Phosphorus solubility in basaltic glass: limitations for phosphorus immobilization in glass and glass-ceramics

The composition of sewage sludge from urban wastewater treatment plants is simulated using P-doped basalts. Electron microscopy analyses show that the solubility of P in the basaltic melt is limited by the formation of a liquid-liquid immiscibility in the form of an aluminosilicate phase and a Ca-Mg-Fe-rich phosphate phase. The rheological behavior of these compositions is influenced by both phase separation and nanocrystallization. Upon a thermal treatment, the glasses will crystallize into a mixture of inosilicates and spinel-like phases at low P contents and into Ca-Mg-Fe phosphate at high P contents. Hardness measurements yield values between 5.41 and 7.66 GPa, inside the range of commercial glasses and glass-ceramics. Leaching affects mainly unstable Mg2+-PO43- complexes

Recycling of tailings from the Barruecopardo tungsten deposit for the production of glass

Peer ReviewedPostprint (author's final draft

Potential of tungsten tailings as glass raw materials

Glasses from different types of tungsten mine tailings were obtained and studied to determine their ability to be used as raw materials of commercial glass. Tailings of granitic composition from Barruecopardo, of calc-silicate wastes from Morille, and of schists and quartz from Panasqueira, were used as raw materials. The addition of CaCO3 and NaCO3 was necessary for the manufacture of the glass. Samples were characterised by XRF, XRD, HSM and DTA-TG. Furthermore, the expansion coefficient, Vickers microhardness and leaching properties were measured. The results show that all the tungsten mine tailings used were suitable for the manufacture of commercial glass, with the addition of calcium and soda. The calc-silicate tailing needs less additive content to produce a glass. Also, they present lower workability temperatures and higher durability. Glasses obtained from all the tested tailings retain the potentially toxic elements in their structure and prevents the environmental pollution.</p

Fe in P-doped basaltic melts: a Mössbauer spectroscopy study

The addition of P to a basalt causes a change in the environment of Fe. At low P contents iron is located in the glass structure and the Fe3+/Fe2+ ratio is about 80/20. Further addition of P causes a collapse of the glass structure related to a phase separation that triggers the crystallization of a more reduced iron-containing phosphate phase with a crystalline structure similar to that of stanfieldite, and Mössbauer parameters similar to those of the alluaudite group, together with the formation of a Fe3+-Fe2+ disordered phase. Their presence increases the viscosity of the melt.Peer ReviewedPostprint (published version

Potential of tungsten tailings as glass raw materials

Glasses from different types of tungsten mine tailings were obtained and studied to determine their ability to be used as raw materials of commercial glass. Tailings of granitic composition from Barruecopardo, of calc-silicate wastes from Morille, and of schists and quartz from Panasqueira, were used as raw materials. The addition of CaCO3 and NaCO3 was necessary for the manufacture of the glass. Samples were characterised by XRF, XRD, HSM and DTA-TG. Furthermore, the expansion coefficient, Vickers microhardness and leaching properties were measured. The results show that all the tungsten mine tailings used were suitable for the manufacture of commercial glass, with the addition of calcium and soda. The calc-silicate tailing needs less additive content to produce a glass. Also, they present lower workability temperatures and higher durability. Glasses obtained from all the tested tailings retain the potentially toxic elements in their structure and prevents the environmental pollution.Peer ReviewedPostprint (author's final draft

Determinación de las curvas viscosidad-temperatura en vidrios históricos: una aproximación a la tecnología de producción

En general, los estudios de vidrios históricos -a diferencia de los de cerámicas antiguas- se centran en su caracterización composicional, cromática, grado de degradación, bioactividad, etc, dejando de lado sus propiedades físico-químicas, en las que se incluye su caracterización térmica y el estudio de la relación viscosidadtemperatura. Sin embargo, estos últimos son factores básicos en la determinación de las condiciones de fabricación del vidrio y de las etapas de su proceso de elaboración (fusión, afinado, acondicionamiento, recocido)

Recycling of tailings from the Barruecopardo tungsten deposit for the production of glass

Tailings from tungsten mining activities in the vicinity of Barruecopardo (Salamanca) represent high environmental pollution. In this paper we present a study of the use of these wastes as raw materials for the manufacture of glass. This procedure aims to contribute to environmental remediation of mining areas through vitrification, a process which offers an alternative for stabilization of hazardous wastes. In addition, the marketing of the obtained product would provide an additional income to the mining areas. The chemical composition of the tailings to be used as raw materials was determined by X-ray fluorescence and their mineralogy by X-ray diffraction. Wastes are of granitic composition enriched in potentially toxic elements. For this study, a representative sample of mining wastes of sandy grain size was used to make the glass. On the basis of its composition, glass was formulated by adding 29.28 mass% of CaCO3 and 14.03 mass% of Na2CO3 and a green glass was produced. Crystallisation temperatures, obtained by DTA, were 875 and 1022 °C and the melting temperature was 1175 °C. The transition temperature of glass was of 644 °C. The temperatures for the fixed viscosity points, and the working temperatures were obtained. A thermal treatment induced devitrification to produce a glass-ceramic made of nepheline and wollastonite. Leaching tests of the obtained glass confirm its capacity to retain potentially toxic elements

