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Assessment of solar panel waste glass in the manufacture of sepiolite based clay bricks
Materials Letters 218 (2018) 346–348
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Assessment of solar panel waste glass in the manufacture of sepiolite based clay bricks Juan Jimenez-Millan, Isabel Abad, Rosario Jimenez-Espinosa, Africa Yebra-Rodriguez ⇑ Department of Geology and CEACTierra, University of Jaen, Campus Las Lagunillas s/n, 23071 Jaen, Spain
a r t i c l e
i n f o
Article history: Received 21 December 2017 Received in revised form 31 January 2018 Accepted 11 February 2018 Available online 12 February 2018 Keywords: Siliceous waste glass Sepiolite Clay bricks Glass-ceramic Electron microscopy
a b s t r a c t The incorporation to construction materials is a potential solution for the recycling of silicon residues derived from the solar panels siliceous glass. Sepiolite is a fibrous clay mineral that, due to its physicochemical characteristics, imparts an exceptional white color to the ceramics. Due to high plasticity, the sepiolite should be mixed with complementary raw materials to allow its ceramic use. The aim of this work is to evaluate the suitability of sepiolite in clay brick production by using two siliceous materials as degreaser: diatomaceous earth and solar thermal glass waste. The siliceous materials reduce the plasticity of the sepiolite, provide strength and render these glass-ceramics an interesting material from the industrial point of view. Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction The renewal of the photovoltaic installations generates a considerable volume of silicon residues derived from the solar panels siliceous glass. The incorporation to construction materials is a potential solution for the recycling of by-products to reduce environmental impact [1–4]. Glass waste is a valuable source of oxides, mainly SiO2. During the forming process, the glass acts as a degreaser because it is a non-plastic raw material, with the concomitant reduction of the molding humidity and the consequent reduction in the drying shrinkage [5–7]. During sintering, the glass acts as a flux, forming a viscous liquid that fills the pores of the material and contributes to its densification and therefore to the increase of the mechanical resistance [8]. Moreover, the use of glass reduces the firing temperature and firing time [9], and the hardness and degree of crystallization of the ceramics progressively increases during the firing process as a result of secondary recrystallization during solid state sintering. Sepiolite is a fibrous phyllosilicate resulting from the molecular organization of an ideal unit Si12O30Mg8(OH)4(OH2)48H2O [10]. The structural, compositional and physical characteristics of sepiolite render this clay mineral a suitable ceramic material. The sepiolite gives the ceramic pieces a white color that is difficult to obtain with other raw materials. High sepiolite content promotes faster sintering at lower temperatures, sintered materials with ⇑ Corresponding author. E-mail address: [email protected] (A. Yebra-Rodriguez). https://doi.org/10.1016/j.matlet.2018.02.049 0167-577X/Ó 2018 Elsevier B.V. All rights reserved.
