Removal of Antibiotic Florfenicol by Sulfide-Modified Nanoscale Zero-Valent Iron

Abstract

Florfenicol (FF, CHClFNOS), an emerging halogenated organic contaminant of concern was effectively degraded in water by sulfidized nanoscale zerovalent iron (S-nZVI). Sulfidized nZVI (62.5 m g) that was prepared using a one-step method resulted in small Fe/Fe-sulfide particles that were more stable against aggregation than unsulfidized nZVI (10.2 m g). No obvious removal of FF was observed by unsulfidized nZVI. S-nZVI degraded FF, having a surface area normalized reaction rate constant of 3.1 × 10 L m min. The effects of the S/Fe molar ratio, initial FF concentration, initial pH, temperature, and water composition on the removal of FF by S-nZVI, and on the formation of reaction products, were systematically investigated. Both dechlorination and defluorination were observed, resulting in four degradation products (CHClFNOS, CHFNOS, CHNOS, and CHNOS). High removal efficiencies of FF by S-nZVI were achieved in groundwater, river water, seawater, and wastewater. The reactivity of S-nZVI was relatively unaffected by the presence of both dissolved ions and organic matter in the waters tested.

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

“…Recently, it was shown by us and others that the sulfidation of NZVI lowers its reactivity with water and other non‐target hydrophilic contaminants (e.g., NO 3 − ), while increasing its reactivity with target contaminants like chlorinated solvents and antibiotics. [ 25–31 ] Several mechanisms have been hypothesized for the enhanced reactivity and selectivity of sulfidized nanoscale zerovalent iron (SNZVI) compared to NZVI. First, SNZVI is more hydrophobic than NZVI, resulting in lower interaction with water and charged solutes, and greater interaction with hydrophobic contaminants.…”

Adsorptive and Reductive Removal of Chlorophenol from Wastewater by Biomass-Derived Mesoporous Carbon-Supported Sulfide Nanoscale Zerovalent Iron

“…The diffraction peak of S-nZVI@MC is sharper, indicating that sulfidation can enhance the crystallinity of nZVI. There is no peak of sulfur species (FeS or FeS2) on the XRD pattern of S-nZVI@MC, which may be due to the low sulfur content or poor crystallinity of sulfur species [25]. After 3 h of reaction with TCP, the peak intensity of S-nZVI@MC has no obvious decrease.…”

“…However, a weaker diffraction peak of Fe2O3 was observed, indicating that only part of the nZVI reacted with TCP. In addition, the reaction between such non-target reactants as H2O and nZVI should be effectively inhibited, which is attributed to the protection effect of FeS [25]. In order to further verify the formation of Fe and S before and after the reaction with TCP, XPS spectra were further analyzed.…”

“…Before reaction, two broad peaks at 724.8 eV (Fe 2p1/2 ) and 711 eV (Fe 2p2/3 ) corresponding to iron oxides (Fe 2+ and Fe 3+ ) are obvious (Figure 4c), because a portion of nZVI could be oxidized after the reaction with SO 4 2− during preparation or testing process, resulting in the formation of iron oxides or iron sulfides. However, it is worth noting that XPS can only detect a material surface of several nanometers' depth, and the Fe 0 core may not be effectively detected [25]. The content of Fe (II) and Fe (III) is 64.56% and 35.54% before reaction.…”

Nanomaterials for the Abatement of Pharmaceuticals and Personal Care Products from Wastewater

“…Even more recently, Cao et al have shown that NZVI with a sulfur based shell, (S-NZVI) is able to degrade florfenicol (FF), which is considered a target molecule for ABs. The removal efficiencies were good in groundwater, river water, seawater, and wastewater [63]. In their interesting system, the shell is formed by Fe x S y , which has a higher affinity with the hydrophobic part -Cl and -F group on FF compared to the more hydrophilic iron oxides-hydroxides and also facilities electron transfer due to a lower bandgap than Fe x O y .…”