ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Struvite nucleation and crystal growth kinetics from cattle liquid manure

Anna Stanclik, Nina Hutnik, Krzysztof Piotrowski, and Andrzej Matynia

Wroclaw University of Science and Technology, Faculty of Chemistry, Wroclaw, Poland

E-mail: krzysztof.piotrowski@polsl.pl

Abstract: Cattle liquid manure (CLM) in future may become excellent raw material for the solid mineral fertilizers production. Phosphates(V) recovery from CLM can be done, e.g. through reaction crystallization of sparingly soluble salts: magnesium and ammonium phosphate(V) hexahydrate MgNH₄PO₄·6H₂O (MAP, struvite) or/and calcium phosphates(V). The original kinetic calculations based on experimental test results concerning continuous reaction crystallization of sparingly soluble phosphates(V) from cattle liquid manure in a continuous laboratory DT MSMPR (Draft Tube, Mixed Suspension Mixed Product Removal) crystallizer with internal circulation of suspension driven by propeller stirrer are presented. Two kinetic models of continuous mass crystallization in MSMPR crystallizer: SIG (Size Independent Growth) and RE SDG (Rojkowski Exponential Size Dependent Growth) were adopted. Advantageous effects of: low pH (8.5), elongated mean residence time of suspension in a crystallizer (3600 s) and magnesium ions excess in relation to phosphate(V) ions concentration (1.2:1) on the process results were observed. Under the considered process conditions linear crystal growth rates of struvite were: G from 4.11 × 10⁻³ to 1.01 × 10⁻² µm s⁻¹ and G_∞ from 5.30 × 10⁻³ to 1.02 × 10⁻² µm s⁻¹.

Keywords: Cattle liquid manure (CLM) ; Struvite ; Continuous reaction crystallization ; SIG MSMPR kinetic model ; SDG MSMPR kinetic model ; Phosphorus recycling 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0613-5

Chemical Papers 73 (3) 555–563 (2019)