Other waste materials generated in steel industry are blast furnace sludge and blast furnace flue dust, which have also been explored as possible adsorbents. Jallan and Pandey reported the use of blast furnace sludge as adsorbent without any treatment for the removal of some toxic ions, viz. Pb2+, Ni2+, Cd2+, Cu2+, Zn2+ and CN−. It was found by them that sludge has a good adsorptive capacity for metal ions as well as cyanide but the maximum adsorption (9 mg/g) was poor in the case of Zn2+. Sludge was also tested as adsorbent by López-Delgado et al. for the removal of some heavy metal ions who reported that metal ions were adsorbed in the order, Pb2+ > Ni2+ > Cd2+ > Cu2+ > Zn2+. The process was found to be endothermic and the adsorption data fitted both to Freundlich and Langmuir isotherms. Patnaik and Das investigated the use of blast furnace flue dust as adsorbent for the removal of hexavalent chromium and found the applicability of first-order kinetics for the adsorption process.