Application of heterogenous catalyst of tris(1,10)-phenanthroline iron(II) loaded on zeolite for the photo-Fenton degradation of methylene blue

Ferroin in dyes degradation by Fenton-like process: a chemical waste recycling perspective

Published literature describes the formation of the Fe (II)-phenanthroline complex (ferroin) as a stop way for Fenton processes, reducing radical yield. By contrast, this study presents evidence that ferroin can be activated by UVA in mildly acidic media in a photo-Fenton-like process. Because ferroin is the main waste from total iron determination in environmental samples, a recycling approach is suggested. Based on the best practices of waste management planning, an application of the proposed method for treating another chemical waste is presented. Titrimetric ammonia determination waste containing 2.67 mg L^-1 methyl red azo dye and 1.33 mg L^-1 methylene blue was degraded using the optimized experimental conditions: pH = 5.2-5.4; [H₂O₂] = 310 mg L^-1; [ferroin] = 1.4 mg L^-1; temperature = 36 ± 1 °C; reaction time = 165 min under UVA irradiation. Attenuation of most intense spectroscopic bands for the dyes achieved 94% (510 nm) and 96% (665 nm) reduction for methyl red and methylene blue, respectively, with degradation of ferroin itself. The present work brings empirical evidence that is possible to recycle ferroin as photo-Fenton-like process catalyst, as well as determine the best conditions for providing less acidic treated effluents with negligible suspended solid concentration, better than that obtained from classical photo-Fenton processes.

Catalytic Oxidation of Methylene Blue by Use of Natural Zeolite-Based Silver and Magnetite Nanocomposites

This work reports the synthesis of natural zeolite-based silver and magnetite nanocomposites and their application for the catalytic oxidation of methylene blue in water. The zeolite was impregnated with 5.5 wt.% Fe in the form of magnetite nanoparticles with size of 32 nm, and with 6.4 wt.% Ag in the form of silver oxide and metallic silver nanoparticles with sizes of 42 and 20 nm, respectively. The results showed that physical adsorption contributed to the removal of methylene blue by 25–36% and that Fe3O4@NZU is superior to Ag2O@NZU and Ag0@NZU, leading to 55% removal without oxidant and 97% in the presence of H2O2. However, there is no evidence of significant mineralization of methylene blue. The application of reaction rate models showed that the reaction order changes from zero to first and second order depending on the H2O2 concentration.

The ability of brown-rot fungus Daedalea dickinsii to decolorize and transform methylene blue dye

The ability of Daedalea dickinsii to decolorize and transform methylene blue (MB) dye was investigated. MB was decolorized in potato dextrose agar medium after adding MB at concentrations of 50, 75, and 100 mg L^-1. D. dickinsii decolorized MB with decolorization index values of 0.92, 0.90, and 0.88 at MB concentrations of 50, 75, and 100 mg L^-1, respectively. The 100 mg L¹ MB concentration was selected for biotransformation in liquid potato dextrose broth medium. D. dickinsii transformed approximately 54% of the MB after a 14-day incubation. 3-(Dimethylamino)-7-(methylamino) phenothiazine (C₁₅H₁₆N₃S), 3,7-bis(dimethylamino)-4aH-phenothiazin-5-one (C₁₆H₁₉N₃SO), and 4-(dimethylamino)-2-[m(dimethylamino) phenylsulfinyl] benzenamine (C₁₆H₂₁N₃SO) were detected as MB metabolic products. This is the first report of MB transformation by the brown-rot fungi D. dickinsii. These results indicate that D. dickinsii can be used to decolorize and biotransform MB dye.

Photo-Fenton process in a Co(ii)-adsorbed micellar soft-template on an alumina support for rapid methylene blue degradation

Co(ii)-mediated photo-Fenton degradation of methylene blue was achieved for the first time on the admicellar layer supported on an alumina surface.

Accelerated generation of free radicals by iron oxide nanoparticles in the presence of an alternating magnetic field

The surfaces of iron oxide nanoparticles are capable of catalytically generating reactive oxygen species (ROS) through the Fenton and Haber-Weiss reactions. Fenton chemistry has been shown to be temperature dependent with an increase in activity up to 40 °C and then a decrease above this temperature as the hydrogen peroxide degrades into oxygen and water which limits the reaction. When exposed to an alternating magnetic field (AMF), iron oxide nanoparticles absorb the energy from the magnetic field and convert it into heat. In this study, we observed an increase in the degradation of methylene blue when a suspension of magnetite nanoparticles (Fe3O4) was exposed to an AMF indicating there was an increase in the ROS generation in response to the AMF. The increase in ROS generation compared to the Arrhenius prediction was both time and concentration dependent; in which we observed a decrease in ROS enhancement with increased time of exposure and concentration. We postulate that the decrease is due to agglomeration in the presence of the field. As the nanoparticles agglomerate, there is a decrease in surface area per mass limiting the reaction rate.

Application of a montmorillonite clay modified with iron in photo-Fenton process. Comparison with goethite and nZVI

Iron pillared clay (Fe-PILC) was prepared from a montmorillonite and was characterized by scanning electron microscopy and X-ray fluorescence. Fe-PILC catalytic activity was evaluated in photo-Fenton processes applied to the degradation of 2-clorophenol. Different catalyst loads were assayed. The Fe-PILC allowed almost complete degradation of the contaminant. An increase in the contaminant degradation rate was observed, following leaching of iron during catalytic assays, which suggest the existence of a homogeneous photo-Fenton mechanism. The catalytic performance of the Fe-PILC was compared with that for goethite and zero valent iron nanoparticles. Differences were found regarding the achieved degradation levels, the efficiency in oxidant consumption, and the extension of iron leaching.

Heterogeneous Fenton catalysts for the abatement of organic pollutants from aqueous solution: a review

Fenton processes have gained much attention in the field of wastewater treatment during recent years.

Tunable synthesis of SiO2-encapsulated zero-valent iron nanoparticles for degradation of organic dyes

A series of nanocomposites consisting of zero-valent iron nanoparticles (ZVI NPs) encapsulated in SiO2 microspheres were successfully synthesized through a successive two-step method, i.e., the wet chemical reduction by borohydride followed by a modified Stöber method. The as-synthesized nanocomposites were characterized using X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer, and inductively coupled plasma-atomic emission spectrometer. The catalytic performance of SiO2-encapsulated ZVI nanocomposites for the degradation of organic dyes was investigated using methylene blue (MB) as the model dye in the presence of H2O2. The results showed that the degradation efficiency and apparent rate constant of the degradation reaction were significantly enhanced with increased ZVI NPs encapsulated in SiO2 microspheres, whereas the dosage of H2O2 remarkably promoted degradation rate without affecting degradation efficiency. The content-dependent magnetic property ensured the excellent magnetic separation of degradation products under an external magnet. This strategy for the synthesis of SiO2-encapsulated ZVI NPs nanocomposites was low cost and easy to scale-up for industrial production, thereby enabling promising applications in environmental remediation.