title: Effect of ferrous metal presence on lead leaching in municipal waste incineration bottom ashes.
abstract: The recovery of ferrous and non-ferrous metals from waste to energy (WTE) ash continues to advance as the sale of removed metals improves the economics of waste combustion. Published literature suggests that Fe and Fe oxides play a role in suppressing Pb leaching in the Toxicity Characteristic Leaching Procedure (TCLP); further removal of ferrous metals from WTE ashes may facilitate higher Pb leaching under the TCLP. Eight WTE bottom ash size-fractions, from three facilities, were evaluated to assess the effect of metallic Fe addition and ferrous metal removal on TCLP leaching. Metallic Fe addition was demonstrated to reduce Pb leaching; the removal of ferrous metals by magnet resulted in a decrease in total available Pb (mg/kg) in most ash samples, yet Pb leachability increased in 5 of 6 ash samples. The research points to two chemical mechanisms to explain these results: redox interactions between Pb and Fe and the sorption of soluble Pb onto Fe oxide surfaces, as well as the effect of the leachate pH before and after metals recovery. The findings presented here indicate that generators, processors, and regulators of ash should be aware of the impact ferrous metal removal may have on Pb leaching, as a substantial increase in leaching may have significant implications regarding the management of WTE ashes.
authors.affiliation: Department of Environmental Engineering Sciences, University of Florida, P.O. Box 116450, Gainesville, FL 32611-6450, USA.
authors.forename: Wesley N
authors.initials: WN
authors.lastname: Oehmig
authors.affiliation: Department of Environmental Engineering Sciences, University of Florida, P.O. Box 116450, Gainesville, FL 32611-6450, USA.
authors.forename: Justin G
authors.initials: JG
authors.lastname: Roessler
authors.affiliation: Department of Natural Sciences, Voorhees College, P.O. Box 678, Denmark, SC 29042, USA.
authors.forename: Jianye
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Environmental Engineering Sciences, University of Florida, P.O. Box 116450, Gainesville, FL 32611-6450, USA. Electronic address: ttown@ufl.edu.
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Townsend
mesh_terms: D060729:Coal Ash / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D017745:Incineration; D007854:Lead / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods
chemical_list: D060729:Coal Ash; D005290:Ferric Compounds; D005296:Ferrous Compounds; C000499:ferric oxide; D007854:Lead; C034236:ferrous oxide
keywords: Ash; Incineration; Iron; Leaching; Lead; TCLP