Lead removal from aqueous solutions by granulated blast-furnace slag

The removal of lead by sorption on granulated blast-furnace slag has been investigated as a function of pH, the metal ion concentration, the particle size and the amount of sorbent. It has been established that the process occurs with increasing pH. It was found that the dependence of the process on pH is similar to the dependence of the formation of soluble and insoluble hydrolysis products of lead on pH, but the efficient lead removal by granulated slag is occurred at pH values lower than precipitation pH values, i.e. the sorption is a predominating process. The equilibrium in the slag/lead solution system is described by the Freundlich adsorption isotherm. The constants in the Freundlich equation have been calculated for different slag particle sizes at pHin=5.0–5.1. The percentage of lead removal at equilibrium increases with increasing slag amount but the sorption capacity decreases. Depending on the conditions, a percent lead removal of 97–98% can be achieved. The results obtained could be useful for the application of granulated slag for the Pb-ions removal from industrial waste water.