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Recovery of ammonia from wastewater through chemical precipitation
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Bianchi, Lavinia, Kirwan, Kerry, Alibardi, Luca, Pidou, Marc and Coles, Stuart R. (2020) Recovery of ammonia from wastewater through chemical precipitation. Journal of Thermal Analysis and Calorimetry . doi:10.1007/s10973-019-09108-5 (In Press)
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WRAP-recovery-ammonia-wastewater-chemical-precipitation-Coles-2019.pdf - Published Version - Requires a PDF viewer. Available under License Creative Commons Attribution 4.0. Download (2029Kb) | Preview |
Official URL: http://dx.doi.org/10.1007/s10973-019-09108-5
Abstract
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 (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.
| Item Type: | Journal Article | |||||||||
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| Subjects: | Q Science > QD Chemistry Q Science > QE Geology |
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| Divisions: | Faculty of Science > WMG (Formerly the Warwick Manufacturing Group) | |||||||||
| Library of Congress Subject Headings (LCSH): | Decomposition (Chemistry), Chemical weathering, Thermogravimetry | |||||||||
| Journal or Publication Title: | Journal of Thermal Analysis and Calorimetry | |||||||||
| Publisher: | Springer | |||||||||
| ISSN: | 1388-6150 | |||||||||
| Official Date: | 2020 | |||||||||
| Dates: |
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| Date of first compliant deposit: | 12 December 2019 | |||||||||
| DOI: | 10.1007/s10973-019-09108-5 | |||||||||
| Status: | Peer Reviewed | |||||||||
| Publication Status: | In Press | |||||||||
| Access rights to Published version: | Open Access | |||||||||
| RIOXX Funder/Project Grant: |
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