Stabilization of air pollution control residues by utilizing geopolymerisation to produce secondary building materials

Incineration is a powerful waste management tool which is employed in many countries. However, air pollution control residues are a by-product produced as a result of flue gas treatment, a key requirement for incineration. Air pollution control residues are classified as hazardous waste and are becoming increasingly difficult to dispose of in the UK due to tightening legislation. Therefore recycling of air pollution control residues as secondary building materials is an attractive option. Geopolymerisation offers advantages with regards to stabilizing heavy metals and has been investigated here as a means to reducing leaching rates of key elements in air pollution control residues collected from three UK based incinerators. The role of soluble chloride phases was also investigated by pre-treating the air pollution control residues with a washing procedure. Geopolymerisation was found to immobilize metals such as Ba, Pb and Ni, however it did not positively affect the mobility of As, Sb and Se. Chloride leaching rates were also reduced although not to an acceptable level and the mobility of soluble chloride phases are one of the key challenges when attempting to reuse air pollution control residues.