lower porosity and higher toughness and strength [11–13]. However, the high plasticity of the sepiolite makes it difficult to form by means of the classic extrusion or pressing techniques. Moreover, the high contraction of the fired pieces could trigger thermo-mechanical stresses during the firing process, which implies low resistance of the obtained material. The mixture with complementary raw materials in different proportions could allow its ceramic use. The aim of this work is to evaluate the suitability of sepiolite in clay brick production. For this purpose, two siliceous materials were used as degreaser: diatomaceous earth and solar thermal glass waste, and the resulting bricks analyzed from the technical and mineralogical point of view. 2. Materials and methods The ceramic formulation of two different mixtures was proposed due to the high liquid limit (297.3% H2O), plastic limit (103.3% H2O) and plasticity index (194.0% H2O) of the sepiolite. Sepiolite from Vicálvaro (Spain) was provided by TOLSA. Diatomaceous earth was collected at the province of Jaén [14]. Waste glass from solar panels was provided by Fundación Innovarcilla (Bailén, Spain). The materials were dry ground (hammer mill Royal Triumph H6300/1, 3 mm sieve). Two ceramic formulations were prepared by mixing 20 wt% sepiolite and 80 wt% diatomite (mixture1) and 70 wt% mixture1 plus 30 wt% waste glass (mixture2) with water until a consistency of 1.4 kg/cm2 was achieved (pocket penetrometer Tascabili ST 207). The mixtures were shaped by paste extrusion in a laboratory extruder (Verdés, Monobloc 050-C/OR)
J. Jimenez-Millan et al. / Materials Letters 218 (2018) 346–348
into pieces 120 28 17 mm3. The specimens were air dried for 24 h, dried in a force air oven at 105 °C until constant mass and length, and afterwards fired at 975, 1025 and 1075 °C for 3 h (furnace ITTEC CB CBN-50). The technical properties of the glassceramic samples were determined as the mean value of four/six determinations: density (mercury immersion displacement), water absorption (UNE-EN ISO 10,545-3), shrinkage (differential length before and after the drying/firing) and strength (material testing machine HOYTOM CM-C, load cell 5 kN, 100 mm span, displacement rate 10 mm/min and 5 mm/min for the dried/fired specimens). Thermal dilatometric analysis was used to observe the sintering process (DIL, horizontal dilatometer Linseis L76/1400, static atmosphere). The mineralogical analyses of the raw sepiolite and specimens were carried out by using X-ray Diffraction (XRD, PANanalytical Empyrean diffractometer, PIXcel-3D detector, CuKa radiation, automatic slit, 40 kV, 30 mA, 0.01°2h step size, 100 s integration time). Microtextural analysis was performed in a Scanning Electron Microscope (SEM) Carl Zeiss MERLIN equipped with
Table 1 Ceramic properties of the specimens.
Drying shrinkage (%) Firing shrinkage (%) Dry density (%) Fired density (%) Dry-strength (Kg/ cm2) Fired-strength (Kg/ cm2) Water absorption (%)
Mixture1 (975 °C; 1025 °C; 1075 °C)
Mixture2 (975 °C; 1025 °C; 1075 °C)
6.4 ± 0.1
5.7 ± 0.1
3.9 ± 0.1; 6.7 ± 0.2; 16.5 ± 0.3 1.25 ± 0.01 1.19 ± 0.01; 1.31 ± 0.01; 2.06 ± 0.01 32 ± 2
4.7 ± 0.1; 10.8 ± 0.2; 13.8 ± 0.1 1.39 ± 0.01 1.44 ± 0.01; 1.82 ± 0.01; 2.11 ± 0.01 28 ± 2
81 ± 5; 123 ± 15; 410 ± 26
95 ± 8; 226 ± 16; 374 ± 28
43.4 ± 0.1; 36.4 ± 0.6; 4.5 ± 0.1
31.8 ± 0.3; 16.5 ± 0.5; 0.7 ± 0.1
347
EDX Oxford facility which allowed punctual microanalysis in thinpolished sections. 3. Results and discussion The mixture with glass waste (mixture2) exhibits less drying shrinkage than the samples with only diatomaceous earth as degreaser (Table 1), which implies lower risk of breakage in the bricks made with the mixture containing glass waste. The values of dry bulk density are also higher, which means higher compactness of the bricks. Regarding the dry-strength, both mixtures show acceptable values of minimum strength to be mechanically manipulated in an industrial manufacturing process. In relation to the fired bricks, the mixture2 samples show higher shrinkage values at 975 and 1025 °C (i.e., higher densification of the material due to the liquid phase formed from the glass waste at high temperature which gradually fills the pores) but a lower value at 1075 °C than that of mixture1 (without glass waste) due to higher content of sepiolite. The increase in the shrinkage values and the concomitant densification of the samples lead to an increase in the mechanical strength of the specimens manufactured with glass waste (95, 226 and 374 kg/cm2); therefore these ceramics can be considered as high resistance materials. Water absorption is an indirect measurement of open porosity. The specimens manufactured with glass waste show less water absorption capacity, hence lower open porosity than the specimens manufactured without glass waste. The dilatometric analyses show that in the first stages of heating, the dilatation of the pure sepiolite is very low (Fig. 1), which indicates the refractory behavior of this mineral at low firing temperature. At ca. 340 °C a contraction of the material takes place. There are no significant modifications of the specimens up to ca. 825 °C, when a strong contraction of approximately 1.5% occurs. Finally, the material shrinks again from ca. 950 °C, reaching the maximum contraction velocity at ca. 1030 °C, after which the shrinkage process slows down. The total shrinkage of the speci-
Fig. 1. Dilatometric curves and the first derivative (DDIL curves) of raw sepiolite and the two studied formulations up to 1100 °C.
