The production of novel glass-ceramics from problematic UK wastes using borates

• Main Author: Dimech, Joan Christine
• Published: Imperial College London 2009
• Subjects: 666
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506903

Incineration of waste is increasing in the UK as landfill resources diminish. Municipalwaste incineration produces waste residues; bottom ash, fly ash and air pollutioncontrol (APC) residues. The present research project focuses on APC residues, whichare a hazardous waste arising from cleaning of incineration flue gases. APC residuesmust be pre-treated before disposal at hazardous landfill or placed in permanentsecure storage. The aim of this research project was to produce novel glass-ceramicsfrom optimised combinations of waste materials to provide a stabilised, safe materialof value and to provide an alternative to disposal. Pre-treatment of the APC residuesby washing was necessary to remove soluble chloride phases. Electrostaticprecipitator (EP) dust and soda-lime glass cullet were combined with the washed APCresidues as sources of glass forming oxides and borate. An optimised boratecontainingsilicate glass was produced from the wastes, from which dense, sinteredglass-ceramics and bulk glass-ceramics were successfully fabricated. A powdersintering method was used to produce a dense sintered material from washed APCresidues, EP dust and glass cullet. It was determined that the use of commerciallyavailable sodium borate (Neobor?) could be used to replace the waste source ofborate to produce a sintered material of equal mechanical and physical properties. Themain crystalline phases of all heat treated materials were wollastonite and gehlenite. The resulting mechanical and physical properties of the glass-ceramics and sinteredmaterials indicated they would be acceptable as construction materials. The results ofthe research project indicate that thermal treatment is a convenient technology for thesafe utilisation of a problematic waste (APC residues from municipal wasteincineration) in new products of potential commercial interest.