Investigation of thermal degradation pathway and kinetics of struvite recovered from dairy wastewater via thermogravimetric studies
摘要
Thermodynamic studies of struvite provide constructive insights into the energy efficiency of recovery processes, particularly for scaling up operations. Over and above that, thermodynamic stability of struvite offers a comprehensive understanding of its behaviour, enabling effective recovery, storage and utilization while minimizing environmental impacts. Subsequently, authors in the present study evaluated thermodynamic behaviour of struvite using thermogravimetric analysis (TGA). TGA analysis of struvite is undertaken over a temperature span of 23 °C to 800 °C at numerous heating rates like 5 °C min−1, 10 °C min−1 and 20 °C min−1. Various iso-conversional models like Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) are deployed to assess the kinetic parameters of struvite during thermal decomposition. The activation energy values obtained from 0.2–0.7 conversion factors using KAS and FWO models are 34.59–269.48 kJ mol−1 and 39.37–266.63 kJ mol−1, respectively. Further, pre-exponential factor (A) values are determined using Coats–Redfern technique. Additionally, thermodynamic factors like Enthalpy (ΔH), Gibbs free energy (ΔG) and Entropy (ΔS) are also investigated in the current study. The thermal degradation of struvite crystals, as evidenced by thermodynamic data, is associated with an irreversible and non-spontaneous process.