Effect of metal oxide as antibacterial agent on thermoplastic starch/metal oxide biocomposites properties

ABSTRACT

This research was purposed at studying the effect of the addition of metal oxide (MO) as antibacterial agent on thermoplastic starch (TPS) properties. TPS/MO biocomposites with 0.1 until 2.0 phr of metal oxide were prepared. Antibacterial activity of TPS and TPS/MO biocomposites against bacteria was investigated. The inhibition zone of biocomposite films was dramatically increased along with the increasing of metal oxides contents. The addition of ZnO content resulted in an increase in inhibition zone for E. coli and S. aureus. The incorporation of MO into TPS/MO biocomposites tends to reduce mechanical properties, the mass loss and T50% of TPS/MO biocomposites.     

Solution-blow spun PLA/SiO2 nanofiber membranes toward high efficiency oil/water separation

With the ever frequent of industrial organic solvent emissions and oil spillages, the development of high efficiency oil/water separation materials has attracted extensive attention. Here, PLA-based nanofiber membranes modified with metal oxides (SiO₂, TiO₂, Al₂O₃, and CeO₂) are fabricated through blow spinning the mixed solution of polylactic acid (PLA) and metal oxide nanoparticles (NPs). Results shows that the addition of SiO₂ NPs significantly increases the hydrophobicity of the membranes, while maintaining the excellent superoleophilicity. The PLA/SiO₂ nanofiber membranes demonstrate a higher separation performance than pure PLA, PLA/TiO₂, PLA/Al₂O₃, and PLA/CeO₂ nanofiber membranes with high separation efficiency (~100%) and permeation flux (17,800 L m⁻² h⁻¹ for n-heptane), as well as prominent oil adsorption capacity (19.9 g/g for n-hexane). The successful fabrication of metal oxides modified PLA nanofiber membranes with high separation and adsorption ability, and excellent durability hold great application potential in the field of oily wastewater treatment.     

Performance of geopolymer foams of blast furnace slag covered with poly(lactic acid) for wastewater treatment

This research investigated a new method to produce geopolymer foams from blast furnace slag (BFS) with poly(lactic acid) (PLA) covering the developed porosity into the materials. A porous alkali-activated material was developed, and a biodegradable polymer was used to cover the geopolymer in the bulk state. Geopolymer foams were synthesized with a sodium metasilicate solution, and the porosity was developed by adding hydrogen peroxide (H₂O₂). Foams of materials were produced with two stoichiometries of 1.4 and 1.6 g/L between solid/liquid with a hydrogen peroxide solution. The dimensional stability was achieved after coating geopolymer foams with PLA, improving the molding capacity on different geometries for the composite materials. Specimens of the geopolymer foam/PLA composites were characterized by X-ray fluorescence (XRF), Fourier transformed infrared (FTIR), thermogravimetry (TGA), and field emission gun scanning electron microscopy (FEG-SEM). The permeation analysis of metal oxide particles through the composites foam specimens was performed using water dispersions containing bismuth oxide or titanium oxide. The test resulted in high performance in the retention of particulate materials. The highlights of the results indicated the efficiency in the synthesis of geopolymer foam, a good formation of porosity, and an effective PLA coating on the internal interfaces of geopolymer foam through the development of a new bulk state coating method, improving the dimensional stability and the retention of bismuth and titanium oxides particles by the produced geopolymer foams for water depollution.     

TIC-09-Mesoporous Niobium-Based Mixed Metal Oxides Containing Mo, V, and Te for Propane Oxidative Dehydrogenation

The novel thermally stable mesoporous multicomponent MNbO _x (M = V, Mo, and Te) mixed metal oxides were successfully synthesized by evaporation-induced self-assembly (EISA) employing niobium oxide as a major structural component. The formation of nanocrystalline M1 phase as part of the ordered mesoporous structure was investigated. These mixed metal oxide phases displayed good thermal stability (up to 400 °C), large pore sizes (up to 14 nm), high surface areas (up to 230 m²/g) and flexible inorganic wall compositions. Thermally stable mesoporous Nb₂O₅ supported metal M/Nb (M = MoVTeNb) oxides were obtained by incipient-wetness impregnation (IWI) technique. The comparison between mesoporous bulk mixed and supported mixed metal oxides (MNbO _x and M/Nb) were addressed. The catalytic roles of the constituent metal oxides were investigated in oxidative dehydrogenation (ODH) of propane. The methods described in this paper represent promising synthetic approaches for the design of novel catalytic mixed metal oxides.     

