TY - JOUR A1 - Steckenmesser, D. A1 - Vogel, Christian A1 - Herzel, Hannes A1 - Félix, R. A1 - Adam, Christian A1 - Steffens, D. T1 - Thermal treatment of sewage sludge for phosphorus fertilizer production: a model experiment JF - Journal of Plant Nutrition N2 - Phosphorus (P) resource availability and quality is declining and recycling P-fertilizers from waste materials are becoming increasingly important. One important secondary P resource is sewage sludge (SSL) where P is often bound as aluminum phosphate (Al-P), iron phosphate (Fe-P) and polyphosphate (poly-P), respectively. Thermal treatment in different ways is a promising way in P recycling to produce highly plant-available P-fertilizers. To investigate mechanisms behind transformation of hardly available P-species toward plant-available P forms we treated a model SSL containing different kinds of defined P sources by low-temperature conversion (LTC) at 500 °C and subsequent thermochemical treatment of the LTC product with Na additives (TCT) at 950 °C, respectively. Pot experiments with ryegrass were carried out to determine the plant availability of P of the different treatments. The poly-P (here pyrophosphates) based fertilizers had a very high plant availability after both thermal treatments. During LTC treatment the plant availability of the Fe-P and Al-P variants increased because of the Formation of Fe(II) phosphates and/or pyro-/polyphosphates. Especially the formation of Al-polyphosphate shows a high plant availability. The subsequent TCT further increased strongly the plant availability of the Fe-P variants because of the formation of highly plant-available CaNaPO4. Thus, a direct TCT without prior LTC probably also produce CaNaPO4 and is recommended for Fe-P based SSL. However, a molar Ca/P ratio of � 1 in the fertilizer is favorable for CaNaPO4 formation. Thus, the knowledge on the source of primary P in SSL is essential for choosing the accurate thermal treatment method to produce highly plant-available P-fertilizers from SSL. KW - Phosphorus KW - Sewage sludge KW - X-ray diffraction KW - X-ray absorption near-edge structure (XANES) spectroscopy KW - Fertilizer PY - 2021 DO - https://doi.org/10.1080/01904167.2021.1994595 SN - 0190-4167 VL - 45 IS - 8 SP - 1123 EP - 1133 PB - Taylor & Francis Online AN - OPUS4-53755 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schraut, Katharina A1 - Adamczyk, Burkart A1 - Adam, Christian A1 - Stephan, D. A1 - Meng, Birgit A1 - Simon, Sebastian A1 - von Werder, Julia T1 - Synthesis and characterisation of alites from reduced basic oxygen furnace slags JF - Cement and Concrete Research N2 - Basic oxygen furnace slags (BOFS) are by-products of the steelmaking process. Several researchers have studied the production of Portland cement clinker and metallic iron from BOFS via a reductive treatment. In this study, we applied a carbothermal reduction of BOFS in a technical-scale electric arc furnace and characterised the clinker-like products. Those clinker-like non-metallic products (NMPs) had a chemical and mineralogical composition comparable to clinker for ordinary Portland cement (OPC) and contained large elongated alite crystals as major component. The pure NMPs reacted more slowly and achieved a lower degree of hydration compared with commercial OPC. If the reactivity of the products can be further increased by employing specific adaptations, it can be used as a full clinker substitute for OPC. Nevertheless, it is also an option to use the material without further modifications as a cement component or concrete addition, which contributes to the strength development in both cases. KW - BOFS KW - Hydration products KW - Thermal analysis KW - X-ray diffraction PY - 2021 DO - https://doi.org/10.1016/j.cemconres.2021.106518 SN - 0008-8846 VL - 147 SP - 6518 PB - Elsevier Ltd. AN - OPUS4-52939 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -