title: Phosphorus in recycling fertilizers - analytical challenges.
abstract: The importance of secondary raw materials for phosphorus (P) fertilizer production is expected to increase in the future due to resource depletion, supply risks, and heavy metal contamination of fossil phosphate resources. Municipal wastewater is a promising source for P recovery. In Germany for instance, it contains almost 50% of the total amount of P that is currently applied as mineral fertilizer. Several procedures have been developed to recover and re-use P resulting in a growing number of recycling fertilizers that are currently not regulated in terms of fertilizer efficiency. We tested various materials and matrices for their total P content, solubility of P in neutral ammonium citrate (Pnac) and water, and performed robustness tests to check if existing analytical methods are suitable for those new materials. Digestion with inverse aqua regia was best suited to determine the total P content. Pnacsample preparation and analyses were feasible for all matrices. However, we found significant time and temperature dependencies, especially for materials containing organic matter. Furthermore, several materials didn't reach equilibrium during the extractions. Thus, strict compliance of the test conditions is strongly recommended to achieve comparable results.
authors.affiliation: Beuth University of Applied Sciences, Luxemburger Str. 10, 13353 Berlin, Germany. Electronic address: krueger-oliver@t-online.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Krüger
authors.affiliation: Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter Str. 11, 12489 Berlin, Germany. Electronic address: christian.adam@bam.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Adam
mesh_terms: D019343:Citric Acid / Q000737:chemistry; D005308:Fertilizers / Q000032:analysis*; D006851:Hydrochloric Acid / Q000737:chemistry; D006858:Hydrofluoric Acid / Q000737:chemistry; D017745:Incineration; D007220:Industrial Waste; D017942:Nitric Acid / Q000737:chemistry; D010472:Perchlorates / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D059027:Recycling / Q000379:methods*; D012722:Sewage / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D013696:Temperature
chemical_list: D005308:Fertilizers; D007220:Industrial Waste; D010472:Perchlorates; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D010758:Phosphorus; D019343:Citric Acid; D017942:Nitric Acid; D012972:Sodium Hydroxide; C481046:ammonium citrate; D006851:Hydrochloric Acid; D006858:Hydrofluoric Acid; C576518:Perchloric Acid; C022102:aqua regia
keywords: Analytical methods; Phosphorus recovery; Plant availability; Recycling fertilizer; Robustness tests