Electrolytic Reduction of Spent Nuclear Oxide Fuel as Part of an Integral Process to Separate and Recover Actinides from Fission Products

Abstract

Bench‐scale tests were performed to study an electrolytic reduction process that converts metal oxides in spent nuclear fuel to metal. Crushed spent oxide fuel was loaded into a permeable stainless steel basket and submerged in a molten salt electrolyte of LiCl–1 wt% Li₂O at 650°C. An electrical current was passed through the fuel basket and a submerged platinum wire, effecting the reduction of metal oxides in the fuel and the formation of oxygen gas on the platinum wire surface. Salt and fuel samples were analyzed, and the extent of fission product separation and metal oxide reduction was determined.     

Nanocrystalline transition metal oxides and their composites with reduced graphene oxide and carbon nanotubes for photocatalytic applications

Transition metal oxide nanoparticles (CuO, ZnO & Fe₂O₃) and mixed metal oxides CuO. ZnO.Fe₂O₃ were fabricated by facile co-precipitation approach for photocatalytic treatment of organic dyes. The structural features, phase purity, crystallite size and morphology of individual and mixed metal oxides were analysed by X-rays diffraction patterns (XRD) and scanning electron microscopic (SEM) analysis. Electrical behaviour of CuO, ZnO, Fe₂O₃ and mixed metal oxides CuO. ZnO.Fe₂O₃ was explored by current-voltage (I-V) measurements. Functional groups present in the synthesized metal oxides were investigated by Fourier transform infrared spectroscopy (FTIR) which ensures the existence of M-O functional groups in the samples. The optical bandgap analysis was carried out by UV–visible spectroscopic technique which revealed that the blend of three different transition metal oxides reduced the bandgap energy of mixed metal oxides. The reason behind this reduced bandgap energy is formation of new electronic state which arises due to the metal-oxygen interactions. Moreover, the nanocomposites of CuO.ZnO.Fe₂O₃ with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) were prepared to study the effect of the carbonaceous materials on the rate of photodegradation. These carbonaceous nanomaterials have plethora properties which can bring advancement in sector of photocatalytic treatment of wastewater. The photocatalytic experiments were performed using methylene blue (MB) as standard dye for comparative study of metal oxides and their composites with rGO and CNTs. The percentage degradation of methylene blue (MB) by nanocomposite CuO.ZnO.Fe₂O₃/rGO is 87% which is prominent among all samples. This result ascribed the photocatalytic aspects of reduced graphene oxide along with mixed metal oxides.     

Effect of promoters on catalytic performance of Cr/SiO2 catalysts in oxidative dehydrogenation of ethane with carbon dioxide

Several acidic and basic oxide promoted Cr/SiO₂ catalysts were prepared and investigated in oxidative dehydrogenation of ethane in the presence of carbon dioxide. The effects of SO₄ ^2–, WO₃ and alkali metal oxides (Li₂O, Na₂O, and K₂O) on the catalytic activity were studied. It is found that sulfation of silica produces a positive effect on ethane conversion and ethylene yield while tungstation and addition of strong basic promoters (alkali metal oxides) suppress the catalytic activity. Characterization indicates that the varying activity of the promoted catalysts can be attributed to the difference in acid/base property and redox potential.     

Aggregation of polylactide with carboxyl groups at one chain end in the presence of metal cations

Polylactides with one or more carboxyl groups at one chain end were synthesized by cationic polymerization according to activated monomer mechanism and by application of “thiol-yne” click chemistry for subsequent functionalization. End groups of such obtained polylactides were converted into ionic groups by neutralization of polymer solutions with metal oxides, mainly calcium oxide, and the aggregation of individual stereoisomers as well as that of the mixture of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) was investigated. The extent and progress of the aggregation was followed by viscosity measurements, and aggregated polymers in the solid state were examined by SEM and DSC. Solution viscosity increase was observed upon the aggregation of individual PLA stereoisomers, whereas PLA stereocomplex precipitation occurred in the case of the aggregation of PLLA/PDLA/metal oxide mixture.     

