title: Immobilization of aqueous cadmium by addition of phosphates.
abstract: In situ immobilization of heavy metals in polluted soils using phosphates leads to formation of products which are highly insoluble and thermodynamically stable over a broad pH and Eh range. In this research effectivity of Cd ions immobilization (initial [Cdaq]-4.800 mM) from aqueous solutions by different phosphorus compounds (K2HPO4, NH4H2PO4 and "Polifoska 15" fertilizer) was compared at pH in the range 4.00-9.00 and for reaction times 2-1440 h. The highest reduction of cadmium concentration (>99%), owing due to the formation of cadmium phosphates, was observed for all used phosphorus sources within pH range of 6.75-9.00. Uptake of cadmium for pH< or =5.00 did not exceed 80% and was lowest in the reaction with "Polifoska 15" fertilizer (28.25%). Identification of phases formed in the reactions using XRD, FTIR and SEM-EDS-EBSD was carried out. It was noticed that crystallinity of formed solid decreased with pH increase. Formation of Cd5H2(PO4)4.4H2O was observed in acidic conditions (pH< or =5.00), at pH approximately 7.00 mixture of following cadmium phosphates Cd(H2PO4)2, Cd3(PO4)2 and Cd5H2(PO4)4.4H2O was formed. Amorphic cadmium phosphates were noticed in alkaline conditions (pH>8.50).
authors.affiliation: AGH-UST University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, al. Mickiewicza 30, 30-059 Cracow, Poland. jmatusik@geol.agh.edu.pl <jmatusik@geol.agh.edu.pl>
authors.forename: Jakub
authors.initials: J
authors.lastname: Matusik
authors.forename: Tomasz
authors.initials: T
authors.lastname: Bajda
authors.forename: Maciej
authors.initials: M
authors.lastname: Manecki
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D014867:Water
chemical_list: D010710:Phosphates; D012989:Soil Pollutants; D002104:Cadmium; D014867:Water