the total decomposition of the sample. As can be seen, there is a slight mass loss of about 1.5%. The rapid initial mass loss is characteristic of desorption or desiccation processes. From this point onwards, the loss may be related to the oxidation-reduction reactions that take place when the material is heated. Many elements in the materials can potentially be oxidised, such as metal oxides (at higher oxidation rates), and/or may remain as trace metals in the tailings. However, this is a very small variation despite the high temperatures, so that the performed thermal stability experiments show that iron tailings are stable up to, at least, 1000°C. Figure 5 b shows the DSC curves representing the power-energy (mW) variation as a function of temperature. An endothermic peak appears at around 590°C. Nevertheless, it does not imply a mass change, since it is not reflected in the TGA results, but associated with a phase transition. This phase change could be solid-solid or solid-liquid (melting). In any case, the appearance of an exothermic component after this transition can only be explained by understanding that the new phase formed is unstable, so this exothermic contribution in the DSC signal indicates a continuous transformation to a more stable phase. The specific heat curve obtained is showed in Fig. 5 c. An approximately constant trend is observed up to the temperature of 590°C associated with the transition observed in DSC analysis. From this temperature, a clear decrease is observed because the transition is associated with a phase change towards a metastable structure which produces an exothermic contribution. It should be noted that from about 800°C this exothermic contribution exceeds the value of the heat required to heat the sample. Therefore, from this temperature onwards, negative values are obtained. The maximum specific heat is recorded from 300°C with values around 990 J/kg K. The thermal conductivity of iron tailings was measured from room temperature up to 450°C (Fig. 6 ). From the density and specific heat data thermal diffusivity (α) values were obtained following the next Eq. ( 1 ): $$\:\lambda\:=\alpha\:·\rho\:·{C}_{s}$$ 1 Where λ is the thermal conductivity (W/mK), \(\:\rho\:\) is the density (g/cm 3 ) and C s (J/g K) is the specific heat capacity. An interval of maximum stability is observed between 100 and 275 degrees, with minimal variation in conductivity. Thermal diffusivity is a measure of how quickly a material reacts to temperature changes. Materials with a high thermal diffusivity will heat or cool quickly; conversely, substances with a low thermal diffusivity will heat or cool slowly. Thus, thermal diffusivity is an important property when considering unsteady-state heat transfer situations, that is, in the charge-discharge cycles. It can be seen in both cases that there is a noticeable decrease in conductivity and diffusivity from 300°C onwards. The results show very promising iron tailings properties for use as thermal energy storage material. Furthermore, the TGA analysis carried out demonstrated shows that there is hardly any mass variation, which ensures the thermal stability of iron tailings in a wide temperature range up to 1000°C. Overall, the results obtained indicate the high suitability of this mining waste for TES technologies. 3.3 Comparison of iron tailings with other TES materials Once the technical feasibility of iron tailings has been discussed, a comparison with other TES materials commonly used is presented (Table 1 ). Molten salt, concrete, sand, cast steel, NaCl and crushed rock are the most common solid sensible thermal energy storage materials, but the table also shows other residues that have been analysed as TES material such as EAF slag or fly ashes. Table 1 Comparisons between iron tailings and common thermal storage materials Material Specific Heat (J/kg K) Bulk density (kg/m 3 ) Thermal conductivity (W/m K) Price (€/t) Reference Rock 1000–1060 1500–2800 2.50–3.5 50–90 38 – 40 Alumina 800–1157 3950–3960 11.98 315 29 , 41 Concrete 850–920 2200–2300 1.50–2.37 80 41 , 42 Cast steel 600 7800 40.00 5000 43 , 44 Cast iron 560 7200 37.00 1000 45 Silica sand 710–900 2200–2500 1.83–2.25 20 44 , 46 Magnetite 850 4962 - 135 39 NaCl 850 2160 0.51 150 44 Water 2400 1000 - 1.5 47 Molten salts 1500–1600 1870–2600 0.52-2.00 625–700 41 , 48 , 49 BOF slag 910 3807 - - 39 Fly ashes 714 2962 1.16 - 50 Cofalit® 800–1034 3120 1.4–2.1 8 41 , 48 EAF slag 912 3770 1.41 - 41 Iron tailings 780–990 2948 0.12–0.25 - - The analysed iron tailings exhibit thermal properties similar to those of the materials currently in use. Although they have low thermal conductivity, they have a high calorific value and density. The specific heat and density properties enable the calculation of total energy stored (Q) as follows (2): $$\:Q=\rho\:{\:C}_{p}\:\varDelta\:T$$ 2 Where \(\:\rho\:\) is the density (kg/cm 3 ), C s (J/kg K) is the specific heat capacity and ΔT the temperature interval. Figure 7 presents a comparison between the energy stored (at 573K) in each of the materials and the energy cost. The cost of the waste has been taken as 0, assuming only transport costs are necessary. For the calculation, the maximisation of stored energy along with the minimization of total material cost have been considered as criteria. These results represent the theoretical minimum value, as the calculation does not account for practical thermal storage issues such as charge/discharge conditions, heat losses, and other parameters. As can be seen, iron tailings have a highly competitive performance. A preliminary estimate indicates the potential for a reduction of about 3 times the total cost of the current most used storage material (molten salts), which could lead to a significant cost reduction in the storage system and thus to a reduction of the LCOE (levelized cost of electricity). The performance of iron tailings is similar to Cofalit which is also cheap (8 €/t) although when it is treated by plasma torch, its price increases to (1200 €/t) 31 . 