Removal of toxic metals from industrial sludge by fixing in brick structure

The aim of this study was to test utilization possibilities of industrial sludge in masonry industry, as well as risk of toxic elements leaching potential. Sludge is generated in a hot-dip galvanizing process after waste water neutralization. This waste is considered to be hazardous due to the presence of toxic elements, which can be fixed within heavy clay matrix after thermal treatment. Relatively large amounts of toxic metals were found in used raw materials, but their leachability reduces to a negligible level after firing at 1020 °C. The results show that sludge can be used to produce eco-friendly bricks.

► Sludges generated in hot galvanizing are used as supplement in heavy clay bricks.
► Sludges contain toxic metals fixed within mineral structure during bricks firing.
► Strength drops with sludge share while porosity and water absorption increase.
► Amounts of most analyzed microelements are not detectable during leaching in water.