Ag loaded B-doped-g C3N4 nanosheet with efficient properties for photocatalysis

Three material engineering strategies in the form of doping (Boron-doping), nanostructuring (nanosheet (NS) formation) and decorating with plasmonic nanoparticles (loading with Ag metal), were integrated to improve the photocatalytic activity of graphitic carbon nitride (gC₃N₄). Concentrations of B-doping and Ag-loading were optimized to maximize the catalytic performance in the final nanocomposite of Ag-loaded B-doped gC₃N₄ NS. Combined effect of all three strategies successfully produced over 5 times higher rate towards degradation of organic dye pollutant, when compared to unmodified bulk gC₃N₄. Detailed characterization results revealed that incorporation of B in gC₃N₄ matrix reduces the band gap to increase the visible light absorption, while specific surface area is significantly enhanced upon formation of NS. Decoration of Ag nanoparticles (NPs) on B-doped gC₃N₄ NS assists in fast transfer of photogenerated electrons from gC₃N₄ to Ag NPs owing to the interfacial electric field across the junctions and thus reduces the recombination process. Investigations on individual strategies revealed that decoration of Ag NPs to induce better charge separation, is the most effective route for enhancing the photocatalytic activity.

Hierarchically structured ternary heterojunctions based on Ce3+/ Ce4+ modified Fe3O4 nanoparticles anchored onto graphene oxide sheets as magnetic visible-light-active photocatalysts for decontamination of oxytetracycline

The main prerequisite of an active visible-light-driven photocatalyst is to effectively utilize the visible light to induce electron-hole (e^-/h⁺) pairs of expanded lifetime. To this end, for the first time, the ternary heterojunctions of CeO₂/Fe₃O₄ /Graphene oxide and Ce³⁺/ Fe₃O₄ /Graphene oxide (CeO₂/Fe₃O₄/GO and Fe_2.8Ce_0.2O₄/GO) were prepared via facile ultrasonic-assisted procedures and employed for destruction of oxytetracycline (OTC) under visible light irradiation. The changes in the relative crystal structure, morphology, atomic and surface functional group composition, magnetic, and optic properties of magnetite were uncovered by various techniques. The substantial degradation and mineralization of OTC via visible light/Fe_2.8Ce_0.2O₄/GO system were thoroughly discussed in terms of narrowed band gap energy, the principal function of Ce³⁺/Ce⁴⁺ and Fe²⁺/Fe³⁺ redox pairs and GO platelets, enhanced charge separation and transfer, and enlarged active surface area. Furthermore, the performance of visible light/Fe_2.8Ce_0.2O₄/GO system was evaluated for treating real wastewater and its efficiency was investigated using a number of enhancers and scavengers. Finally, the generated byproducts in the course of photodegradation were determined and the oxidation pathway, photocatalytic kinetics, and plausible mechanism were proposed. The results confirmed that the introduced Ce ions and graphene oxide sheets boost the photo-catalytic efficiency of magnetite for photodegradation of OTC.

Cerium-substituted magnetite: Fabrication, characterization and sonocatalytic activity assessment

The present paper reports the sonocatalytic activity of cerium-substituted-magnetite for removal of oxytetracycline (OTC). The catalyst was prepared through a chemical route (co-precipitation, Fe_3-xCe_xO₄) and a mechanical procedure (CeO₂/Fe₃O₄). Subsequently, the physico-chemical characteristics of both samples were determined using XRD, BET, SEM, EDX, TEM, Dot-mapping, FT-IR, DRS, and VSM analysis and compared to pristine magnetite and ceria. Afterwards, the effects of various operational conditions were assessed on sonocatalytic performance of Fe_2.8Ce_0.2O₄ for OTC removal and the obtained optimal conditions were applied to compare the resulted DE with so-synthesized Fe₃O₄, CeO₂, and CeO₂/Fe₃O₄ samples. Fe_2.8Ce_0.2O₄ (0.75 g/L) exhibited great catalytic performance for sono-degradation of OTC under its unchanged pH and US power of 300 W, wherein about 88% and 64% of OTC was removed at its initial concentrations of 20 and 50 mg/L. Moreover, the effects of the addition of a number of oxidants, organic and inorganic compounds and gases on the sonocatalytic degradation of OTC were evaluated under the identical condition. The obtained results presented an effective sonocatalytic system based on the synergistic action of Fe_2.8Ce_0.2O₄ under ultrasonic irradiation.