4 Conclusions Mine tailings are an unavoidable waste generated during iron ore mining operations, of which millions of tonnes are generated worldwide. Given the importance of steel, and therefore of iron ore mining, solutions are needed to recover this waste. On the other hand, research and development studies on thermal energy storage materials are a hot topic among the research community, particularly those focusing on sensible heat storage materials. Numerous scientists have worked on TES materials and their respective technologies. In this study, thermophysical and chemical characterization of iron tailings from the mining industry has been performed for its potential use as material for thermal storage systems. Up to temperatures of 590°C no change in the internal structure or phase transition of the material was noted, a temperature range within the normal working spectrum for other commonly used materials, such as molten salts. In cases requiring higher temperatures, more specific testing would be necessary, as the present analysis cannot ascertain whether the endothermic peak around 600°C indicates a solid-solid or solid-liquid phase change. Compared to materials currently in use, the heat capacity is medium (0.78–0.99 J/K-g) although the thermal conductivity is low (0.12–0.25 W/mK). According to the results obtained, each m 3 of iron tailing has a storage capacity of 464.53 kWh at very low cost, involving only the transport of the material. Replacing molten salt with iron tailings would mean a reduction of approximately 2.5 €/kWh. This study opens up a new potential market for the valorisation of the iron tailings produced linked to the field of renewable energies that no one had yet considered. This article sets out the first steps of the research, with future lines of development analysing the appropriate equipment for the incorporation of iron tailings and their viability on a pilot scale. The implementation of this environmentally friendly alternative would reduce the need to exploit natural resources, which in turn would lead to environmental and economic savings. It would also give a second life to a waste that is produced in large quantities worldwide, in line with the principles of the circular economy. Finally, the recovery of iron tailings would avoid the disposal of a huge amount of this industrial waste, which also entails significant environmental risks depending on the conditions of deposition. In the face of new climate trends, production should be reduced to the minimum necessary, and the reuse and recycling of elements that cannot be returned to the environment due to their properties should be encouraged. Declarations Author contributions Marina Díaz-Piloneta: Conceptualization, Methodology, Investigation, Writing Original Draft, Writing-Review & Editing, Visualization. Marta Terrados-Cristos, M ethodology, Investigation, Writing Original Draft, Supervision, Visualization. Francisco Ortega-Fernández, Conceptualization, Validation, Resources, Writing Original Draft, Supervision. Gemma Martínez-Huerta: Investigation, Writing-Review & Editing, Project administration. Valeriano Álvarez-Cabal: Methodology, Validation, Resources , Writing-original draft, Project administration. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6850038","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":473054952,"identity":"e1547b79-12d2-4dc2-9fb6-bb97e426d4ef","order_by":0,"name":"Marina Diaz-Piloneta","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIie3OwQsBQRTH8VdTby8vrjbiX3jaIlH+lZXa02wpVze1LnL2fyjnrVdc1F6VUlJODqKcJCtyoYmbw3wvM4f5ND8Am+0fk8dBACoGYAD8gaD/JYlfN+LvdmXmantc9taFqrM45zudRmsESg4m4gqyp2ddqg3DaX7MQSsCDHImwgLc1ugTxykhFg+BKsZhLM5B9DUlyX73JNmTcRgLlfthlJKlxjsppr+AcZgr1FXh6E52Xp04KKLCipFkkvnkpM9+k5P2ZkWXBpUG/a1x2IfUj+9tNpvN9t4N9u9AIsxND+oAAAAASUVORK5CYII=","orcid":"","institution":"University of Oviedo","correspondingAuthor":true,"prefix":"","firstName":"Marina","middleName":"","lastName":"Diaz-Piloneta","suffix":""},{"id":473054953,"identity":"9eb40e13-6ecf-4a6a-a5bf-62cb9b9e3cd3","order_by":1,"name":"Marta Terrados-Cristos","email":"","orcid":"","institution":"University of Oviedo","correspondingAuthor":false,"prefix":"","firstName":"Marta","middleName":"","lastName":"Terrados-Cristos","suffix":""},{"id":473054955,"identity":"12506652-4353-498a-9904-6bfd716de2e1","order_by":2,"name":"Gemma Martinez-Huerta","email":"","orcid":"","institution":"University of Oviedo","correspondingAuthor":false,"prefix":"","firstName":"Gemma","middleName":"","lastName":"Martinez-Huerta","suffix":""},{"id":473054959,"identity":"efd830ab-2479-487b-b7a7-2c1e2f7e5dde","order_by":3,"name":"Francisco Ortega-Fernandez","email":"","orcid":"","institution":"University of Oviedo","correspondingAuthor":false,"prefix":"","firstName":"Francisco","middleName":"","lastName":"Ortega-Fernandez","suffix":""},{"id":473054963,"identity":"289b58a7-2fa5-4fec-8d44-3f6d2f0282a2","order_by":4,"name":"Valeriano Alvarez-Cabal","email":"","orcid":"","institution":"University of Oviedo","correspondingAuthor":false,"prefix":"","firstName":"Valeriano","middleName":"","lastName":"Alvarez-Cabal","suffix":""}],"badges":[],"createdAt":"2025-06-09 02:53:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6850038/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6850038/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-24061-0","type":"published","date":"2025-11-17T15:56:51+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85005528,"identity":"638d5fc6-c3e1-496a-9aaf-862c2d78ea43","added_by":"auto","created_at":"2025-06-19 21:20:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":254455,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Iron ore main producers. (b) Metals production worldwide in 2021. (c) Iron tailings generation per year.