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...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2018 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/668461 |
| Acceso en línea: | http://hdl.handle.net/10803/668461 |
| Access Level: | acceso abierto |
| Palabra clave: | Residus perillosos Residuos peligrosos Hazardous wastes Depuració d'aigües residuals Depuración de aguas residuales Purification of sewage Llots de depuradora Lodos de depuradora Sewage sludge Ciències Experimentals i Matemàtiques 55 |
| Sumario: | 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. |
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