title: Mechanisms for the aging-induced reduction of lead solubility in scrubber residues from municipal solid waste combustion.
abstract: This manuscript elucidates the mechanisms responsible for aging-induced reduction in lead leaching from scrubber residues. Leaching tests (JLT13) were conducted on 48 types of scrubber residues and lead solubility was found to be significantly reduced independent of incinerator type or type of gas treatment method. Reaction kinetics that result in lead solubility reduction were shown to be proportional to carbon dioxide partial pressure and in many cases were limited by mass transfer to the residue. With forced gas convection through the residue and a CO2 partial pressure of 0.3%, the concentration of lead in leachate was reduced from 84 mg L(-1) to < 0.5 mg L(-1) in two days. Ettringite analogs (Ca6Al2 (SO4) 3(OH)2 . 26H2O) were identified by X-Ray Diffraction in the wetted scrubber residues early in the aging process; these appear to have been converted into gypsum (CaSO4 . 2H2O) and vaterite (CaCO3) in the aged material. All of these solid phases are believed to substitute lead into their crystal structure and evidence for this attenuation mechanism is presented.
authors.affiliation: Department of Civil Engineering, Faculty of Engineering, Fukuoka University, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Shimaoka
authors.forename: Kentaro
authors.initials: K
authors.lastname: Miyawaki
authors.forename: Masashi
authors.initials: M
authors.lastname: Soeda
authors.forename: Masataka
authors.initials: M
authors.lastname: Hanashima
authors.forename: Tsuneyuki
authors.initials: T
authors.lastname: Yoshida
authors.forename: Toshihito
authors.initials: T
authors.lastname: Uchida
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
authors.forename: T Taylor
authors.initials: TT
authors.lastname: Eighmy
mesh_terms: D000397:Air Pollution / Q000517:prevention & control; D002245:Carbon Dioxide / Q000737:chemistry; D003460:Crystallization; D017745:Incineration; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D011312:Pressure; D012037:Refuse Disposal; D012995:Solubility; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D007854:Lead