Mine wastes that are deposited near the abandoned mining sites without proper treatment have risk of contaminant spread, especially by heavy metal leaching. Several industrial wastes such as BOF slags are being researched to stabilize the heavy metals in the mine wastes these days. BOF slags contain lots of Fe2O3 and CaO, and it is well known that heavy metals can be stabilized by adsorption onto Fe2O3 surface, or/and precipitation induced by CaO. Because water as well as BOF slags is needed for heavy metal stabilization, BOF slag and water contents play important roles on stabilization efficiency. In this research, a mine waste highly contaminated with As (about 165,946 mg/kg) was tested for stabilization using BOF slags with different stabilizing conditions (i.e. BOF slag and water contents). Batch tests were conducted with 0.5, 3, 5, and 10 wt% of BOF slag mixed with 10 g of the mine waste. Various moisture contents (0.05, 0.2, 0.5, 1.0 L/kg) were given for each set. After agitated for 1 hour in the room temperature, the mixtures (BOF slags and mine waste) were dried in the 60°C oven, then leached using TCLP method. Leached amounts of As were measured with ICP-OES, and their stabilization efficiencies were quantified. As BOF slag contents increased (0.5, 3, 5, and 10 wt%), As stabilization efficiency increased (22, 42, 80, and 92%, respectively, when 0.2 L/kg water was added). On the other hand, the increase in water contents (from 0.05 to 1.0 L/kg) decreased As stabilization efficiency (from 78 to 22%, when 3 wt% BOF slags were added). Since the supernatant during the stabilizing process was alkaline condition (pH 10.5), Ca2+ in the supernatant can react with water to be precipitated in Ca(OH)2 form. When Ca(OH)2 are precipitated on the surface of BOF slags, this might block the As sorption site. Larger amount of Ca(OH)2 on the surface of BOF slags was detected by X-ray photoelectron spectroscopy (XPS) when 1.0 L/kg water was treated, compared to when 0.05 L/kg water was treated. When the supernatant pH during the stabilizing process was lowered from 10.5 to 8.8 so that Ca(OH)2 was barely formed, As stabilization efficiency was not affected by water contents. This research may contribute to selecting heavy metal stabilizing conditions using BOF slags.

Effect of water contents on arsenic stabilization in mine waste using basic oxygen furnace (BOF) slags

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.