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/fdb803f5c977459f48e49e19.png"},{"id":85005866,"identity":"4295abdd-4c76-4d19-be4f-6a71b7caac1a","added_by":"auto","created_at":"2025-06-19 21:28:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":51866,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental design program.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/68392f02afed38655ff6f47d.png"},{"id":85005525,"identity":"d40e0b83-94c9-407b-ae0f-27365be5c091","added_by":"auto","created_at":"2025-06-19 21:20:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":31742,"visible":true,"origin":"","legend":"\u003cp\u003eChemical composition of iron tailings analysed compared to other places.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/12db087d170306983fdb96f4.png"},{"id":85005527,"identity":"1ece4f96-6b69-4178-89a3-3bae15f96c91","added_by":"auto","created_at":"2025-06-19 21:20:51","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":79701,"visible":true,"origin":"","legend":"\u003cp\u003eParticle–size distribution curve of tailings as received.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/0e68467a5ffbfcab236dbaff.png"},{"id":85005538,"identity":"0e308a0d-66d9-4570-925d-068014d06297","added_by":"auto","created_at":"2025-06-19 21:20:51","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":270692,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Thermal gravimetric analysis of iron tailings. (b) Records of the DSC analysis. (c) Specific heat capacity of the sample as a function of temperature.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/d40731dfcea872ad08c14e52.png"},{"id":85005963,"identity":"bd507e41-3d1e-4969-823e-37952f6b3639","added_by":"auto","created_at":"2025-06-19 21:36:51","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":151191,"visible":true,"origin":"","legend":"\u003cp\u003eThermal conductivity and thermal diffusivity of iron tailings.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/99b7dd6695efe2f888a8d3e0.png"},{"id":85005536,"identity":"f63705f3-554f-44d1-8334-75f1f05b7546","added_by":"auto","created_at":"2025-06-19 21:20:51","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":175797,"visible":true,"origin":"","legend":"\u003cp\u003eComparison between storage density and energy cost of iron tailings and different materials.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/a0fe75bb00ab20027ded4e79.png"},{"id":96650112,"identity":"d137e247-02f2-49f6-b1a9-644837fefb80","added_by":"auto","created_at":"2025-11-24 16:08:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1680675,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6850038/v1/7df8c874-1b3d-42c9-ba20-93bb9bbc2e2f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Experimental characterization of iron mining tailings as sustainable material for thermal energy storage","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eSteel is the main material used in construction, manufacturing, transportation, and many other sectors, making iron ore and iron mining a critical activity for economic, social and technological development and infrastructure projects worldwide. Iron ore accounted for 93% of the metals mined in 2021, with 2,600\u0026nbsp;million tonnes extracted (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) [1]. Furthermore, iron ore is produced worldwide. The US Department of the Interior and Geological Survey \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e collect statistics for this material, listed Australia as the largest producer of iron ore (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eHowever, mining operations result in the production of massive volumes of waste materials, including the mine tailings that result from the beneficiation of the ore \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. The accumulation of iron mine tailing is an environmental problem that has been much discussed, mainly due to the high amount annually generated. The global production of iron ore tailings in mining industry was estimated at 1.4\u0026nbsp;billion tonnes of tailings per year (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec) \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Achieving sustainable growth while addressing environmental concerns is paramount.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThere are many investigations for analyse the used iron ore tailings in different applications \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Open literature suggest that iron ore tailings can be converted into different types of ceramics \u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e: tiles, glass, bricks, etc., including structural or functional materials such as cement, concrete \u003csup\u003e\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e or road materials \u003csup\u003e\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Most studies focus on civil engineering, but despite the growing body of research, many proposed solutions fail to penetrate the market to limited low cost-effectiveness. Consequently, there is an increasing tendency to diversify and look for other environmental applications in different fields \u003csup\u003e\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. In this way, this paper proposes a novel application of iron mining tailings in the energy storage sector, to solve two major problems in two major industries.