348
J. Jimenez-Millan et al. / Materials Letters 218 (2018) 346–348
Fig. 2. SEM backscattered images of the fired specimens. Di: diopside; Qz: quartz (or polymorphs); Wo: wollastonite; Kfs: K-feldspar.
mens to the selected test T is about 6.5%. After heating, the samples of pure sepiolite show no signs of melting. Therefore the observed contractions correspond to mineralogical transformations in the material and not to vitrification. The dilatometric behavior of the formulated mixtures is similar to that of sepiolite, but both mixtures present a small contraction around 700 °C due to the decarbonation of the diatomite clay, as shown by the DDIL curves (first derivative of the dilatometric curves). Moreover, the deceleration of the shrinkage from 1025 °C occurs in samples of mixture1 and not in samples of mixture2 (i.e., it is a more fluxing mixture). The total shrinkage in the samples is 12.4% (without glass waste) and 9.1% (with glass waste). XRD data reveal the following mineralogical content in the raw material: 92% sepiolite, 2% quartz, 2% K-Feldspar, 2% Mg-smectite, 2% Illite. XRD patterns of the fired specimens reveal the presence of quartz, wollastonite and pyroxenes in all samples. In mixture1, Kfeldspar and cristobalite appear only after firing at high temperature (from 1025 °C). The mixture2 presents feldspar and tridimite in all specimens. The specimens fired at lower temperature (975 °C) show finer grain size and higher heterogeneity than the specimens fired at higher temperature. The fine grain matrix in the samples without glass wastes corresponds to enstatite and wollastonite with dispersed quartz crystals, (Fig. 2A–B). Periclase crystals and fossil fragments (diatom algae) have also been identified. The sintering of the samples is evident at 1025 °C, due to the presence of glass filaments. The sintering process completes at 1075 °C, and the samples develop a vitreous and vesiculated matrix (Fig. 2B). The samples with glass wastes show similar evolution at increasing temperature (Fig. 2C). The development of radial large crystals of diopside and wollastonite around (partially replacing) the original siliceous glass fragments of the raw material is particularly characteristic (Fig. 2C). 4. Conclusions The siliceous materials (diatomaceous earth and waste glass from solar panels) reduce the plasticity of the sepiolite, provide strength and render these glass-ceramics an interesting material from the industrial point of view. Moreover, the recycling of waste
glass from solar panels brings an important added value from the environmental point of view. Acknowledgements This study was supported by RNM-325 Research Group (CICE, Junta de Andalucia, Spain) and Research Team EI_RNM05-2017 (University of Jaen, Spain). The authors thank technical and human support provided by CICT of Universidad de Jaen (MINECO, JA, FEDER). References [1] P. Chawakitchareon, W. Tiansiri, Utilization of glass scrap as raw material for ceramic tile production, Thai Environ. Eng. J. 1 (2008) 103–112. [2] K.L. Lin, T.C. Chu, C.J. Cheng, C.H. Lee, T.C. Chang, K.S. Wang, Recycling solar panel waste glass sintered as glass-ceramics, Environ. Prog. Sustain. 31 (2012) 612–618. [3] A. Shayan, A. Xu, Value-added utilization of waste glass in concrete, Cem. Concr. Res. 34 (2004) 81–89. [4] I. Iglesias, Martín, A. Acosta Echeverría, E. García-Romero, Recycling of residual IGCC slags and their benefits as degreasers in ceramics, J. Environ. Manage. 129 (2013) 1–8. [5] I. Demir, Reuse of waste glass in building brick production, Waste Manage. Res. 27 (2009) 572–577. [6] M. Dondi, G. Guarini, M. Raimondo, C. Zanelli, Recycling PC and TV waste glass in clay bricks and roof tiles, Waste Manage. 29 (2009) 1945–1951. [7] V. Loryuenyong, T. Panyachai, K. Kaewsimork, C. Siritai, Effects of recycled glass substitution on the physical and mechanical properties of clay bricks, Waste Manage. 29 (2009) 2717–2721. [8] K.-L. Lin, T.-C. Lee, C.-L. Hwang, Effects of sintering temperature on the characteristics of solar panel waste glass in the production of ceramic tiles, J. Mater. Cycles Waste. Manag. 