Current single-atom studies in the perdisulfate (PDS) system were focused on transition metals, but researching La-series metals might provide new insights for the efficient utilization of this system. The original structure’s Zn was evaporated at high temperatures, thereby we utilized Zeolitic Imidazolate Frameworks (ZIFs) as a substrate to synthesize a type of La-SACs catalysts. The La single atom in this work was identified to the La-N 4 configuration through La-L3 X-ray edge absorption spectroscopy. Experimental observations in suspension demonstrated that the PDS activation capability of La is on par with, if not superior to, that of transition metals such as Co and Cu. Tetracyclines (10 mg/L) were eliminated within 30 min via La-N-C + PDS systems and the pseudo-first-order was higher than 0.0929 min −1 . The Hydrogen bond between PDS and La-N-C and active electron of d orbital in La atoms had the significant influence on the generation of ROS ( 1 O 2 and •OH). Furthermore, the excellent electron transfer of La-N-C also promoted the activation rate of PDS. The findings of this study indicated that La could play a crucial part in PDS catalyst for degradation of organic pollutes in aquatic environment, providing the new method for exploration of single-atom materials in PDS systems.
Qibo Liu,Jingce Bi,Zhouxiao Zhai,Wen Tian,Ningning Liu,Xia Zhang,Zhuopeng Wang,Huanying Zhou,Yide Han
Rate-limiting mass transfer is a critical issue for using iron-based catalysts supported by zeolites to activate peroxydisulfate (PDS) in the field of advanced oxidation processes (AOPs). In this study, hierarchically porous Fe-SAPO-34-DGC was synthesized via combing in-situ encapsulation method with dry gel conversion (DGC) technology. Tetracycline (TC) was applied as a model pollutant, about 91.5% TC in Fe-SAPO-34-DGC/PDS system can be degraded within 90 min, while it can be achieved for about 150 min in Fe-SAPO-34-HT/PDS system. Meanwhile, the degradation rate constant of Fe-SAPO-34-DGC/PDS system is 0.02391 min -1 , which is approximately 1.6 times higher than that of Fe-SAPO-34-HT/PDS system. The excellent catalytic performance of Fe-SAPO-34-DGC is caused by well dispersed iron-oxide species (the size about 1.47 nm) in cha cage and nanoplate-like morphology as well as mesoporous structure, resulting in the generation of more active sites for PDS activation and faster mass transfer and easier access to active sites. Moreover, the characterized results indicate that the absence of Si(3Al) species is favorable of the formation of nanoplate-like morphology, further leading to the formation of the mesoporous structure because of stacking. Besides, iron-oxide species in Fe-SAPO-34-DGC are confined in cha cage that can effectively keep back its leaching. Furthermore, the possibility of membrane reactor established by Fe-SAPO-34-DGC for practical environmental water treatment was evaluated. Therefore, this method combing in-situ encapsulation method with dry gel conversion technology provides an alternative pathway for construction of iron-based catalysts supported by zeolites to remove organic pollutants through PDS activation.
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