\u003c/p\u003e \u003cp\u003eRenewable energy sources, particularly solar and wind, dace the challenge of intermittent generation, heavily reliant on resource availability \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Energy storage systems are thus pivotal for enabling the widespread adoption of renewable energy by mitigating supply-demand imbalances \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThere are different types of energy storage solutions that can be classified into five main groups: electrochemical (batteries), electrical, thermal, chemical and mechanical energy storage systems \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. High temperature thermal energy storage (TES) promising solution for large-scale energy storage, offering higher load capacity and longer storage duration compared to battery technologies \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTES technologies, categorized into sensible heat, latent heat or thermochemical reactions, find applications in seasonal and bulk energy storage \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The last two are not yet mature, compared to sensible heat storage technology that is the most widely used system in large-scale concentrated solar power plants worldwide \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. This technology is based on the ability of materials to heat up and cool down. The thermal energy is employed to increase the temperature of a material (liquid or solid, e.g., water, sand, molten salts, rocks\u0026hellip;) that is later cooled down to recover the energy \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. In comparison with the other two thermal storage technologies, sensible-thermal storage systems have relatively low capital costs \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe quantity of energy stored is mainly determined by the specific thermal capacity of the material. According to Khare et al. \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e appropriate material requires:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThermophysical properties: small density changes versus temperature, high heat capacity and heat transport properties.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eChemical properties: chemical stability, non-toxic, non-flammable, low potential reactivity.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEconomic properties: abundant materials with low cost of manufacturing into suitable shapes.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe highest commercially viable materials for sensible heat storage applications are water and different mixtures of molten salts \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Nevertheless, this storage system has many drawbacks related to the use of molten salts, particularly the relatively high cost of the storage components.\u003c/p\u003e \u003cp\u003eAs fossil fuel resources diminish and environmental policies evolve, the development of innovative, cost-effective, and efficient TES systems has become imperative for achieving global energy sustainability. Thus, the search for new low-cost storage materials is pivotal in attaining cost-effective thermal storage alternatives. Furthermore, the availability of storage material in sufficient quantity is a key factor. Lack of availability or even a conflict over the end use of the TES material can lead to price fluctuations and puts the development of storage systems at risk.\u003c/p\u003e \u003cp\u003eThe characteristics of the materials to be used have been extensively studied, but environmental aspects are often given less consideration in the selection of a storage material. Leveraging various industrial by-products as heat storage materials presents a viable with a dual objective: obtaining a viable and cost-effective TES material while reducing mining environmental impact.\u003c/p\u003e \u003cp\u003eSeveral solutions have been proposed in this filed such as inert ceramics obtained from the treatment of the asbestos waste (Cofalit) \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e, fly ashes from the incineration of municipal solid waste \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e or ashes from coal-fired thermal power plants \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis study proposes iron tailings, which is one of the main wastes of the mining industry as a heat storage material. Introducing iron tailings into the energy recovery or production sectors opens new avenues for valorising this waste material while addressing pressing environmental and energy challenges.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cp\u003eThe iron ore tailings samples were collected from an iron mine in Canada. An experimental design program for this research project was developed to achieve the presented objectives (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). First, a comprehensive analysis of the physicochemical properties was performed according to international regulations. Then, different specific tests were carried out to analyse the thermal properties of the material.