TY - JOUR A1 - Stemann, Jan A1 - Peplinski, Burkhard A1 - Adam, Christian T1 - Thermochemical treatment of sewage sludge ash with sodium salt additives for phosphorus fertilizer production - Analysis of underlying chemical reactions T2 - Waste management N2 - Stocks of high grade phosphate rock are becoming scarce, and there is growing concern about potentially harmful impurities in conventional phosphorus fertilizers. Sewage sludge ash is a promising secondary phosphorus source. However, to remove heavy metals and convert the phosphorus contained in sewage sludge ash into mineral phases available to plants, an after-treatment is required. Laboratory-scale calcination experiments of sewage sludge ash blended with sodium salts using dried sewage sludge as a reducing agent were carried out at 1000 °C. Thus, the Ca3(PO4)2 or whitlockite component of raw sewage sludge ash, which is not readily plant available, was converted to CaNaPO4 (buchwaldite). Consequently, nearly complete phosphorus solubility in ammonium citrate (a well-established indicator for plant availability) was achieved. Moreover, it was shown that Na2CO3 may be replaced by moderately priced Na2SO4. However, molar ratios of Na/P > 2 were required to achieve >80% phosphorus solubility. Such over-stoichiometric Na consumption is largely caused by side reactions with the SiO2 component of the sewage sludge ash – an explanation for which clear evidence is provided for the first time. PB - Pergamon Press CY - New York, NY KW - Phosphorus recovery KW - Plant availability KW - Solubility in ammonium citrate KW - Whitlockite-to-buchwaldite transformation PY - 2015 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/33876 AN - OPUS4-33876 SN - 0956-053X VL - 45 SP - 385 EP - 390 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany