ZnO, AgCl and AgCl/ZnO nanocomposites incorporated chitosan in the form of hydrogel beads for photocatalytic degradation of MB, E. coli and S. aureus.

Significant improvement of effective and low-cost decolorization and disinfecting technologies is required to address the problems created by dyes and dangerous microorganisms from water and wastewaters. This article expresses the degradation of methylene blue (MB), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as gram negative and positive bacteria via a chitosan/AgCl/ZnO (CS/AgCl/ZnO) nanocomposite hydrogel beads system as a photocatalyst under visible light irradiation. The techniques such as FT-IR, SEM, EDAX, TGA, and XRD were applied to recognize the synthesized beads. Decolorization and disinfection experimental results revealed that the hydrogel beads system effectively degrade MB and bacteria. Also, the effects of the initial amount of catalysts, pH, coions and initial concentration of dye on the photocatalytic decolorization were investigated. Moreover, kinetics analysis indicates that the photocatalytic degradation rate of MB and bacteria can be described by Langmuir-Hinshelwood (L-H) and Weibull inactivation models, respectively. We provide a reusable and recoverable effective organic/inorganic photocatalyst in the form of beads that could solve the disadvantages of powder photocatalytic, without reducing the efficiency.

Cross-linked chitosan in nano and bead scales as drug carriers for betamethasone and tetracycline.

Chitosan nanoparticles and chitosan beads were synthesized through the ionic gelation procedure in which sodium citrate was used as the cross-linking agent. The prepared nanoparticles were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), zeta potential, and Fourier transform infrared (FT-IR) spectroscopy. The synthesized nanoparticles and beads were examined as drug carriers for controlled release of two important drugs including betamethasone and tetracycline. For this purpose, various properties such as swelling behavior, loading capacity, encapsulation efficiency, and release degree of the particles were obtained. The effect of pH on the aforementioned parameters was also studied. The results indicated that the amount of drug released from chitosan nanoparticles is lower than that released from chitosan beads. It was also found that the release degree for both of the drugs at the pH of 4.8 is much larger than that at the pH of 7.4.

Ultrasonic-assisted synthesis of ZrO2 nanoparticles and their application to improve the chemical stability of Nafion membrane in proton exchange membrane (PEM) fuel cells.

Zirconium dioxide (ZrO2) nanoparticles were fabricated successfully via ultrasonic-assisted method using ZrO(NO3)2·H2O, ethylenediamine and hydrazine as precursors in aqueous solution. Morphology, structure and composition of the obtained products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance spectroscopy (DRS). Then, the synthesized nanoparticles were used to prepare Nafion/ZrO2 nanocomposite membranes. The properties of the membranes were studied by ion exchange capacity (IEC) proton conductivity (σ), thermal stability and water uptake measurements. The ex-situ Fenton's test was used to investigate the chemical stability of the membranes. From our results, compared with Nafion membrane, the nanocomposite membrane exhibited lower fluoride release and weight loss. Therefore, it can concluded that Nafion/ZrO2 nanocomposite exhibit more chemical stability than the pure Nafion membrane. ATR-FTIR spectra and SEM surface images of membranes also confirm these results.

Sonocatalytic degradation of 2-hydroxyethyl cellulose in the presence of some nanoparticles.

The degradation of 2-hydroxyethyl cellulose (HEC) by means of ultrasound irradiation and its combination with heterogeneous catalysts such as TiO2 (Rutile and Anatase), Montmorillonite Clay (MMT), ZnO and Fe3O4 nanoparticles was investigated. The effect of the type and quantity of nanoparticles, the initial molecular weight of polymer and the different ultrasonic power have been studied. Degradation behavior of HEC was studied through FTIR, XRD and SEM techniques and kinetics of degradation was studied by viscometry. Also, reduce in molecular weight (Mw) of polymer was investigated by gel permeation chromatography (GPC) analysis. The results of experiments suggested that the sonocatalytic degradation of HEC were remarkably higher than sonolytic degradation. However, the catalytic activity of nanoparticles in contrast to the ultrasonic irradiation was different. The experimental results revealed that the best HEC degradation can be obtained when the added Fe3O4 amount was 0.4 g/L. Furthermore, kinetic analysis of the polymer degradation process was carried out in this study.

Polyvinyl alcohol:starch:carboxymethyl cellulose containing sodium montmorillonite clay blends; mechanical properties and biodegradation behavior.

The focuses of this study were to investigate the effect of sodium montmorillonite clay (MMT-Na) content on the physical properties and extent of enzymatic hydrolysis Polyvinyl Alcohol (PVA): Starch (S): Carboxymethyl Cellulose (CMC) nanocomposites using enzyme -amylase. The results of this work have revealed that films with MMT-Na content at 5 wt% exhibited a significantly reduced rate and extent of starch hydrolysis. The results suggest that this may have been attributed to interactions between PVA:S:CMC and MMT-Na that further prevented enzymatic attack on the remaining starch phases within the blend. The total solids that remained after 4320 min were 65.46 wt% (PVA:S:CMC); 67.91 wt% (PVA:S:CMC:1% MMT-Na); 78.43 wt% (PVA:S:CMC:3% MMT-Na); 80.24 wt% (PVA:S:CMC:5% MMT-Na). The rate of glucose production from each nanocomposite substrates were decresed significantly as the MMT-Na percentage increased from 0 to 5% (W/W). At the level of 5% (W/W) MMT-Na, the films showed the lowest rate of glucose production values (18.95 µg/ml h). With the increase of the MMT concentration from 0 to 5%, the UTS increased 5 from 18.36 to 20.38 MPa, however, the strain to break (SB) decreased noticeably from 35.56 to 5.22%.

Sonolytic, sonocatalytic and sonophotocatalytic degradation of chitosan in the presence of TiO2 nanoparticles.

The degradation of chitosan by means of ultrasound irradiation and its combination with heterogeneous (TiO(2)) was investigated. Emphasis was given on the effect of additives on degradation rate constants. Ultrasound irradiation (24 kHz) was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. The extent of sonolytic degradation increased with increasing ultrasound power (in the range 30-90 W), while the presence of TiO(2) in the dark generally had little effect on degradation. On the other hand, TiO(2) sono-photocatalysis led to complete chitosan degradation in 60 min with increasing catalyst loading. TiO(2) sonophotocatalysis was always faster than the respective individual processes due to the enhanced formation of reactive radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of relative viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan did not change after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested.

Calculation of the rate constant for the ultrasonic degradation of aqueous solutions of polyvinyl alcohol by viscometry.

Ultrasonic degradation of polyvinyl alcohol (PVA) was carried out in aqueous solution at 25 degrees C. In this experiment, the effect of solution concentration on the rate of degradation was investigated. Kinetics of degradation was studied by viscometry method. The calculated rate constants indicate that degradation rate of PVA solutions decreases with increasing of solution concentration (C= g lit(-1)). The calculated rate constants correlated in terms of reverse concentration and relative viscosity of PVA solutions. This behavior in the rate of degradation was interpreted in terms of viscosity and concentration of polymer solution. With increasing solution concentration, viscosity increases and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased.