Chemical precipitation is a consolidated technique applied in wastewater treatment to remove and recover phosphorous and ammonium that remain in the effluent after the anaerobic digestion treatment. The precipitate is magnesium ammonium phosphate hexahydrate (MgNH 4 PO 4 ·6H 2 O), also known as struvite, and it is sold as a slow-release fertiliser. However, the value of struvite is quite low and has a limited market. Furthermore, it precipitates with heavy metals and other impurities that need to be removed to make the fertiliser commercially viable. This study looked at the thermal decomposition of struvite to recover added value products and recycle the magnesium for further precipitation. A kinetic study was carried out to understand the mechanism of decomposition and the formation of the different solid phases, which is fundamental for the design and optimisation of the technology. The thermogravimetric study confirmed that thermal decomposition is possible, but ammonia could not be completely released below 250 °C. The thermal analysis also led to the determination of the energy required for the decomposition, found to be 1.87 kJ g −1 , which also includes the evaporation of water and ammonia. The kinetic study through the isoconversional method showed the presence of two major reactions, and the model-fitting approach identified the diffusion model as the best fit for the first reaction. The activation energy of the first reaction found with this method was 0.24 kJ g −1 , comparable with the data obtained from the isoconversional method. The two-stage decomposition reactions were proposed, and the final calcination product was confirmed as magnesium pyrophosphate, which could be used in agriculture or dissolved in diluted mineral acids solution to separate the phosphate from the magnesium.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Le narrazioni della migrazione si caratterizzano per complessità, intensità e molteplici finalità tra loro composite: di natura amministrativa (l'audizione davanti alla Commissione Territoriale per la richiesta di Protezione Internazionale), sociale (il colloquio sociale per l'apertura della cartella e per la progettazioneorientamento), educativa (i colloqui educativi per la progettazione dei PEI1 e del PDI) e psicologica (i colloqui terapeutici individuali di gruppo e i vari setting etnopsicologici). Troppo spesso sospesi tra narrazioni tossiche e strumentalizzazioni spettacolarizzanti (Fiorucci, 2017) i discorsi della migrazione rappresentano, invece, una possibilità educativa ed educante, una risorsa potenzialmente efficace per una solida e restitutiva relazione educativa. Questa riflessione teorica è frutto di analisi autoetnografica, dei memo narrativi (Charmaz, 2014) raccolti dal 2011 al 2018 nella pratica educativa in accoglienza e nella ricerca Dottorale relativa all'educazione dei Msna costruita tra il 2015 e il 2018.

No abstract

No abstract