Mesoporous molecular sieves: alkylation of anisole using tert-butylalcohol

Mesoporous aluninosilicate Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 and 100 have been synthesized under hydrothermal condition and these materials were characterized by XRD, FTIR, BET and pyridine adsorption techniques. The catalytic performance was examined in the vapor phase tert-butylation of anisole with tert-butanol at the temperatures between 150 and 250 °C under atmospheric pressure. The results indicate that Al-MCM-41 (25) was found to be more active than its relatives. The major products are found to be 4-tert-butyl anisole (4-TBA), 2-tert-butyl anisole (2-TBA) and 2,4 di-tert-butyl-anisole (2,4-DTBA). Maximum conversion of anisole is observed at 175 °C and decreased thereafter with increasing temperature. The influence of molar feed ratio, influence of temperature, WHSV and time on stream on the selectivity of products was investigated and the results are discussed.     

A comprehensive bulk chlorine decay model for simulating residuals in water distribution systems

Chlorine decay models provide efficient ways to develop disinfection strategies for water distribution systems, provided they account separately for bulk and wall decay, and accurately describe decay with a single set of coefficients. The augmented two-reactant (2RA) model is shown to be the simplest model to accurately describe effects of rechlorination dose/timing on bulk chlorine decay, in combination with effects of initial concentration and temperature over long periods. The two-reactant (2R) and variable reaction-coefficient (VRC) models provided predictions of comparable accuracy under higher and successive rechlorination doses at constant temperature. However, the 2RA model provides a more general basis for strategy development, as the VRC model cannot describe the effect of temperature variation. The minimal data-set required for 2RA calibration was similar for all cases considered. The 2RA model is readily applied by incorporation into system modelling software such as the multi-species extension (MSX) to EPANET software.     

Fracture behaviour of cross-linked collagen fibres

Mechanical properties such as stress - strain, fracture behaviour and thermal behaviour were studied for cross-linked collagen fibres. The shrinkage temperature of cross-linked fibres shows increase in temperature when compared to the control. The results on measurements of breaking strength and strain show significant change when compared with that of the control. The morphological features of the fractured ends of cross-linked fibres were indicative of certain specific patterns. A critical observation of these patterns indicate the role played by the nature of cross-linking agents on the mechanism of failure of these fibres.     

Bio-assisted synthesis and characterization of nanostructured bismuth (III) sulphide using Clostridium acetobutylicum

Nanostructured bismuth (III) sulphide is synthesized at room temperature using a hydrogen sulphide producing microorganism namely Clostridium acetobutylicum. On contrary to chemical routes involving both the high and room temperature methods, the present experimental procedure involves a bio-assisted approach. This method is free from the usage of toxic and hazardous chemicals making it an environment friendly route. The synthesized bismuth sulphide is characterized using transmission electron microscope (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). From our experiments we find that bismuth sulphide produced using this bio-assisted approach exhibits a hexagonal shaped plate-like structures and is stabilized by the extracellular proteins present in the culture medium.     

Microbiological quality of sous-vide cook chill fish cakes during chilled storage (3 °C)

Fish cakes prepared from emperorbream ( Lethrinus lethrinus ) were vacuum packed (VP), conventionally cook-chilled (CCC) and sous-vide cook-chilled (SVCC) and examined for their microbiological quality and safety during chilled storage (3 °C) for a period of 3, 5 and 16 weeks, respectively, in comparison with conventional pack(CP). The shelf life of CP, VP, CCC and SVCC packs of fish cakes were 2, 2, 4 and 16 weeks, respectively, based on the acceptable break point of the overall sensory scores. The total bacterial counts were 5 log cfu g⁻¹, in CP, VP and CCC packs; and 3 log cfug⁻¹ in SVCC pack on sixteenth week. Total lactic acid bacteria were 2 log cfu g⁻¹ on 2 and 3 weeks in CP and VP, respectively. Staphylococci were detected in all packs on sixteenth week at 2 log cfu g⁻¹. Total bacilli were detected in CP and VP at 3 log cfu g⁻¹ level after 2 weeks. Aeromonads were detected after 1, 2 and 4 weeks in CP, VP and CCC packs at 3 log cfu g⁻¹. Total anaerobic sulphite-reducing clostridia were detected only in CP and CCC packs at 3 MPN counts g⁻¹ level on the final day.     

Removal of citric acid from aqueous solution by catalytic wet peroxidation using effective mesoporous Fe‐MCM‐41 molecular sieves

The presence of citric acid in decontamination waste can cause complexation of radioactive cations, resulting in interferences in their removal by various treatment processes such as chemical precipitation and ion exchange, and may pose a potential danger to the environment. Mesoporous Fe‐MCM‐41 molecular sieves (Si/Fe = 25, 50, 75 and 100) were synthesized hydrothermally and characterized by X‐ray diffraction, N₂ adsorption studies, diffuse reflectance UV‐visible spectroscopy, electron paramagnetic resonance and transmission electron microscopy to evaluate the removal of citric acid from aqueous solution by the wet peroxidation method. The effect of time, pH, Si/Fe ratios of Fe‐MCM‐41 and temperature has been studied to achieve efficient removal of citric acid from the aqueous solution. Unlike homogeneous Fe³⁺ catalysis, more mineralization of citric acid was achieved by heterogeneous catalysis with Fe‐MCM‐41 with the percentage removal of total organic carbon of citric acid following the order Fe‐MCM‐41 (Si/Fe = 25) > Fe‐MCM‐41 (Si/Fe = 50) > Fe‐MCM‐41 (Si/Fe = 75) > Fe‐MCM‐41 (Si/Al = 100). Moreover, it was also observed that during the reaction only a minimum amount of iron is leaching from Fe‐MCM‐41. Copyright © 2007 Society of Chemical Industry     

Effect of cellulase pretreatment of raw and bleached cotton fibers on properties of hydroentangled nonwoven fabrics

This study was undertaken to investigate the effect of enzymatic pretreatment of cotton (polysaccharides) fibers on the properties of resulting nonwoven fabric. Enzymatic treatment is known to improve the esthetical properties of fabrics but will likely lead to a reduction in strength. In the case of nonwovens the strength loss can be even more drastic as cellulase may attack bonded areas of the fabric. In this work, raw and bleached cotton fibers were treated with enzyme solutions prior to fabric formation to avoid possible damage to the bonded areas and improve strength retention. These fibers were first modified with commercially available whole cellulases and monocomponent endoglucanase enzyme solutions. Then they were formed into a fabric and bonded via hydroentangling. Parameters such as bending modulus, fabric tenacity, fiber strength, length and reducing power were measured for each sample. The pretreatment of cotton fibers prior to fabric formation showed that the resulting nonwovens could be stronger and more drapeable than the same fabric composed of untreated fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of fiber orientation in uni-directional glass epoxy laminate using acoustic emission monitoring

Acoustic emission(AE) can be used for in situ structural health monitoring of the composite laminates. One of the main issues of AE is to characterize different dam-age mechanisms from the detected AE signals. In the present work,pure resin and GFRP composites laminates with different stacking sequences such as 0,90,angle ply[±45 ],cross-ply [0 /90 ] are used to trigger different failure mechanisms when subjected to tensile test with AE monitoring. The study of failure mechanisms is facilitated by the choic...