Long-Term Solidification/Stabilization and Toxicity Characteristic Leaching Procedure for an Electric Arc Furnace Dust

Abstract

The effect of cure age and mix design are investigated for the stabilization of lead and cadmium in an electric arc furnace dust. Within the first year, cadmium leaching is negligible for all mix designs, whereas lead solidification/stabilization is influenced by the selection of mix design. After one year, 370-day results for lead and cadmium are nearly equal for corresponding mix designs. Furthermore, within the range of 370-day results, the rank of cadmium and lead results is the same and is established by mix design. The mix design determines the ultimate toxicity characteristic leaching procedure (TCLP) outcome, which is suspected to be the result of the extent of development of the calcium silicate phase. The comparison of TCLP data with hydroxide solubility curves indicates that extract pH values decreased with increasing cure age; TCLP results were below the hydroxide solubility curve, but they generally followed the amphoteric shape of the hydroxide solubility curve. TCLP results after 2 days of curing may be deceptive because mix designs with more binder improve with longer cure times while mix designs with less binder that are acceptable early may degrade with age.