Owing to its strong chemical inertness, sulfur hexafluoride (SF 6 ) is intrinsically resistant to degradation. Accordingly, a composite material was developed by coupling sulfidated nanoscale zero-valent iron (S-nZVI) with fly ash-derived zeolite ZSM-5, forming a multi-level heterostructure for efficient SF 6 degradation. Experimental results confirmed that the composite exhibited exceptional low-temperature degradation performance, achieving complete removal of 2 vol% SF 6 at 600 °C with a specific degradation amount of 206.1 mL/g. Remarkably, effective degradation was still maintained at 300 °C, surpassing the previously reported minimum temperature limit (∼450 °C) for SF 6 degradation. Kinetic analysis revealed a near-zero-order reaction behavior with an apparent activation energy of only 27.61 kJ/mol, indicating that the initial stage was dominated by adsorption, diffusion, or interfacial electron transfer rather than S F bond cleavage. Comprehensive characterization showed that the composite possessed Fe 0 /FeS and FeS/ZSM-5 dual heterointerfaces, serving simultaneously as adsorption carriers, electron donors and acceptors. Specifically, the microporous framework of ZSM-5 physically confines nonpolar SF 6 molecules through van der Waals and confinement effects, enriching their local concentration and forming a favorable adsorption-activation interface. Electrons released by Fe 0 migrate directionally to these enrichment sites under the drive of the multi-level heterostructure, enabling concurrent adsorption and electron-induced activation of SF 6 , and thereby facilitating S F bond cleavage. The resulting fluoride ions initially react with Fe 0 to generate FeF 3 , which subsequently interacts with the silicate framework to produce SiF 4 , establishing a mediated fluorine migration pathway from SF 6 to SiF 4 and enabling deep degradation with sustained reactivity.
Fluorite tailings (FT), a byproduct of fluorite ore processing, pose significant environmental risks due to improper disposal. This study presents a sustainable approach to repurpose FT into lightweight ceramsite through pelletizing and sintering. Systematic investigations of microstructural evolution revealed that the effects of raw material ratios (FT:clay=6:4–9:1), sintering parameters (1150–1250 °C, 10–50 min), and SiC addition (0–1%) were governed by feldspar formation and pyroplastic mass development. Thermodynamic calculations and differential thermal analysis further elucidated phase transformation pathways. Optimal conditions (70% FT, 30% clay, 1210 °C, 30 min, 0.5% SiC) yielded ceramsite with a compressive strength of 4.63 MPa, apparent density of 0.890 g/cm 3 , and 1-hour water absorption of 0.21%. Microstructural characterization (SEM/ICT) confirmed a dense shell encapsulating uniform spherical pores (0.4–0.6 sphericity, 0–2 mm diameter), explaining the exceptional water resistance. Crucially, fluorine migration mechanisms were identified: Fluorine speciation evolved from cubic CaF 2 to hexagonal CaF 2 /Mg 3 SiO 4 F 2 during sintering, with subsequent encapsulation in the feldspar-pyroplastic matrix reducing fluoride leaching to 0.87 mg/L (7.05 mg/L in raw FT). This work demonstrates a viable strategy for transforming FT into high-performance construction materials while immobilizing fluorine, addressing dual waste management and contamination challenges.
危险品化学品经营许可证（带存储）