In this research, greigite (Fe 3 S 4 ) was innovatively applied for the enhancement of PDS/Fe(II) system. From XRD and SEM analyses, Fe 3 S 4 was successfully synthesized and appeared uniform sphere-like particles with a petal-like structure. Trichloroethylene (TCE), as the target, was significantly degraded from 28.5 % to 92.8 % in PDS/Fe(II)/Fe 3 S 4 system. The enhanced mechanisms, differences, and superiority of Fe 3 S 4 against the other three iron sulfides were elucidated as follows: (1) on account of the abundant reduction sites on its surface, Fe 3 S 4 could not only directly release Fe(II) and accelerate Fe(II) regeneration by sulfur substances, but also participate in the process of O 2 − • generation, and (2) the reaction mainly took place on Fe 3 S 4 surface, in which the surface-bound reactive species (RSs) were of great importance for TCE degradation. Through EPR, quantification, and scavenging tests of RSs, HO•, SO 4 − •, and O 2 − • were all the dominant RSs responsible for TCE removal. Besides, these enhanced systems had high tolerance on complex water conditions and could remediate various contaminants in actual groundwater. Three TCE degradation pathways were deduced in four iron sulfide-enhanced systems and the toxicities of intermediates were evaluated, recommending that Fe 3 S 4 -enhanced system was of the least toxicity and most favorable for application in practice.
Wei Liu,Jinrong Tian,Chengliang Mao,Zhenfeng Wang,Jia Liu,Randy A. Dahlgren,Lizhi Zhang,Xuedong Wang
Herein, sulfur vacancies in magnetic greigite (SVs-Fe 3 S 4 ) nanosheets were synthesized by a one-step solvothermal method by adjusting the ethylene glycol : water ratio. Electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS) revealed that SV-rich Fe 3 S 4 and SV-poor Fe 3 S 4 were acquired using 100% ethylene glycol and 100% water as solvent, respectively. A peroxidase-like activity assay demonstrated that maximum reaction rates for H 2 O 2 -mediated oxidation of 3,3′,5,5′-tetramethyl-benzidine (TMB) catalyzed by the SV-rich Fe 3 S 4 was 2.3 times higher than SV-poor Fe 3 S 4 . Density functional theory (DFT) calculations and reactive oxygen species (ROS) detection confirmed that the enhanced peroxidase-like activity by SV-rich Fe 3 S 4 was attributed to efficient adsorption of H 2 O 2 and subsequent decomposition to hydroxyl radicals (•OH) on the SVs sites of Fe 3 S 4 . The SV-rich Fe 3 S 4 nanozyme was employed to develop a simple, highly sensitive and selective assay for glucose detection with a linear range of 0.5–150 μM and a detection limit of 0.1 μM (S/N = 3). A smartphone application (App) was designed and applied to efficiently detect serum glucose with the integrated analytical system based on the SV-rich Fe 3 S 4 . These new findings highlight the important role of surface defects in nanozymes on generating peroxidase-like activity for glucose detection in point-of-care diagnosis.
In this study, greigite (Fe 3 S 4 ) was used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for sulfamethoazine (SMT) degradation in water. The possible influencing factors such as oxidant concentration, sulfur sources, iron sources and initial pH were investigated. Experimental results showed that SMT could be completely removed at 0.1 mM PMS in 15 min in Fe 3 S 4 /PMS system. 96.7% of SMT was removed at 1.0 mM PDS in 60 min in Fe 3 S 4 /PDS system. Both systems had good performance over a wide pH range of 3–9. In addition, different sulfur sources could affect the crystal structure, morphology and composition of the synthesized catalysts, while different iron sources had little influence. Quenching experiments and electron paramagnetic resonance (EPR) test evidenced that the activation of PMS and PDS by Fe 3 S 4 was a multi-reactive oxygen species process with the coexistence of •OH, SO 4 •− , O 2 •− and 1 O 2 . SO 4 •− was the main active species in the Fe 3 S 4 /PMS system, while SO 4 •− and •OH were the main free radicals in the Fe 3 S 4 /PDS system. X-ray photoelectron spectroscopy (XPS) experiments showed that Fe(II) on Fe 3 S 4 surface effectively activated PMS and PDS, and S 2− species were key factors controlling Fe(II) regeneration and subsequent activation of PMS and PDS. However, the consumption of Fe(II) and S 2− in Fe 3 S 4 /PDS system was higher than that in Fe 3 S 4 /PMS system. In addition, in the two systems, the degradation intermediates of SMT and their practical application were also evaluated. This study provided a systematic evaluation of the performance of Fe 3 S 4 /PMS and Fe 3 S 4 /PDS systems for treatment of antibiotic contaminated water.
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