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Temperature impact assessment on struvite solubility product: a thermodynamic modeling approach

Hanhoun, Mary and Montastruc, Ludovic and Azzaro-Pantel, Catherine and Biscans, Béatrice and Freche, Michèle and Pibouleau, Luc Temperature impact assessment on struvite solubility product: a thermodynamic modeling approach. (2011) Chemical Engineering Journal, vol. 167 (n° 1). pp. 50-58. ISSN 1385-8947

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Official URL: http://dx.doi.org/10.1016/j.cej.2010.12.001

Abstract

This work addresses the problem of phosphorus recovery from wastewater by struvite precipitation, which is chemically known as magnesium ammonium phosphate hexahydrate MgNH4PO4·6H2O. The struvite solubility product values that are reported in the literature were found to vary significantly, from one solution to another and over the range of the experimental conditions as well. The various factors affecting the struvite solubility include pH, ionic strength and temperature. The struvite solubility product is yet a very important parameter to determine the supersaturation ratio. A thermodynamic model for phosphate precipitation is proposed to determine the phosphate conversion rate and the value of struvite solubility product for a temperature range between 15 and 35 °C. This model is based on numerical equilibrium prediction of the study system Mg–NH4–PO4–6H2O. The mathematical problem is represented by a set of nonlinear equations that turns, to an ill-conditioned system mainly due to the various orders of magnitude of the involved variables. These equations have first been solved by an optimization strategy with a genetic algorithm to perform a preliminary search in the solution space. The procedure helps to identify a good initialization point for the subsequent Newton–Raphson method. A series of experiments were conducted to study the influence of pH and temperature on struvite precipitation and to validate the proposed model.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at Chemical Engineering Journal : http://www.sciencedirect.com/science/journal/13858947
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
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Deposited By:Leila Abdelouhab

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