Characterization of methanol-tolerant Pd–WO3 and Pd–SnO2 electrocatalysts for the oxygen reduction reaction in direct methanol fuel cells

Palladium (Pd) catalysts containing nanosized metal oxides, tungsten oxide (WO₃) and tin oxide (SnO₂), supported on carbon black (Pd–MO_x/C) were synthesized, and the effect of the metal oxide on the oxygen reduction reaction (ORR) in a direct methanol fuel cell (DMFC) was investigated. The SEM images showed that the Pd nanoparticles were highly dispersed on the carbon black, and the metal oxide particles were also distributed well. Pd/C and Pd–WO₃/C catalysts as cathode materials for the ORR in DMFCs showed activity similar to or better than that of Pt/C, whereas Pd–SnO₂/C showed no improvement in catalytic activity.     

Anatase–rutile transformation in doped titania under argon and hydrogen atmospheres

Abstract

Pure titania pulp containing amorphous titania was heated at different temperatures and times. Above 650°C anatase phase was evolved and between 900 and 1000°C, anatase–rutile transformation occurred. The anatase–rutile transformation in TiO₂ in the presence of different transition metal oxides, namely Fe₂O₃, Cr₂O₃, NiO, CuO and MnO₂ under argon and hydrogen atmospheres was investigated. The different phases of TiO₂ were determined using powder X-ray diffraction (XRD). The anatase–rutile transformation temperature was found to be lowered in the presence of transition metal oxides. The transformation temperature was found to vary much in argon and hydrogen atmospheres compared to air in the presence of the metal oxides. Also the method of preparation of metal oxide doped TiO₂ influences rutilation. Other methods such as chemical analysis, surface area measurements and crystallite size calculation were used for the characterisation of the samples. The surface area of heated samples was found to be decreased while crystallite size increased due to rutilation on heating. The samples were also observed under a scanning electron microscope to characterise the microstructural changes associated with each thermal treatment and atmosphere. The morphology of doped titania changes much on heating due to phase modification. The atmosphere of heating also has important effect on deciding the morphology of rutilated titania.     

The effect of sodium on the catalytic activity of ZnO–Al2O3/ZSM-5 and SnO–Al2O3/ZSM-5 for the transesterification of vegetable oil with methanol

In order to elucidate the effect of sodium on the activity of ZSM-5 supported metal oxides catalysts (ZnO–Al₂O₃/ZSM-5 and SnO–Al₂O₃/ZSM-5) for the transesterification of soybean oil with methanol, ZSM-5 supported metal oxides were prepared with and without sodium hydroxide by impregnation. The metal compositions of the ZSM-5 supported metal oxide catalysts and the metal concentrations dissolved from the catalysts to the methylester phase were measured by SEM-EDS and inductive coupled plasma spectroscopy, respectively. The catalytic activity of ZnO–Al₂O₃/ZSM-5 and SnO–Al₂O₃/ZSM-5 containing sodium did not originate from surface metal oxides sites, but from surface sodium sites or dissolved sodium leached from the catalyst surface.     

Rheology and crystallisation of PLA containing PLA-grafted nanosilica

Abstract

PLA/SiO₂ nanocomposites (PLAS) were prepared by premixing in chloroform solution and then melt extrusion. SiO₂ were surface grafted via ring-opening polymerisation of L-Lactide before blending. Crystallisation and rheological properties of PLAS were investigated as a function of SiO₂ content. It was identified from differential scanning calorimetry cooling plots that the addition of SiO₂ could improve crystallisation rate and relative crystallinity of PLA. Meanwhile, SiO₂ had affected rheological properties of PLA. Pure PLA and PLAS were both typical shear-thinning fluid, and shear viscosity of PLAS was higher than pure PLA. In dynamic sweep test, the linear viscoelastic regions with critical strains of PLAS decreased with the increasing SiO₂ content compared with pure PLA. The G′, G″ and tan?δ versus ω of PLAS were all improved. The results of rheological tests indicated that the addition of SiO₂ had effect on the structure of PLA molecular chain and had formed network structure in PLA matrix.     

