Process development for the removal of zinc and cadmium from wastewater using slag - A blast furnace waste material

Blast furnace slag, a waste generated in steel plants in India, has been converted into a low cost potential adsorbent. The resulting product has been characterized and used for the removal of zinc and cadmium. The effect of particle size, contact time, and surface loading of zinc and cadmium on the adsorbent for their removal have been studied at the optimum pH (6.0 for Zn2+ and 5.0 for Cd2+). Kinetic studies were undertaken to show the mechanistic aspects of the process and to obtain the thermodynamic parameters. Sorption data have been correlated with both Langmuir and Freundlich adsorption models. Column operations were also performed in an attempt to simulate industrial conditions. Some feasibility experiments have been performed with a view to recovering Zn2+ and Cd2+ and for the chemical regeneration of the spent columns without dismantling them.