title: Immobilization and volume reduction of heavy metals in municipal solid waste fly ash using nano-size calcium and iron-dispersed reagent.
abstract: This study was conducted to examine the synthesis and application of novel nano-size calcium/iron-based composite material as an immobilizing and separation treatment of the heavy metals in fly ash from municipal solid waste incineration. After grinding with nano-Fe/Ca/CaO and with nano-Fe/Ca/CaO/[PO₄], approximately 30 wt% and 25 wt% of magnetic fraction fly ash were separated. The highest amount of entrapped heavy metals was found in the lowest weight of the magnetically separated fly ash fraction (i.e., 91% in 25% of treated fly ash). Heavy metals in the magnetic or nonmagnetic fly ash fractions were about 98% and 100% immobilized, respectively. Additionally, scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDS) observations indicate that the main fraction of enclosed/bound materials on treated fly ash includes Ca/PO₄-associated crystalline complexes. After nano-Fe/Ca/CaO/[PO₄] treatment, the heavy metal concentrations in the fly ash leachate were much lower than the Japan standard regulatory limit for hazardous waste landfills. These results appear to be extremely promising. The addition of a nano-Fe/Ca/CaO/PO₄mixture with simple grinding technique is potentially applicable for the remediation and volume reduction of fly ash contaminated by heavy metals.
  
  
  CONCLUSIONS
  After grinding with nano-Fe/Ca/CaO and nano-Fe/Ca/CaO/[PO₄], approximately 30 wt% and 25 wt% of magnetic fraction fly ash were separated. The highest amount of entrapped heavy metals was found in the lowest weight of the magnetically separated fly ash fraction (i.e., 91% in 25% of treated fly ash), whereas heavy metals either in the magnetic or nonmagnetic fly ash fractions were about 98% and 100% immobilized. These results appear to be very promising, and the addition of nano-Fe/Ca/CaO/PO₄mixture with simple grinding technique may be considered potentially applicable for the remediation and volume reduction of contaminated fly ash by heavy metals.
authors.affiliation: a Department of Civil and Environmental Engineering , University of Ulsan , Ulsan , Republic of Korea.
authors.forename: Srinivasa Reddy
authors.initials: SR
authors.lastname: Mallampati
authors.affiliation: b Department of Environmental Sciences , Prefectural University of Hiroshima , Hiroshima , Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Mitoma
authors.affiliation: c Politehnica University of Bucharest , Department of Organic Chemistry , Bucharest , Romania.
authors.forename: Cristian
authors.initials: C
authors.lastname: Simion
authors.affiliation: a Department of Civil and Environmental Engineering , University of Ulsan , Ulsan , Republic of Korea.
authors.forename: Byoung Ho
authors.initials: BH
authors.lastname: Lee
mesh_terms: D002118:Calcium / Q000737:chemistry; D060729:Coal Ash / Q000032:analysis*; D017745:Incineration; D007202:Indicators and Reagents / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D019216:Metals, Heavy / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D062611:Solid Waste / Q000032:analysis; D013052:Spectrometry, X-Ray Emission
chemical_list: D060729:Coal Ash; D007202:Indicators and Reagents; D019216:Metals, Heavy; D062611:Solid Waste; D007501:Iron; D002118:Calcium