Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Abstract

Despite the vital roles of reactive radical species in the coupled iron–carbon composite/persulfate (PS) system for eliminating pollutants, nonradical contributions are typically overlooked. Herein, we developed two efficient magnetic iron–char composites via low-temperature (BCFe-400) and high-temperature (BCFe-700) pyrolysis. The two composites activated PS through nonradical pathways for sulfamethoxazole (SMX) degradation. In the BCFe-400/PS system, high-valent iron Fe­(IV) was the dominant active species for the oxidation, evidenced by methyl phenyl sulfoxide-based probe tests, Mössbauer spectroscopy, and in situ Raman analyses with kinetic evaluation. In the BCFe-700/PS system, surface-mediated electron transfer dominated the oxidation, and the nonradical regime was probed by the electrochemical test and in situ Raman analysis. Furthermore, the BCFe-400/PS system maintained high efficiency in continuous degradation of SMX due to the feasible Fe2+generation toward Fe­(IV) formation. In the BCFe-700/PS system, the stability of the system was limited due to the hindered electron transfer between the surface reactive complex (i.e., BCFe-700–PS*) and SMX, and thermal treatment would help recover the reactivity. Both BCFe-400/PS and BCFe-700/PS systems exhibited high performances for SMX removal in the presence of chloride and humic acid and in real water matrixes (e.g., seawater, piggery wastewater, and landfill leachate), exhibiting the great merits of the nonradical system. Overall, the study would provide new insights into PS activation by iron-loaded catalysts to efficiently degrade pollutants via nonradical pathways.

Efficient degradation of organic dyes using peroxymonosulfate activated by magnetic graphene oxide

“…Recently, it was demonstrated that high-valent iron-oxo species played a role in the PMS-based oxidation process when iron-containing materials were used as the catalysts. 36,61,62 Similar to the case reported previously, 36 k app for CBB removal decreased in the presence of PMSO (Fig. 4a).…”

Degradation of Organic Contaminants in the Fe(II)/Peroxymonosulfate Process under Acidic Conditions: The Overlooked Rapid Oxidation Stage

“…HA was apt to compete with organic contaminants for SO 4 •– since HA could be readily scavenged by SO 4 •– at a rate constant of 6.8 × 10 3 L·mg C –1 s –1 . In contrast, the degradation of organic contaminants by Fe­(IV) would be slightly influenced by HA because of the inert reactivity of Fe­(IV) toward HA. − The degradation of phenol was mainly ascribed to Fe­(IV), whereas Fe­(IV) and SO 4 •– contributed almost equally to the degradation of estradiol (Figure d). Therefore, the presence of HA had a negligible effect on the degradation of phenol but inhibited the degradation of estradiol in the rapid oxidation stage of the Fe­(II)/PMS process.…”

Insights into singlet oxygen generation and electron-transfer process induced by a single-atom Cu catalyst with saturated Cu-N4 sites

“…As shown in Figure 5 F, the open-circuit potential (OCP) of SA-Cu-NC sharply rises with the addition of PMS and gradually reaches a plateau (potential of the SA-Cu-NC+PMS∗ complex). After the addition of BPA, electron transfer process of BPA to SA-Cu-NC+PMS∗ complex results in a decline of OCP, accompanied by the oxidation of BPA and reduction of PMS ( Liang et al., 2021 ; Ren et al., 2022 ; Tan et al., 2020 ). In contrast, the potential of NC increases slightly upon the addition of PMS, and the subsequent addition of BPA causes an increase in the equilibrium potential.…”