Effect of Copper and Zinc Ions on Struvite Nucleation and Crystal Growth Kinetics in Various Process Environments
Nina Hutnik 1  
,   Anna Stanclik 1  
,   Krzysztof Piotrowski 2  
,   Andrzej Matynia 1  
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Wroclaw University of Science and Technology, Faculty of Chemistry, Wroclaw, Poland
Silesian University of Technology, Department of Chemical Engineering and Process Design, Gliwice, Poland
Krzysztof Piotrowski   

Silesian University of Technology, ks. M. Strzody 7, 44 - 100, Gliwice, Poland
Submission date: 2019-02-19
Acceptance date: 2019-07-21
Online publication date: 2020-02-13
Publication date: 2020-03-31
Pol. J. Environ. Stud. 2020;29(3):2225–2233
We determined the kinetic parameters of struvite continuous reaction crystallization in aqueous solutions of phosphate(V) ions with selected impurities: copper or/and zinc ions. The simplified kinetic model for ideal continuous MSMPR (mixed suspension mixed product removal) crystallizer – SIG (size-independent growth) model frame was adopted for the calculations. Nuclei population densities, nucleation rates and crystal linear growth rates of nuclei up to macroscopic size range were determined based on crystal size distributions of the solid products. We concluded that within the assumed process parameter ranges the linear growth rate of struvite crystals varied within the 4.11∙10–9-1.62∙10–8 m/s range in the presence of copper ions and within the 4.53∙10–9-1.51∙10–8 m/s range in the presence of zinc ions. Nucleation rate, however, varied within the 6.8∙107-2.0∙109 1/(sm3) and 6.3∙107-1.7∙109 1/(sm3) ranges, appropriately. These are large differences demonstrating the significant influence of impurities together with process technological parameters on struvite continuous reaction crystallization kinetics and thus – in consequence – on the manufactured product quality. We also experimentally proved that the effect of copper ions on struvite reaction crystallization is more advantageous than zinc ions action.