Kaolin from Acoculco (Puebla, Mexico) as a raw material: mineralogical and thermal characterization

The present study determined the mineralogy and thermal properties of kaolin from Acoculco (Puebla), at the eastern Trans-Mexican Volcanic Belt and compared it with the nearby deposits of Agua Blanca (Hidalgo) and Huayacocotla (Veracruz). The mineralogy of the kaolins was determined by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Thermal behaviour was studied by differential thermal analysis, dilatometry and hot-stage microscopy. The Acoculco deposit is composed mainly of kaolinite and SiO2 minerals. In the case of Agua Blanca and Huayacocotla, alunite is abundant in places and minor anatase is also present locally. The Acoculco kaolins are Fe-poor and relatively rich in some potentially toxic elements (Zr, Sb, Pb). They undergo a relatively small amount of shrinkage (∼3-4 vol.%), during firing at 20-1300°C and cooling down to 20°C, except when >10 wt.% alunite is present. These kaolins are a suitable raw material for the ceramics industry. Other applications (pharmaceuticals, cosmetics) would require an enrichment process to eliminate impurities such as Fe oxides

Modelization of the vitrification of sewage sludge using a basaltic matrix

[eng] Sewage sludge is a high volume, potentially toxic waste generated during the decontamination process of wastewater. Improved solutions for waste disposal require its conversion into an end product or at least a raw material for new applications. The chemical composition of sewage is similar to that of a basalt enriched in P and Ca, hence it may be inertized by vitrification. The experimental strategy is based on producing glasses from mixtures containing basalt, P and/or Ca to study the production of glass from sewage sludge. Selected glass compositions are then doped with toxic elements (Ba, Cr, Cu, Ni and Zn) to assess the possibility of using the SS like glass as an inertization matrix for hazardous wastes. Part of these glasses are taken as parent compositions to obtain glass-ceramics, which may offer improved properties. The characterization of the glasses and glass-ceramics includes the study of their composition (electron microprobe), texture (scanning and transmission electron microscopy), structure (Raman and Mössbauer spectroscopies), thermal behavior (differential thermal analysis) and crystallization (X-Ray diffraction) macroscopic properties (density, viscosity, glass transition temperature and microhardness) and the chemical resistance (leaching tests). These analyses have shown that the solubility of each element in the basalt glass is limited by either crystallization or phase separation processes. Their large Fe contents cause a pervasive nucleation that has a large influence in the glass transition temperature, crystal growth, viscosity and microhardness and texture. It is of particular importance the delay caused by crystallization in the decrease of viscosity with increasing temperature. However, all the glasses have a viscosity low enough to be melted at temperatures about 1450 ºC . The presence of nuclei also causes the formation of a fine-grained texture of mostly diopside (together with akermanite and nepheline) in the glass-ceramics. In particular, the magnetite nuclei are the germ for the crystallization of diopside. All the compositions seem to effectively bind the elements in the corresponding glass structure, as the leaching levels comply with the limits for them to be considered inert. Moreover, their microhardness is in the range of commercial glasses and glass-ceramics used in the construction industry. In conclusion, sewage sludge compositions show potential to be used as raw material for the production of commercial glasses and glass<ceramics following the spirit of circular economy.[cat] Els llots de depuradora són un residu de volum elevat i potencialment tòxic que es genera durant el procés de descontaminació de les aigües. Millorar el processament dels residus implica convertir­los en un material reutilitzable o en una matèria primera. Aquests llots es poden assimilar a un basalt enriquit en P i Ca;; per tant, és possible inertitzar-­los mitjançant la vitrificació. Es proposa un estudi de l’efecte del P, el Ca i els dos elements combinats per determinar quin efecte tenen en la formació del vidre. Certes composicions escollides es doparan amb elements tòxics (Ba, Cr, Cu, Ni, Zn) per determinar la possibilitat d’usar una matriu basada en els llots per a la inertització de residus perillosos. També s’estudia l’obtenció de vitroceràmics a partir d’aquests vidres per millorar­ne les propietats. La caracterització dels vidres i els vitroceràmics inclou la composició química (microsonda electrònica), textura (microscòpia electrònica de rastreig i transmissió), estructura (espectroscòpies Raman i Mössbauer), anàlisi tèrmica diferencial, cristal·lització (Difracció de Raigs X), propietats macroscòpiques (viscositat, densitat, temperatura de transició vítria i microduresa) i la resistència a l’atac químic (assajos de lixiviació). Els elevats continguts en Fe dels vidres generen una nucleació extensiva que influeix en la transició vítria, el creixement cristal·lí, la viscositat i la microduresa. Els vidres es poden elaborar a temperatures inferiors a 1450 ºC. La nucleació també permet la formació d’una textura de gra fi en els vitroceràmics; la magnetita actua com a nucli per a la formació del diòpsid. Totes les composicions inertitzen adequadament els elements potencialment tòxics de manera que es poden considerar inerts. La microduresa està en el rang dels materials vitris i vitroceràmics usats en construcció. Per tant, tenen potencial per ser usades com a matèria primera per a la producció de vidres i vitroceràmics comercials complint amb els principis de l’economia circular

