Surface charge on chitosan/cellulose nanowhiskers composite via functionalized and untreated carbon nanotube

Improvement in chitosan (CS) was achieved by solution casting using cellulose nanowhiskers (CNWs) and multiwall carbon nanotubes (MWCNTs) to synthesize CS/CNW functionalized/treated MWCNTs (CS/CNWs/f-MWCNTs) and CS/CNW untreated MWCNTs (CS/CNWs/Un-MWCNTs) nanocomposite films. A comparison between effects of f-MWCNTs and Un-MWCNTs on CS/CNWs matrix have been studied with respect to change in their physical and mechanical properties. The surface morphology, chemical composition, mechanical properties and temperature decomposition of CS/CNWs/f-MWCNTs and CS/CNW/Un-MWCNTs nanocomposite films were characterized by Energy Dispersion Spectroscopy (EDS), Field Emission Scanning Electron Microscope (FESEM), Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). FESEM has shown that f-MWCNTs and Un-MWCNTs were well dispersed in CS/CNWs structure. Decrease in film ductility was observed with addition of Un-MWCNTs or f-MWCNTs. Moreover, Tensile strength (TS) and Young's modulus (YM) were increased with f-MWCNTs and seemed to be decreased in case of Un-MWCNTs. However, a decrease in elongation at break (EB) has experienced with addition of f-MWCNTs and Un-MWCNTs. Furthermore, thermal stability of chitosan composites presented a delay or prevention from degradation of CS/CNWs due to the strong interactions. Such modification in chitosan can improve its mechanical and surface properties. Hence, chitosan derived composites could achieve more applicability in packaging, medicinal and environmental applications

Green biosynthesis of Fe3O4 nanoparticles using Chlorella vulgaris extract for enhancing degradation of 2,4 dinitrophenol

Objectives: This study aimed to provide the excellent role of Chlorella vulgaris extract as a green, reducing agent for improving and enhancing the effectiveness and performance of as-prepared NPs, which is higher than bare Fe3O4. Methods: The extract of the algal cell of Chlorella vulgaris is used as a green, reducing agent was used to prepare green Fe3O4 NPs to improve and enhance the degradation effectiveness of 2,4 dinitrophenol (2,4 DNP) in their aqueous solution using UV irradiation. The as-synthesized bare Fe3O4 and green Fe3O4 NPs were characterized using UV–VIS spectroscopy, TEM, SEM, EDX, XRD, and FT-IR spectroscopy to determine bandgap energy, particle size, structural morphology, crystallite nature, phase structure, elemental compositions, and existed functional group. Results: SEM and TEM images indicated that the as-synthesized NPs have a regular spherical shape with a mean size ranging between 13.68 and 31.71 nm. The energy bandgap (Eg) indicated the green Fe3O4 NPs have low values (2.73 and 2.3 eV) than bare Fe3O4 (2.89 eV). The maximum degradation of 2,4 DNP was achieved at pH = 8, 90 min contact time, 0.35 g/L catalyst dose, and 100 mg/L 2,4 DNP concentration. Conclusion: The degradation results proved that green Fe3O4 NPs have more effectiveness than bare Fe3O4 NPs

Synthesis and Characterization of CeO2/CuO Nanocomposites for Photocatalytic Degradation of Methylene Blue in Visible Light

Removal of hazardous organic dyes from polluted water bodies requires the introduction of strong adsorbents and photocatalysts to industrial wastewaters. Herein, photocatalytic CeO2 nanoparticles and CeO2/CuO nanocomposite were synthesized following a co-precipitation method for low cost elution of methylene blue (MB) from water. The crystallinity and surface structure of the as-prepared materials have been analyzed using characterization techniques including X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), ultra-violet visible spectroscopy (UV–Vis), and Fourier-transform infrared spectroscopy (FTIR). The average particle size of both the nano scaled samples were approximately 20–30 nm. The photocatalytic properties of CeO2/CuO were investigated under visible light against methylene blue (MB). The results showed 91% photodegradation of MB organic pollutant in 3 h as monitored by UV–Vis spectroscopy. Absorbance peaks appeared at around 670 nm corresponding to degradation of MB. Such output displayed the effectiveness of Ce nanocomposites for environmental benefits. Hence, CeO2/CuO nanocomposite could be useful for treatment of industrial wastewaters by removing hazardous MB dye

Preparation of α-MoO3 from H3PMo12O40 precursor: synthesis of 1,2-cyclohexanediol from cyclohexene over α-MoO3-TiO2 catalyst

