Effect of additives on heavy metal immobilization during vitrification of tannery sewage sludge

The aim of this study was to evaluate the effect of additives such as waste moulding sands (WMS) and dolomite flotation waste (F) on heavy metal immobilization during vitrification of tannery sewage sludge. Sewage sludge with addition of waste moulding sands of 25-45 vol. % and flotation waste of 5-25 vol. % was used in the vitrification process. The study demonstrated a direct correlation between the WMS fraction in the vitrified formulations and heavy metal immobilization in the obtained vitrificates. Vitrification of sewage sludge with these additives resulted in obtaining vitreous products with reduced heavy metal leaching properties; the lowest content of heavy metals in the leachates was found in the vitrificates with the highest content of waste moulding sands.