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Physicochemical analysis\u003c/h2\u003e \u003cp\u003eIron tailings were characterized in terms of chemical composition (X-ray fluorescence, XRF) and physical properties (permeability, particle size distribution and density).\u003c/p\u003e \u003cp\u003eXRF is an elemental, semi-quantitative analysis technique based on the ability of atoms to absorb energy from a source of X-ray radiation. As a consequence, secondary X-rays are emitted, which will have an intensity proportional to the concentration of the X-rays in the sample. an intensity proportional to the concentration of each element. The equipment used in this case is the ARL-ADVANT-XP.\u003c/p\u003e \u003cp\u003eThe permeability coefficient of iron tailings was determined using a constant load perimeter in which the vertical flow of water through a test tube is laminar according to ISO 17892-11:2019. Particle size distribution was obtained by sieving iron tailings (ISO 17892-4:2016) and density and porosity was determined according to ISO 17892-3:2015.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Thermal properties\u003c/h2\u003e \u003cp\u003eFor thermal properties, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were performed using a simultaneous TGA/DTA and TGA/DSC thermal analyser (SETARAM TG-DSC Setsys).\u003c/p\u003e \u003cp\u003eThermogravimetry is based on the measurement of the change in mass of a sample when subjected to a change in temperature in a controlled atmosphere. In a DTA, both the sample and a reference material, which is thermally, physically and chemically inert, are subjected to a temperature variation.\u003c/p\u003e \u003cp\u003eThermogravimetry and calorimetry analysis are thermal analytical techniques in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature. TGA was performed from room temperature to 1000\u0026deg;C at a heating rate of 10\u0026deg;C/min, in an air atmosphere. DSC was conducted from room temperature up to 1000\u0026deg;C, heating speed of 10\u0026deg;C/min and in argon atmosphere to avoid reactive effects such as oxidation or combustion when using air.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Physicochemical analysis\u003c/h2\u003e \u003cp\u003eThe influence factors of chemical composition of iron tailings mainly depend on the local iron ore resources. Variety is mainly caused by the great difference of physical and chemical properties of iron ore resources in different parts of the world. The chemical composition of materials from different mines is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe tailings are mainly composed of SiO\u003csub\u003e2\u003c/sub\u003e but also have significant percentages of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Depending on the type of ore, appreciable amounts of CaO and MgO may be present. In the case of the iron tailings analysed in this work, they have a lower silica content which is compensated by a higher iron content.\u003c/p\u003e \u003cp\u003eTailings analysed have very fine size and 44.9% of void content. The particle\u0026ndash;size distribution curve of tailings as received is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe density obtained for iron tailings are in consonance with different materials reported in literature which are used/studied as high temperature sensible TES materials such as high temperature concretes (2,250 kg/m\u003csup\u003e3\u003c/sup\u003e) \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e, Cofalit (3,120 kg/m\u003csup\u003e3\u003c/sup\u003e) \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e or castable ceramics (3,500 kg/m\u003csup\u003e3\u003c/sup\u003e) \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. High density improves energy storage density which reduces the volume of the thermal energy storage system \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Regarding the mean flow (0.0138 mL/s), hydraulic gradient (6.90 m/m) and permeability coefficient (5.04 x10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e m/s) obtained, they report slightly lower values than conventional materials.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Thermal properties\u003c/h2\u003e \u003cp\u003eIn order to determine the thermal stability of the iron tailings in the complete operation temperature range, thermalgravimetric analysis were carried out. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the measured mass difference obtained from the experiments as a function of temperature. The TGA results are usually presented as \u0026lsquo;mass loss\u0026rsquo; (TG%) since, at the beginning of the test, the balance is tared to 0 and the losses of mass are represented by negative values from this initial point with a minimum value of -100% which would correspond to the total decomposition of the sample.\u003c/p\u003e \u003cp\u003eAs can be seen, there is a slight mass loss of about 1.5%. The rapid initial mass loss is characteristic of desorption or desiccation processes. From this point onwards, the loss may be related to the oxidation-reduction reactions that take place when the material is heated. Many elements in the materials can potentially be oxidised, such as metal oxides (at higher oxidation rates), and/or may remain as trace metals in the tailings. However, this is a very small variation despite the high temperatures, so that the performed thermal stability experiments show that iron tailings are stable up to, at least, 1000\u0026deg;C.