Recycling of Al-rich industrial sludge in refractory ceramic pressed bodies

Ramos

2007

Ceramics International

Mullite was produced from a mixture of raw wastes with high contents of silica and aluminium hydroxides. The first were wastes from slate rocks and had muscovite, chlorite and quartz as their main crystalline phases. The second were aluminium sludges resulting from the physicochemical treatment of the wastewaters generated by aluminium surface treatment industries. As-received raw materials were weighed to produce the 2:1 alumina:silica stoichiometric mixture, corresponding to an excess of alumina relatively to the ideal 3:2 mullite composition. The nonisothermal activation energies for primary (431 kJ/mol) and secondary mullite crystallization (454 kJ/mol) were determined by differential dilatometry. Sintered products were composites of mullite and a-alumina dispersed in a glassy phase and presented flexural strengths higher than 100 MPa after sintering temperatures at 1285 8C. #

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mullitization kinetics from silica- and alumina-rich wastes

Ramos

2007

Ceramics International

Bol. Soc. Esp. Ceram. Vidr.

“…In other hand, the recycling of an Al-rich anodising sludge as a major component of different ceramic compositions has been tested (8)(9)(10). Full characterization and specification of pre-treatment needs of the Al-sludge, and its mixture with natural components, such as kaolin and clays has been studied and related before (8,9).…”

Section: Introductionmentioning

confidence: 99%

“…Full characterization and specification of pre-treatment needs of the Al-sludge, and its mixture with natural components, such as kaolin and clays has been studied and related before (8,9). The main goal was to prove that this waste can be regarded as a useful raw material for other industries, such as ceramic, thus reducing the negative environmental impact associated with landfill and preserving non-renewable nature resources.…”

Section: Introductionmentioning

confidence: 99%

Evolución de la espectroscopia de impedancia sobre cuerpos extruidos basados en barros de anodizado ricos en Al

Ribeiro¹,

Abrantes²,

Labrincha³

2006

Alumina based ceramic materials, containing Al-rich sludge as the major component, were processed by extrusion. The sludge derived from the wastewater treatment of aluminium anodising industrial process. Long rods were produced using a vacuum screw extruder, by a careful control of all relevant processing parameters. Then, thick discs were obtained by cutting dried selected rods, to be tested as probes for sintering-dependent electrical properties. The sintering process was followed by performing common dilatometric/thermal analyses but the evolution of electrical conductivity, estimated by impedance spectroscopy (IS), was also used for this purpose. Results show that sintering-dependent morphological evolution up to 1300ºC strongly affects the electrical behaviour of samples, and as a consequence IS seems to be a useful technique to follow the firing process.Keywords: alumina waste-based materials; impedance spectroscopy; sintering; microstructural development Evolución de la espectroscopia de impedancia sobre cuerpos extruidos basados en barros de anodizado ricos en Al.Los materiales cerámicos basados en alúmina, conteniendo barros ricos en Al como componente mayoritario fueron procesados por extrusión. Los barros empleados provienen de tratamientos de lavado de residuos de un proceso industrial de anodizado de aluminio. Se produjeron varillas empleando un extrusor de tornillo en vacío con control de todos los parámetros relevantes del proceso. A partir de varillas seleccionadas, se obtuvieron por corte en seco discos cerámicos para evaluar la dependencia de la sinterización y las propiedades eléctricas. El proceso de sinterización se siguió mediante ensayos dilatométricos y análisis térmicos, junto con la evolución de la conductividad eléctrica mediante espectroscopia de impedancia. Los resultados mostraron la evolución de la sinterización y la dependencia morfológica hasta 1300ºC, que afecta fuertemente a la respuesta eléctrica y como consecuencia la espectroscopia de impedancia parece ser una técnica útil en el seguimiento de los procesos de cocción.Palabras clave: Materiales basados en residuos de alúmina, espectroscopia de impedancia, sinterización, desarrollo microestructural.

Electrical characterization of mullite/alumina bodies based on Al-rich anodizing sludge by impedance spectroscopy

Ribeiro

Ferreira

et al. 2003

Ionics

Abstract. Al-rich sludge produced fi'om an industrial anodising and surface treatment processes had been tested in the fabrication of mullite/alumina-based refractor' materials, by using unidirectional dry pressing as shaping technique. Mixtures with common natural silica-containing materials, like ball clay, kaolin and/or diatomite were prepared in order to achieve interesting final fired refractor 5, and/or electrical insulating compositions. Microstructural changes upon sintering and crystalline phase evolution are detailed and their relationship with the electrical behaviour is now studied, by the use of impedance spectroscopy.