Microwave-Assisted Synthesis of Cobalt Oxide/Reduced Graphene Oxide (Co3O4–rGo) Composite and its Sulfite Enhanced Photocatalytic Degradation of Organic Dyes

One-pot synthesis of Co3O4 nanocrystals on reduced graphene oxide (rGO) was carried out by reacting cobalt nitrate, L-arginine, extract of Laportae aestuans as oxidant, fuel and reducing agent, respectively, in a domestic microwave. Morphologies of Co3O4–rGo (RGCO) composite was elucidated using UV-Vis, FT-IR, TEM, SEM, EDX, XRD and photoluminescence spectroscopies. The synthesized RGCO composite was applied as heterogeneous photocatalyst in the activation of Na2SO3 (sulfite) as sacrificial agent to degrade cationic dyes: rhodamine B (RhB) and methylene blue (MB), under visible light, at neutral pH 7.0. Photocatalytic performance of as-prepared RGCO was significantly enhanced in the presence of Na2SO3. Enhanced photocatalytic activity of RGCO was attributed to the synergistic effects between sulfite radicals generated in situ, and reduced graphene oxide, in which rGO served as electron sink to suppress recombination of photogenerated charge carriers. Plausible mechanistic pathways responsible for the activation of sulfite anions in situ are presented in this paper.

Preparation, Physical Characterization and Adsorption Properties of Synthesized Co–Ni–Cr Nanocomposites for Highly Effective Removal of Nitrate: Isotherms, Kinetics and Thermodynamic Studies

In the current effort, the Co–Ni–Cr Nanocomposites were synthesized by chemical method and characterized by means of scanning electron micrographs (SEM), X-ray diffraction (XRD), Fourier trans from infra-red (FTIR), and vibration sample magnetization (VSM). In the final step, these nanoparticles were used to study the nitrate removal efficiency from aqueous solution. The effect of important factor including pH, concentration of Nitrate (NO3 −) ion, contact time and nanoparticle dose were studied in order to find the optimum adsorption conditions. A maximum of removal of the nitrate was observed at pH 4, initial concentration of 40 mg L−1, amount of nanoparticle of 0.06 g L−1 and contact time 60 min. The adsorption isotherm values were obtained and analyzed using the Langmuir, Frenudlich, Temkin and Dubinin–Radushkevich equations, the Temkin isotherm being the one that showed the best correlation coefficient (R2 = 0.999). In addition to, the adsorption kinetics studied by the pseudo-first-order, pseudo-second-order, Elovich model, Ritchie and intraparticle diffusion models. The experimental data fitted to pseudo-second-order (R2 = 0.999).

Sol-Gel Sonochemical Triton X-100 Templated Synthesis of Fe2O3/ZnO Nanocomposites Toward Developing Photocatalytic Degradation of Organic Pollutants

The existing work emphasizes mainly to advance the low surface features of zinc oxide (ZnO) by dispersion of Fe2O3 nanoparticles on the ZnO surface fabricated via a sol-gel route with Triton X-100 as a structure and capping agent to synthesis a novel series of Fe2O3/ZnO nanocomposites (NCs) with novel features assembling between the two nanoparticle materials. Fe2O3/ZnO is an effective semiconductor which has higher efficiency in the removal of numerous organic dyes and other pollutants. The NCs was characterized via HRTEM, XRD, FTIR, BET, RS and UV–Vis DRS. A photocatalytic performance of the fabricated Fe2O3/ZnO nanocomposites was estimated by continual degradation of the methylene blue dye (MB) as an organic pollutant in aqueous solution. The comparison between pure ZnO (NPs) and Fe2O3/ZnO (NCs) show advanced photocatalytic performance under both UV and sunlight irradiation. The impact of several parameters, for example, dopant contents, photocatalytic dosage, pH, chemical oxygen demand (COD) and point of zero charge (PZC) were evaluated and discussed. In addition, the protective species’ role was estimated via a radical scavenger route. The photo-degradation data shown that the Fe2O3/ZnO (10 wt%) semiconductor is the fit photocatalyst between the fabricated semiconductors for the methylene blue dye (MB) degradation. The intensity reduction peak of UV emission and the intensity increment of visible emission were led to the lessening in recombination between electrons and holes which are finally responsible for the maximum photocatalytic performance of Fe2O3/ZnO nanocomposites. The gained results confirmed that the dopant content is the major factor in photocatalytic degradation activity.

Adsorption of Dye from Wastewater onto ZnO Nanoparticles-Loaded Zeolite: Kinetic, Thermodynamic and Isotherm Studies

The adsorption process of methylene blue (MB) and its removal from aqueous solution at initial pollutant concentration range of 1–7 ppm was investigated. Zeolite-A (Z) and its ZnO-loaded species (Z/ZnO) were prepared via microwave technique from natural resource and applied for dye removal. The loading of ZnO was governed by the cation exchange property of zeolite, followed by calcination. Experimentally, Z and Z/ZnO were tested using X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and N2 adsorption-desorption. The examined parameters such as concentration of dye, contact time, ZnO dose and solution pH were traversed. Three isothermal models were analyzed. Kinetic studies indicated that, the adsorption of MB matched with pseudo-second order model. The maximum removal efficiency at pH 3, increased from 67.8% for Z to 94.8% for Z/ZnO modified with 3% ZnO loads (Z/ZnO(3%)). Parameters such as ΔH, ΔS, ΔG, S* and Ea were thermodynamically calculated. Langmiur isotherm and pseudo-second order models were the best fitting for the obtained data. The results indicated that, the adsorption of MB dye is spontaneous and endothermic, the removal efficiency is favored by increasing the temperature. ZnO-zeolite has much higher adsorption capacity for eliminating MB dye than that of the un-loaded zeolite.