Synergistic effect of metal oxides on the flame retardancy and thermal degradation of novel intumescent flame‐retardant thermoplastic polyurethanes

The synergistic effects of some metal oxides on novel intumescent flame retardant (IFR)–thermoplastic polyurethane (TPU) composites were evaluated by limiting oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimetry, and scanning electron microscopy. The experimental data indicated that the metal oxides enhanced the LOI value and restricted the dropping of the composites. The IFR–TPU composites passed the UL‐94 V‐0 rating test (1.6 mm) in the presence of magnesium oxide (MgO) and ferric oxide (Fe₂O₃) at 35 wt % IFR loading, whereas only the MgO‐containing IFR–TPU composite reached a UL‐94 V‐0 rating at 30 wt % IFR loading. The TGA results show that the metal oxides had different effects on the process of thermal degradation of the IFR–TPU compositions. MgO easily reacted with polyphosphoric acid generated by the decomposition of ammonium polyphosphate (APP) to produce magnesium phosphate. MgO and Fe₂O₃ showed low flammability and smoke emission due to peak heat release rate, peak smoke production rate, total heat release, and total smoke production (TSP). However, zinc oxide brought an increase in the smoke production rate and TSP values. Among the metal oxides, MgO provided an impressive promotion on the LOI value. The alkaline metal oxide MgO more easily reacted with APP in IFRs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymerization of methyl methacrylate in water in presence of the metal oxides TiO2 and Cu2O

Rates of sodium bisulfite-initiated polymerization of methyl methacrylate in water were determined in absence and in presence of the metal oxides TiO₂ and Cu₂O at 30°, 40°, 50°, and 60°C. Cuprous oxide and titanium dioxide enhanced the rate of polymerization and reduced the molecular weight as compared with the figures obtained in absence of oxide, the effect of the former being more pronounced than the latter. With TiO₂, the rate was increased from 2.3 to 3.2 × 10^?5, while with Cu₂O, it was increased to 8.6 × 10^?5 mole/l./sec, both at concentrations of 9 g/l. water. The apparent energy of activation for the polymerization of methyl methacrylate between 40°C and 50°C was found to be 15.6 kcal/mole in absence of the metal oxides, and 7.6 kcal/mole and 2.8 kcal/mole in presence of titanium dioxide and cuprous oxide, respectively. The number-average molecular weight was found to decrease slightly with the addition of TiO₂ but to decrease greatly when Cu₂O was added.     

Oxygen evolution on semiconducting oxides

The oxygen evolution reaction is of particular interest to secondary metal air batteries and water electrolysis plants. However, most of the earlier work has been on precious metals and there are no guidelines for the choice of semiconducting oxides as oxygen evolving electrodes. In this study, the role of the metal/metal oxide or the lower metal oxide/higher metal oxide couple in determining the minimum voltage required for the evolution of oxygen is emphasized, together with other essential requirements such as electrical resistivity, electrode microstructure, corrosion resistance and catalytic properties. A survey of various metal oxides based on the above criterion suggested that NiCo₂O₄ is of particular interest and Teflon bonded electrodes based on this material gave over 13000 A/m² at 1.63 V vs dhe, 70°C, 5 N KOH.     

Total oxidation of propane over Cu-Mn mixed oxide catalysts prepared by co-precipitation method

The catalytic activity of Cu-Mn mixed oxides with varying Cu/Mn ratios prepared by co-precipitation method was examined for the total oxidation of propane. The nature and phase of the metal oxide species formed were characterized by various methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (TPR) as well as BET surface area measurement. The co-precipitation method provides highly interdispersed copper and manganese metallic elements forming Cu-Mn mixed oxide of spinel structure (Cu_1.5 Mn_1.5O₄). Besides the spinel-type Cu-Mn mixed oxide, CuO or Mn₂O₃ phases could be formed depending on the Cu/Mn molar ratio of their precursors. The catalytic activity of Cu-Mn mixed oxide catalyst for propane oxidation was much higher than those of single metal oxides of CuO and Mn₂O₃. The higher catalytic activity likely originates from a synergic effect of spinel-type Cu-Mn mixed oxide and CuO. The easier reducibility and BET surface area seems to be partially responsible for the high activity of Cu-Mn mixed oxide for total oxidation of propane.     

