Analysis of the effects of different types of carbonation treatments aimed at allowing the unrestricted reuse of waste incineration bottom ash

The mineral fraction of waste incineration bottom ash (BA) generally presents suitable physical and technical properties for use as secondary material in construction. However, its total content and especially leachingof specific metals, metalloids and saltsgreatly hindersits reuse,which is excluded completely in severalCountries,or carried out only under restricted conditions in others. Natural weathering is a widely applied treatment to improve the leaching behaviour of BA before reuse,but typically does not allow to achieve the requirements for unrestricted reuse. The aim of this study was to analyze the effects of accelerated carbonation treatments on the leaching behaviour of the mineral fraction of Refuse Derived Fuel (RDF) incineration BA. The treatment wascarried outunder enhanced operating conditions both via the wet route,applying a low liquid to solid ratio(L/S),and the slurry phase one(at a L/S of 5 l/kg) in view of improvingtheenvironmental behaviour of the BA so to allow its reuse underunrestricted conditions. Overall, the results showed that for the type of analysed BA both carbonation treatments allowedto significantly decrease the release of constituents such as Pb,Cu,Ba and Zn. In addition,the slurryphaseroute showed to relevantlyreduce the release of chlorides,sulphates and Cr.The release from the treatment product of this latter constituent proved to decrease particularly at the highest temperature tested (100 °C). A maximum CO2uptake of around 7% in the product of both carbonation routes was attained.