Lattice oxygen release characteristics of perovskite oxygen carriers synergized with iron-rich sludge ash

Given that both sludge ash and iron-based oxygen carriers (OCs) are rich in the active component Fe₂O₃, it is necessary to investigate whether there exists a synergistic effect that enhances oxygen transport and stabilizes OCs. This work focuses on lattice oxygen release characteristics and reduction kinetics of industrially prepared CaMn_0.5Fe_0.5O_3-δ perovskite OCs (POC), sewage sludge ash (SSA), and their 1:1 mixture (POC/SSA) using thermogravimetric analysis (TGA) via varying hydrogen concentrations (5-25 %) and terminal temperatures (800-900 °C). The results reveal that the presence of SSA slightly delays the oxygen uncoupling process of POC, with the actual weight loss being slightly higher than the theoretical weighted value. This difference diminishes as terminal temperature increases. Notably, POC/SSA exhibits significant synergistic effects under low temperatures and highly reducing atmospheres, particularly at 25 % H₂ and 800 °C, where the actual weight loss (14.52 %) exceeds the theoretical value (12.96 %). The activation energy (E_a) of the reduction for the mixed sample is 46.135 kJ/mol, which is 1.973 kJ/mol lower than the theoretical weighted value, indicating a positive synergistic effect. This is attributed to the optimization of oxygen migration pathways via interfacial active sites and lattice defects, thereby enhancing the reactivity of POC. Furthermore, the SSA in synergy significantly increases the specific surface area of POC (from 14.28 m²/g to 137.6 m²/g) and pore volume, further improving reaction performance. This study provides valuable insights into the application of chemical looping technology for sludge treatment.