17 (2015) 194–200. [9] J.-Y. Hwang, X. Huang, A. Garkida, A. Hein, Waste coloured glasses as sintering aid in ceramic tiles production, JMMCE 5 (2006) 119–129. [10] B.F. Jones, E. Galán, Sepiolite and palygorskite, in: S.W. Bailey (Ed.), Hydrous Phyllosilicates (exclusive of micas), Reviews in Mineralogy 19, Washington D. C, Mineralogical Society of America, 1988, pp. 631–674. [11] A.A. Goktas, Z. Misirli, T. Baykara, Sintering behaviour of sepiolite, Ceram. Int. 23 (1997) 305–311. [12] E. Gunay, T.O. Ozkan, Production of porous ceramics from sepiolite based minerals, Ind. Ceram. 21 (2001) 145–149. [13] L.J. Wang, J.S. Liang, X.F. Di, X.M. Pei, Effects of sepiolite mineral nano-fiber on strength and toughness of ceramics, Appl. Mech. Mater. 320 (2013) 599–606. [14] M.A. Bustillo, M.J. López, García, Age, distribution and composition of miocene diatom bearing sediments in the Guadalquivir Basin, Spain, Geobios 30 (1997) 335–350.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Assessment of solar panel waste glass in the manufacture of sepiolite based clay bricks Juan Jimenez-Millan, Isabel Abad, Rosario Jimenez-Espinosa, Africa Yebra-Rodriguez ⇑ Department of Geology and CEACTierra, University of Jaen, Campus Las Lagunillas s/n, 23071 Jaen, Spain
a r t i c l e
i n f o
Article history: Received 21 December 2017 Received in revised form 31 January 2018 Accepted 11 February 2018 Available online 12 February 2018 Keywords: Siliceous waste glass Sepiolite Clay bricks Glass-ceramic Electron microscopy
a b s t r a c t The incorporation to construction materials is a potential solution for the recycling of silicon residues derived from the solar panels siliceous glass. Sepiolite is a fibrous clay mineral that, due to its physicochemical characteristics, imparts an exceptional white color to the ceramics. Due to high plasticity, the sepiolite should be mixed with complementary raw materials to allow its ceramic use. The aim of this work is to evaluate the suitability of sepiolite in clay brick production by using two siliceous materials as degreaser: diatomaceous earth and solar thermal glass waste. The siliceous materials reduce the plasticity of the sepiolite, provide strength and render these glass-ceramics an interesting material from the industrial point of view. Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction The renewal of the photovoltaic installations generates a considerable volume of silicon residues derived from the solar panels siliceous glass. The incorporation to construction materials is a potential solution for the recycling of by-products to reduce environmental impact [1–4]. Glass waste is a valuable source of oxides, mainly SiO2. During the forming process, the glass acts as a degreaser because it is a non-plastic raw material, with the concomitant reduction of the molding humidity and the consequent reduction in the drying shrinkage [5–7]. During sintering, the glass acts as a flux, forming a viscous liquid that fills the pores of the material and contributes to its densification and therefore to the increase of the mechanical resistance [8]. Moreover, the use of glass reduces the firing temperature and firing time [9], and the hardness and degree of crystallization of the ceramics progressively increases during the firing process as a result of secondary recrystallization during solid state sintering. Sepiolite is a fibrous phyllosilicate resulting from the molecular organization of an ideal unit Si12O30Mg8(OH)4(OH2)48H2O [10]. The structural, compositional and physical characteristics of sepiolite render this clay mineral a suitable ceramic material. The sepiolite gives the ceramic pieces a white color that is difficult to obtain with other raw materials. High sepiolite content promotes faster sintering at lower temperatures, sintered materials with ⇑ Corresponding author. E-mail address: [email protected] (A. Yebra-Rodriguez). https://doi.org/10.1016/j.matlet.2018.02.049 0167-577X/Ó 2018 Elsevier B.V. All rights reserved.
