A green synthesis of nanocatalysts based on reduced graphene oxide/magnetic nanoparticles for the degradation of Acid Red 1

Recent trends in magnetic spinel ferrites and their composites as heterogeneous Fenton-like catalysts: A review

In recent years, there has been a growing interest in utilizing spinel ferrite and their nanocomposites as Fenton-like catalysts. The use of these materials offers numerous advantages, including ability to efficiently degrade pollutants and potential for long-term and repeated use facilitated by their magnetic properties that make them easily recoverable. The remarkable catalytic properties, stability, and reusability of these materials make them highly attractive for researchers. This paper encompasses a comprehensive review of various aspects related to the Fenton process and the utilization of spinel ferrite and their composites in catalytic applications. Firstly, it provides an overview of the background, principles, mechanisms, and key parameters governing the Fenton reaction, along with the role of physical field assistance in enhancing the process. Secondly, it delves into the advantages and mechanisms of H2O2 activation induced by different spinel ferrite and their composites for the removal of organic pollutants, shedding light on their efficacy in environmental remediation. Thirdly, the paper explores the application of these materials in various Fenton-like processes, including Fenon-like, photo-Fenton-like, sono-Fenton-like, and electro-Fenton-like, for the effective removal of different types of contaminants. Furthermore, it addresses important considerations such as the toxicity, recovery, and reuse of these materials. Finally, the paper presents the challenges associated with H2O2 activation by these materials, along with proposed directions for future improvements.

Enhanced photocatalytic degradation of toxic contaminants using Dy2O3-SiO2 ceramic nanostructured materials fabricated by a new, simple and rapid sonochemical approach

The present study is on the fabrication of new photocatalytic nanocomposites (Dy2O3-SiO2) employing a basic agent, tetraethylenepentamine (Tetrene), through a simple, efficient and, quick sonochemical approach. The features of the fabricated photocatalytic nanocomposite were examined employing a variety of microscopic and spectroscopic methods such as XRD, EDS, TEM, FTIR, DRS, and FESEM. The outcomes of morphological studies demonstrated that by proper tuning of sonication time and ultrasonic power (10 min and 400 W), a porous nanocomposite composed of sphere-shaped nanoparticles with a particle size in the range of 20 to 60 nm could be fabricated. The energy gap for the binary Dy2O3-SiO2 nanophotocatalyst was determined to be 3.41 eV, making these nanocomposite favorable for removing contaminants. The photocatalytic performance of the optimal nanocomposite sample was tested for photodecomposition of several contaminants including erythrosine, thymol blue, eriochrome black T, Acid Red 14, methyl orange, malachite green, and Rhodamine B. The binary Dy2O3-SiO2 nanophotocatalyst exhibited superior efficiency toward the decomposition of the studied contaminants. It was able to degrade the erythrosine pollutant more effectively (92.9%). Optimization studies for the photocatalytic decomposition of each contaminant demonstrated that the best performance could be achieved at a specific amount of contaminant and nanocatalyst. Trapping experiments illustrated that hydroxyl radicals were more effectively involved in the decomposition of contaminant molecules by Dy2O3-SiO2 nanophotocatalyst.

Peroxidase-mimetic activity of a nanozyme with uniformly dispersed Fe3O4 NPs supported by mesoporous graphitized carbon for determination of glucose

A Fe₃O₄/mesoporous graphitized carbon (Fe₃O₄/m-GC) composite was prepared through a facile calcination method with iron-based metal-organic frameworks (Fe-MOFs) as a sacrificial template. After carbonization, the Fe₃O₄ nanoparticles were uniformly dispersed in the mesoporous carbon support, resulting in spatial structural stability. The mesoporous carbon support obtained was highly graphitized and exhibited eminent electrical conductivity, which accelerated the electron transfer between the Fe₃O₄ nanoparticles by Fe(II)/Fe(III) redox cycles and m-GC by C = C_sp2/C-C_sp3 redox cycles, leading to the excellent peroxidase-mimetic activity of Fe₃O₄/m-GC. K_m values for tetramethylbenzidine (TMB) and H₂O₂ were 26.8 and 15.8 times lower than that of natural horseradish peroxidase, respectively. Taking advantage of the peroxidase-mimetic activity of Fe₃O₄/m-GC, a colorimetric assay was fabricated for detecting glucose in the range 0.5 ~ 200 μM, with a limit of detection of 0.24 μM. Fig 1 A Schematic illustration of the preparation process of Fe₃O₄/m-GC, B schematic illustration of a proposed synergistic catalytic mechanism of TMB oxidation by Fe₃O₄/m-GC.

Synthesis of magnetic tungsten disulfide/carbon nanotubes nanocomposite (WS2/Fe3O4/CNTs-NC) for highly efficient ultrasound-assisted rapid removal of amaranth and brilliant blue FCF hazardous dyes

In this research, the potentiality of magnetic tungsten disulfide/carbon nanotubes nanocomposite (WS₂/Fe₃O₄/CNTs-NC) as an adsorbent for the ultrasound-assisted removal of amaranth (AM) and brilliant blue FCF (BB FCF) dyes was investigated. The experiments were conducted using a central composite design (CCD) with the inputs of solution pH (X₁: 2.0-10), adsorbent mass (X₄: 4-20 mg), AM concentration (X₂: 10-50 mg L^-1), BB FCF concentration (X₃: 10-50 mg L^-1), and sonication time (X₅: 2-12 min). At the optimum conditions, the removal percentages of 99.30% and 98.50% were obtained for AM and BB FCF, respectively. The adsorption of the dyes was described by Langmuir isotherm and pseudo-second-order (PSO) kinetic models. The maximum adsorption capacities of AM and BB FCF were 174.8 mg g^-1 and 166.7 mg g^-1, respectively. The adsorption thermodynamic study showed that the adsorption of the dyes occurred endothermically and spontaneously. The removal percentages of AM and BB FCF from the real samples were in the range of 94.52-99.65% for the binary solutions. The removal percentage for each dye after five cycles of adsorption/desorption was > 90%. This work provides a useful insight to the potential application of CNTs-based magnetic nanocomposite for the treatment of wastewaters contaminated with dyes.

Toward enhanced catalytic activity of magnetic nanoparticles integrated into 3D reduced graphene oxide for heterogeneous Fenton organic dye degradation

Composite Fenton nanocatalyst was prepared by water-based in situ creation of Fe3O4 nanoparticles integrated within the self-assembly 3D reduced graphene oxide (rGO) aerogel. The hybrid applied for the degradation of Acid Green 25 (AG-25) organic dye in an aqueous solution, in the presence of H2O2. By investigating the conditions that maximize the dye adsorption by the 3D composite, it was found that the pH of the solution should be adjusted between the pKa of the functional groups present on the rGO surface (carboxylic acid) and that of the dye (sulfonic acid) to promote electrostatic interactions dye-3D structure. Performed under these conditions, Fenton degradation of AG-25 in presence of H2O2 was completed in less than 30 min, including all the intermediate products, as demonstrated by MALDI-TOF-MS analysis of the aqueous solution after discoloration. Moreover, this was achieved in a solution with as high a dye concentration of 0.5 mg/mL, with only 10 mg of 3D composite catalyst, at room temperature and without additional energy input. The high performance was attributed to the creation of charge-transfer complex between rGO and Fe3O4 nanoparticles throughout covalent bond C-O-Fe, the formation of which was promoted by the in situ synthesis procedure. For the first time, up to the authors' knowledge, AG-25 degradation mechanism was proposed.