B4C/metal boride composites derived from B4C/metal oxide mixtures

This study examines the reactions occurring from room temperature to 2180 °C during the heating under argon of mixtures of B₄C and metal oxides, as well as the properties of the ceramic composites prepared by these reactions. The cations of the oxides investigated, belonged to the transition metal and to the lanthanide groups. The mixtures underwent solid-state reactions in the range between 1100 and 1900 °C. These reactions resulted in composites in which the metal borides and B₄C are the majority phases. The boron carbide/metal boride(s) mixtures resulted from these reactions exhibited a sintering aptitude significantly higher than that of pure boron carbide. The improvement in the sintering aptitude was proportional to the oxide content present in the initial mixture, up to an upper limit. B₄C/boride(s)-type composites, exhibiting bulk densities ≥97% TD, could be prepared for certain compositions by pressureless heating at 2180 °C. The ceramic parts prepared under these conditions are characterized by strength and hardness values similar to those determined for pure boron carbide.     

Effects of reduction of metal oxide sorbents on reactivity and physical properties during hot gas desulphurization in IGCC

In this study, the changes of physical properties and reactivity of the metal oxide sorbents were investigated under the reducing conditions of coal gas. Metal oxide sorbents are converted into metal sulphides as a result of reaction with H₂S in synthesis gas. This could cause the reduced reactivity of sorbents if the metal oxides were converted into metallic elements due to the reduction by either hydrogen or carbon monoxide. In this experiment, the changes of physical properties and reactivity of the metal oxides were investigated over the temperature range 480-700 °C. It is confirmed that the reactivity of sulphidation and the reduction of metal oxide increased with increasing temperature. Even though the sulphur capacity of the sorbents in the early stage was high, it reduced rapidly due to the progressive reduction of metal oxides as the sulphidation/regeneration process was repeated. The reduction of metal oxide and the extent of reduction were verified by measuring the amount of oxygen consumed and the amount of SO₂ produced during the regeneration of sulphidated sorbents with the aids of a gas analyser. It was concluded that the reactivity of the metal oxide sorbents was influenced by reduction with coal gas at high temperature.     

Synergistic effects of organically modified montmorillonite in combination with metal oxides on the fire safety enhancement of intumescent flame-retarded epoxy resins

Synergistic effects of organically modified montmorillonite (OMMT) in combination with different metal oxides (Bi₂O₃, Sb₂O₃, and MoO₃) on the fire safety enhancement of the intumescent flame-retarded epoxy resins (EPs) were systematically evaluated. The results from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that the OMMT and metal oxides acquire a uniform distribution in the EP matrix, and OMMT platelets exhibit a fully exfoliated state. The flammability and thermogravimetry (TG) tests show that the intumescent flame retardant (IFR)-OMMT-metal oxide ternary system can endow EPs with the higher synergistic efficiencies on the enhancement of flame retardancy, smoke suppression properties, and charring ability compared to those of IFR or IFR-OMMT system, and the synergistic efficiency is the following order: IFR/OMMT/Sb₂O₃ > IFR/OMMT/MoO₃ > IFR/OMMT/Bi₂O₃. In particular, the sample, filled with 1.5 wt% OMMT, 1.5 wt% Sb₂O₃, and 27 wt% IFR, passes the UL94 V-0 rating and acquires the highest limiting oxygen index value of 28.5% among the samples. The IFR-OMMT-metal oxide ternary system exerts a better synergistic effect on the generation of crosslinking and aromatic structures that supply the excellent charring effect and barrier effect for the EPs, and the synergistic efficiency of IFR-OMMT-metal oxide ternary system is varied with the types of metal oxides.