lower porosity and higher toughness and strength [11–13]. However, the high plasticity of the sepiolite makes it difficult to form by means of the classic extrusion or pressing techniques. Moreover, the high contraction of the fired pieces could trigger thermo-mechanical stresses during the firing process, which implies low resistance of the obtained material. The mixture with complementary raw materials in different proportions could allow its ceramic use. The aim of this work is to evaluate the suitability of sepiolite in clay brick production. For this purpose, two siliceous materials were used as degreaser: diatomaceous earth and solar thermal glass waste, and the resulting bricks analyzed from the technical and mineralogical point of view. 2. Materials and methods The ceramic formulation of two different mixtures was proposed due to the high liquid limit (297.3% H2O), plastic limit (103.3% H2O) and plasticity index (194.0% H2O) of the sepiolite. Sepiolite from Vicálvaro (Spain) was provided by TOLSA. Diatomaceous earth was collected at the province of Jaén [14]. Waste glass from solar panels was provided by Fundación Innovarcilla (Bailén, Spain). The materials were dry ground (hammer mill Royal Triumph H6300/1, 3 mm sieve). Two ceramic formulations were prepared by mixing 20 wt% sepiolite and 80 wt% diatomite (mixture1) and 70 wt% mixture1 plus 30 wt% waste glass (mixture2) with water until a consistency of 1.4 kg/cm2 was achieved (pocket penetrometer Tascabili ST 207). The mixtures were shaped by paste extrusion in a laboratory extruder (Verdés, Monobloc 050-C/OR)
J. Jimenez-Millan et al. / Materials Letters 218 (2018) 346–348
into pieces 120 28 17 mm3. The specimens were air dried for 24 h, dried in a force air oven at 105 °C until constant mass and length, and afterwards fired at 975, 1025 and 1075 °C for 3 h (furnace ITTEC CB CBN-50). The technical properties of the glassceramic samples were determined as the mean value of four/six determinations: density (mercury immersion displacement), water absorption (UNE-EN ISO 10,545-3), shrinkage (differential length before and after the drying/firing) and strength (material testing machine HOYTOM CM-C, load cell 5 kN, 100 mm span, displacement rate 10 mm/min and 5 mm/min for the dried/fired specimens). Thermal dilatometric analysis was used to observe the sintering process (DIL, horizontal dilatometer Linseis L76/1400, static atmosphere). The mineralogical analyses of the raw sepiolite and specimens were carried out by using X-ray Diffraction (XRD, PANanalytical Empyrean diffractometer, PIXcel-3D detector, CuKa radiation, automatic slit, 40 kV, 30 mA, 0.01°2h step size, 100 s integration time). Microtextural analysis was performed in a Scanning Electron Microscope (SEM) Carl Zeiss MERLIN equipped with
Table 1 Ceramic properties of the specimens.
