High-Temperature Mineral Formation After Firing Clay Materials Associated with Mined Coal in Teruel (Spain)
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applied sciences Article High-Temperature Mineral Formation after Firing Clay Materials Associated with Mined Coal in Teruel (Spain) Manuel Miguel Jordán 1,* , Sergio Meseguer 2 , Francisco Pardo 3 and María Adriana Montero 1 1 Department of Agrochemistry and Environment (GEA-UMH), University Miguel Hernández, Elche. Avda. de la Universidad s/n, 03202 Elche, Alicante, Spain; [email protected] 2 Unit of Applied Mineralogy, Jaume I University, Campus de Riu Sec s/n, 1280 Castellón, Spain; [email protected] 3 Department of Education Sciences, CEU Cardenal Herrera University, Calle Grecia 31, 12006 Castellón, Spain; [email protected] * Correspondence: [email protected]; Tel.: +34-966658416 Received: 1 April 2020; Accepted: 28 April 2020; Published: 29 April 2020 Abstract: The production of porcelain stoneware has experienced a considerable increase. Therefore, it was necessary to undertake an investigation that would allow knowing the mineralogical evolution that porcelain stoneware undergoes during the firing process, as well as establishing the influence of the formation of mullite and other mineral or vitreous phases and their quantification. The firing transformations of mine spoils associated with mined coal in the Utrillas-Escucha-Estercuel and Ariño-Andorra areas are studied in this paper. The mineralogical composition of the bulk mine spoils is kaolinite, illite, chlorite, and smectites (in traces), with quartz and feldspar, and minor hematite, calcite, and dolomite. The main objective is to understand the generation of high-temperature mineral phases after firing, and their quantification. The formation of mullite and other high-temperature phases are studied from samples that include variable proportions of illite. Samples with a high content of illite generate mullite at 995 ◦C. Cristobalite was not detected as a high-temperature phase. Mullite is the most abundant mineral. The hercynite content is higher at low temperatures (995 ◦C), and hematite content is higher at 1150 ◦C. The vitreous phase represents about 50% of fired bodies. Despite observing a porous microstructure, the non-porous areas are well sintered. Keywords: Teruel; clay spoils; firing transformations; phase generation; vitreous phase; XRD; FTIR 1. Introduction The province of Teruel (NE Spain) has historically been an important coal mining area. In this area there are still abundant coal deposits, but coal mining has ceased in recent decades. In this paper, firing transformations [1] of mine spoils from the mined coal in the Utrillas-Escucha-Estercuel and Ariño-Andorra regions are studied (Figure1). The production of porcelain stoneware has experienced a considerable increase since its initial development in Italy in the late 1970s [2]. The valuation of these mine spoils can bring economic and environmental benefits [3]. However, this increase in manufacture was not accompanied by the necessary research to know the scope of the reactions that take place during the firing process of the ceramic pieces. It is worth noting the fact that the few publications that exist on the porcelain stoneware microstructure refer, above all, to issues of porosity and glass formation, without addressing the study of mullite formation and mineral quantification [1,2]. Therefore, it was considered necessary to undertake an investigation that would allow knowing the mineralogical and microstructural evolution that porcelain stoneware undergoes during its firing process, as well as establishing the influence of the mullite crystalline phase formation on some Appl. Sci. 2020, 10, 3114; doi:10.3390/app10093114 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 10 allowAppl. Sci.knowing2020, 10 ,the 3114 mineralogical and microstructural evolution that porcelain stoneware undergoes2 of 9 during its firing process, as well as establishing the influence of the mullite crystalline phase formationproperties on as some open properties porosity [ 2as]. open For production porosity [2]. of For porcelain production stoneware, of porcelain ball clays stoneware, are required ball clays [2]. In arethe required Spanish [2]. ceramic In the cluster,Spanish white ceramic ceramic cluster, clays white have ceramic usually clays been have imported usually from been Ukraine,imported France, from Ukraine,and the UKFrance, [3]. However,and the UK a greater[3]. However, knowledge a greater of the knowledge mine spoils of from the themine lignite spoils mines from in the Teruel lignite will minesallow in their Teruel incorporation will allow as their new incorporation raw materials as in new the mainraw materials ceramic companies in the main [4– ceramic6]. The futurecompanies use of [4–6]these The spoils future will use represent of these significant spoils will savings represent in productionsignificant savings costs [3]. in production costs [3]. FigureFigure 1. 