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb shows the DSC curves representing the power-energy (mW) variation as a function of temperature. An endothermic peak appears at around 590\u0026deg;C. Nevertheless, it does not imply a mass change, since it is not reflected in the TGA results, but associated with a phase transition. This phase change could be solid-solid or solid-liquid (melting). In any case, the appearance of an exothermic component after this transition can only be explained by understanding that the new phase formed is unstable, so this exothermic contribution in the DSC signal indicates a continuous transformation to a more stable phase.\u003c/p\u003e \u003cp\u003eThe specific heat curve obtained is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. An approximately constant trend is observed up to the temperature of 590\u0026deg;C associated with the transition observed in DSC analysis. From this temperature, a clear decrease is observed because the transition is associated with a phase change towards a metastable structure which produces an exothermic contribution. It should be noted that from about 800\u0026deg;C this exothermic contribution exceeds the value of the heat required to heat the sample. Therefore, from this temperature onwards, negative values are obtained. The maximum specific heat is recorded from 300\u0026deg;C with values around 990 J/kg K.\u003c/p\u003e \u003cp\u003eThe thermal conductivity of iron tailings was measured from room temperature up to 450\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). From the density and specific heat data thermal diffusivity (α) values were obtained following the next Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e):\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\lambda\\:=\\alpha\\:\u0026middot;\\rho\\:\u0026middot;{C}_{s}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere λ is the thermal conductivity (W/mK), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\rho\\:\\)\u003c/span\u003e\u003c/span\u003e is the density (g/cm\u003csup\u003e3\u003c/sup\u003e) and C\u003csub\u003es\u003c/sub\u003e (J/g K) is the specific heat capacity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAn interval of maximum stability is observed between 100 and 275 degrees, with minimal variation in conductivity.\u003c/p\u003e \u003cp\u003eThermal diffusivity is a measure of how quickly a material reacts to temperature changes. Materials with a high thermal diffusivity will heat or cool quickly; conversely, substances with a low thermal diffusivity will heat or cool slowly. Thus, thermal diffusivity is an important property when considering unsteady-state heat transfer situations, that is, in the charge-discharge cycles. It can be seen in both cases that there is a noticeable decrease in conductivity and diffusivity from 300\u0026deg;C onwards.\u003c/p\u003e \u003cp\u003eThe results show very promising iron tailings properties for use as thermal energy storage material. Furthermore, the TGA analysis carried out demonstrated shows that there is hardly any mass variation, which ensures the thermal stability of iron tailings in a wide temperature range up to 1000\u0026deg;C. Overall, the results obtained indicate the high suitability of this mining waste for TES technologies.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Comparison of iron tailings with other TES materials\u003c/h2\u003e \u003cp\u003eOnce the technical feasibility of iron tailings has been discussed, a comparison with other TES materials commonly used is presented (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Molten salt, concrete, sand, cast steel, NaCl and crushed rock are the most common solid sensible thermal energy storage materials, but the table also shows other residues that have been analysed as TES material such as EAF slag or fly ashes.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparisons between iron tailings and common thermal storage materials\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecific Heat (J/kg K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBulk density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eThermal conductivity (W/m K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePrice (\u0026euro;/t)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c7\" namest=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRock\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1000\u0026ndash;1060\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1500\u0026ndash;2800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.50\u0026ndash;3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e50\u0026ndash;90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan additionalcitationids=\"CR39\" citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlumina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e800\u0026ndash;1157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3950\u0026ndash;3960\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e315\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcrete\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e850\u0026ndash;920\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2200\u0026ndash;2300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.50\u0026ndash;2.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCast steel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCast iron\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e560\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSilica sand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e710\u0026ndash;900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2200\u0026ndash;2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.83\u0026ndash;2.