A series of α -MoO _3 -TiO _2 mixed oxides were prepared by calcining a mixture of the heteropolyacid H _3 PMo _12 O _40 and TiO _2 at temperatures ranging from 350 °C to 600 °C. The mixed oxides thus prepared were characterized and tested for the oxidation of cyclohexene by the oxidizing mixture H _2 O _2 /CO _2 . FTIR and XRD characterizations showed that the Keggin structure of H _3 PMo _12 O _40 was preserved for calcination temperatures below 400 °C. Above 450 °C, Keggin’s structure collapses. XRD analysis revealed that as the calcination temperature increased, more orthorhombic α -MoO _3 was formed. Analysis of the reaction mixture by GC-MS showed that oxidation by the H _2 O _2 /CO _2 mixture leads to 1,2-cyclohexanediol as the main product and to 2-cyclohexene-1-one and 2-cyclohexene-1-ol as minor products. Oxidation by H _2 O _2 /CO _2 mixture proved to be more effective than H _2 O _2 alone and CO _2 alone. The conversion (69.4%) and the 1,2-cyclohexanediol selectivity (93.2%) obtained over α -MoO _3 -TiO _2 mixed oxides, higher than that obtained with TiO _2 monoxide and α -MoO _3 monoxide, suggest a synergistic effect between TiO _2 and α -MoO _3 . This efficient and stable catalyst after reuse can be developed for the synthesis of diols

Plant extract induced biogenic preparation of silver nanoparticles and their potential as catalyst for degradation of toxic dyes

This study focusses on the synthesis of silver nanoparticles (Ag-nPs) by citrus fruit (Citrus paradisi) peel extract as reductant while using AgNO3 salt as source of silver ions. Successful preparation of biogenic CAg-nPs catalyst was confirmed by turning the colorless reaction mixture to light brown. The appearance of surface Plasmon resonance (SPR) band in UV-Vis spectra further assured the successful fabrication of nPs. Different techniques such as FTIR, TGA and DLS were adopted to characterize the CAg-nPs. CAg-nPs particles were found to excellent catalysts for reduction of Congo red (CR), methylene blue (MB), malachite green (MG), Rhodamine B (RhB) and 4-nitrophenol (4-NP). Reduction of CR was also performed by varying the contents of NaBH4, CR and catalyst to optimize the catalyst activity. The pseudo first order kinetic model was used to explore the value of rate constants for reduction reactions. Results also interpret that the catalytic reduction of dyes followed the Langmuir–Hinshelwood (LH) mechanism. According to the LH mechanism, the CAg-nPs role in catalysis was explained by way of electrons transfer from donor (NaBH4) to acceptor (dyes). Due to reusability and green synthesis of the CAg-nPs catalyst, it can be a promising candidate for the treatment of water sources contaminated with toxic dyes.</p

Effects of Cr2O3 Content on Microstructure and Mechanical Properties of Al2O3 Matrix Composites

Al2O3-Cr2O3 refractories are completely substitution solid solutions and can effectively resist slag erosion when used as an industrial furnace lining. In order to provide suitable chromium corundum refractory with excellent slag resistance and mechanical properties for smelting reduction ironmaking, Al2O3-Cr2O3 samples with different mass percentages (0, 10, 20, 30, 40 wt.%) of Cr2O3 were prepared by a normal pressure sintering process to study its sintering properties, mechanical properties, thermal shock resistance, and microstructure. The results of densification behavior showed that the introduction of Cr2O3 deteriorates the compactness, the relative density and volume shrinkage rate of the composite material decrease with the increase of the Cr2O3 content, and the apparent porosity increases accordingly. In terms of mechanical properties, the hardness, compressive strength, and flexural strength of Al2O3-Cr2O3 material decrease gradually with the increase of Cr2O3. After 10 and 20 thermal shock cycles, the flexural strengths of the samples all decreased. With the increase of Cr2O3 in these samples, the loss rate of flexural strength gradually increased. Considering the slag resistance and mechanical properties of the composite material, the Al2O3-Cr2O3 composite refractory with Cr2O3 content of 20–30% can meet the requirements of smelting reduction iron making kiln lining

Mechanochemical functionalization of mesoporous carbons for the catalytic transformation of trans-ferulic acid into vanillin