Kinetic modeling of sonocatalytic performance of Gd-doped CdSe nanoparticles for degradation of Acid Blue 5

CdSe and Gd-doped CdSe nanoparticles were synthesized using a simple hydrothermal method, and their catalytic activity was examined toward degradation of Acid Blue 5 (AB5) in the sonocatalytic process. The structure and morphology of as-prepared nanomaterials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Branauer, Emmett and Teller (BET) and Fourier infrared spectroscopy (FT-IR) techniques. Among the synthesized samples, 4% Gd-doped CdSe nanoparticles demonstrated the highest catalytic activity with band gap energy of 1.61eV. The effect of dopant content, initial dye concentration, catalyst dosage, ultrasonic power and inorganic radical scavengers on the degradation efficacy of AB5 was evaluated. The produced intermediates of AB5 degradation during sonocatalytic process were verified using gas chromatography-mass spectroscopy (GC-MS) technique. A novel intrinsic kinetic model for prediction of AB5 degradation efficiency was proposed. A good agreement was obtained between developed model and experimental data (R²>0.94).

Application of doped photocatalysts for organic pollutant degradation - A review

Advanced oxidation process involves production of hydroxyl radical for industrial wastewater treatment. This method is based on the irradiation of UV light to photocatalysts such as TiO₂ and ZnO for photodegradation of pollutant. UV light is used for irradiation in photocatalytic process because TiO₂ has a high band gap energy which is around 3.2 eV. There can be shift adsorption to visible light by reducing the band gap energy to below 3.2 eV. Doped catalyst is one of the means to reduce band gap energy. Different methods are used for doped catalyst which uses transition metals and titanium dioxide. The band gap energy of three types of transition metals Fe, Cd and Co after being doped with TiO_2, are around 2.88 ev, 2.97ev and 2.96 ev, respectively which are all below TiO₂ energy. Some of the transition metals change the energy level to below 3.2 eV and the adsorption shifts to visible light for degradation of industrial pollutant after being doped with titanium dioxide. This paper aims at providing a deep insight into advanced oxidation processes, photocatalysts and their applications in wastewater treatment, doping processes and the effects of operational factors on photocatalytic degradation.

Ammonia-modified graphene sheets decorated with magnetic Fe3O4 nanoparticles for the photocatalytic and photo-Fenton degradation of phenolic compounds under sunlight irradiation

Synthesis of easily separable and eco-friendly efficient catalyst with both photocatalytic and photo-Fenton degradation properties is of great importance for environment remediation application. Herein, ammonia-modified graphene (AG) sheets decorated with Fe₃O₄ nanoparticles (AG/Fe₃O₄) as a magnetically recoverable photocatalyst by a simple in situ solution chemistry approach. First, we have functionalized graphene oxide (GO) sheets by amide functional group and then Fe₃O₄ nanoparticles (NPs) are doped onto the functionalized GO surface. The AG/Fe₃O₄ nanocomposite showed efficient photocatalytic activity towards degradation of phenol (92.43%), 2-nitrophenol (2-NP) (98%) and 2-chlorophenol (2-CP) (97.15%) within 70-120min. Consequently, in case of photo-Fenton degradation phenomenon, 93.56% phenol, 98.76% 2-NP and 98.06% of 2-CP degradation were achieved within 50-80min using AG/Fe₃O₄ nanocomposite under sunlight irradiation. The synergistic effect between amide functionalized graphene and Fe₃O₄ nanoparticles (NPs) enhances the photocatalytic activity by preventing the recombination rate of electron-hole-pair in Fe₃O₄ NPs. Furthermore, the remarkable reusability of the AG/Fe₃O₄ nanocomposite was observed up to ten cycles during the photocatalytic degradation of these phenolic compounds.

Treatment of textile effluent containing recalcitrant dyes using MOF derived Fe-ZSM-5 heterogeneous catalyst

Fe-ZSM-5 is synthesized through a newly established 2-step process. 82% yield of Fe-ZSM-5 catalyst is possible at low temperature and pressure. 100% degradation of dyes is achieved with lesser amounts of catalyst and H₂O₂.