Iron oxide nanoparticles as heterogeneous electro-Fenton catalysts for the removal of AR18 azo dye

Abstract

Iron oxides nanoparticle as heterogeneous electro-Fenton catalysts for the removal of AR18 azo-dye Heterogeneous electro-Fenton mineralization of Acid Red 18 (AR18) in aqueous solution was studied with magnetite Fe3O4 (MNPs) and hematite Fe2O3 (HNPs) nanoparticles as catalysts. High mineralization yields of AR18 were obtained with magnetite, 81% TOC removal after 180 min of electrolysis in 40 mg.L-1 Fe3O4, pH 3.0, at 50mA of current intensity and in 50 mM Na2SO4. In order to explain the obtained mineralization yield achieved with MNPs, the quantification of hydrogen peroxide (H2O2), hydroxyl radical (•OH) and iron leaching were performed at 50 and 100 mA. From the high iron concentration found in the bulk solution and the slight impact of the catalyst mass concentration on TOC removal, the formation of hydroxyl radicals occurs mainly through homogeneous process. In the presence of hydroxyl radical scavenger, degradation remained total after 15 min showing the involvement of a direct electrochemical oxidation of the dye at the electrode surface. The hydroxyl radical oxidation is responsible for at least 50% of mineralization.

A proposed synergetic mechanism for metal fume fever involving ZnO and Fe3O4 nanoparticles

“…This crystal structure enables the mixed-valence iron oxide to undergo efficient electron transfer from Fe(II) and Fe(III) in the octahedral sites 33 . In other words, the two ion species constituent of magnetite can be reversibly oxidized and reduced without modifying the crystal structure 34 . The rational thinking in terms of redox potential leads to the assumption that the standard redox potential for ≡Fe(III)/≡Fe(II) at the Fe 3 O 4 NP surface would necessarily be lower than the corresponding value for Fe(III)/Fe(II) in solution (E° = 0.77 V).…”

“…In terms of mechanism, the efficient heterogeneous Fenton-like reaction observed with Fe 3 O 4 NP at neutral pH, where the role of dissolved ions might be neglected, implies the formation of high-valent iron species such as ≡Fe(IV) as intermediates 33 . In addition, both the high surface/volume ratio and the location of active sites at the particle surface are responsible for the improved catalytic activity of the Fe 3 O 4 NP in comparison to its bulk counterpart 34 . This heterogeneous Fenton-like reaction represents a well-established mineralization procedure to achieve reductive degradation of numerous organic pollutants via the generation of hydroxyl radicals 28 , 33 , 35 – 37 .…”

Review: Clay-Modified Electrodes in Heterogeneous Electro-Fenton Process for Degradation of Organic Compounds: The Potential of Structural Fe(III) as Catalytic Sites

“…Early publications involving heterogeneous catalysis in the electro-Fenton process involved natural occurring iron minerals such as goethite, magnetite and pyrite [14]. However, iron oxides result in both homogeneous and heterogeneous catalysis depending on the pH [15][16][17], referred to here as pseudo-heterogeneous catalysts. Under acidic conditions, iron oxides tend to dissolve, releasing into solution Fe(II) or Fe(III) ions that are reduced to Fe(II) in the cathode (Equation ( 1)).…”

Degradation of methyl orange by the Fenton-like reaction of pyrite-activated hydrogen peroxide forming the Fe(III)/Fe(II) cycle

“…With the rapid development of printing and dyeing textile industries, the large amount of printing and dyeing wastewater produced has become one of the main water pollution sources in the world (Gu et al, 2021;Pinedo-Hernández et al, 2022). Printing and dyeing wastewater has a complicated composition, high concentration of pollutants, poor biochemical properties, and is difficult to treat (Ben Hafaiedh et al, 2020;Domingues et al, 2019;Shukla and Remya, 2021). Among the contaminants, methyl orange (MO) contains -N=N-and is a typical azo dye (Aghdasinia et al, 2016;.…”