Comparative study of Fe/Mn modified two kinds of municipal waste activated persulfate for organic dye degradation

This study explored the reuse of two types of municipal waste, waterworks sludge (WS) and autoclaved aerated concrete fragments (AAC), as heterogeneous peroxydisulfate (PDS) activators for the removal of safranin T (ST). After Fe/Mn modification, the obtained FeMn-WS and FeMn-AAC were systematically characterized using scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to investigate their morphological features, elemental composition, and valence states, revealing distinct structural and chemical properties between the two materials. Batch experiments revealed that FeMn-AAC+PDS exhibited superior ST removal capacity (59.1 %) compared to FeMn-WS+PDS (44.0 %), primarily due to the adsorption capacity of FeMn-AAC. However, the addition of ascorbic acid (AA) reversed this trend, with FeMn-WS+PDS achieving significantly higher removal efficiency (71.8 %) than FeMn-AAC+PDS (59.9 %). Mechanistic studies via radical quenching experiments, electron paramagnetic resonance (EPR) and linear sweep voltammetry (LSV) revealed that the FeMn-WS+PDS system was dominated by radical pathways, while the FeMn-AAC+PDS system relied on non-radical pathways. The effects of multiple parameters on the removal of ST were comprehensively investigated. Interestingly, low temperature was found to be highly advantageous for the FeMn-AAC+PDS system, with up to 90 % of ST removed within 5 min of reaction. Furthermore, total organic carbon (TOC) analysis and liquid chromatography-mass spectrometry (LC-MS) were employed to identify the degradation pathway of ST. This work highlights the potential of reusing municipal waste as eco-friendly PDS activators, offering a sustainable approach for simultaneous wastewater decontamination and waste recycling.