Recovery of ammonia from wastewater through chemical precipitation

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dc.contributor.authorBianchi, Lavinia
dc.contributor.authorKirwan, Kerry
dc.contributor.authorAlibardi, Luca
dc.contributor.authorPidou, Marc
dc.contributor.authorColes, Stuart R.
dc.date.accessioned2020-01-30T15:49:45Z
dc.date.available2020-01-30T15:49:45Z
dc.date.issued2019-12-11
dc.description.abstractChemical 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 (MgNH4PO4·6H2O), 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.en_UK
dc.identifier.citationBianchi L, Kirwan K, Alibardi L, et al., (2019) Recovery of ammonia from wastewater through chemical precipitation: Investigating the kinetic mechanism and reactions pathway of struvite decomposition. Journal of Thermal Analysis and Calorimetry, Available online 11 December 2019en_UK
dc.identifier.issn1388-6150
dc.identifier.urihttps://doi.org/10.1007/s10973-019-09108-5
dc.identifier.urihttp://dspace.lib.cranfield.ac.uk/handle/1826/15048
dc.language.isoenen_UK
dc.publisherSpringeren_UK
dc.rightsAttribution 4.0 International*
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/*
dc.subjectAmmonia recoveryen_UK
dc.subjectSruvite precipitationen_UK
dc.subjectStruvite thermal decompositionen_UK
dc.subjectKinetic mechanismen_UK
dc.subjectWastewater treatmenten_UK
dc.titleRecovery of ammonia from wastewater through chemical precipitationen_UK
dc.typeArticleen_UK

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