Effect of Amino Acids on Magnesium Ammonium Phosphate Hexahydrate (Struvite) Crystallization

Struvite crystallization was investigated in the presence of different amino acids at 37°C and pH 8.0 in a continuous crystallization system. Crystal size distributions, filtration rates and morphologies of struvite crystals were determined and discussed as a function of amino acid concentration. The change of morphology depending on the amino acid type and concentration affected the filtration characteristics of struvite crystals. The crystal size distributions of the final products obtained at investigated experimental conditions were evaluated by using modified form of Abegg, Stevens and Larson (ASL) model. Thermogravimetric and differential thermal analysis have been used for thermal characterization of struvite crystals by measuring the changes in their physicochemical properties as a function of increasing temperature with time. The Coats-Redfern integral method was used to evaluate the kinetic parameters in the decomposition sequence observed in the TGA curves. In the presence of all investigated amino acids, the form of precipitate was struvite and newberyite formation was not observed.