Drying shrinkage (%) Firing shrinkage (%) Dry density (%) Fired density (%) Dry-strength (Kg/ cm2) Fired-strength (Kg/ cm2) Water absorption (%)
Mixture1 (975 °C; 1025 °C; 1075 °C)
Mixture2 (975 °C; 1025 °C; 1075 °C)
6.4 ± 0.1
5.7 ± 0.1
3.9 ± 0.1; 6.7 ± 0.2; 16.5 ± 0.3 1.25 ± 0.01 1.19 ± 0.01; 1.31 ± 0.01; 2.06 ± 0.01 32 ± 2
4.7 ± 0.1; 10.8 ± 0.2; 13.8 ± 0.1 1.39 ± 0.01 1.44 ± 0.01; 1.82 ± 0.01; 2.11 ± 0.01 28 ± 2
81 ± 5; 123 ± 15; 410 ± 26
95 ± 8; 226 ± 16; 374 ± 28
43.4 ± 0.1; 36.4 ± 0.6; 4.5 ± 0.1
31.8 ± 0.3; 16.5 ± 0.5; 0.7 ± 0.1
347
EDX Oxford facility which allowed punctual microanalysis in thinpolished sections. 3. Results and discussion The mixture with glass waste (mixture2) exhibits less drying shrinkage than the samples with only diatomaceous earth as degreaser (Table 1), which implies lower risk of breakage in the bricks made with the mixture containing glass waste. The values of dry bulk density are also higher, which means higher compactness of the bricks. Regarding the dry-strength, both mixtures show acceptable values of minimum strength to be mechanically manipulated in an industrial manufacturing process. In relation to the fired bricks, the mixture2 samples show higher shrinkage values at 975 and 1025 °C (i.e., higher densification of the material due to the liquid phase formed from the glass waste at high temperature which gradually fills the pores) but a lower value at 1075 °C than that of mixture1 (without glass waste) due to higher content of sepiolite. The increase in the shrinkage values and the concomitant densification of the samples lead to an increase in the mechanical strength of the specimens manufactured with glass waste (95, 226 and 374 kg/cm2); therefore these ceramics can be considered as high resistance materials. Water absorption is an indirect measurement of open porosity. The specimens manufactured with glass waste show less water absorption capacity, hence lower open porosity than the specimens manufactured without glass waste. The dilatometric analyses show that in the first stages of heating, the dilatation of the pure sepiolite is very low (Fig. 1), which indicates the refractory behavior of this mineral at low firing temperature. At ca. 340 °C a contraction of the material takes place. There are no significant modifications of the specimens up to ca. 825 °C, when a strong contraction of approximately 1.5% occurs. Finally, the material shrinks again from ca. 950 °C, reaching the maximum contraction velocity at ca. 1030 °C, after which the shrinkage process slows down. The total shrinkage of the speci-
Fig. 1. Dilatometric curves and the first derivative (DDIL curves) of raw sepiolite and the two studied formulations up to 1100 °C.
348
J. Jimenez-Millan et al. / Materials Letters 218 (2018) 346–348
Fig. 2. SEM backscattered images of the fired specimens. Di: diopside; Qz: quartz (or polymorphs); Wo: wollastonite; Kfs: K-feldspar.
