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Free-volume hole size evaluated by positron annihilation lifetime spectroscopy in the amorphous part of poly ( ethylene a b s t r a c tChitosan is a linear copolymer composed of (1 / 4)elinked 2-acetamido-2-deoxy-b-D-glucan (GlcNAc) and 2-amino-2-deoxy-b-D-glucan (GlcN) units in varying proportions, having a high molecular weight and strong intra-and intermolecular hydrogen bondings. Sonication has become an alternative for degrading chitosan into low-molecular-weight chitosan (LMWC), chitosan oligomers and glucosamine. In this study, chitosan was treated with sonication at 40 C and 60 C for 30 min and 120 min with various acetic acid concentrations (0.2% v/ve1% v/v); the very-low-concentration acid solution functioned both as a solvent and catalyst. After sonication, the samples were tested for changes in molecular weight, water soluble proportion of chitosan (chitosan oligomers and glucosamine), degree of deacetylation, degree of crystallinity, and morphology. The soluble and insoluble product yields at low concentration (0.5% v/v) at 40 and 60 C were 33.66e39.37 % and 32.43e34.26%, respectively. The main product was 5-hydroxy methyl furfural with composition 92.16e99.43%. At high concentrations (1% v/v), the soluble product and insoluble yields were 43.72e49.74% and 43.1e50.26%, respectively. The main product was glucosamine with composition 77.75e93.16% of glucosamine. There were changes in the morphology and crystallinity of the degraded chitosan, but no change in the chemical structure. The crystallinity had a tendency to increase. The degree of deacetylation tended to decrease due to the glucosamine breakage.

Zeolitic Imidazolate Framework (ZIF) membranes have been considered as promising membrane for gas separation processes due to their robustness and good separation capabilities. The separation of hydrogen (H2) from larger gases is one of their potential applications. Among the different types of ZIF, ZIF-8 is considered as potential candidates for H2 separation owing to its small aperture size and excellent chemical stability. In recent years, ZIF-8 membranes have been fabricated on both inorganic and polymeric substrates. The fabrication of the ZIF-8 layer on polymeric substrates is more challenging than its inorganic counterpart because of the incompatibility issue between organic substrates and ZIF-8. However, the flexible nature of polymeric substrates offers better mechanical stability at high pressure than inorganic substrates. The purpose of this mini-review is to present the state of the art and challenges of research on ZIF-8 membrane synthesis on different polymeric substrates. These challenges include the formation of cracks and defects due to compatibility issues and membrane stability at different operating conditions. Current research results showed excellent gas separation properties of ZIF-8 membranes on polymeric substrates that can surpass the trade-offline of gas permeability and selectivity.

TiO 2-Fe 3 O 4-Bentonite photocatalytic material has been developed to inactivate of Escherichia coli. The syntheses of the TiO 2-Fe 3 O 4 based photocatalyst have been carried out by sol-gel method. The bentonite used for porous support was obtained from Pacitan, Indonesia. The photocatalyst material will capture energy of UV radiation followed by the electron excitation and oxidationreduction reactions. Because of the processes, the various types of pollutants and microorganisms can be decomposed and reduced. The electron excitation will induce the formation of hydroxyl radical and O 2. These radicals are responsible to decompose the cell wall of bacteria and further damage the bacteria's cytoplasmic membrane. Decomposing of cytoplasmic membrane causes lipid peroxidation in the membrane, and then losing their viability. It is followed by the death of bacterial cell. This study conducted a series of Escherichia coli inactivation by using photocatalyst material of TiO2-Fe 3 O 4-Bentonite which was irradiated with UV light. The photocatalytic inactivation of Escherichia coli was conducted in a reactor under ultraviolet (325 nm) exposing. The photocatalytic degradation was observed for 5 hours to determine the optimum initial bacteria concentration, intensity of UV light and also photocatalyst concentration. The inactivation kinetic was approached by Chick-Watson and Hom kinetic models. The colonies calculations were conducted by Total Plate Count. The optimum condition was achieved for 300 minutes process to reach 7 bacterial log reduction units for an average bacterial inoculum size of 3.8 × 10 4 CFU/ml. All disinfection experiments showed a non-linear bacterial inactivation kinetic profile, which is started with shoulder lag followed by a log reduction and the tailing curve. The inactivation kinetics of Escherichia coli using TiO 2-Fe 3 O 4-Bentonite photocatalytic material system satisfactorily obeyed the Hom kinetic model.

Texturing by instantaneous controlled pressure drop is used to modify texture of banana slices, which was aimed to improve properties of banana flour. Texturing step is inserted between initial and final hot air drying steps. The aim of this research is to investigate the effect of the texturing on the dehydration kinetic, physical properties and nutritional characteristic of banana. Some impacts of the texturing have been identified. The results of this work showed that the texturing increased the effective moisture diffusivity and the water holding capacity, but reduced the oil holding capacity of banana. This work also showed that the banana texturing inhibited the transformation of banana starch to reduction of sugar that might be attributable to enzyme deactivation during the texturing process. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

Summary For chito oligomer production, the efficient hydrolysis of chitosan to smaller substances is important. The focus of this study is to explore the formation and changes in the chitosan degradation product and properties after chitosan hydrolysis in subcritical water. The hydrothermal process was pressurized by supercritical CO2 used as the pressurized fluid and catalyst. Pre‐treatment sonication was also used to change the molecular weight of the chitosan. The effect of the reaction time on the formation of various products and chitosan residue was studied. The chitosan was pre‐treated by sonication at 60 °C for 120 min before subjected to the hydrothermal process at 200 °C and pressure of 23 MPa for 3‐5 min. The chitosan water slurry of 1 wt % in a batch reactor was rapidly heated to the reaction temperature for a specific time. After the reaction, the product was rapidly cooled in a cooling medium. The total yield reached about 15% based on the initial chitosan at 200 °C in 5 min. Upon an increase in the reaction time, the side group of monomers (NH2 or N‐acetyl) tended to be attacked and replaced by OH to produce glucose and also partially degrade into 5‐HMF. The hydrothermal process had no significant effect on the chitosan structure except for the changes in the inter‐ and intramolecular hydrogen bondings of chitosan and the degree of crystallinity of the chitosan residue in the range of 19.2 to 28.9%.

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