Study of Struvite: Characterization and Drying Kinetics

The presence of phosphorus and nitrogen in wastewater causes the precipitation of struvite, a highly adhesive scale that clogs pipes. Therefore, its removal offers a dual benefit, as it is used in agriculture as a fertilizer. This study focuses on the characterization, thermogravimetric analysis, and kinetics of two drying methods-convective drying and infrared radiation drying-as well as empirical modeling and, finally, an investigation of struvite desorption isotherms. Thermogravimetric analysis shows that struvite begins to lose water at 67°C, meaning it is stable up to that temperature. The final product, according to X-ray diffraction analysis, corresponds to a diphosphate. Infrared radiation drying is faster than convective drying. Their effects on struvite are the same. The characteristic curve of the drying rate is well described by a third-degree polynomial equation. Modeling the reduction in water content over time shows that the logarithmic model is the most appropriate.