Increasing demand and supply risks are likely to increase the use of fertilizers produced from recycled products and wastes. In order to ensure safe fertilizer application reliable information on the content of carcinogenic and ecotoxic hexavalent chromium species (Cr(VI)) are required. Since the existing analytical methods have been developed for conventional fertilizers their suitability for the new materials have to been tested. Thus, wet-chemical extraction of Cr(VI) was applied to several matrices and respective quality control materials spiked with Cr(III) and Cr(VI) compounds. Cr(VI) amounts were generally below 2 mg/kg except for a thermally post-treated sewage sludge ash (SSA) that displayed 12.3 mg/kg. The presence of organic matter e.g. in sludge or precipitated struvite led to a reduction of spiked Cr(VI) and hampered sound recovery experiments. Cr(VI) reduction was also observed in SSA, presumably due to the presence of Fe(II) compounds. Even though matrices pose an analytical challenge the tested procedure may be adapted for general application to recycled fertilizers.
Determination of chromium (VI) in primary and secondary fertilizer and their respective precursors
Oliver Krüger, F. Fiedler, Christian Adam, Christian Vogel, R. Senz
Chemosphere Volume 182, September 2017, Pages 48-53
BAM Department Materials and the Environment, Division Thermochemical Residues Treatment and Resource Recovery