International audienc

Energy storage applications of CdMoO₄ microspheres

In this study, a one-step hydrothermal method was used to synthesize cadmium molybdenum oxide and revealed cationic cetyltrimethylammonium bromide surfactant effects on material preparation and energy storage characteristics. X-ray diffraction confirmed tetragonal-phase CdMoO4. Symmetric stretching modes of molybdenum oxide were confirmed from a Raman spectrum. A Fourier-transform infrared spectrum confirmed the presence of functional groups. Scanning electron microscopy images revealed a bunch of hierarchical microspheres of about 100–200 nm diameter. The specific capacitance achieved for CdMoO4, 0.1 M CTAB + CdMoO4, and 0.2 M CTAB + CdMoO4 were 200 F/g, 310 F/g, and 382 F/g, respectively, at 0.5 A/g. In addition, long-term cyclic stability for the best performing electrode (0.2 M CTAB + CdMoO4) material was investigated to explore cyclic performances of the supercapacitor. During the experiment, 86.01% capacity was retained after 5000 cycles at 5 A/g. The product activity is promising for high-efficiency supercapacitors due to the ease of production, environmentally friendly nature, and low cost of the synthesized material.This work was supported by RUSA, UGC-SAP, DST-FIST, DST-PURSE grants. The authors extend their appreciation to the Researchers supporting project number (RSP-2020/247) King Saud University, Riyadh, Saudi Arabia

Heterostructured SmCoO₃/rGO composite for high-energy hybrid supercapacitors

A supercapacitor is an efficient energy storage system that acts as an excellent booster to deliver high power density required for batteries and fuel cells. Recently, composite material–based supercapacitors have attracted much more interest as promising greener and more capable candidates in energy-saving use. In this work, samarium cobalt oxide–decorated reduced graphene oxide (SmCoO₃/rGO) was prepared employing solvothermal route and used as reliable electrode material. The maximum specific capacity achieved was 30.80 mAh/g for 1 A/g of SmCoO₃/rGO nanocomposite with capacity retention of 86.95%@5A/g over 5000 charge discharge cycles. Better electrochemical performance of samarium and reduced graphene oxide nanostructures prevent the transfer of electrons through electrochemical active sites, creating electronic and structural diversity of electro active material. In addition, SmCoO₃/rGO/AC hybrid supercapacitor device that delivered good energy and power density of 52 W h/kg and 752 W/kg at 1 A/g was designed. 74.28% capacitive retention and 98.26% coulombic efficiency was maintained over 15,000 cycles.This work was supported by RUSA, UGC-SAP, DST-FIST, DST-PURSE grants. The authors extend their appreciation to the Researchers supporting project number (RSP-2020/247) King Saud University, Riyadh, Saudi Arabia

New Method Based on the Direct Analysis in Real Time Coupled with Time-of-Flight Mass Spectrometry to Investigate the Thermal Depolymerization of Poly(methyl methacrylate)

In this work, the isothermal decomposition of poly(methyl methacrylate) synthesized in bulk by the radical route of methyl methacrylate in the presence of azobisisobutyronitrile as the initiator was carried out and monitored for the first time with the DART-Tof-MS technique at different temperatures. Nuclear magnetic resonance (NMR) analysis revealed a predominantly atactic microstructure, and size-exclusion chromatography (SEC) analysis indicated a number average molecular weight of 3 &times; 105 g&middot;mol&minus;1 and a polydispersity index of 2.47 for this polymer. Non-isothermal decomposition of this polymer carried out with thermogravimetry analysis (TGA) showed that the weight loss process occurs in two steps. The first one starts at approximately 224 &deg;C and the second at 320 &deg;C. The isothermal decomposition of this polymer carried out and monitored with the DART-Tof-MS method revealed only one stage of weight loss in this process, which begins at approximately 250 &deg;C, not far from that of the second step observed in the case of the non-isothermal process conducted with the TGA method. The results obtained with the MS part of this technique revealed that the isothermal decomposition of this polymer regenerates a significant part of methyl methacrylate monomer, which increases with temperature. This process involves radical chain reactions leading to homolytic chain scissions and leading to the formation of secondary and tertiary alkyl radicals, mainly regenerating methyl methacrylate monomer through an unzipping rearrangement. Although they are in the minority, other fragments, such as the isomers of 2-methyl carboxyl, 4-methyl, penta-2,4-diene and dimethyl carbate, are also among the products detected. At 200 &deg;C, no trace of monomer was observed, which coincides with the first step of the weight loss observed in the TGA. These compounds are different to those reported by other researchers using TGA coupled with mass spectrometry in which methyl isobutyrate, traces of methyl pyruvate and 2,3-butanonedione were detected