Spinel Ferrite Mediated Photo‐Fenton Degradation of Phenolic Analogues: A Detailed Study Employing Two Distinct Inorganic Oxidants

Abstract

The present work demonstrates the applicability of ferrites as photo-Fenton catalysts for deterioration of different phenolic derivatives. To analyze optimal reaction conditions, experiments are performed with four magnetic spinel ferrites MFe 2 O 4 (M ¼ Co, Cu, Ni, and Zn) and two inorganic oxidants, i.e., hydrogen peroxide (HP) and potassium peroxymonosulfate (PMS). The reactions are performed using p-nitrophenol as phenolic probe. CuFe 2 O 4 and CoFe 2 O 4 possessed excellent ability to activate HP and PMS, respectively, among all four synthesized catalysts. A noteworthy aspect of two oxidizing agents is that the concentration of PMS used during the reaction is four times less than HP. Further, the broad pH activity of PMS provides a significant advantage over HP. The optimal reaction conditions, when HP is the oxidant in the photo-Fenton degradation, are 0.50 g L À1 MFe 2 O 4 , pH 2.5, and 8.8 mM HP. Although PMS is active in a wide pH range (2-10), adequate reaction conditions are 0.50 g L À1 MFe 2 O 4 , natural pH, and 2.2 mM PMS.The photo-Fenton activity of ferrites is extended to the degradation of different nitro-and chloro-analogs of phenol (2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol) with only two ferrites (CuFe 2 O 4 and CoFe 2 O 4 ). A comparative study is performed with the two oxidants (HP and PMS) with positive results. Finally, stability and reusability of magnetic ferrites as catalysts are also studied to prove their use in phenolic solution treatment.

Graphene@Metal Sulfide/Oxide Nanocomposites as Novel Photo‐Fenton‐like Catalysts for 4‐Nitrophenol Degradation

“…Then, the UV irradiation should excite electrons from the valence band to the nanocomposites conduction band, generating electron‐hole pairs. The Fe 2+ (and Fe 3+ , that can be reduced to Fe 2+ by radiation) species from Fe 3 O 4 , namely the presented at the surface exposed octahedral sites, and/or the Cu + (and Cu 2+ ) species from CuS should react with H 2 O 2 to produce hydroxyl radicals; simultaneously, the Fe 3+ and/or Cu 2+ species are regenerating to complete the Fe 3+ /Fe 2+ and Cu 2+ /Cu + cycles, respectively, returning the catalysts to their original states [104–106] . Finally, the 4‐NP molecules should be attacked by the generated hydroxyl radicals, and decomposed ideally into CO 2 , H 2 O and nitrate ions [104,105] .…”

“…In the dark, the basic principles of the heterogeneous Fenton process should be the same described [108] . However, in the presence of light, additional advantageous phenomena should occurs, namely (i) the photo‐reduction of Fe 3+ to Fe 2+ , which is the active catalyst; (ii) the production of extra hydroxyl radicals by each generated Fe 2+ by the process described in (i); (iii) the absorption of light by 4‐NP molecules that can induce fast electron transfer between 4‐NP and Fe 3+ on the catalyst's surface; (iv) the photocatalytic cleavage of H 2 O 2 can occurs and generate a higher number of active species in reaction mixture, namely extra hydroxyl radicals that should intervene in the further 4‐NP oxidation steps [106,110] . All these phenomena allow to improve significantly the catalytic performance of the photo‐Fenton process in comparison with the respective Fenton process and support the photo‐Fenton catalytic results obtained in this work and in the comparative Fenton control assay.…”

Synthesis of magnetic CuFe2O4/Fe2O3 core-shell materials and their application in photo-Fenton-like process with oxalic acid as a radical-producing source

“…It should be noted that MB has the maximum absorption at 664 nm whereas the light spectra of both our UVA and visible lamps (Figure 1, measured by a StellarNet spectrometer USB4C00211) does not show any peak around this wavelength. Furthermore, the capacity of our lamps is only 9 W, much lower than that of other works [Liu et al 2012, Sharma et al 2018, which allows us to avoid the selfsensitization of MB molecules. At given time intervals, aliquots (5 mL) of solution were collected, followed by the separation of catalytic powder from the solution by a magnet.…”

“…In order to overcome these obstacles, several magnetic photo-Fenton-like catalysts were developed in the literature [Heidari et al 2019, Liu et al 2012, Sharma et al 2015, Sharma and Singhal 2018 (in general, the photo-Fenton-like reactions are the advanced oxidation processes using oxidants other than H 2 O 2 and transition metals as catalysts other than iron under illumination [Rodríguez-Narváez et al 2019]). These heterogeneous magnetic catalysts relies on the ferrite materials which belong to the spinel structure with the common formula M 2+ Fe 3+ 2 O 4 (M = Fe, Mn, Cu, Zn, Ni).…”

Magnetic and Photocatalytic Properties of Nanodispersed Ferrites Co$_x$Ni$_y$Zn$_{1-x-y}$Fe$_2$O$_4$

“…Крім того, це високостабільні напівпровідники, що мають величину забороненої зони близько 2,0 еВ. Це дає змогу використовувати їх як фотокаталізатори [14,15] [16], або синтезувати композити, поєднавши його з іншими сполуками [17].…”