Use of colloidal silica to obtain a new inert from municipal solid waste incinerator (MSWI) fly ash: first results about reuse

The MSWI (Municipal Solid Waste Incinerator) fly ash may represent a potential health and environmental hazard for its high heavy metal content. Fly ash is commonly disposed in specific landfills to prevent the leaching of pollutants into underground aquifers. Several technologies (for example, thermal treatment, physical/chemical separation, and stabilization/solidification techniques) have been developed for treatment of fly ash to obtain second-hand inert materials. Moreover, reuse of these materials is strictly dependent on their physical and mechanical features. Possible applications of these materials are clinkering, road pave, and construction works where, specific performances are required. Recently, at the University of Brescia (Italy) a new process has been developed to inertize fly ash, by means of colloidal silica. The new inertization process involves low temperature reactions and produces a final material named COSMOS (Colloidal Silica Medium to Obtain Safe inert) that can be employed as a filler substituting natural materials such as carbon black, sand, etc. The project is supported by LIFE program of the European Community (LIFE + 2008 project ENV/IT/000434). In this study we present results about the reuse of COSMOS in different high quality controlled plaster materials. An appropriate waste management, based on the principles of sustainable development, is based on the principle that waste cannot be considered as something to eliminate but rather a potential resource.