Effective heterogeneous electro-Fenton process for the degradation of a malodorous compound, indole, using iron loaded alginate beads as a reusable catalyst

Abstract

Fe-ABs were fabricated by simple gelation procedure at 25 °C. The incorporation of iron on beads was confirmed by EDS results. The Fe-ABs catalyst present good stability and can be used for at least four times without obvious decrease in activity. Mineralization pathways of indole was proposed. In this work the characterization and the performance of iron immobilized in alginate beads (Fe-ABs) as catalyst for heterogeneous electro-Fenton (EF) treatment of a malodorous compound, indole, was investigated. Experimental results demonstrated that indole was effectively removed through the electro-Fenton process; while in the considered experimental conditions, the performances of EF were only slightly improved by the addition of UVA radiation. The most efficient operating conditions were achieved at pH 3.0 in the presence of 200 mg.L-1 Fe-ABs catalyst (corresponding to an average iron concentration of 64 mg L-1) with a current density of 0.53 mA cm-2. Under these conditions, 60 min were sufficient to completely degrade 20 mg L −1 of indole, whose removal was found to obey the pseudo-first order model. In terms of organic carbon removal, about 90% mineralization yield was reached in the optimal conditions for 7 h heterogeneous electro-Fenton treatment time. UPLC-MS/MS analysis was applied to identify and follow the evolution of indole oxidation products. Five stable organics intermediates were observed and four of them were identified as dioxindole, isatin, oxindole and anthranilic acid. A reaction sequence was therefore proposed for indole degradation according to the detected products. Subsequent attack of these intermediates by •OH radicals led to the formation of short chain acids such as succinic, acetic, oxamic and oxalic identified by ion-exclusion chromatography.

Reactive oxygen and iron species monitoring to investigate the electro-Fenton performances. Impact of the electrochemical process on the biodegradability of metronidazole and its by-products

“…Total dissolved iron species were quantified by atomic absorption spectrometry (AA140, VARIAN spectrometer, Palo Alto, USA) with air/acetylene flame at 372 nm. Ferrous ions were quantified by the orthophenanthroline complexometric method, detailed in a previous work (Ben Hammouda et al, 2016).…”

Degradation of Rhodamine B at neutral pH using modified sponge iron as a heterogeneous electro‐Fenton catalyst

“…Because excess iron leakage in solution could inhibit the yield of ·OH, as shown in Eq. , the terminal decolorization efficiency of RhB solution by the PTFE modified sponge iron was higher than the unmodified one . …”

Electro-Fenton catalyzed with magnetic chitosan beads for the removal of Chlordimeform insecticide

“…On the other hand, to avoid problems related to the loss of dissolved iron and the production of solid sludge, recent investigations focused on the possibility of using heterogeneous catalysts [27][28][29][30][31]. For this purpose, magnetite Fe 3 O 4 has attracted a great attention as efficient catalyst for the heterogeneous Fenton process due to its simple handling, ease of recovery with an external magnetic field, oxidative stability, biological compatibility, strong superparamagnetic behavior and its high catalytic activities [32][33][34].…”