Chemical characterization and leaching of treated fly ash from a MSWI plant

With the aim of reducing landfill deposition the incorporation of industrial waste into the cement matrix of building materials is becoming common practice. An assessment of the elements and compounds present in the waste that have a detrimental effect on cement hydration or on the environment, Such as lead, zinc, chromium and sulphates, should always be performed. Fly ashes from the heat recovery and air pollution control systems of MSWI plants are classified as hazardous wastes owing to the concentration of potentially hazardous heavy metals as well as their high salt content. Waste pre-treatment represents a possible approach to prepare these residues for incorporation into building materials as it will reduce their Pollution potential. This paper presents the results of the chemical characterization of two fly ash mixtures, collected at different locations from a Portuguese MSWI plant, before and after a selected pretreatment, and an evaluation of their leaching behaviour.