Removal of Lead and Chromium by Activated Slag—A Blast-Furnace Waste

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Abstract
The blast-furnace waste generated in steel plants has been converted into a low-cost adsorbent. The resulting activated slag has been characterized and used for the removal of lead and chromium. The effect of pH, sorbent dosage, adsorbate concentrations, presence of other metal ions, temperature, and contact time on the sorption of lead and chromium were studied in batch experiments. Kinetic studies were undertaken to have an idea of the mechanistic aspects of the process. The uptake of lead is found to be greater than that of chromium. Adsorption on activated slag follows both Freundlich and Langmuir models. In addition, a series of fixed-bed experiments were performed in an attempt to simulate industrial conditions. The bed-depth-service-time (BDST) model proposed by Hutchins was successfully applied to the sorptive removal of lead. Some experiments were also performed with a view to recover Pb2+ and chemically regenerate the spent slag columns in situ.