mens to the selected test T is about 6.5%. After heating, the samples of pure sepiolite show no signs of melting. Therefore the observed contractions correspond to mineralogical transformations in the material and not to vitrification. The dilatometric behavior of the formulated mixtures is similar to that of sepiolite, but both mixtures present a small contraction around 700 °C due to the decarbonation of the diatomite clay, as shown by the DDIL curves (first derivative of the dilatometric curves). Moreover, the deceleration of the shrinkage from 1025 °C occurs in samples of mixture1 and not in samples of mixture2 (i.e., it is a more fluxing mixture). The total shrinkage in the samples is 12.4% (without glass waste) and 9.1% (with glass waste). XRD data reveal the following mineralogical content in the raw material: 92% sepiolite, 2% quartz, 2% K-Feldspar, 2% Mg-smectite, 2% Illite. XRD patterns of the fired specimens reveal the presence of quartz, wollastonite and pyroxenes in all samples. In mixture1, Kfeldspar and cristobalite appear only after firing at high temperature (from 1025 °C). The mixture2 presents feldspar and tridimite in all specimens. The specimens fired at lower temperature (975 °C) show finer grain size and higher heterogeneity than the specimens fired at higher temperature. The fine grain matrix in the samples without glass wastes corresponds to enstatite and wollastonite with dispersed quartz crystals, (Fig. 2A–B). Periclase crystals and fossil fragments (diatom algae) have also been identified. The sintering of the samples is evident at 1025 °C, due to the presence of glass filaments. The sintering process completes at 1075 °C, and the samples develop a vitreous and vesiculated matrix (Fig. 2B). The samples with glass wastes show similar evolution at increasing temperature (Fig. 2C). The development of radial large crystals of diopside and wollastonite around (partially replacing) the original siliceous glass fragments of the raw material is particularly characteristic (Fig. 2C). 4. Conclusions The siliceous materials (diatomaceous earth and waste glass from solar panels) reduce the plasticity of the sepiolite, provide strength and render these glass-ceramics an interesting material from the industrial point of view. Moreover, the recycling of waste
glass from solar panels brings an important added value from the environmental point of view. Acknowledgements This study was supported by RNM-325 Research Group (CICE, Junta de Andalucia, Spain) and Research Team EI_RNM05-2017 (University of Jaen, Spain). The authors thank technical and human support provided by CICT of Universidad de Jaen (MINECO, JA, FEDER). References [1] P. Chawakitchareon, W. Tiansiri, Utilization of glass scrap as raw material for ceramic tile production, Thai Environ. Eng. J. 1 (2008) 103–112. [2] K.L. Lin, T.C. Chu, C.J. Cheng, C.H. Lee, T.C. Chang, K.S. Wang, Recycling solar panel waste glass sintered as glass-ceramics, Environ. Prog. Sustain. 31 (2012) 612–618. [3] A. Shayan, A. Xu, Value-added utilization of waste glass in concrete, Cem. Concr. Res. 34 (2004) 81–89. [4] I. Iglesias, Martín, A. Acosta Echeverría, E. García-Romero, Recycling of residual IGCC slags and their benefits as degreasers in ceramics, J. Environ. Manage. 129 (2013) 1–8. [5] I. Demir, Reuse of waste glass in building brick production, Waste Manage. Res. 27 (2009) 572–577. [6] M. Dondi, G. Guarini, M. Raimondo, C. Zanelli, Recycling PC and TV waste glass in clay bricks and roof tiles, Waste Manage. 29 (2009) 1945–1951. [7] V. Loryuenyong, T. Panyachai, K. Kaewsimork, C. Siritai, Effects of recycled glass substitution on the physical and mechanical properties of clay bricks, Waste Manage. 29 (2009) 2717–2721. [8] K.-L. Lin, T.-C. Lee, C.-L. Hwang, Effects of sintering temperature on the characteristics of solar panel waste glass in the production of ceramic tiles, J. Mater. Cycles Waste. Manag. 17 (2015) 194–200. [9] J.-Y. Hwang, X. Huang, A. Garkida, A. Hein, Waste coloured glasses as sintering aid in ceramic tiles production, JMMCE 5 (2006) 119–129. [10] B.F. Jones, E. Galán, Sepiolite and palygorskite, in: S.W. Bailey (Ed.), Hydrous Phyllosilicates (exclusive of micas), Reviews in Mineralogy 19, Washington D. C, Mineralogical Society of America, 1988, pp. 631–674. [11] A.A. Goktas, Z. Misirli, T. Baykara, Sintering behaviour of sepiolite, Ceram. Int. 23 (1997) 305–311. [12] E. Gunay, T.O. Ozkan, Production of porous ceramics from sepiolite based minerals, Ind. Ceram. 21 (2001) 145–149. [13] L.J. Wang, J.S. Liang, X.F. Di, X.M. Pei, Effects of sepiolite mineral nano-fiber on strength and toughness of ceramics, Appl. Mech. Mater. 320 (2013) 599–606. [14] M.A. Bustillo, M.J. López, García, Age, distribution and composition of miocene diatom bearing sediments in the Guadalquivir Basin, Spain, Geobios 30 (1997) 335–350.