1. LocationLocation of of the the studied sampling areas.areas. Legend:Legend: OE:OE: Oliete-Estercuel; Oliete-Estercuel; AA: AA: Ariño-Andorra Ariño-Andorra [3]. [3]. Mine spoils from the lignite mines associated with the Lignitos de Escucha (Escucha Lignites) andMine Arenas spoils de Utrillasfrom the (Utrillas lignite kaoliniticmines associated sands) formationswith the Lignitos belong de to Escucha the upper (Escucha part of theLignites) Lower andCretaceous Arenas de [3]. Utrillas These mine(Utrillas spoils kaolinitic have a greatsands) importance formations in belong the ceramic to the cluster upper ofpart Castell of theón Lower (Spain), Cretaceousdue to their [3]. possibilities These mine for spoils being have used a as great ceramic impo rawrtance materials in the Theseceramic clayed cluster mine of spoilsCastellón for industrial(Spain), dueuses, to ontheir the basispossibilities on their for mineralogy being used and as chemical ceramic composition, raw materials can These be classified clayed asmine ball spoils clays [1for–3 ]. industrialSome of these uses, spoils on the are basis mined on nowadaystheir mineralogy [4]. High-temperature and chemical composition, mineral phases can are be generatedclassified inas firingball claysprocesses. [1–3]. MineralSome of phase these transformations spoils are mined in a nowa ceramicdays firing [4]. processHigh-temperature have previously mineral been phases described are in generatedliterature [in3,7 ].firing Previously, processes. a powerful Mineral study phase was tr carriedansformations out on the in determination a ceramic firing of high-temperature process have previouslymineral phases been described using these in mineliterature spoils [3,7]. as ceramic Previously, raw materiala powerful [3]. study The formationwas carried of mulliteout on the and determinationother high-temperature of high-temperature phases were mineral studied phases in 2015 using [3]. However,these mine it spoils was not as possibleceramic toraw quantify material the [3].mineral The formation phases and of themullite vitreous and phaseother high-temperature present for each firing phases temperature. were studied There in 2015 is no [3]. information However, in itthe was literature not possible about to the quantify quantification the mineral of high-temperature phases and the phasevitreous generation phase present and amorphous for each firing phase temperature.formation from There these is no mine information spoils for in di thefferent litera firingture about temperatures. the quantification Knowledge of high-temperature and quantification phaseof high-temperature generation and minerals amorphous generated phase usingformation these from mine these spoils mine as raw spoils materials for different is interesting firing in temperatures.industrial processes Knowledge for manufacturing and quantification stoneware of hi andgh-temperature ceramic tiles, asminerals well as refractorygenerated ceramics using these [5–9 ]. mineIn this spoils work, as raw for thematerials first time, is interesting a quantification in industrial of mineral processes phase for inmanufacturing the thermal transformationsstoneware and ceramicexperienced tiles, as by well kaolinitic as refractory mine spoils ceramics has been [5–9]. carried In this out. work, The for ceramic the first industry time, a hasquantification been shown of to mineralhave great phase potential in the thermal to absorb transformations industrial waste experienced [8,9]. However, by kaolinitic the commercial mine spoils production has been carried of tiles out.from The waste ceramic materials industry is very has been limited shown and, to in have some great countries, potential non-existent. to absorb industrial Some reasons waste include [8,9]. However,possible contaminationthe commercial by production the waste used,of tiles the from absence waste of relevantmaterials standards, is very limited and slow and, acceptance in some countries,by industry non-existent. and consumers. Some reasons The main include objectives possible of this contamination paper are:(i) by to the understand waste used, the the generation absence ofof relevant high-temperature standards, mineraland slow phases acceptance after firing;by industry (ii) to addressand consumers. a quantitative The main approach objectives to minerals of this paperand amorphousare: (i) to understand phases present the ge inneration ceramic tileof high-temperature bodies; (iii) to study mine theral microstructure phases after firing; and porosity (ii) to addressof ceramic a quantitative tile bodies; approach and (iv) to to contribute minerals and to a amorphous better knowledge phases of present