Enhanced Oxidation of Antibiotics by Ferrate Mediated with Natural Organic Matter: Role of Phenolic Moieties

Abstract

The increasing presence of antibiotics in water sources threatens public health and ecosystems. Various treatments have been previously applied to degrade antibiotics, yet their efficiency is commonly hindered by the presence of natural organic matter (NOM) in water. On the contrary, we show here that nine types of NOM and NOM model compounds improved the removal of trimethoprim and sulfamethoxazole by ferrate(VI) (FeVIO4 2–, Fe(VI)) under mild alkaline conditions. This is probably associated with the presence of phenolic moieties in NOMs, as suggested by first-order kinetics using NOM, phenol, and hydroquinone. Electron paramagnetic resonance reveals that NOM radicals are generated within milliseconds in the Fe(VI)–NOM system via single-electron transfer from NOM to Fe(VI) with the formation of Fe(V). The dominance of the Fe(V) reaction with antibiotics resulted in their enhanced removal despite concurrent reactions between Fe(V) and NOM moieties, the radicals, and water. Kinetic modeling considering Fe(V) explains the enhanced kinetics of antibiotics abatement at low phenol concentrations. Experiments with humic and fulvic acids of lake and river waters show similar results, thus supporting the enhanced abatement of antibiotics in real water situations.

Large‐Scale Continuous and In Situ Photosynthesis of Hydrogen Peroxide by Sulfur‐Functionalized Polymer Catalyst for Water Treatment

“…The presence of natural organic matter, especially phenolic organics, in the actual water body normally has a negative impact on the removal of target pollutants. [36] Taking CIP as the target pollutant, our system maintains sufficient removal performance in lake water and in the presence of phenol (Figure S27a), which further confirms the application potential of the system for real water treatment. It is also shown that the photo-self-Fenton system exhibits better degradation performance than that of the photo-Fenton system (with the addition of 120 μM H 2 O 2 , the same concentration of H 2 O 2 produced by panel reactor with TTP).…”

Influence of Divalent Cation Inhibition and Dissolved Organic Matter Enhancement on Phenol Oxidation Kinetics by Manganese Oxides

“…Divalent cations can enhance DOM sorption to the manganese oxide surface via ligand-exchange or cation-bridging mechanisms − and could affect phenolic compound kinetics in two ways (Figure S1). First, enhanced sorption of DOM to the manganese oxide surface may block reactive sites from phenolic target compounds because DOM is thought to sorb and react via phenolic moieties; ,,− thus, competitive sorption could result in slower removal of the target compound. Second, enhanced DOM sorption to the mineral surface could result in increased oxidation of DOM and an increase in radical intermediates generated when phenolic moieties within DOM react with manganese oxides via a one-electron transfer (i.e., as observed for individual phenols ,,,, ).…”

“…We further hypothesized that the observed increases in bisphenol A oxidation were driven by interactions between radicals generated when DOM is oxidized by acid birnessite. The reaction of phenols with manganese oxides first generates a phenoxy radical intermediate by a one-electron transfer. ,,,, As DOM is likely oxidized via phenolic moieties, ,,− this radical formation is potentially a key intermediate in the DOM oxidation process as well. Previous work has proposed that radical intermediates from oxidized phenols ,,− or model compounds indirectly transform organic contaminants, thereby increasing the observed oxidation rate constants of target compounds.…”

“…The reaction of phenols with manganese oxides first generates a phenoxy radical intermediate by a one-electron transfer. ,,,, As DOM is likely oxidized via phenolic moieties, ,,− this radical formation is potentially a key intermediate in the DOM oxidation process as well. Previous work has proposed that radical intermediates from oxidized phenols ,,− or model compounds indirectly transform organic contaminants, thereby increasing the observed oxidation rate constants of target compounds. However, direct evidence of this mechanism has not been identified in the presence of DOM.…”

“…The rate enhancement of sulfonamide oxidation by manganese oxides with organic matter and model compounds was attributed to radical-mediated interactions. , Similarly, the oxidation rate enhancement of phenolic compound mixtures was attributed to radical-mediated interactions based on quenching experiments . While DOM is suspected to be oxidized primarily via phenolic moieties, ,,− evidence for this mechanism of rate enhancement for phenolic compounds with organic matter is lacking. Furthermore, it is challenging to identify the mechanisms leading to inhibition or enhancement due to variability in experimental conditions (e.g., organic carbon concentration, pH, and manganese oxide type; Table S1) and lack of DOM composition data.…”