Modelization of the vitrification of sewage sludge using a basaltic matrix

Sewage sludge is a high volume, potentially toxic waste generated during the decontamination process of wastewater. Improved solutions for waste disposal require its conversion into an end product or at least a raw material for new applications. The chemical composition of sewage is similar to that of a basalt enriched in P and Ca, hence it may be inertized by vitrification. The experimental strategy is based on producing glasses from mixtures containing basalt, P and/or Ca to study the production of glass from sewage sludge. Selected glass compositions are then doped with toxic elements (Ba, Cr, Cu, Ni and Zn) to assess the possibility of using the SS like glass as an inertization matrix for hazardous wastes. Part of these glasses are taken as parent compositions to obtain glass-ceramics, which may offer improved properties. The characterization of the glasses and glass-ceramics includes the study of their composition (electron microprobe), texture (scanning and transmission electron microscopy), structure (Raman and Mössbauer spectroscopies), thermal behavior (differential thermal analysis) and crystallization (X-Ray diffraction) macroscopic properties (density, viscosity, glass transition temperature and microhardness) and the chemical resistance (leaching tests). These analyses have shown that the solubility of each element in the basalt glass is limited by either crystallization or phase separation processes. Their large Fe contents cause a pervasive nucleation that has a large influence in the glass transition temperature, crystal growth, viscosity and microhardness and texture. It is of particular importance the delay caused by crystallization in the decrease of viscosity with increasing temperature. However, all the glasses have a viscosity low enough to be melted at temperatures about 1450 ºC . The presence of nuclei also causes the formation of a fine-grained texture of mostly diopside (together with akermanite and nepheline) in the glass-ceramics. In particular, the magnetite nuclei are the germ for the crystallization of diopside. All the compositions seem to effectively bind the elements in the corresponding glass structure, as the leaching levels comply with the limits for them to be considered inert. Moreover, their microhardness is in the range of commercial glasses and glass-ceramics used in the construction industry. In conclusion, sewage sludge compositions show potential to be used as raw material for the production of commercial glasses and glass<ceramics following the spirit of circular economy.Els llots de depuradora són un residu de volum elevat i potencialment tòxic que es genera durant el procés de descontaminació de les aigües. Millorar el processament dels residus implica convertir­los en un material reutilitzable o en una matèria primera. Aquests llots es poden assimilar a un basalt enriquit en P i Ca;; per tant, és possible inertitzar-­los mitjançant la vitrificació. Es proposa un estudi de l’efecte del P, el Ca i els dos elements combinats per determinar quin efecte tenen en la formació del vidre. Certes composicions escollides es doparan amb elements tòxics (Ba, Cr, Cu, Ni, Zn) per determinar la possibilitat d’usar una matriu basada en els llots per a la inertització de residus perillosos. També s’estudia l’obtenció de vitroceràmics a partir d’aquests vidres per millorar­ne les propietats. La caracterització dels vidres i els vitroceràmics inclou la composició química (microsonda electrònica), textura (microscòpia electrònica de rastreig i transmissió), estructura (espectroscòpies Raman i Mössbauer), anàlisi tèrmica diferencial, cristal·lització (Difracció de Raigs X), propietats macroscòpiques (viscositat, densitat, temperatura de transició vítria i microduresa) i la resistència a l’atac químic (assajos de lixiviació). Els elevats continguts en Fe dels vidres generen una nucleació extensiva que influeix en la transició vítria, el creixement cristal·lí, la viscositat i la microduresa. Els vidres es poden elaborar a temperatures inferiors a 1450 ºC. La nucleació també permet la formació d’una textura de gra fi en els vitroceràmics; la magnetita actua com a nucli per a la formació del diòpsid. Totes les composicions inertitzen adequadament els elements potencialment tòxics de manera que es poden considerar inerts. La microduresa està en el rang dels materials vitris i vitroceràmics usats en construcció. Per tant, tenen potencial per ser usades com a matèria primera per a la producció de vidres i vitroceràmics comercials complint amb els principis de l’economia circular