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMagnetite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e850\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4962\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e135\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNaCl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e850\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWater\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMolten salts\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1500\u0026ndash;1600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1870\u0026ndash;2600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.52-2.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e625\u0026ndash;700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e,\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOF slag\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e910\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3807\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFly ashes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e714\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2962\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCofalit\u0026reg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e800\u0026ndash;1034\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.4\u0026ndash;2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEAF slag\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e912\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3770\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eIron tailings\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003e780\u0026ndash;990\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e2948\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003e0.12\u0026ndash;0.25\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003e-\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003e-\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe analysed iron tailings exhibit thermal properties similar to those of the materials currently in use. Although they have low thermal conductivity, they have a high calorific value and density.\u003c/p\u003e \u003cp\u003eThe specific heat and density properties enable the calculation of total energy stored (Q) as follows (2):\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:Q=\\rho\\:{\\:C}_{p}\\:\\varDelta\\:T$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\rho\\:\\)\u003c/span\u003e\u003c/span\u003e is the density (kg/cm\u003csup\u003e3\u003c/sup\u003e), C\u003csub\u003es\u003c/sub\u003e (J/kg K) is the specific heat capacity and ΔT the temperature interval. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e presents a comparison between the energy stored (at 573K) in each of the materials and the energy cost.\u003c/p\u003e \u003cp\u003eThe cost of the waste has been taken as 0, assuming only transport costs are necessary. For the calculation, the maximisation of stored energy along with the minimization of total material cost have been considered as criteria. These results represent the theoretical minimum value, as the calculation does not account for practical thermal storage issues such as charge/discharge conditions, heat losses, and other parameters.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs can be seen, iron tailings have a highly competitive performance. A preliminary estimate indicates the potential for a reduction of about 3 times the total cost of the current most used storage material (molten salts), which could lead to a significant cost reduction in the storage system and thus to a reduction of the LCOE (levelized cost of electricity). The performance of iron tailings is similar to Cofalit which is also cheap (8 \u0026euro;/t) although when it is treated by plasma torch, its price increases to (1200 \u0026euro;/t) \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eMine tailings are an unavoidable waste generated during iron ore mining operations, of which millions of tonnes are generated worldwide. Given the importance of steel, and therefore of iron ore mining, solutions are needed to recover this waste. On the other hand, research and development studies on thermal energy storage materials are a hot topic among the research community, particularly those focusing on sensible heat storage materials. Numerous scientists have worked on TES materials and their respective technologies. In this study, thermophysical and chemical characterization of iron tailings from the mining industry has been performed for its potential use as material for thermal storage systems.\u003c/p\u003e \u003cp\u003eUp to temperatures of 590\u0026deg;C no change in the internal structure or phase transition of the material was noted, a temperature range within the normal working spectrum for other commonly used materials, such as molten salts. In cases requiring higher temperatures, more specific testing would be necessary, as the present analysis cannot ascertain whether the endothermic peak around 600\u0026deg;C indicates a solid-solid or solid-liquid phase change.\u003c/p\u003e \u003cp\u003eCompared to materials currently in use, the heat capacity is medium (0.78\u0026ndash;0.99 J/K-g) although the thermal conductivity is low (0.12\u0026ndash;0.25 W/mK). According to the results obtained, each m\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e of iron tailing has a storage capacity of 464.53 kWh at very low cost, involving only the transport of the material. Replacing molten salt with iron tailings would mean a reduction of approximately 2.5 \u0026euro;/kWh.