title: Stabilization of heavy metals in MSWI fly ash using silica fume.
abstract: The objective of this work was to investigate the feasibility and effectiveness of silica fume on stabilizing heavy metals in municipal solid waste incineration (MSWI) fly ash. In addition to compressive strength measurements, hydrated pastes were characterized by X-ray diffraction (XRD), thermal-analyses (DTA/TG), and MAS NMR ((27)Al and (29)Si) techniques. It was found that silica fume additions could effectively reduce the leaching of toxic heavy metals. At the addition of 20% silica fume, leaching concentrations for Cu, Pb and Zn of the hydrated paste cured for 7 days decreased from 0.32 mg/L to 0.05 mg/L, 40.99 mg/L to 4.40 mg/L, and 6.96 mg/L to 0.21 mg/L compared with the MSWI fly ash. After curing for 135 days, Cd and Pb in the leachates were not detected, while Cu and Zn concentrations decreased to 0.02 mg/L and 0.03 mg/L. The speciation of Pb and Cd by the modified version of the European Community Bureau of Reference (BCR) extractions showed that these metals converted into more stable state in hydrated pastes of MSWI fly ash in the presence of silica fume. Although exchangeable and weak-acid soluble fractions of Cu and Zn increased with hydration time, silica fume addition of 10% can satisfy the requirement of detoxification for heavy metals investigated in terms of the identification standard of hazardous waste of China.
authors.affiliation: School of Environment Science and Engineering, Donghua University, Shanghai 201620, PR China; State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai 201620, PR China.
authors.forename: Xinying
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Environment Science and Engineering, Donghua University, Shanghai 201620, PR China; State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai 201620, PR China.
authors.forename: Quanyuan
authors.initials: Q
authors.lastname: Chen
authors.affiliation: School of Environment Science and Engineering, Donghua University, Shanghai 201620, PR China.
authors.forename: Yasu
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Mineral Industry Research Organisation, Solihull B37 7HB, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Tyrer
authors.affiliation: School of Environment Science and Engineering, Donghua University, Shanghai 201620, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
mesh_terms: D060729:Coal Ash / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D060729:Coal Ash; D019216:Metals, Heavy; D012822:Silicon Dioxide
keywords: Fly ash; Municipal solid waste; Pozzolanic reaction; Silica fume; Stabilization