Title: Kinetic conditions of struvite continuous reaction crystallisation from wastewater in presence of aluminium(III) and iron(III) ions

Authors: Nina Hutnik; Anna Stanclik; Krzysztof Piotrowski; Andrzej Matynia

Addresses: Wroclaw University of Science and Technology, Faculty of Chemistry, Wybrzeze Wyspianskiego 27, 50–370 Wroclaw, Poland ' Wroclaw University of Science and Technology, Faculty of Chemistry, Wybrzeze Wyspianskiego 27, 50–370 Wroclaw, Poland ' Silesian University of Technology, Department of Chemical Engineering and Process Design, M. Strzody 7, 44–101 Gliwice, Poland ' Wroclaw University of Science and Technology, Faculty of Chemistry, Wybrzeze Wyspianskiego 27, 50–370 Wroclaw, Poland

Abstract: Kinetic parameters of the continuous struvite reaction crystallisation process from aqueous solutions containing phosphate(V) ions with impurities: aluminium(III) or/and iron(III) ions were determined. A simplified kinetic model of ideal mixed suspension mixed product removal (MSMPR) crystalliser - size independent growth (SIG) was adopted. Nuclei population densities, nucleation rates and crystal linear growth rates were determined from product crystal size distributions. It was concluded that within the assumed process parameter ranges, the linear growth rate of struvite crystals in presence of aluminium(III) ions varied from 4.53 · 10⁻⁹ to 1.89 · 10⁻⁸ m/s, whereas in presence of iron(III) ions it was within the 4.59 · 10⁻⁹ − 1.62 · 10⁻⁸ m/s range. Nucleation rate varied within the 3.8 · 10⁷ − 1.6 · 10⁹ 1/(sm³) and 4.5 · 10⁷ − 1.2 · 10⁹ 1/(sm³) ranges, correspondingly. These large differences show significant influence of impurities and technological parameters on the struvite reaction crystallisation kinetics, thus on the product quality. It was experimentally demonstrated that aluminium(III) ions affect struvite reaction crystallisation more advantageously than iron(III) ions.

Keywords: struvite; phosphate (V) ions; aluminium (III) ions; iron (III) ions; continuous reaction crystallisation; SIG MSMPR kinetic model; wastewater; phosphorus recycling.

DOI: 10.1504/IJEP.2018.099466

International Journal of Environment and Pollution, 2018 Vol.64 No.4, pp.358 - 374

Accepted: 21 Nov 2018
Published online: 06 May 2019 *

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