Structural, Dielectric and Magnetic Studies of Perovskite [Gd1−xMxCrO3 (M = La, Co, Bi)] Nanoparticles: Photocatalytic Degradation of Dyes

Nanoparticles (NPs) of Gd1−xMxCrO3 (M = La, Co, Bi) were synthesized by microemulsion techniques, involving simultaneous single ion substitution philosophy. Structural, magnetic, dielectric properties, morphology, elemental analysis and distribution size of fabricated nano-crystalline were determined. The techniques employed for investigation are X-ray diffraction (XRD), vibrating sample magnetometer (VSM), dielectric measurement and scanning electron microscopy (SEM), energy dispersive X-ray (EDX), photoluminescence (PL) and atomic force microscopy (AFM), respectively. XRD pattern confirm that all the as-synthesized NPs have orthorhombic structure and successfully substituted of different metal ions into the regular crystal structure of GdCrO3. The lattice parameters X-ray density, bulk density, porosity and grain size were calculated from XRD pattern of Gd1−xMxCrO3 (M = La, Co, Bi) substituted and un-substituted GdCrO3. The magnetic hysteresis loop of fabricated product confirmed that the entire sample exhibits ferromagnetic behavior at room temperature. It was also found that the fabricated NPs show excellent photocatalytic activity (PCA) against Congo-red, about 78.24% after 55 min of incubation.

Thermal and Rheological Study of Nanocomposites, Reinforced with Bi-Phase Ceramic Nanoparticles

In this study the synthesis of bi-phase nanoparticles of Fe1.46Zn0.5La0.04Cu0.5O4 (FZLCs) ceramics were first carried out by Sol-gel method and then nanocomposites of FZLCs with polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyethylene oxide (PEO) were prepared by one-pot blending technique. XRD, FT-IR, TG/DTA and SEM techniques were applied for complete characterization of composites. Rheological and dielectric properties of all nanocomposites were studied in detail for their comparative performance. TGA results reveal the highly thermal stability for all nanocomposites in this order i.e. FLZCs/PEO > FLZCs/PVA > FZLCs/PVP > FZLCs/PEG. Rheological properties show that these materials are rigid, pseudo plastic and non-Newtonian in nature. The increase in values for storage modulus (G′) and loss modulus (G′′) with increasing angular frequency owed to the shear thinning behavior of these nanocomposites. Dielectric properties show good agreement to that of energy storage substances which means that these materials have potential to be applied in storage devices.

Synthesis and Characterization of BaAl2O4 Catalyst and its Photocatalytic Activity Towards Degradation of Methylene Blue Dye

Hexagonal BaAl2O4 catalyst has been prepared using a gamma-ray irradiation assisted polyacrylamide gel method. The catalysts synthesized at different calcining temperatures were analyzed to insight into their effects on the structural, crystalline, surface morphology, color, optical, fluorescence and photocatalytic properties of the hexagonal BaAl2O4 catalyst. Increasing the calcining temperature has obvious influences on the crystallinity, color, optical properties and the formation of the hexagonal BaAl2O4 catalyst. The optical energy gap (Eg) value of the hexagonal BaAl2O4 catalyst increases with the increasing of calcining temperature. TEM image of the pure hexagonal BaAl2O4 catalyst shows a morphology of flake structure and aggregation. Raman spectroscopy of the pure hexagonal BaAl2O4 catalyst exhibits four luminescent background peaks at 400, 415, 428 and 445 nm mainly due to the oxygen vacancies (VO), Ba vacancies (VBa) and some color centers exists in the BaAl2O4 sample. A comparison of photocatalytic activity among samples for degradation of methylene blue (MB) dye indicates that the pure hexagonal BaAl2O4 catalyst exhibits highest photocatalytic activity under the irradiation of both visible and ultraviolet light. Based on the fluorescence experiment, electrochemical and active species tests, the high photocatalytic activity of the pure hexagonal BaAl2O4 catalyst to be related to hole (h+) and hydroxyl radical (⋅OH) and also to the defects in the sample.

Identify the Active Phase of Fe–CN Composites for Oxidation Removal of Rhodamine B with H2O2

Fe-containing carbon nitrides (Fe–CN) prepared with various CN precursors, including dicyandiamide, melamine, guanidine hydrochloride and urea, were characterized by X-ray diffraction, thermal gravimetric analysis, N2 physisorption, transmission electron microscopy, X-ray photoelectron spectroscopy and atomic emission spectrometer measurements, and used as catalysts to catalyze the rhodamine B oxidation with H2O2 as oxidant. Characteristic results showed that Fe–CN exhibits different compositions, properties and catalytic performances if different CN precursors are used. The Fe–CN prepared from dicyandiamide contains mainly CN phase and certain amounts of surface Fe2O3 phase, exhibits the best activity; while that prepared from urea contains mainly Fe2O3 phase and few amounts of CN phase, exhibits the worst activity. Contrasting experiments conducted under light irradiation, with a supported Fe/CN_D catalyst, and that using a washed catalyst, suggested that the surface Fe2O3 is the active site of the reaction.