Immobilisation of metals from bottom sediments using two additives and thermal treatment

A major problem associated with the land-based management of bottom sediments is their contamination with metals. The aims of the study were: 1) to use two additives for the immobilisation of metals; and 2) to evaluate the effect of three combustion temperatures on metal content and bottom sediment properties. The mixtures were prepared using contaminated bottom sediment and the following waste materials: cellulosic waste and biomass ash. In the second experiment, the bottom sediment samples were subjected to a thermal process, and three temperatures were chosen 500/800/950 °C. Overall, the addition of cellulosic waste and biomass ash to acidic, metal-contaminated bottom sediments significantly improved the properties of the resulting mixtures, including an increase in the pH value, sorption capacity, macronutrient content, and a decrease in the content and mobility of metals (Cd, Zn, Pb, Cr). The study confirmed the effectiveness of the thermal process on a significant reduction in the ecotoxicity of the sediments, a reduction in total content of elements, and a decrease in their leachability, and thus mobility, with increasing process temperature. The study results revealed that the converted contaminated bottom sediments can be effectively managed, provided that further studies on their technical application are carried out.