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Mechanisms of phosphorous removal by cement-bound ochre pellets

Littler, James, Geroni, Jennifer N., Sapsford, Devin James ORCID:, Coulton, R. and Griffiths, Anthony John 2013. Mechanisms of phosphorous removal by cement-bound ochre pellets. Chemosphere 90 (4) , pp. 1533-1538. 10.1016/j.chemosphere.2012.08.054

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Hydrous ferric oxide (here termed ‘ochre’) sludge, an abundant waste product produced from the treatment of acid mine drainage (AMD), was used in this study for the removal of phosphorus (in the form of phosphate ions) from contaminated waters. The phosphorus uptake capacities of both raw and pelletized AMD solids were compared using batch and column tests. Addition of a cement binder to the AMD solids during pellet production led to significantly increased P-loading of the resultant solids compared to the raw sludge. Additionally, the pellets were found to continue to remove P in tests up to 7 d in duration whereas the unbound AMD sludge appeared to approach equilibrium with phosphate solution after approximately 60 min of contact time. In line with previous studies P uptake by the AMD solids was found to be primarily via adsorption. By contrast calcium phosphate precipitation was found to be the dominant removal mechanism for the cement-bound ochre pellets with a relatively small proportion of removal attributable to the AMD solids. SEM–EDX analysis of the surface of used pellets showed a Ca:P molar ratio close to that of hydroxyapatite (HAP). Continuous column tests on these pellets showed a rapid decrease in P removal capacity by the pellets over time, attributable to the formation of a passivating HAP surface layer

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Subjects: Q Science > QD Chemistry
T Technology > T Technology (General)
Publisher: Elsevier
ISSN: 0045-6535
Last Modified: 10 Dec 2022 02:19

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