Yangchen Zhu,Fei Wang,Beihai Zhou,Huilun Chen,Rongfang Yuan,Yiyue Zhang,HuanHuan Geng,Yuxin Liu,Hao Wang
Sulfadiazine (SDZ) entering the environment has an adverse impact on animal, plant, and human health, it is important to find effective ways to remove SDZ from the aquatic environment. This work comprehensively explored the degradation of SDZ by MoS 2 in photocatalysis and Fe 2+ activation of potassium peroxodisulfate (PDS) from both theoretical and experimental aspects. The PDS/Fe 2+ /MoS 2 system had a faster PDS conversion rate and a higher degradation efficiency for SDZ compared with PDS/Fe 2+ and PDS/MoS 2 . The degradation rate of the PDS/Fe 2+ /MoS 2 system to SDZ reached 97.1% within 60 mins. The degradation rate is higher under acidic conditions compared with alkaline conditions. Free radical capture experiments and EPR tests showed that the degradation of SDZ was the result of a variety of free radicals, among which the SO 4 · − , 1 O 2 and h + played a major role. The chemical morphology and composition of MoS 2 , as well as the changes in the concentration of Fe ions in different valence states were explored and the changes in the O-O and, S-O bond lengths, and differential charge density of PDS in the MoS 2 and, Fe 2+ /MoS 2 systems were calculated by DFT. The results showed that both MoS 2 and Fe 2+ significantly increased the conversion rate of PDS. The activation of PDS on the Fe-modified MoS 2 surface had stronger active sites. MoS 2 can promote the cycle of Fe 3+ /Fe 2+ and the conversion of PDS. According to the intermediate products measured by LC-MS/MS, as well as the frontier molecular orbitals and Fukui function diagrams of SDZ and SDZ* calculated by quantum chemistry, four degradation paths of SDZ were speculated and confirmed the existence of the self-sensitized photodegradation process of SDZ in the system.
The Fe 2+ -activated persulfate and H 2 O 2 (Fe 2+ /persulfate/H 2 O 2 ) system achieved 94% removal of four mixed sulfonamides with 300-s treatment and possessed excellent complementarity and stability over a wide pH (3–11) and temperature (5–65°C) range. The quenching and electron spin resonance spectroscopy results confirmed the coexistence of sulfate radicals and hydroxyl radicals in the coupled system, which were responsible for the elimination of sulfonamides under ambient conditions. The reaction rate constants of sulfate radicals and hydroxyl radicals at possible reactive sites distinguished the difference in removal ratios of four sulfonamides, according to experimental determination and density functional theory calculations. The removal ratio of sulfathiazole was higher than others because its calculated reaction rate constants of sulfate radicals and hydroxyl radicals were higher than those of sulfamerazine, sulfamethoxazole, and sulfamethazine. The finding provided a reference for investigating the removal mechanism of mixed organic pollutants in the presence of multiple free radicals.
Heterocyclic compounds in high-salinity wastewater are highly resistant to degradation, posing significant treatment challenges. A hybrid micro-nano bubble Fenton system (FT-MNBs) was developed to enhance Fe2+activation via interfacial effects. The FT-MNBs achieved a significantly higher indole degradation rate (0.0380 min−1) compared with micro and nano bubbles (MNBs) alone (0.0046 min−1) and conventional Fenton (0.01008 min−1). In real coking wastewater with a total dissolved solid (TDS) content of 3.266 g/L, FT-MNBs achieved COD removal efficiencies of 93.42% (initial COD 200 mg/L) and 72.54% (initial COD 10,000 mg/L), demonstrating excellent adaptability and efficiency in treating refractory high-salt organic wastewater. Electron spin resonance confirmed •OH as the main reactive species. Molecular simulations revealed that the MNB interface enhances the adsorption energy of Fe and H2O2, alters the Fe 3d orbital to better overlap with the O–O 2p orbital, and increases electron density—thus promoting O–O bond cleavage and free radical generation. The FT-MNBs not only enhances reaction kinetics but also offer scalability and energy efficiency, showing great potential for advanced industrial wastewater treatment.
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