\u003c/p\u003e \u003cp\u003eThis study opens up a new potential market for the valorisation of the iron tailings produced linked to the field of renewable energies that no one had yet considered. This article sets out the first steps of the research, with future lines of development analysing the appropriate equipment for the incorporation of iron tailings and their viability on a pilot scale.\u003c/p\u003e \u003cp\u003eThe implementation of this environmentally friendly alternative would reduce the need to exploit natural resources, which in turn would lead to environmental and economic savings. It would also give a second life to a waste that is produced in large quantities worldwide, in line with the principles of the circular economy. Finally, the recovery of iron tailings would avoid the disposal of a huge amount of this industrial waste, which also entails significant environmental risks depending on the conditions of deposition. In the face of new climate trends, production should be reduced to the minimum necessary, and the reuse and recycling of elements that cannot be returned to the environment due to their properties should be encouraged.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor contributions\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMarina D\u0026iacute;az-Piloneta:\u0026nbsp;\u003c/strong\u003eConceptualization, Methodology, Investigation, Writing Original Draft, Writing-Review \u0026amp; Editing, Visualization. \u003cstrong\u003eMarta Terrados-Cristos, M\u003c/strong\u003eethodology,\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eInvestigation, Writing Original Draft, Supervision, Visualization. \u003cstrong\u003eFrancisco Ortega-Fern\u0026aacute;ndez,\u0026nbsp;\u003c/strong\u003eConceptualization, Validation, Resources, Writing Original Draft, Supervision. \u003cstrong\u003eGemma Mart\u0026iacute;nez-Huerta:\u0026nbsp;\u003c/strong\u003eInvestigation, Writing-Review \u0026amp; Editing, Project administration. \u003cstrong\u003eValeriano \u0026Aacute;lvarez-Cabal:\u0026nbsp;\u003c/strong\u003eMethodology,\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eValidation, Resources\u003cstrong\u003e,\u0026nbsp;\u003c/strong\u003eWriting-original draft, Project administration.\u003c/p\u003e\n\u003cp\u003eDeclaration of competing interest\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003eData Availability Statement\u003c/p\u003e\n\u003cp\u003eNo datasets were generated or analysed in this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBhutada, G. 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Given the importance of steel, and therefore, iron ore mining, solutions are needed to recover this waste. Despite global efforts, the current proposed solutions struggle to reach the market due to cost-effectiveness issues. This study explores a potential solution, presenting iron tailings as a viable, economical, and sustainable material for thermal energy storage systems. This technology is crucial for addressing renewable energy intermittency and capturing industrial waste heat. The experimental analysis carried out confirm the effectiveness of iron tailings in this field, with a density of up to 450 kWh/m\u003csup\u003e3\u003c/sup\u003e. The material stands up safety, minimal environmental impact, and favourable thermophysical properties at a low investment cost. This innovative application not only addresses energy challenges but also contributes to resolving the waste management crisis in the iron mining industry.\u003c/p\u003e","manuscriptTitle":"Experimental characterization of iron mining tailings as sustainable material for thermal energy storage","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-19 21:20:46","doi":"10.21203/rs.3.rs-6850038/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-01T10:39:14+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-30T13:13:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-21T13:29:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"151790998691232761276488108489065957236","date":"2025-08-13T20:42:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"151485078809346398262910574289903194293","date":"2025-08-11T20:30:26+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-17T13:20:33+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-17T13:19:11+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-13T18:20:14+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-13T06:58:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-06-09T02:38:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"902b133b-171e-4d41-b61b-efccd17cfa36","owner":[],"postedDate":"June 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":50237919,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":50237920,"name":"Earth and environmental sciences/Environmental social sciences/Sustainability"}],"tags":[],"updatedAt":"2025-11-24T16:01:14+00:00","versionOfRecord":{"articleIdentity":"rs-6850038","link":"https://doi.org/10.1038/s41598-025-24061-0","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-11-17 15:56:51","publishedOnDateReadable":"November 17th, 2025"},"versionCreatedAt":"2025-06-19 21:20:46","video":"","vorDoi":"10.1038/s41598-025-24061-0","vorDoiUrl":"https://doi.org/10.1038/s41598-025-24061-0","workflowStages":[]},"version":"v1","identity":"rs-6850038","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6850038","identity":"rs-6850038","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}