Sorption of heavy metals on blast furnace sludge

An investigation into the use of sludge, a by-product of the steel industry, as an adsorbent for the removal of heavy metals from liquid effluents was carried out. Gases produced in the blast furnace were washed and led towards a Dorr thickener where the sludge was obtained as a suspension. The sorption of Pb2+, Zn2+, Cd2+, Cu2+ and Cr3+ on the sludge was investigated by determination of adsorption isotherms. The effects of time, equilibrium temperature and concentration of metal solution on sludge adsorption efficiency was evaluated. The adsorption process was analyzed using the theories of Freundlich and Langmuir and the thermodynamic values of ΔG, ΔH and ΔS corresponding to each adsorption process were calculated. Blast furnace sludge was found to be an effective sorbent for Pb, Zn, Cd, Cu and Cr–ions within the range of ion concentrations employed.