title: Chemical state of chromium in sewage sludge ash based phosphorus-fertilisers.
abstract: Sewage sludge ash (SSA) based P-fertilisers were produced by thermochemical treatment of SSA with Cl-donors at approximately 1000°C. During this thermochemical process heavy metals are separated as heavy metal chlorides via the gas phase. Chromium cannot be separated under normal conditions. The risk of the development of toxic Cr(VI) during the thermochemical process was investigated. X-ray Absorption Spectroscopy measurements showed that SSA and thermochemically treated SSA with CaCl2, MgCl2 and NaCl contain Cr(III) compounds only. In contrast, treating SSA with elevated quantities of Na2CO3, to enhance the plant-availability of the phosphate phases of the fertiliser, developed approximately 10-15% Cr(VI). Furthermore, Raman microspectroscopy showed that using Mg-carbonate reduces the risk of a Cr(VI) development during thermochemical treatment. Additionally, leaching tests showed that only a Cr-water solubility>10% is an indicator for Cr(VI) in SSA based P-fertilisers.
authors.affiliation: School of Chemistry, Monash University, Wellington Road, Clayton 3800, Victoria, Australia; BAM Federal Institute for Materials Research and Testing, Division 4.4 Thermochemical Residues Treatment and Resource Recovery, Unter den Eichen 87, D-12205 Berlin, Germany. Electronic address: cv.vogel@yahoo.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Vogel
authors.affiliation: BAM Federal Institute for Materials Research and Testing, Division 4.4 Thermochemical Residues Treatment and Resource Recovery, Unter den Eichen 87, D-12205 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Adam
authors.affiliation: Australian Synchrotron, 800 Blackburn Road, Clayton 3168, Victoria, Australia; Department of Physics, La Trobe University, Bundoora 3086, Victoria, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Kappen
authors.affiliation: School of Chemistry, Monash University, Wellington Road, Clayton 3800, Victoria, Australia; Department of Materials Engineering, Monash University, Wellington Road, Clayton 3800, Victoria, Australia.
authors.forename: Tara
authors.initials: T
authors.lastname: Schiller
authors.affiliation: School of Chemistry, Monash University, Wellington Road, Clayton 3800, Victoria, Australia; The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, E. Radzikowskiego 152, 31-342 Kraków, Poland.
authors.forename: Ewelina
authors.initials: E
authors.lastname: Lipiec
authors.affiliation: School of Chemistry, Monash University, Wellington Road, Clayton 3800, Victoria, Australia.
authors.forename: Don
authors.initials: D
authors.lastname: McNaughton
mesh_terms: D002857:Chromium / Q000737:chemistry*; D005308:Fertilizers; D010758:Phosphorus / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D012995:Solubility; D013059:Spectrum Analysis, Raman; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005308:Fertilizers; D012722:Sewage; D002857:Chromium; D010758:Phosphorus
keywords: Chromium; Fertiliser; Raman microspectroscopy; Sewage sludge ash; X-ray Absorption Spectroscopy